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#1
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Audio Cyclopedia - A highly recommended book
One often sees references on this group to RDH, but very
few people seem to know about the excellent book entitled Audio Cyclopedia, by Howard Tremaine, who was a designer at McCurdy Industries, a Canadian company manufacturing studio and broadcast equipment. The book, in question and answer format, is comprised of 25 sections, with more than 1700 pages. The second edition, fourth printing, which is the edition most often seen, was published in 1975, is mainly tube/valve orientated but does also have some SS circuits. Chapters include: Basic Principles of Sound Acoustics, Studio techniques. Microphones, Attenuators, Vacuum Tubes, Transistors and Diodes, Audio Amplifiers, Disc Recording, Cutting Heads Magnetic Recording Loudspeakers. Power Supplies, Test Equipment. Audio-frequency measurement Installation Charts and tables. I am told by a former colleague from the UK who worked also at Canadian Broadcasting that the book was one of their training manuals. Highly recommended! -- Iain |
#2
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote: One often sees references on this group to RDH, but very few people seem to know about the excellent book entitled Audio Cyclopedia, by Howard Tremaine, who was a designer at McCurdy Industries, a Canadian company manufacturing studio and broadcast equipment. The book, in question and answer format, is comprised of 25 sections, with more than 1700 pages. The second edition, fourth printing, which is the edition most often seen, was published in 1975, is mainly tube/valve orientated but does also have some SS circuits. Chapters include: Basic Principles of Sound Acoustics, Studio techniques. Microphones, Attenuators, Vacuum Tubes, Transistors and Diodes, Audio Amplifiers, Disc Recording, Cutting Heads Magnetic Recording Loudspeakers. Power Supplies, Test Equipment. Audio-frequency measurement Installation Charts and tables. I am told by a former colleague from the UK who worked also at Canadian Broadcasting that the book was one of their training manuals. Highly recommended! -- Iain I found a copy in a local technical college library in 1995 and I paid 10c a page to copy 1,000 pages on the photocopier over two days. The Audio Encyclopedia is a good book, to be sure, and slightly more modern than RDH4, but it all mainly obsolete now like most of what is in RDH4 because we have developed better ways of achieving good sound in loungerooms compared to what was done in 1960. But for anyone whose mind is stuck in the past, and who has unlimited time to waste during funded retirement for fixing old junk, the AE is a good guide. For myself, its a reference book, and I seldom need to read it now because I just apply basic known principles to overcome problems and get on with it. I have very limited time, and have to earn my money, so I cannot waste time on junk. I condensed what I need know and what 95% of other ppl need to know at my website for good loungeroom sound. But for those into cutting LP records or movie track sound et all, and I don't know anyone at all interested, and willing to spend the time alone making progress the AE is helpful, but one still has to learn what isn't in the books by doing an apprenticeship. There are dozens of intersting schematics of commercial circuit designs in the AE but I won't ever be using many... Patrick Turner. |
#3
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Audio Cyclopedia - A highly recommended book
The AC comes in three editions, of which the second is far and away the
most common. Unlike the RDH 4, whose price has come down a lot since it was put up for free, legal download, it is still copyright in the US and elsewhere so it can't be freely distributed. Furthermore, Tremaine's family are apparently being prickish and refusing to allow reprint. Apparently the publishers of "The New Audio Cyclopedia", wished to put a .pdf of both earlier editions in as a cd-rom with the new one and the family were impossible to deal with. CUT COPYRIGHT TERMS TO REASONABLE LENGTH!!!!!!!! The AC is not primarily about domestic hi-fi and is, like a lot of the old Audel's and Sams books, written in Q and A format. Nonetheless it is quite informative as long as one does not expect to be fed and burped and changed by a book, let alone one dating from 1969. It is important to remember before slagging old tube equipment that it was not built to mil spec and was not intended to hold up for 50+ years. They did not realistically expect anyone in 2008 to give a flying Philadelphia cream cheese about amplifiers made in 1958. That's true of American, British, or German equipment, or any other. Whether Quad Leak or Radford, marantz, McIntosh or Fisher, or Klangfilm or Siemens, it has in fact held up better than anyone thought it would. I have several military radios, a Collins S-Line ham receiver and a lot of old test equipment that was built better, but it cost the price of a house. -- Message posted using http://www.talkaboutaudio.com/group/rec.audio.tubes/ More information at http://www.talkaboutaudio.com/faq.html |
#4
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Audio Cyclopedia - A highly recommended book
On Jul 29, 12:05*am, "BretLudwig" wrote:
(snip) *It is important to remember before slagging old tube equipment that it was not built to mil spec and was not intended to hold up for 50+ years. They did not realistically expect anyone in 2008 to give a flying Philadelphia cream cheese about amplifiers made in 1958. That's true of American, British, or German equipment, or any other. Whether Quad Leak or Radford, marantz, McIntosh or Fisher, or Klangfilm or Siemens, it has in fact held up better than anyone thought it would. Agreed, but it can also be "remanufactured" to even better than original specs (modern caps and resistors) as long as the iron is good. As long as we can get the tubes it should live "forever"... well, you know what I mean. Cheers, Roger |
#5
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Audio Cyclopedia - A highly recommended book
"Engineer" wrote in message ... On Jul 29, 12:05 am, "BretLudwig" wrote: (snip) It is important to remember before slagging old tube equipment that it was not built to mil spec and was not intended to hold up for 50+ years. They did not realistically expect anyone in 2008 to give a flying Philadelphia cream cheese about amplifiers made in 1958. That's true of American, British, or German equipment, or any other. Whether Quad Leak or Radford, marantz, McIntosh or Fisher, or Klangfilm or Siemens, it has in fact held up better than anyone thought it would. Agreed, but it can also be "remanufactured" to even better than original specs (modern caps and resistors) as long as the iron is good. Yes- But that's the heart of the problem. Try to find a coil winder who can make you a transformer *precisely* to the Williamson or Radford specification. I am, not sure about the situation in the US but in the EU out of some thirty or so commercial transformer manufacturers, there seem to be only two that can work to such a high standard. Iain |
#6
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Audio Cyclopedia - A highly recommended book
Engineer wrote: On Jul 29, 12:05 am, "BretLudwig" wrote: (snip) It is important to remember before slagging old tube equipment that it was not built to mil spec and was not intended to hold up for 50+ years. They did not realistically expect anyone in 2008 to give a flying Philadelphia cream cheese about amplifiers made in 1958. That's true of American, British, or German equipment, or any other. Whether Quad Leak or Radford, marantz, McIntosh or Fisher, or Klangfilm or Siemens, it has in fact held up better than anyone thought it would. Agreed, but it can also be "remanufactured" to even better than original specs (modern caps and resistors) as long as the iron is good. As long as we can get the tubes it should live "forever"... well, you know what I mean. Cheers, Roger But even if the iron is crook, it to can be replaced with better mades. Its a case of replacing the handle and the blade of dad's old axe, but the nice box for the axe still has a use. Patrick Turner. |
#7
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote: "Engineer" wrote in message ... On Jul 29, 12:05 am, "BretLudwig" wrote: (snip) It is important to remember before slagging old tube equipment that it was not built to mil spec and was not intended to hold up for 50+ years. They did not realistically expect anyone in 2008 to give a flying Philadelphia cream cheese about amplifiers made in 1958. That's true of American, British, or German equipment, or any other. Whether Quad Leak or Radford, marantz, McIntosh or Fisher, or Klangfilm or Siemens, it has in fact held up better than anyone thought it would. Agreed, but it can also be "remanufactured" to even better than original specs (modern caps and resistors) as long as the iron is good. Yes- But that's the heart of the problem. Try to find a coil winder who can make you a transformer *precisely* to the Williamson or Radford specification. I have demonstrated to myself that doing "*precisely*" what Raddy or Willy done all those years ago is a ******thon. One does not need vertically divided bobbins for starters. In most cases, one can improve the design of any given amp made over 20 years ago by removing all the circuitry and parts and re-doing the whole damn amp in the manner I have described in many ways at my website. Most ancient designs of OPT were focused mainly on minimizing copper and iron because GOSS and copper had a real price many times what the real price is now. Skilled winding tradespeople were both cheap and plentiful in 1958, so guess what, how did they manage some performance quality without much iron or copper? They made special laminations with a larger window area to centre core area ratio so more turns could be placed on. The modern trend is for much lower winding resistances which will withstand a saturated KT88 indefinately. Old OPT just heat up and die with shorted turns. Wiily's OPT had 4,400 P turns of terribly thin fragile wire. Core was a 44mm stack of 32 tongue material, and window was 75mm x 25mm. Nowdays one would use 2,200 turns with 60 stack of 51mm tongue to get saturation at the same F as in the original Willy OPT at the same voltage applied. But because the P wire would be so much thicker, and the S wire size, the OPT would produce 64W easily at less than 5% winding losses, instead of Willy's 16W and 10% winding losses. My website gives an enormous amount of info on how to wind excellent OPT that will perform better than the Willy models ever did and which will be more rugged. I've never seen the actual winding plans for the Radford amps. Old secret stuff. Bah, let them keep thie bloody secrets, I don't care, what I will wind will be better anyway. I am, not sure about the situation in the US but in the EU out of some thirty or so commercial transformer manufacturers, there seem to be only two that can work to such a high standard. Lundahl and Sowter? I have just nearly completed reforming a VAC 7070 amp with a quad of 300B per channel. The brand of OPT used is unknown, but they do seem to have a big simularity to something made by Hammond, which is the brand used by many hobbyists in the US and elsewhere. Hammond ain't the cream though. It don't matter though, because the VAC OPT do have **enough** bandwidth to allow faultless and blameless wonderful sound and technical performance. So we have a situation where the Hammond is the main choice because its affordable and good enough. Something wound like an old Williamson would be 3 times the price, and a waste of money imho. If I was a commercial winder, I'd charge twice what Hammond does, because I know I'd offer a slightly better performance at HF due to much better interleaving, and better ranges of impedance matches *without* wasting turns on the secondary. See my website for details. Feel free to wind anything you fancy at my website such as OPT No1. Clever dicks will do a lot better than I have. Patrick Turner. Iain |
#8
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Audio Cyclopedia - A highly recommended book
Pat T
"I've never seen the actual winding plans for the Radford amps. Old secret stuff. Bah, let them keep thie bloody secrets, I don't care, what I will wind will be better anyway. I am, not sure about the situation in the US but in the EU out of some thirty or so commercial transformer manufacturers, there seem to be only two that can work to such a high standard. Lundahl and Sowter? I have just nearly completed reforming a VAC 7070 amp with a quad of 300B per channel. The brand of OPT used is unknown, but they do seem to have a big simularity to something made by Hammond, which is the brand used by many hobbyists in the US and elsewhere. Hammond ain't the cream though. It don't matter though, because the VAC OPT do have **enough** bandwidth to allow faultless and blameless wonderful sound and technical performance. So we have a situation where the Hammond is the main choice because its affordable and good enough. Something wound like an old Williamson would be 3 times the price, and a waste of money imho. If I was a commercial winder, I'd charge twice what Hammond does, because I know I'd offer a slightly better performance at HF due to much better interleaving, and better ranges of impedance matches *without* wasting turns on the secondary. See my website for details. Feel free to wind anything you fancy at my website such as OPT No1. Clever dicks will do a lot better than I have. Patrick Turner." Visit any transformer plant winding stuff under 25 lbs. or so piece weight, you'll see a largely dickless workforce. Transformer winding is women's work, quite literally, on a commercial basis. -- Message posted using http://www.talkaboutaudio.com/group/rec.audio.tubes/ More information at http://www.talkaboutaudio.com/faq.html |
#9
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Audio Cyclopedia - A highly recommended book
BretLudwig wrote: Pat T "I've never seen the actual winding plans for the Radford amps. Old secret stuff. Bah, let them keep thie bloody secrets, I don't care, what I will wind will be better anyway. I am, not sure about the situation in the US but in the EU out of some thirty or so commercial transformer manufacturers, there seem to be only two that can work to such a high standard. Lundahl and Sowter? I have just nearly completed reforming a VAC 7070 amp with a quad of 300B per channel. The brand of OPT used is unknown, but they do seem to have a big simularity to something made by Hammond, which is the brand used by many hobbyists in the US and elsewhere. Hammond ain't the cream though. It don't matter though, because the VAC OPT do have **enough** bandwidth to allow faultless and blameless wonderful sound and technical performance. So we have a situation where the Hammond is the main choice because its affordable and good enough. Something wound like an old Williamson would be 3 times the price, and a waste of money imho. If I was a commercial winder, I'd charge twice what Hammond does, because I know I'd offer a slightly better performance at HF due to much better interleaving, and better ranges of impedance matches *without* wasting turns on the secondary. See my website for details. Feel free to wind anything you fancy at my website such as OPT No1. Clever dicks will do a lot better than I have. Patrick Turner." Visit any transformer plant winding stuff under 25 lbs. or so piece weight, you'll see a largely dickless workforce. Transformer winding is women's work, quite literally, on a commercial basis. Aha, you know the secret behind secret men's business. Its women. And indeed they wound many trannies, and made most of the tubes, and other radio coils and they did anything that suited their ability for quickly doing dexterous work repeatedly. Not many women worked in the design offices afaik. So that's where the clever dicks were; beavering away to produce good designs. In the next office along the corridoor, some ******* called Bean Kownter laboured away to dumb down the design to make it use less women's work to wind it. Its a **** of a world you know :-) Patrick Turner. -- Message posted using http://www.talkaboutaudio.com/group/rec.audio.tubes/ More information at http://www.talkaboutaudio.com/faq.html |
#10
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Audio Cyclopedia - A highly recommended book
"Patrick Turner" wrote in message ... I've never seen the actual winding plans for the Radford amps. Old secret stuff. Bah, let them keep thie bloody secrets, I don't care, what I will wind will be better anyway. All good coilwinders are very careful about giving away too much information. I suppose that's understandable really. It's their living and they have had to learn what they know the hard way. I once talked to Dr. Gavin Sowter about cloning a Radford OPT. He said, "Hmm, quite a challenge. It is extremely complex. In the spec for the STA100 which Radford wrote for the BBC, he stated, "the amplifier can run indefinitely at full power into an open or short-circuit load. I have never seen such a claim from any other maker! I am, not sure about the situation in the US but in the EU out of some thirty or so commercial transformer manufacturers, there seem to be only two that can work to such a high standard. Lundahl and Sowter? Indeed. I have just nearly completed reforming a VAC 7070 amp with a quad of 300B per channel. The brand of OPT used is unknown, but they do seem to have a big simularity to something made by Hammond, which is the brand used by many hobbyists in the US and elsewhere. Hammond ain't the cream though. They seem to have several different standards of transformers for differing requirements. A chap I once spoke to at an audio fair, who made very handsome custom-built Williamsons told me that he had never been able to make one work properly with a Hammond. I have used Hammond iron (mainly mains xformers), and found them to be OK, but their regulation is not as good as the more expensive makers. Feel free to wind anything you fancy at my website such as OPT No1. An acquaintance of mine has been looking for a coilwinding machine for several years. He come accross all kinds of junk, but never a hig-quality machine. AVO in the UK used to make one, I think it was marketed under the name McCade or something similar. It could wind four bobbins simultaneously. I have never seen one, especially for sale. I have a feeling that the Radford machines were built in-house. I rememember on a visit to the Ashton Vale factory seeing three or four machines. Clever dicks will do a lot better than I have. I doubt that many people have enen an inclination to try Those of use who fettle tube amps have little enough spare time as it is, without dabbling in the black arts as well:-) Regards to all Iain |
#11
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote: "Patrick Turner" wrote in message ... I've never seen the actual winding plans for the Radford amps. Old secret stuff. Bah, let them keep thie bloody secrets, I don't care, what I will wind will be better anyway. All good coilwinders are very careful about giving away too much information. I suppose that's understandable really. It's their living and they have had to learn what they know the hard way. I once talked to Dr. Gavin Sowter about cloning a Radford OPT. He said, "Hmm, quite a challenge. It is extremely complex. Bull****. I have heard this bull**** often. Its all bull**** so the guy can avoid treading on toes, or taking any time to talk to anyone. Sowter won't talk to us right here, and what's he worried about? Is he a snob? Is he worried that 4 hobbyists will "steal" his ideas during the next 12 mths? How the **** are those hobbyists ever going to wind something more cheaply than what happens in the Sowter factory? Radford OPT are just OPT, right? Follow the golden rules in RDH4, and you get an outcome at least as good as Radford, or what anyone else can achieve, or better. My 400W rated OPT in my 300 watt PP amps have 100 stack x 51 core section, GOSS wasteless. P = 1,050 turns in 5 sections, two layers each. Sec has 6 six single layer sections each divided into 24 t + 48 t each to give a wide range of lossless load matches. So all up there are 17 windings in my "complex" tranny which isn't very complex at all. Because the insulation between P and S = 0.75mm, the Cshunt is low, and because the interleaving pattern is 6S x 5P, I get 250W bandwidth from 19Hz at saturation to 270kHz, -3dB, for what is a tranny for 1,200 ohms : 5.6 ohms with 1,050 : 72 turn ratio. In the spec for the STA100 which Radford wrote for the BBC, he stated, "the amplifier can run indefinitely at full power into an open or short-circuit load. I have never seen such a claim from any other maker! I have never seen any tube amp able to sustain high levels into a short circuit. Of course, the above statement you quote is a lie, and grossly misleading. Full PO of 100 watts cannot ever be sustained into an open circuit, or a short circuit!!!!! If the load was say 1 ohm, you might get 50W at clipping, not 100W. But all the amps I have seen which were meant to have 8 ohms connected will die in the arse pretty soon if 1 ohm or a short is connected and the input level is left at the same level as used to make 100W into 8 ohms. If you work out the anode dissipation when the amp begins to clip into 1 ohm, you'll be horrified. I am, not sure about the situation in the US but in the EU out of some thirty or so commercial transformer manufacturers, there seem to be only two that can work to such a high standard. Lundahl and Sowter? Indeed. I have just nearly completed reforming a VAC 7070 amp with a quad of 300B per channel. The brand of OPT used is unknown, but they do seem to have a big simularity to something made by Hammond, which is the brand used by many hobbyists in the US and elsewhere. Hammond ain't the cream though. They seem to have several different standards of transformers for differing requirements. A chap I once spoke to at an audio fair, who made very handsome custom-built Williamsons told me that he had never been able to make one work properly with a Hammond. The guy probably had hardly any idea about critical damping. Hardly anyone does. I replaced the Chinese OPT in a Jolida 520 with Hammond 1650P and they worked fine. The original 520 wasn't very stable. Not much GNFB. Many Chinese made amps cannot use a high amount of GNFB because their OPT are so bleedin awful, and because the makers have no idea about critical damping. Production is controlled by dumb arse entrepreneurs, and the marketting ensures hordes of equally dumb arse customers roll in to spend up big. Jolida cost over $3,500 in shops here and retail price is at least 20dB above the cost of production at the sweatshops. In the 520, I kept the original amount of NFB and stabilised it just fine. The Hammond were only marginally better, ie, hardly much better at all compared to the original Chinese OPT, one of which had shorted turns on one side of its vertically divided bobbin. I pulled the chinese OPT to peices to find the ****ed up turns and the burnt wires. What a ****ing mess i found!!! The ambition of joint venture American-Chinese management was to make a nice OPT, but in the making, the fuctard Chinese underpaid overworked cretins in chinese slave labour sweatshops failed miserably to maintain quality, and the layers soon became jumbled, plain insulation tape was used for P-S insulation, and frankly, the Chinese product was absolute crap. No real quality control. With the Hammond, sure, things get fiddly-diddly if you insist on 20dB GNFB, like Willy did in 1947. Like the Chinese Jolida OPT, Hammond doesn't use much interleaving in that particular OPT. Hammond have released a new range of OPT which entirely avoids having to adjust winding connections to get the 4, 8 or 16 ohm outlets. The new range just has one S winding with the full S = 16, 0.7 of the winding = 8 ohms, and the CT = 4 ohms, without the ability to parallel each 1/2 sec to get low losses and leakage with 4 ohms. But even ARC use the one S winding suits all approach. So they have worsened the quality!!! Why?, because buyers want things simple, and cannot understand anything even slightly complex any more. But even with a tranny with 270kHz of BW, you still have troubles with stability. The troubles mean oscillation happens at a higher F than it does with an OPT with a poorer BW. I have used Hammond iron (mainly mains xformers), and found them to be OK, but their regulation is not as good as the more expensive makers. You pay more for more interleaving less shunt C, less leakage, and quality. Feel free to wind anything you fancy at my website such as OPT No1. An acquaintance of mine has been looking for a coilwinding machine for several years. He come accross all kinds of junk, but never a hig-quality machine. AVO in the UK used to make one, I think it was marketed under the name McCade or something similar. It could wind four bobbins simultaneously. I have never seen one, especially for sale. I have a friend in Sydney who recently bought a winding lathe made in Germany 50 years or more ago from an 80 yr old who finally retired. He says he's able to put on 10,000 turns of fine wire in an ESL step up tranny in neat layers before morning tea time. And he never breaks a wire and it traverses perfectly. There are winding machines out there. I couldn't find one either so I made my own. Its slow, because there isn't any auto traversing mech, but I get a perfect coil with persistance. There is more to making an OPT or PT or choke than just the winding. There is the designing, the winding, the finding parts, wire, core, insulations, then assembly, varnishing, potting, testing and terminations. There are risks and dangers of ****ing up your work at each and every process. I have a feeling that the Radford machines were built in-house. I rememember on a visit to the Ashton Vale factory seeing three or four machines. Clever dicks will do a lot better than I have. I doubt that many people have enen an inclination to try Those of use who fettle tube amps have little enough spare time as it is, without dabbling in the black arts as well:-) OPTs are NOT a black art. Its just plain simple engineering and trade work that has been mainly forgotten in western nations as a direct result of using SS which can be direct coupled to any load. The Chinese are now making nearly all the transformers used in western countries because the pay rate in China is $2 per day, but in London or Berlin or new York its $100 per day. And because workers in the west mainly don't actually work, but sit in front of screens and get fat arses. Everyone who buys chinese goods supports the foul unjust social economic status quo where the workers of China are screwed into the dust. The Chinese are going to try to get rich and in doing so will blacken the planet with their soot and the West doesn't want to pay them a fair wage to fund anti CO2 emission measures. Its a completely fuct up world. It should be just as economically viable and evironmentally friendly to set up a factory to anything in any country, because each worker of the world should get the same pay for the same work. Communism couldn't provide that. Capitalism can't either. I just wind all my own OPT for my own projects, **** the rest of the world; it can do whatever, I don't give a ****. I also give all my secrets away freely. But they are NOT really MY secrets, but just common good knowledge widely known by competent tranny winders of the past, present and future. Patrick Turner. Regards to all Iain |
#12
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Audio Cyclopedia - A highly recommended book
"Patrick Turner" wrote in message ... Iain Churches wrote: "Patrick Turner" wrote in message ... I've never seen the actual winding plans for the Radford amps. Old secret stuff. Bah, let them keep thie bloody secrets, I don't care, what I will wind will be better anyway. All good coilwinders are very careful about giving away too much information. I suppose that's understandable really. It's their living and they have had to learn what they know the hard way. I once talked to Dr. Gavin Sowter about cloning a Radford OPT. He said, "Hmm, quite a challenge. It is extremely complex. Bull****. I have heard this bull**** often. I have dealt with Sowter since the mid 60s, and know many of the people there personally. BS is not something in which they indulge. But, I do remember John Widgery telling me that the Radford STA100 primary had twenty separate sections in series and parallel, some with reversed polarity.´That sounds pretty complex to me! Its all bull**** so the guy can avoid treading on toes, or taking any time to talk to anyone. Sowter won't talk to us right here, and what's he worried about? Is he a snob? Dr Gavin Sowter ?? A gentleman, but certainly not a snob. One of the nicest men you could have wished to have met. He is now in the great transformer winding shop in the sky. In the spec for the STA100 which Radford wrote for the BBC, he stated, "the amplifier can run indefinitely at full power into an open or short-circuit load. I have never seen such a claim from any other maker! I have never seen any tube amp able to sustain high levels into a short circuit. Of course, the above statement you quote is a lie, and grossly misleading. You can be sure the people at the Beeb amd many others, tried it. Arthur Radford would have been foolish indeed to make such a statement if it could be proved to be true. I will try to find the amp spec and copy it for you. Full PO of 100 watts cannot ever be sustained into an open circuit, or a short circuit!!!!! I have such an amplifier, but its value it such that I would be unwilling to abuse it in any way. Personally it makes little difference to me either way. I certainly would not get hot under the collar about it:-) Lundahl and Sowter? Indeed. I have just nearly completed reforming a VAC 7070 amp with a quad of 300B per channel. A chap I once spoke to at an audio fair, who made very handsome custom-built Williamsons told me that he had never been able to make one work properly with a Hammond. The guy probably had hardly any idea about critical damping. Hardly anyone does. IIRC he mentioned that excess leakage inductance was the problem with Hammond iron at that time. The situation may or may not have improved. I cannot say. Regards to all Iain |
#13
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Audio Cyclopedia - A highly recommended book
IOt appears the original Audio Cyclopedia is highly thought of, so I
have asked my ocal library to see if they can find me a copy. There appears to be a modern replacement called The New Audio Cyclopedia. Is it any good? Cheers Ian |
#14
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Audio Cyclopedia - A highly recommended book
"Ian Thompson-Bell" wrote in message ... It appears the original Audio Cyclopedia is highly thought of, so I have asked my ocal library to see if they can find me a copy. The second edition was ubiquitous, and used by studios and broadcasting authorities as a teaching manual. Your library should be able to find you a copy. I have seen it also in the UK for sale second hand for about UKP 35 I actually have two copies of the second edition. One of these, almost mint, I keep by my easy chair in the music room is for relaxed reading. The other copy is next to my bench. It got left out in the snow last winter. Don't asky why and how, it's a long story!! There appears to be a modern replacement called The New Audio Cyclopedia. Is it any good? Is this written by Tremaine? Or is it someone trying to cash in on his reputation ? The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. He also has a book on the practical aspects of building, called "Building Valve Amplifiers" One of the chapters is entitled "Metalwork for Poets" ! Morgan Jones has a first class BBC pedigree, and a very enjoyable writing style. Iain |
#15
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote: "Patrick Turner" wrote in message ... Iain Churches wrote: "Patrick Turner" wrote in message ... I've never seen the actual winding plans for the Radford amps. Old secret stuff. Bah, let them keep thie bloody secrets, I don't care, what I will wind will be better anyway. All good coilwinders are very careful about giving away too much information. I suppose that's understandable really. It's their living and they have had to learn what they know the hard way. I once talked to Dr. Gavin Sowter about cloning a Radford OPT. He said, "Hmm, quite a challenge. It is extremely complex. Bull****. I have heard this bull**** often. I have dealt with Sowter since the mid 60s, and know many of the people there personally. BS is not something in which they indulge. But, I do remember John Widgery telling me that the Radford STA100 primary had twenty separate sections in series and parallel, some with reversed polarity.´That sounds pretty complex to me! So bloody what? 20 P sections is NOT especially complex for any OPT. Usually, some winders say all sorts of crap to ppl to make sure they think only the High Priests of Tube Audio are entitled to come up with valid OPT designs and be able to wind them properly. What is usually meant by a "section" isn't something you are familiar with, and Widgery did a grand job in pulling wool right over your eyes. A section of a Primary winding is one that is defined as being all of a group of turns which are located between Secondary sections on each side. So when some buffon say, "Aw gees mate, there are 20 sections that there primary.." it implies there would be 21 sections of secondary in a bobbin winding section with consecutive sections arranged as SPSPSPSPSPSPSPSPSPSPSPSPSPSPSPSPSPSPSPSPSPS. This would give the OPT disgustingly high C shunt, and be very poor practice. 21 P sections when mentioned without definitions that you should have insisted upon like I would, could mean that there were 21 primary layers of wire which happens to be a very common number of P layers. These layers, you may have discovered had you got the whole truth and nothing but the truth from Widgery, might have been divided into say 5 sections if you were lucky, say 4L + 4L + 5L + 4L + 4L, with the CT for the B+ 1/2 way along the 5L centre section of P. Its highly likely there are 4 single layer sections of secondary, perhaps divided into sub sections, but all very ordinary good practice that i am 100% sure Radford wasn't going to try to exceed lest he saddle himself with terrible quality control problems. But in fact with decent winding machinery and in a mass production regime, winding complexity isn't all that difficult if you have the right tradeswomen who've been well trained after years of winding all kinds of stuff. Perhaps the Primary sections of 4 layers each were subdivided into layers connected "strangly" with regard to winding direction and sequencing to reduce shunt capacitance. But Widgery did nothing except deliberatly conceal the truth if indeed he ever really knew it, and he bull****ted to boost his ego and aura with the audience that comprised yourself. Its all bull**** so the guy can avoid treading on toes, or taking any time to talk to anyone. Sowter won't talk to us right here, and what's he worried about? Is he a snob? Dr Gavin Sowter ?? A gentleman, but certainly not a snob. One of the nicest men you could have wished to have met. He is now in the great transformer winding shop in the sky. I can't disagree. I never met him, and being dead is a fair excuse for not being present here. But we never hear from anyone who IS at Sowter now. I don't expect them to wade in here because they'd have zero to gain from the experience. In the spec for the STA100 which Radford wrote for the BBC, he stated, "the amplifier can run indefinitely at full power into an open or short-circuit load. I have never seen such a claim from any other maker! I have never seen any tube amp able to sustain high levels into a short circuit. Of course, the above statement you quote is a lie, and grossly misleading. You can be sure the people at the Beeb amd many others, tried it. Arthur Radford would have been foolish indeed to make such a statement if it could be proved to be true. I will try to find the amp spec and copy it for you. Full PO of 100 watts cannot ever be sustained into an open circuit, or a short circuit!!!!! I have such an amplifier, but its value it such that I would be unwilling to abuse it in any way. Personally it makes little difference to me either way. I certainly would not get hot under the collar about it:-) Maybe you see my point. I am NOT so gullible to believe idiotic claims and half baked explanations. If you have an input sine wave equal to that which causes clipping into 8 ohms, and the outlet has been designed for 8 ohms, then the amp shouldn't overheat, ie, Pda should not quite get up to the rating for the tubes, ie, 42 watts for each KT88. But lemme tellya, if ya run any tube amp with that input voltage, and a shorted output, then expect red hot anodes and maybe a ****ed OPT within 15 minutes if the mains fuses don't blow. Do the calculations for the Pda per KT88, and you'll find the average tube current x average tube voltage is way over 42 watts. Radford amps like all that old stuff do not have active protection, and rely on fuses. Sometimes the fuses work when there is gross overload with a sine wave because the Idc needing to be supplied to the OPT CT goes way high in a fault condition. But it is very easy to blow up many amps with a shorted output with music, and not have any fuses blow. Twice last year I repaired a Quad-II amp driving an ESL57 with an intermittently shorting midrange panel. Boy whatta mess! Radford amps would **** up under the same situation. Lundahl and Sowter? Indeed. I have just nearly completed reforming a VAC 7070 amp with a quad of 300B per channel. A chap I once spoke to at an audio fair, who made very handsome custom-built Williamsons told me that he had never been able to make one work properly with a Hammond. The guy probably had hardly any idea about critical damping. Hardly anyone does. IIRC he mentioned that excess leakage inductance was the problem with Hammond iron at that time. The situation may or may not have improved. I cannot say. The LL with a 1650P is a bit too high. I know, I used a pair in a Jolida 502 3 mths ago to replace the horrible Chinese OPTs, one of which had got shorted turns after 8 years. The Chinese didn't get the critical damping right, but I did. Leak made OPT with 50mH of LL and boy they were crap, but you can get around these defects if you know how, see my pages on it. I routinely wind OPT with less than 5mH for the same applications. Instead of Leaks woeful low amount of interleaving, I use at least a 5S x 4P section arrangement. So before you praise up what Radford done, define exactly what he really did do. If you asked Leak about his trannies, you'd get all this hogwash about how ****in marvellous they were. But really, Leak OPT were ****in horrid, and worse than the Chinese crap. Sure these things are touted to be "complex" and hard to wind. BS, most OPT are not complex at all, but the winders always crap on about their difficulties, to make themselves look like heroes who should be knighted by QE2. Some need sending to Siberia to teach them about the truth ahd hard work. They talk utter BS and never reveal the REAL details of what they do. The original Williamson design is one that is defined OPENLY and FREELY in TRANSPARENT detail in RDH4 had two side by side indentical bobbins with a lot of complexity if that is what it was. Take a look and the simple 1 paragraph description of it. Get anything like that paragraph from Widgery? I rest my case. Patrick Turner. Regards to all Iain |
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Audio Cyclopedia - A highly recommended book
In article ,
"Iain Churches" wrote: The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. He also has a book on the practical aspects of building, called "Building Valve Amplifiers" One of the chapters is entitled "Metalwork for Poets" ! Morgan Jones has a first class BBC pedigree, and a very enjoyable writing style. I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Regards, John Byrns -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
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Audio Cyclopedia - A highly recommended book
"flipper" wrote in message ... On Mon, 04 Aug 2008 10:18:06 -0500, John Byrns wrote: In article , "Iain Churches" wrote: The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. He also has a book on the practical aspects of building, called "Building Valve Amplifiers" One of the chapters is entitled "Metalwork for Poets" ! Morgan Jones has a first class BBC pedigree, and a very enjoyable writing style. I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Could you elaborate on what the goof was? In the preface to the second edition, Morgan Jones makes a reference to a number of howlers "for which the author can only humbly aplogize" Its a 500 page book packed with information, tips, schematics and formulae. That there were a few errors, now corrected, is not a surprise. Most still regard his books as some of the most important in sustaining the healthy interest in thermionic audio. Regards to all Iain |
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote:
"Ian Thompson-Bell" wrote in message ... It appears the original Audio Cyclopedia is highly thought of, so I have asked my ocal library to see if they can find me a copy. The second edition was ubiquitous, and used by studios and broadcasting authorities as a teaching manual. Your library should be able to find you a copy. I have seen it also in the UK for sale second hand for about UKP 35 I checked it out at Amazon and the cheapest I could find was 185USD. Where in the UK have you seen it for 35 quid? I actually have two copies of the second edition. One of these, almost mint, I keep by my easy chair in the music room is for relaxed reading. The other copy is next to my bench. It got left out in the snow last winter. Don't asky why and how, it's a long story!! There appears to be a modern replacement called The New Audio Cyclopedia. Is it any good? Is this written by Tremaine? Or is it someone trying to cash in on his reputation ? Apparently it includes some of Tremaines work, but is extended to include more recent stuf e.g.digital. I believe Tremaine is NOT credited though. The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. Yes, I have that too. Some useful stuff in there not found elsewhere. He also has a book on the practical aspects of building, called "Building Valve Amplifiers" One of the chapters is entitled "Metalwork for Poets" ! Morgan Jones has a first class BBC pedigree, and a very enjoyable writing style. Iain Cheers Ian |
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Audio Cyclopedia - A highly recommended book
"Ian Thompson-Bell" wrote in message ... Iain Churches wrote: "Ian Thompson-Bell" wrote in message ... It appears the original Audio Cyclopedia is highly thought of, so I have asked my ocal library to see if they can find me a copy. The second edition was ubiquitous, and used by studios and broadcasting authorities as a teaching manual. Your library should be able to find you a copy. I have seen it also in the UK for sale second hand for about UKP 35 I checked it out at Amazon and the cheapest I could find was 185USD. Where in the UK have you seen it for 35 quid? At a bookshop in Twickenham, just a few months ago. The mint copy I have is marked £25-95 on the inside cover. I paid a little more than that for it. There appears to be a modern replacement called The New Audio Cyclopedia. Is it any good? Is this written by Tremaine? Or is it someone trying to cash in on his reputation ? Apparently it includes some of Tremaines work, but is extended to include more recent stuf e.g.digital. I believe Tremaine is NOT credited though. Hmm. Curious! The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. Yes, I have that too. Some useful stuff in there not found elsewhere. By the way Ian, did you manage to get the Feedback Instruments phase shift meter you were thinking to bid for on e-Bay? Regards Iain |
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote:
"Ian Thompson-Bell" wrote in message ... Iain Churches wrote: "Ian Thompson-Bell" wrote in message ... It appears the original Audio Cyclopedia is highly thought of, so I have asked my ocal library to see if they can find me a copy. The second edition was ubiquitous, and used by studios and broadcasting authorities as a teaching manual. Your library should be able to find you a copy. I have seen it also in the UK for sale second hand for about UKP 35 I checked it out at Amazon and the cheapest I could find was 185USD. Where in the UK have you seen it for 35 quid? At a bookshop in Twickenham, just a few months ago. The mint copy I have is marked £25-95 on the inside cover. I paid a little more than that for it. Up here in the wilds of Norfolk the only 2nd hand bookshops we have stock arty farty crap - very little technical stuff and virtually nil electronics. I visit them regularly but balways come away disappointed. There appears to be a modern replacement called The New Audio Cyclopedia. Is it any good? Is this written by Tremaine? Or is it someone trying to cash in on his reputation ? Apparently it includes some of Tremaines work, but is extended to include more recent stuf e.g.digital. I believe Tremaine is NOT credited though. Hmm. Curious! The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. Yes, I have that too. Some useful stuff in there not found elsewhere. By the way Ian, did you manage to get the Feedback Instruments phase shift meter you were thinking to bid for on e-Bay? Unfortunately not - had to go out and missed the end of the auction - wish I had just paid the buy it now price - ah well no matter you can use the oscillator on its own to measure phase. Cheers ian |
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Audio Cyclopedia - A highly recommended book
"flipper" wrote in message ... On Mon, 4 Aug 2008 22:18:00 +0300, "Iain Churches" wrote: "flipper" wrote in message . .. On Mon, 04 Aug 2008 10:18:06 -0500, John Byrns wrote: In article , "Iain Churches" wrote: The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. He also has a book on the practical aspects of building, called "Building Valve Amplifiers" One of the chapters is entitled "Metalwork for Poets" ! Morgan Jones has a first class BBC pedigree, and a very enjoyable writing style. I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Could you elaborate on what the goof was? In the preface to the second edition, Morgan Jones makes a reference to a number of howlers "for which the author can only humbly aplogize" Its a 500 page book packed with information, tips, schematics and formulae. That there were a few errors, now corrected, is not a surprise. Most still regard his books as some of the most important in sustaining the healthy interest in thermionic audio. I'm not concerned with throwing stones. No of course not. I just wanted to be awares in case I run across a site repeating or referencing it. This book is now into its third edition second or third printing. The error to which John refers was in the 1st edition, so unless you buy a second hand copy of the book you will not come across them. Regards to all Iain |
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Audio Cyclopedia - A highly recommended book
John Byrns wrote: In article , "Iain Churches" wrote: The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. He also has a book on the practical aspects of building, called "Building Valve Amplifiers" One of the chapters is entitled "Metalwork for Poets" ! Morgan Jones has a first class BBC pedigree, and a very enjoyable writing style. I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Regards, John Byrns I have a copy of Morgan Jones 'Valve Amplifiers', second edition, and its riddled with errors and sloppy maths without derivations or examples or any depth. Eg, see page 107, with a schematic of a white cathode follower. Why is the anode R of the top triode = 62k???? It looks like a nice oscillator though Away from the mistakes, its got some good stuff. Patrick Turner. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
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Audio Cyclopedia - A highly recommended book
"Patrick Turner" wrote in message ... I have a copy of Morgan Jones 'Valve Amplifiers', second edition, and its riddled with errors and sloppy maths without derivations or examples or any depth. Eg, see page 107, with a schematic of a white cathode follower. Why is the anode R of the top triode = 62k???? Perhaps this is a misprint? Has it been corected in the 3rd edition I wonder? Have you collected together the errors and sent a list of them to the publishers, for acknowledgement and correction in a future edition? This would be of greater use to the tube-audio fraternity that simply denouncing the book here on this group. Iain |
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote: "Patrick Turner" wrote in message ... I have a copy of Morgan Jones 'Valve Amplifiers', second edition, and its riddled with errors and sloppy maths without derivations or examples or any depth. Eg, see page 107, with a schematic of a white cathode follower. Why is the anode R of the top triode = 62k???? Perhaps this is a misprint? Has it been corected in the 3rd edition I wonder? Have you collected together the errors and sent a list of them to the publishers, for acknowledgement and correction in a future edition? This would be of greater use to the tube-audio fraternity that simply denouncing the book here on this group. Iain Sigh, If I was retired, and had all day to do nothing but be "creative" and not worry about earning money, and not having to interrupt my work with digging up drain pipes and repairing /cleaning clogged pipes, and replacing kitchen plumbing now 46 years old, and doing all this stuff a man has to damn well do besides be a good tubologist, then I might get time to properly write a long critique of Mr Jones's book which I feel wasn't proofed well enough by himself or anyone else and then nobody would worry I was just being grumpy on a news group but then I reckon I have gone past the age of 40 and have earned the do-as-you-bloody-well-like license, and now been awarded and official permit from the GOT to be grumpy, because I cannot do as I like because the older I get the better I woz. :-) Errors bedevil authors severly if they don't re read all their work 10 times slowly, and ask what a dumb clod would make of what was being written. I recall writing the last edition of my website over a period of 4 months full time, and boy, did I make some errors! Some got past my editediteditediting, and some good ppl sent me their concerns. There were mainly trivial R or C values, or a wrong line of calculations. I fixed the errors as soon as i was told. I like giving fully worked examples, like RDH4. People like me who don't believe anything they are told, or anything they read unless proof is offered, know how to read books like Jones's. We have a little chuckle now and then, and move right along, realizing that nobody, not even ourselves, are perfect. Patrick Turner. |
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Audio Cyclopedia - A highly recommended book
In article ,
flipper wrote: On Mon, 04 Aug 2008 10:18:06 -0500, John Byrns wrote: In article , "Iain Churches" wrote: The Morgan Jones books are excellent also. I find my second edition of "Valve Amplifiers" most useful. He also has a book on the practical aspects of building, called "Building Valve Amplifiers" One of the chapters is entitled "Metalwork for Poets" ! Morgan Jones has a first class BBC pedigree, and a very enjoyable writing style. I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Could you elaborate on what the goof was? The goof was not a typo or an error in a formula, his idea of placing a build out resistor in the cathode of a concertina phase inverter to equalize the source impedances of the plate and cathode circuits was simply a goofy idea. It was a "bright" idea intended to fix an imagined problem that didn't actually exist, that instead created a real problem. I saw the magazine article and the first edition of his book where he presented this goofy idea, I have never seen the second edition of his book to see how he extricated himself from the predicament he created for himself, although I have been told by people that have seen the second edition that he did somehow extricate himself. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
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Audio Cyclopedia - A highly recommended book
"Patrick Turner" wrote in message ... Iain Churches wrote: "Patrick Turner" wrote in message ... I have a copy of Morgan Jones 'Valve Amplifiers', second edition, and its riddled with errors and sloppy maths without derivations or examples or any depth. Eg, see page 107, with a schematic of a white cathode follower. Why is the anode R of the top triode = 62k???? Perhaps this is a misprint? Has it been corected in the 3rd edition I wonder? Have you collected together the errors and sent a list of them to the publishers, for acknowledgement and correction in a future edition? This would be of greater use to the tube-audio fraternity that simply denouncing the book here on this group. Sigh, If I was retired, and had all day to do nothing but be "creative" and not worry about earning money, and not having to interrupt my work with digging up drain pipes and repairing /cleaning clogged pipes, and replacing kitchen plumbing now 46 years old, and doing all this stuff a man has to damn well do besides be a good tubologist, then I might get time to properly write a long critique of Mr Jones's book which I feel wasn't proofed well enough by himself or anyone else and then nobody would worry I was just being grumpy on a news group but then I reckon I have gone past the age of 40 and have earned the do-as-you-bloody-well-like license, and now been awarded and official permit from the GOT to be grumpy, because I cannot do as I like because the older I get the better I woz. :-) Understood: And taken in the spirit in which I am sure it was intended:-) We have a little chuckle now and then, and move right along, realizing that nobody, not even ourselves, are perfect. Erm. Don't you mean "realizing that nobody, not even ourselves, IS perfect" ? Cheers:-) Iain |
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Audio Cyclopedia - A highly recommended book
"John Byrns" wrote in message ... In article , flipper wrote: I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Could you elaborate on what the goof was? The goof was not a typo or an error in a formula, his idea of placing a build out resistor in the cathode of a concertina phase inverter to equalize the source impedances of the plate and cathode circuits was simply a goofy idea. It was a "bright" idea intended to fix an imagined problem that didn't actually exist, that instead created a real problem. I saw the magazine article and the first edition of his book where he presented this goofy idea, I have never seen the second edition of his book to see how he extricated himself from the predicament he created for himself, although I have been told by people that have seen the second edition that he did somehow extricate himself. John, can you get access to the 2nd edition of Valve Amplifiers? It would be of interest to know if this refers to page 279 of the paragraph which starts "Output resistance with both terminals equally loaded" ? Is not the large difference in output impedance between anode and cathode an important shortcoming of the concertina? Iain |
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote: "Patrick Turner" wrote in message ... Iain Churches wrote: "Patrick Turner" wrote in message ... I have a copy of Morgan Jones 'Valve Amplifiers', second edition, and its riddled with errors and sloppy maths without derivations or examples or any depth. Eg, see page 107, with a schematic of a white cathode follower. Why is the anode R of the top triode = 62k???? Perhaps this is a misprint? Has it been corected in the 3rd edition I wonder? Have you collected together the errors and sent a list of them to the publishers, for acknowledgement and correction in a future edition? This would be of greater use to the tube-audio fraternity that simply denouncing the book here on this group. Sigh, If I was retired, and had all day to do nothing but be "creative" and not worry about earning money, and not having to interrupt my work with digging up drain pipes and repairing /cleaning clogged pipes, and replacing kitchen plumbing now 46 years old, and doing all this stuff a man has to damn well do besides be a good tubologist, then I might get time to properly write a long critique of Mr Jones's book which I feel wasn't proofed well enough by himself or anyone else and then nobody would worry I was just being grumpy on a news group but then I reckon I have gone past the age of 40 and have earned the do-as-you-bloody-well-like license, and now been awarded and official permit from the GOT to be grumpy, because I cannot do as I like because the older I get the better I woz. :-) Understood: And taken in the spirit in which I am sure it was intended:-) We have a little chuckle now and then, and move right along, realizing that nobody, not even ourselves, are perfect. Erm. Don't you mean "realizing that nobody, not even ourselves, IS perfect" ? Well nobody plus one self would be plural, not singular, because there are a heck of a lotta nobodies around. If you had a somebody and you were quite out of your cotton pickin' mind, then that'd be singular. Well, single again, after getting unmarried yet again. Patrick Turner. Cheers:-) Iain |
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Audio Cyclopedia - A highly recommended book
Iain Churches wrote: "John Byrns" wrote in message ... In article , flipper wrote: I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Could you elaborate on what the goof was? The goof was not a typo or an error in a formula, his idea of placing a build out resistor in the cathode of a concertina phase inverter to equalize the source impedances of the plate and cathode circuits was simply a goofy idea. It was a "bright" idea intended to fix an imagined problem that didn't actually exist, that instead created a real problem. I saw the magazine article and the first edition of his book where he presented this goofy idea, I have never seen the second edition of his book to see how he extricated himself from the predicament he created for himself, although I have been told by people that have seen the second edition that he did somehow extricate himself. John, can you get access to the 2nd edition of Valve Amplifiers? It would be of interest to know if this refers to page 279 of the paragraph which starts "Output resistance with both terminals equally loaded" ? Is not the large difference in output impedance between anode and cathode an important shortcoming of the concertina? Not in most amps. While the loads driven by the CPI remain equal, and nothing clips or saturates, ie, as in a Williamson amp, it matters not one bit if one phase is a current source and the other is a voltage source. Patrick Turner. Iain |
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Audio Cyclopedia - A highly recommended book
In article ,
"Iain Churches" wrote: "John Byrns" wrote in message ... In article , flipper wrote: I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Could you elaborate on what the goof was? The goof was not a typo or an error in a formula, his idea of placing a build out resistor in the cathode of a concertina phase inverter to equalize the source impedances of the plate and cathode circuits was simply a goofy idea. It was a "bright" idea intended to fix an imagined problem that didn't actually exist, that instead created a real problem. I saw the magazine article and the first edition of his book where he presented this goofy idea, I have never seen the second edition of his book to see how he extricated himself from the predicament he created for himself, although I have been told by people that have seen the second edition that he did somehow extricate himself. John, can you get access to the 2nd edition of Valve Amplifiers? It would be of interest to know if this refers to page 279 of the paragraph which starts "Output resistance with both terminals equally loaded" ? Hi Iain, I no longer have easy access to any of the Morgan Jones magazine articles or books. The balance of the concertina phase inverter was extensively discussed here in this group at least once in the past. The simplest way to look at the balance question is to consider that ignoring the slight effect caused by the grid to anode and grid to cathode capacitances the same current flows through both the anode and cathode circuits, therefore if the cathode and anode loads are made equal the two output voltages will also be equal since the current in each is the same. How does the sentence you quote above, "Output resistance with both terminals equally loaded", end and what does the next sentence say? I think most everyone here eventually understood that the concertina was inherently balanced irrespective of what the output resistances may be. Relative to the output resistances I think Henry Pasternack and I disagreed, although the disagreement was not about balance. I took a conventional view that the two output impedances were different but that the two output signals ended up equal because the source voltages for the anode and cathode also differed and exactly compensated for the differing output impedances, I think I posted all the relevant equations supporting this view at the time. I basically looked at the anode and cathode source impedances independently, although you do have to consider the actual total anode and cathode loads when doing this analysis. On the other hand IIRC Henry Pasternack took the view that the anode and cathode impedances were actually identical in operation because of the way the signals appear on both the anode an cathode terminals. This view does sort of workout, but you can't test the anode and cathode impedances independently, you have to apply equal and opposite test signals to each when measuring the impedance of either terminal. Is not the large difference in output impedance between anode and cathode an important shortcoming of the concertina? Yes, the large difference in output impedance is important, but only when the concertina is driven into clipping, where the dynamically changing anode and cathode load impedances cause very bizarre clipping behavior. When the grid of the tube driven from the anode conducts, the gain at the cathode doesn't change very much, however when the grid of the tube being driven by the cathode conducts, the gain as seen at the anode increases very greatly leading to grossly asymmetrical waveforms at the two outputs. Morgan Jones build out resistor probably helps moderate this bad clipping behavior, at the expense of balance below clipping level. I had the impression that his point with the build out resistor was to equalize the two source impedances so that the high frequency response would not fall off faster on the anode due to capacitive loading, although in reality the build out resistor actually worsens the balance. Perhaps I misunderstood the reason he suggested the build out resistor and that its real purpose was to mitigate the poor clipping behavior to some extent. What he actually says in the second edition may shed some light on what his original intention was. It would also be interesting to know how he presents the balance issue in the second edition, does he take the Pasternack or the Byrns approach to the analysis? My favorite phase inverter is the floating paraphase, think of it as an inverting opamp in a unity gain configuration. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
#31
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Audio Cyclopedia - A highly recommended book
flipper wrote: On Wed, 06 Aug 2008 12:10:02 GMT, Patrick Turner wrote: Iain Churches wrote: "John Byrns" wrote in message ... In article , flipper wrote: I find it hard to think positively of Morgan Jones ever since his goof with the concertina cathode build out resistor in a magazine article and the first edition of his book. IIRC he flip flopped in the second edition but he should have known better in the first place. It just shows that he didn't bother doing the math, which you should do when making a recommendation that flies in the face of years conventional practice. Could you elaborate on what the goof was? The goof was not a typo or an error in a formula, his idea of placing a build out resistor in the cathode of a concertina phase inverter to equalize the source impedances of the plate and cathode circuits was simply a goofy idea. It was a "bright" idea intended to fix an imagined problem that didn't actually exist, that instead created a real problem. I saw the magazine article and the first edition of his book where he presented this goofy idea, I have never seen the second edition of his book to see how he extricated himself from the predicament he created for himself, although I have been told by people that have seen the second edition that he did somehow extricate himself. John, can you get access to the 2nd edition of Valve Amplifiers? It would be of interest to know if this refers to page 279 of the paragraph which starts "Output resistance with both terminals equally loaded" ? Is not the large difference in output impedance between anode and cathode an important shortcoming of the concertina? Not in most amps. While the loads driven by the CPI remain equal, and nothing clips or saturates, ie, as in a Williamson amp, Are you sure about 'nothing clips' in a Williamson? I mean, with 20dB of NFB, when the output tubes clip the voltage amp is going to try going 100 times the drive voltage and I don't see how the LTP is going to manage that without going into positive grid drive itself. OK, so the amp begins to clip, so there isn't any increasing NFB signal sent to the V1 cathode, so V1 Vgk suddenly begins to increase A times, and the balanced amp which is already having to make maybe 40Vrms to drive the OP grids is asked to double that but into OP tube grid current. This causes the balanced amp to saturate with its own grid I and the concertina gets into trouble. But before the onset of OP tube clipping, the CPI only has to make about 2.5 Vrms to each grid of the balanced amp, and because there isn't any saturation or clipping of anything, the CPI works really well with no strange artifact production. Si while the OP tubes don't clip in a Wiliamson, none of the 6SN7 input or driver tubes will. The Willy amp was designed so that first the OP tubes clip, then the balanced amp and then the CPI and then input. The balanced amp in the W act as a buffer against the micro capacitive FB from OP anodes to the OP grids. So the CPI sees identical a and k loadings to a very high F. But eventually capacitance catches up with the CPI, and anode output falls before the cathode output does. To ensure equal bandwidth at the CPI a and the k, some small value trimmer C across the cathode R of the CPI is advisable. 15pF to 47pF is about right, and the value used is chosen to get a symetrical square wave overshoot at the OPT sec. The CPI is a stage with a lot of local current NFB, and as such acts as a buffer between the input tube and the Miller C of the balanced amp input. The bandwidth of the Willy input/driver amp with 2 x 6SN7 is over 250kHz at the OP tube grids, and is damned excellent. I prefer the use of a single input driving an LTP into one side and with with common cathode CCS. Its not quite as "fast" as a Willy amp, but its slightly simpler, and just as good when NFB is used. But in some recent re-engineering of ARC and Manley amps, I have used an input LTP with cathode CCS to take the input to one grid and NFB to the other, then the output from this goes to a second LTP but with a common Rk taken to -120V, and this worked very well indeed, with almost no 2H in the distortion character that you get with V1 tube as an SET. So it does not matter too much what you use in an input stage and driver stage as long as the noise is SFA, bandwidth is over 150kHz for the output voltage level needed to cause clipping of the OP stage, and without shelving networks applied, and distortion is less than 0.5% at the clipping level for the OP tubes, and the voltage ability is preferably twice what you need for OP tube clipping before the driver amp clips itself without the OP tubes in place; ie loaded by just the bias R cap coupled. If you can easily satisfy all these design requirements, maybe your input driver amp is OK. There are several ways to build a tube amp which has little sonic signature and just presents us the music without smear, glare, coldness, hardness, or damned "tube sound" with all its faults from compromised engineering. So, I can repeat this about the CPI, if used wisely, "it matters not one bit if one phase is a current source and the other is a voltage source." JB and HP had a long running brawl of words about the CPI way back in 2000 when I was told never to mention OPTs or leakage inductance on r.a.t because it'd lead to a flame war all over again. In an ST70, a bootstrapped high gain input pentode must produce slightly more signal that what appears at each OP grid. The CPI between input pentode and OP grids must be able to produce the OP grid to grid signal, ie, twice the OP grid signal, and if that was 30Vrms, then the CPI must make 60Vrms. When the OP tubes clip and draw grid I then the CPI is immediately in serious trouble, and the clipping is asymetrical and ugly. But so darn what? The ST70 is a miserly way to build an amplifier; a bean counter special; something designed by accountants, and to an audiophile, barely acceptable as entry level gear. No matter, its purpose is for hi-fi, and the level was never ever meant to be taken right up to clipping. Teenagers were never invited to parties, or allowed near the hi-fi controls where they immediately press the loudness button, and turn up the bass boost to max, then run everything at window breking volume, which includes clipping, and fusing the tweeters at least. One of The Best sounding low power amplifiers under 12 watts is made with a single 12AX7 with 1/2 as an input triode, and 1/2 as a CPI, and the OP tubes are a pair of EL84 in 40% UL. 15dB GNFB used. Countless commercial amps like Star etc used this basic recipe. The EL84/6BQ5 is a very easy tube to drive. Its a pity that in most integrated chassis where you'll find this circuit for each channel, the line stage amp, tone control amp and phono amp are Z grade, noisy, inaccurate, poor BW, highly distorting and always degrading the sound well before it hits the power amps. Mainly because of bean counters trying to use less tubes, less chassis iron, and less sockets and less PSU filtering, and generally cheating Joe Public out of what he paid for. Patrick Turner. Patrick Turner. Iain |
#32
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Audio Cyclopedia - A highly recommended book
On Aug 7, 5:05�am, Patrick Turner wrote:
Mainly because of bean counters trying to use less tubes, less chassis iron, and less sockets and less PSU filtering, and generally cheating Joe Public out of what he paid for. Patrick Turner. Hi RATs! We each find something of interest in at least some portion of tube amps I like hearing what they sound like when I ... What passes for Audio in the marketplace is very similar to what passes for sex - in the marketplace. "Can't buy me love ..." Money and minds rarely mix ... Bill Gates is not the funniest software (nor hardware) guy I ever met Enjoy your experiments, they are joys beyond measure, once in a while Happy Ears! Al |
#33
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Audio Cyclopedia - A highly recommended book
tubegarden wrote: On Aug 7, 5:05�am, Patrick Turner wrote: Mainly because of bean counters trying to use less tubes, less chassis iron, and less sockets and less PSU filtering, and generally cheating Joe Public out of what he paid for. Patrick Turner. Hi RATs! We each find something of interest in at least some portion of tube amps I like hearing what they sound like when I ... What passes for Audio in the marketplace is very similar to what passes for sex - in the marketplace. "Can't buy me love ..." Money and minds rarely mix ... Bill Gates is not the funniest software (nor hardware) guy I ever met Enjoy your experiments, they are joys beyond measure, once in a while Happy Ears! Al Hmm, I only get paid if my experiments give the best sound possible. Sometimes the experiments are painful; they take such a long time and the pay is very low - Hundreds of hours for just one pair of monoblocs. In the market place the girls don't love you so the sex is cold and dull and propelled by illusions. Good sound must be found after a search for reality without the chill of dull illusion. Patrick Turner. |
#34
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Audio Cyclopedia - A highly recommended book
In article ,
Patrick Turner wrote: The balanced amp in the W act as a buffer against the micro capacitive FB from OP anodes to the OP grids. So the CPI sees identical a and k loadings to a very high F. But eventually capacitance catches up with the CPI, and anode output falls before the cathode output does. To ensure equal bandwidth at the CPI a and the k, some small value trimmer C across the cathode R of the CPI is advisable. 15pF to 47pF is about right, and the value used is chosen to get a symetrical square wave overshoot at the OPT sec. Could you elaborate on this, why it is necessary, is it to compensate for the effects of the capacitances of the CPI grid? JB and HP had a long running brawl of words about the CPI way back in 2000 when I was told never to mention OPTs or leakage inductance on r.a.t because it'd lead to a flame war all over again. As I remember it we both agreed that the circuit was basically balanced, so the brawl must have been over the actual source impedance of the anode and cathode circuits. Thinking about it over the last 24 hours, I suspect that what HP was actually measuring/calculating was the source impedance seen by a load driven as if it were connected between the anode and cathode, or actually half of that value. I don't believe that HP's contrived methodology actually demonstrates that the anode and cathode source impedances are equal as he claimed. One of The Best sounding low power amplifiers under 12 watts is made with a single 12AX7 with 1/2 as an input triode, and 1/2 as a CPI, and the OP tubes are a pair of EL84 in 40% UL. 15dB GNFB used. Countless commercial amps like Star etc used this basic recipe. The EL84/6BQ5 is a very easy tube to drive. Its a pity that in most integrated chassis where you'll find this circuit for each channel, the line stage amp, tone control amp and phono amp are Z grade, noisy, inaccurate, poor BW, highly distorting and always degrading the sound well before it hits the power amps. Mainly because of bean counters trying to use less tubes, less chassis iron, and less sockets and less PSU filtering, and generally cheating Joe Public out of what he paid for. Surely if the basic pair of EL84s and an ECC83 make a good sounding power amplifier, there must be a complimentary "bean counter" approved phono amp and tone control amp to go with it? I assume a "bean counter" would allow two sockets in each stereo channel to be used in providing these functions. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
#35
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Audio Cyclopedia - A highly recommended book
In article ,
flipper wrote: On Thu, 07 Aug 2008 16:20:50 -0500, John Byrns wrote: In article , Patrick Turner wrote: The balanced amp in the W act as a buffer against the micro capacitive FB from OP anodes to the OP grids. So the CPI sees identical a and k loadings to a very high F. But eventually capacitance catches up with the CPI, and anode output falls before the cathode output does. To ensure equal bandwidth at the CPI a and the k, some small value trimmer C across the cathode R of the CPI is advisable. 15pF to 47pF is about right, and the value used is chosen to get a symetrical square wave overshoot at the OPT sec. Could you elaborate on this, why it is necessary, is it to compensate for the effects of the capacitances of the CPI grid? JB and HP had a long running brawl of words about the CPI way back in 2000 when I was told never to mention OPTs or leakage inductance on r.a.t because it'd lead to a flame war all over again. As I remember it we both agreed that the circuit was basically balanced, so the brawl must have been over the actual source impedance of the anode and cathode circuits. Thinking about it over the last 24 hours, I suspect that what HP was actually measuring/calculating was the source impedance seen by a load driven as if it were connected between the anode and cathode, or actually half of that value. I don't believe that HP's contrived methodology actually demonstrates that the anode and cathode source impedances are equal as he claimed. I've seen the classic calculations showing the 'different' anode and cathode source impedances, and it sounds logical, but it doesn't behave that way. What do you mean that "it doesn't behave that way", are you saying that the classic calculations are incorrect? I got into checking that with the 13FD7 'mini Williamson' amp because I'm using large 'grid stoppers' as a HF roll off so the 'different' source impedances became an issue, since they would be 'in series' with the grid stopper resistors, but when I spiced it the thing acts as if the source impedances are identical. I.E. there is no difference in HF roll off (with equal value grid stoppers). To double check I also spiced a standalone concertina with just capacitive loading and got the same results. The fact that "there is no difference in HF roll off" doesn't imply that the anode and cathode source impedances are equal. If, however, you accept that the concertina is balanced as long as the two loads are equal then it's an 'of course' the roll off is the same because the loads are equal, they just vary (equally) with frequency. The response vs. frequency at the two outputs of the concertina are balanced, the source impedances are not. If you keep the 'different impedance' analysis the thing is as cathode impedance drops anode gain increases in exact proportion to the drop across the 'larger' anode impedance. Or, if you use a single common source voltage model (grid), the effect of FB is to make the anode and cathode source impedances appear equal. Only HP and you believe that the anode and cathode source impedances appear equal. The "classic calculations" give the correct results, and show that the anode and cathode source impedances are not equal, that does not prevent the two outputs from being balanced when driving equal loads. You are ignoring a couple of important points that must be considered when using the "classic calculations", if you want to get the correct answer. First when calculating the source impedance at the cathode you must include the total anode load in the calculation, this means not just the plate resistor, but also the coupling capacitor, the following grid resistor, the shunt and miller capacitances of the following tube, et al. Similarly when calculating the source impedance at the anode you must include the total cathode load in the calculations. Second, it isn't sufficient to calculate only the source impedances, you must also calculate the source voltages at the anode and cathode. The trick is that the anode and cathode source voltages vary with frequency in such a way that they cancel the effects of the differing source impedances driving the two loads, the result being that the two output voltages remain balanced even as frequency varies. I'm not good enough to do the math but George E. Jones Jr did it in a 1951 paper on the subject. http://www.diybanter.com/attachment....2&d=1213179423 I will take a look at that article, does it come to the conclusion that the anode and source impedances are equal? -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
#36
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Audio Cyclopedia - A highly recommended book
John Byrns wrote: In article , Patrick Turner wrote: The balanced amp in the W act as a buffer against the micro capacitive FB from OP anodes to the OP grids. So the CPI sees identical a and k loadings to a very high F. But eventually capacitance catches up with the CPI, and anode output falls before the cathode output does. To ensure equal bandwidth at the CPI a and the k, some small value trimmer C across the cathode R of the CPI is advisable. 15pF to 47pF is about right, and the value used is chosen to get a symetrical square wave overshoot at the OPT sec. Could you elaborate on this, why it is necessary, is it to compensate for the effects of the capacitances of the CPI grid? Its not absoluely necessary. It just makes a prettier looking wave above 50khZ. But if you ever do measure a Wiliamson type amp, or one with a CPU drive to the OP tubes, then you'll see that the HF response of the anode output of the CPI sags before the cathode. Some slight C added to the cathode Rk will make the sag even on both anode and cathode. The Ren7070 VAC amp I have just re-wired for a guy had 47pF across a 22k in the CPI. It also had cross coupled neutralising C from anode connections to the OPT back to the oposite grid of the OP 300B. This boosts the HF response with what is positive FB. I abolished this utter BS because the amp has selectable amounts of NFB and in the 10dB FB selection, there was very lousy HF stability. But I left the 47pF across the CPI cathode Rk. JB and HP had a long running brawl of words about the CPI way back in 2000 when I was told never to mention OPTs or leakage inductance on r.a.t because it'd lead to a flame war all over again. As I remember it we both agreed that the circuit was basically balanced, so the brawl must have been over the actual source impedance of the anode and cathode circuits. At the time, you graciously suffered daily broadsides of being called a complete idiot. And of course we know you ain't, and Pasternak is nowhere to be seen. Thinking about it over the last 24 hours, I suspect that what HP was actually measuring/calculating was the source impedance seen by a load driven as if it were connected between the anode and cathode, or actually half of that value. I don't believe that HP's contrived methodology actually demonstrates that the anode and cathode source impedances are equal as he claimed. If you measure the Rout of a CPI SEPARATELY at its anode, its high, and at the cathode ITS LOW. but because at AF the load at a and k remain the same, so too does the balance. One of The Best sounding low power amplifiers under 12 watts is made with a single 12AX7 with 1/2 as an input triode, and 1/2 as a CPI, and the OP tubes are a pair of EL84 in 40% UL. 15dB GNFB used. Countless commercial amps like Star etc used this basic recipe. The EL84/6BQ5 is a very easy tube to drive. Its a pity that in most integrated chassis where you'll find this circuit for each channel, the line stage amp, tone control amp and phono amp are Z grade, noisy, inaccurate, poor BW, highly distorting and always degrading the sound well before it hits the power amps. Mainly because of bean counters trying to use less tubes, less chassis iron, and less sockets and less PSU filtering, and generally cheating Joe Public out of what he paid for. Surely if the basic pair of EL84s and an ECC83 make a good sounding power amplifier, there must be a complimentary "bean counter" approved phono amp and tone control amp to go with it? I assume a "bean counter" would allow two sockets in each stereo channel to be used in providing these functions. You have not had the displeasure to fully examine the woeful attempts by the army of bean counters who controlled what the public bought in 1960. I have, and in nearly every crummy integrated amp, receiver or power + pre set the performance left a lot to be desired. I don't get many sets from 1960 to re-engineer now as I used to 10 years ago. Their owners are usually getting old and deaf, and need to be re-engineered themselves, just to stay alive. Most MM phono stages in 1960 consisted of ONE EF86, as in Quad22, bleedin awful, or two 1/2 of a 12AX7, which was better IMHO, because there was more NFB and the response was more predictable. But most had only nominal adherance to RIAA eq, and actual responses were +/- 3dB and different for each channel. Non deleatable tone controls with similar defects and which had a passive network driven with 1/2 a 12AX7 were horrid. Bean counters ensured that only one tube socket and tube was ever to be used for a single phono channel, and definately not two sockets and tubes. Using a µ-follower stage with a single 12AX7 was utterly out of the question, and made bean counters have a fit of apoplexy and foam at the mouth when some innocent young engineer trotted into the office with prospective design for next year's models. It was with great glee that bean counters adopted solid state devices to replace tubes. They replaced the music as well with something else. Patrick Turner. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
#37
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Audio Cyclopedia - A highly recommended book
The Willy amp was designed so that first the OP tubes clip, then the balanced amp and then the CPI and then input. I think that pretty much goes for any reasonably designed topology. You don't want the voltage stages/PS clipping before the OP tubes, unless maybe you're making a compressor or intentionally creating distortion like in an overdriven guitar preamp or pedal. You got it. The balanced amp in the W act as a buffer against the micro capacitive FB from OP anodes to the OP grids. So the CPI sees identical a and k loadings to a very high F. But eventually capacitance catches up with the CPI, and anode output falls before the cathode output does. Are you speaking of inter electrode capacitances in the CPI itself or the balanced amp grids? Because, if you're speaking of the balanced amp grids the roll off is the same despite the seemingly different CPI anode/cathode impedances. The variations in load at the OP tube anodes cause a change in OP tube gain. The Miller C varies, so the driver stage experiences a change in load as well. If the load on the OP anodes is say low, and then gain is low, so Miller C is low, so the load from Miller makes driver stage gain higher. This might be especially true of a beam tetrode output stage driving ESL speakers where the C of the speaker means the load goes below 2 ohms, at 18kHz, as in Quad ESL57. In a W amp, the CPI is largely buffered from the effects of the Miller C of the OP stage and the change of gain or change of output balance in the balanced drive amp would not have a huge effect on the CPI, let alone on the input stage. To ensure equal bandwidth at the CPI a and the k, some small value trimmer C across the cathode R of the CPI is advisable. 15pF to 47pF is about right, and the value used is chosen to get a symetrical square wave overshoot at the OPT sec. The CPI is a stage with a lot of local current NFB, and as such acts as a buffer between the input tube and the Miller C of the balanced amp input. The bandwidth of the Willy input/driver amp with 2 x 6SN7 is over 250kHz at the OP tube grids, and is damned excellent. I didn't say it wasn't 'excellent'. Just said it clips. I prefer the use of a single input driving an LTP into one side and with with common cathode CCS. Its not quite as "fast" as a Willy amp, but its slightly simpler, and just as good when NFB is used. But in some recent re-engineering of ARC and Manley amps, I have used an input LTP with cathode CCS to take the input to one grid and NFB to the other, then the output from this goes to a second LTP but with a common Rk taken to -120V, and this worked very well indeed, with almost no 2H in the distortion character that you get with V1 tube as an SET. So it does not matter too much what you use in an input stage and driver stage as long as the noise is SFA, bandwidth is over 150kHz for the output voltage level needed to cause clipping of the OP stage, and without shelving networks applied, and distortion is less than 0.5% at the clipping level for the OP tubes, and the voltage ability is preferably twice what you need for OP tube clipping before the driver amp clips itself without the OP tubes in place; ie loaded by just the bias R cap coupled. If you can easily satisfy all these design requirements, maybe your input driver amp is OK. There are several ways to build a tube amp which has little sonic signature and just presents us the music without smear, glare, coldness, hardness, or damned "tube sound" with all its faults from compromised engineering. So, I can repeat this about the CPI, if used wisely, "it matters not one bit if one phase is a current source and the other is a voltage source." It may not matter with excellent OPTs but with the less than ideal OPTs I use CPI clipping can cause HF bursts and the 'excellent' bandwidth along with OP triodes makes it more difficult to control than a 'plain Jane' CPI into a pair of 6BQ5s. Mainly, I think, because that lovely low impedance triode FB more readily shoves the phase shifted crap through the OPT. The low Ra or low driving source resistance of the OP triodes mean that the the second order filtering effect of the poorer OPT becomes undamped, and the response is peaked at the sec, has a high phase shift and any FB becomes positive all too easily. Triode OP stage are wonderful sounding things, but have bothers with damping. The VAC 7070 I have just worked on is no exception with a quad of 300B driving an OPT which is no better than a Hammond with regard LL and Cshunt, so its very necessary to reduce the OLG of the whole input drive amp with a Zobel across the V1 anode load, and have a Zobel at the OPT sec, to get unconditional stability with 12dB GNFB. Now I have a pair of Audion horrors to fix. Same sort of problems. Un-optimised circuitry, N&D way too high, poor stability. JB and HP had a long running brawl of words about the CPI way back in 2000 when I was told never to mention OPTs or leakage inductance on r.a.t because it'd lead to a flame war all over again. In an ST70, a bootstrapped high gain input pentode must produce slightly more signal that what appears at each OP grid. The CPI between input pentode and OP grids must be able to produce the OP grid to grid signal, ie, twice the OP grid signal, and if that was 30Vrms, then the CPI must make 60Vrms. When the OP tubes clip and draw grid I then the CPI is immediately in serious trouble, and the clipping is asymetrical and ugly. Yep, if you don't do something about it. But so darn what? Oscillation bursts is potentially what. Squegging, infact... The ST70 is a miserly way to build an amplifier; a bean counter special; something designed by accountants, and to an audiophile, barely acceptable as entry level gear. No matter, its purpose is for hi-fi, and the level was never ever meant to be taken right up to clipping. Teenagers were never invited to parties, or allowed near the hi-fi controls where they immediately press the loudness button, and turn up the bass boost to max, then run everything at window breking volume, which includes clipping, and fusing the tweeters at least. I hate to ruin your favorite whipping boy but 'bean counters' don't 'pick parts' or perform any other design function. They simply 'count beans' and tell you the sum. Bean counters are employed to say no to engineers. They keep on saying no until the engineers present a design that's cheaper than the competitors are making. The engineers go to Confession before Communion, "Bless me father, for I have Sinned, I sold my ****in soul to the Devil..." " No need to swear my son, three Our Fathers, and six Hail Marys " And so it was that the people of America were jilted at the shop when they bought anything. One of The Best sounding low power amplifiers under 12 watts is made with a single 12AX7 with 1/2 as an input triode, and 1/2 as a CPI, and the OP tubes are a pair of EL84 in 40% UL. 15dB GNFB used. I wonder what would happen if they tried 20dB of GNFB and are they using grid stoppers on the OP tubes? The grid stoppers don't do a lot in polite hi-fi amps. Quad-II don't have them between EF86 drivers and KT66 OP tubes. And really only need to be used to prevent excessive grid currents, or as a kind of limiter to prevent rapid rise of bias in the coupling caps on over drive, something never experienced in hi-fi listening. OK, you see them in an Ampeg SVT at 47k per grid of 6550, but the 6550 are in beam tet mode so Miller is low, and there's a high anode voltage for huge PO levels and anything can and does happen with guitar amps when driven into heavy overdrive. Countless commercial amps like Star etc used this basic recipe. The EL84/6BQ5 is a very easy tube to drive. I know. I did the same thing in my 'Stealth AX; amp, except I'm using the electrically identical 6GK6.. Its a pity that in most integrated chassis where you'll find this circuit for each channel, the line stage amp, tone control amp and phono amp are Z grade, noisy, inaccurate, poor BW, highly distorting and always degrading the sound well before it hits the power amps. Mainly because of bean counters trying to use less tubes, less chassis iron, and less sockets Bean counters count beans, they do not design a damn thing.. and less PSU filtering, and generally cheating Joe Public out of what he paid for. In a free market Joe Public gets exactly what he paid for and is free to pay more if he wants more. My point is that he doesn't get what he paid for. He wants this and that, and reads the sales blurbs, get's fooled into thinking the sales blurbs cover what he thought he wanted, and pays out even in doubt because its the same sorry story at every brandname. Excellence was never wasted upon the masses. There was remarkably good electronics in the moon shot rockets from 1969 onwards, but it didn't extend to Dynacos and Fords. Shareholders, CEOs, marketeers, and bean counters all have to get a big slice of the pie, not leaving much for Joe Consumer. Take a packet of chips from the supermarket. You'd stave to death if that's all you ate, and probably be poisoned. BS rules, OK. Its the modern western capitalist way, bloody awful, until you think of the alternatives. In 1960, I doubt there was a Russian amplifier that was worth buying, and there was, you'd have to wait years for one, or know someone in the Party to get one, and it was a similar deal with the "amazingly innovative and economical Trabant" East German limozine :-) !!!! Patrick Turner. Patrick Turner. |
#38
Posted to rec.audio.tubes
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Audio Cyclopedia - A highly recommended book
Flipper, do you have a real email address?
-Henry moc.ncr@kcanretsaph |
#39
Posted to rec.audio.tubes
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Audio Cyclopedia - A highly recommended book
In article ,
flipper wrote: On Fri, 08 Aug 2008 10:11:02 -0500, John Byrns wrote: In article , flipper wrote: On Thu, 07 Aug 2008 16:20:50 -0500, John Byrns wrote: In article , Patrick Turner wrote: The balanced amp in the W act as a buffer against the micro capacitive FB from OP anodes to the OP grids. So the CPI sees identical a and k loadings to a very high F. But eventually capacitance catches up with the CPI, and anode output falls before the cathode output does. To ensure equal bandwidth at the CPI a and the k, some small value trimmer C across the cathode R of the CPI is advisable. 15pF to 47pF is about right, and the value used is chosen to get a symetrical square wave overshoot at the OPT sec. Could you elaborate on this, why it is necessary, is it to compensate for the effects of the capacitances of the CPI grid? JB and HP had a long running brawl of words about the CPI way back in 2000 when I was told never to mention OPTs or leakage inductance on r.a.t because it'd lead to a flame war all over again. As I remember it we both agreed that the circuit was basically balanced, so the brawl must have been over the actual source impedance of the anode and cathode circuits. Thinking about it over the last 24 hours, I suspect that what HP was actually measuring/calculating was the source impedance seen by a load driven as if it were connected between the anode and cathode, or actually half of that value. I don't believe that HP's contrived methodology actually demonstrates that the anode and cathode source impedances are equal as he claimed. I've seen the classic calculations showing the 'different' anode and cathode source impedances, and it sounds logical, but it doesn't behave that way. What do you mean that "it doesn't behave that way", are you saying that the classic calculations are incorrect? I explained what I meant in the subsequent text. I got into checking that with the 13FD7 'mini Williamson' amp because I'm using large 'grid stoppers' as a HF roll off so the 'different' source impedances became an issue, since they would be 'in series' with the grid stopper resistors, but when I spiced it the thing acts as if the source impedances are identical. I.E. there is no difference in HF roll off (with equal value grid stoppers). To double check I also spiced a standalone concertina with just capacitive loading and got the same results. The fact that "there is no difference in HF roll off" doesn't imply that the anode and cathode source impedances are equal. I think most people would think it implies just that and in most circumstances it does. For example, if you're designing an RIAA filter you include the source impedance of the driving stage in the calculations and if that is 'different' then so would be the compensation. Same thing with a guitar tone stack. If you design a Marshal style tone stack driven by a low impedance cathode follower and then, instead, take from the anode output you get a 'different' response because you have a 'different' source impedance. If, however, you accept that the concertina is balanced as long as the two loads are equal then it's an 'of course' the roll off is the same because the loads are equal, they just vary (equally) with frequency. The response vs. frequency at the two outputs of the concertina are balanced, the source impedances are not. Makes calculating 1/f=2Pi RC a bitch, don't it? If you keep the 'different impedance' analysis the thing is as cathode impedance drops anode gain increases in exact proportion to the drop across the 'larger' anode impedance. Or, if you use a single common source voltage model (grid), the effect of FB is to make the anode and cathode source impedances appear equal. Only HP and you believe that the anode and cathode source impedances appear equal. I said no such thing. I talked about both models but made not one comment about which I 'believed' or preferred. A more reasonable interpretation would be that I suggested both views are simply different ways of looking at the same thing. The "classic calculations" give the correct results, and show that the anode and cathode source impedances are not equal, that does not prevent the two outputs from being balanced when driving equal loads. You are ignoring a couple of important points that must be considered when using the "classic calculations", if you want to get the correct answer. First when calculating the source impedance at the cathode you must include the total anode load in the calculation, this means not just the plate resistor, I'm not ignoring anything and my referencing the classic equations should have given you a clue I'm including all of them. but also the coupling capacitor, the following grid resistor, the shunt and miller capacitances of the following tube, et al. They ain't there in the stand alone CPI test I ran. Nor does it make any difference to the question at hand because they're equal and covered by the caveat of equal load impedances. A theorem I verified by running both a 'whole amp' and standalone CPI simulation. Similarly when calculating the source impedance at the anode you must include the total cathode load in the calculations. Second, it isn't sufficient to calculate only the source impedances, you must also calculate the source voltages at the anode and cathode. The trick is that the anode and cathode source voltages vary with frequency in such a way that they cancel the effects of the differing source impedances driving the two loads, the result being that the two output voltages remain balanced even as frequency varies. Did you bother to read what I said? Because I said exactly that for the 'different impedance' model. However, the whole point to 'equivalent impedance' calculations is so the 'simplified' term can be used in subsequent calculations, like in the RIAA filter I mentioned above. But, in the special case of an equally loaded CPI, it doesn't provide any useful differentiation because, while you can argue all day long that the impedances are 'different', there is no difference in the behavior. As I said, and to which you decided to 'argue' with by saying the same thing, the 'trick' is "as cathode impedance drops anode gain increases in exact proportion to the drop across the 'larger' anode impedance." I.E. the 'source voltages' change. However, another way to look at it is, with equal load impedances, you have a local feedback loop that lowers the 'effective impedance' of the anode and that's not a particularly odd view as it's conceivably a similar mechanism to that used in lowering amplifier 'effective output impedance' with GNFB. Or, conversely (again), if one insists on saying the reflected pentode impedance 'is' the (actual) impedance (equivalent to arguing the CPI source impedances are, 'in fact', different) then the 'source voltage' is changing to compensate for the varying load impedance. The mechanism, in either case, falls apart if the load impedances are not the same, like if the following grid goes positive (since they don't do so at the same time) and then the 'different' source impedances becomes seemingly apparent. Or the feedback loop goes cockeyed (as does GNFB at clipping) because the special case it depends on is no longer valid. I say "seemingly" for the 'different impedance' model because, again, it does not behave as one would expect from a 'simplified' impedance calculation since, when the cathode goes +ve into the following grid, the anode signal changes dramatically even though there is no 'difference' in the load *it is seeing* (at that point in time). And, no, I'm not 'ignoring' that the anode source impedance has changed because of the change in cathode impedance, I'm simply saying that things fall apart so these 'simplified' equations (calculated for the equal load case) no longer hold. I'm not good enough to do the math but George E. Jones Jr did it in a 1951 paper on the subject. http://www.diybanter.com/attachment....2&d=1213179423 I will take a look at that article, does it come to the conclusion that the anode and source impedances are equal? He wasn't dealing with that 'argument', although the 'different source impedance' model would seem to clearly be what leads people to the erroneous 'imbalanced at HF' conclusion, but I suppose it depends on how you look at the results. The roll off can be approximated with cathode source impedance and the roll off is the same for the plate side so one might conclude it has the same effective impedance, because that is the apparent behavior. Flipper, you seem to be flopping all around, trying to walk both sides of the street, or perhaps trying to swim both sides of the pier would be more accurate. The anode and cathode source impedances are either the same or they aren't the same, you can't have it both ways, you have to pick one or the other, they can't both be true. Once you have made your choice, then you can work on trying to justify it. I still don't see how the fact that the two output voltages remain equal as the frequency is varied, in anyway implies that the anode and cathode source impedances are equal? Of course the effects of grid to anode and grid to cathode capacitance do unbalance the concertina at very high frequencies, but I leave that for Patrick to worry about, from my perspective it isn't a problem worth troubling over. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
#40
Posted to rec.audio.tubes
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Audio Cyclopedia - A highly recommended book
John Byrns wrote: In article , flipper wrote: On Fri, 08 Aug 2008 10:11:02 -0500, John Byrns wrote: In article , flipper wrote: On Thu, 07 Aug 2008 16:20:50 -0500, John Byrns wrote: In article , Patrick Turner wrote: The balanced amp in the W act as a buffer against the micro capacitive FB from OP anodes to the OP grids. So the CPI sees identical a and k loadings to a very high F. But eventually capacitance catches up with the CPI, and anode output falls before the cathode output does. To ensure equal bandwidth at the CPI a and the k, some small value trimmer C across the cathode R of the CPI is advisable. 15pF to 47pF is about right, and the value used is chosen to get a symetrical square wave overshoot at the OPT sec. Could you elaborate on this, why it is necessary, is it to compensate for the effects of the capacitances of the CPI grid? JB and HP had a long running brawl of words about the CPI way back in 2000 when I was told never to mention OPTs or leakage inductance on r.a.t because it'd lead to a flame war all over again. As I remember it we both agreed that the circuit was basically balanced, so the brawl must have been over the actual source impedance of the anode and cathode circuits. Thinking about it over the last 24 hours, I suspect that what HP was actually measuring/calculating was the source impedance seen by a load driven as if it were connected between the anode and cathode, or actually half of that value. I don't believe that HP's contrived methodology actually demonstrates that the anode and cathode source impedances are equal as he claimed. I've seen the classic calculations showing the 'different' anode and cathode source impedances, and it sounds logical, but it doesn't behave that way. What do you mean that "it doesn't behave that way", are you saying that the classic calculations are incorrect? I explained what I meant in the subsequent text. I got into checking that with the 13FD7 'mini Williamson' amp because I'm using large 'grid stoppers' as a HF roll off so the 'different' source impedances became an issue, since they would be 'in series' with the grid stopper resistors, but when I spiced it the thing acts as if the source impedances are identical. I.E. there is no difference in HF roll off (with equal value grid stoppers). To double check I also spiced a standalone concertina with just capacitive loading and got the same results. The fact that "there is no difference in HF roll off" doesn't imply that the anode and cathode source impedances are equal. I think most people would think it implies just that and in most circumstances it does. For example, if you're designing an RIAA filter you include the source impedance of the driving stage in the calculations and if that is 'different' then so would be the compensation. Same thing with a guitar tone stack. If you design a Marshal style tone stack driven by a low impedance cathode follower and then, instead, take from the anode output you get a 'different' response because you have a 'different' source impedance. If, however, you accept that the concertina is balanced as long as the two loads are equal then it's an 'of course' the roll off is the same because the loads are equal, they just vary (equally) with frequency. The response vs. frequency at the two outputs of the concertina are balanced, the source impedances are not. Makes calculating 1/f=2Pi RC a bitch, don't it? If you keep the 'different impedance' analysis the thing is as cathode impedance drops anode gain increases in exact proportion to the drop across the 'larger' anode impedance. Or, if you use a single common source voltage model (grid), the effect of FB is to make the anode and cathode source impedances appear equal. Only HP and you believe that the anode and cathode source impedances appear equal. I said no such thing. I talked about both models but made not one comment about which I 'believed' or preferred. A more reasonable interpretation would be that I suggested both views are simply different ways of looking at the same thing. The "classic calculations" give the correct results, and show that the anode and cathode source impedances are not equal, that does not prevent the two outputs from being balanced when driving equal loads. You are ignoring a couple of important points that must be considered when using the "classic calculations", if you want to get the correct answer. First when calculating the source impedance at the cathode you must include the total anode load in the calculation, this means not just the plate resistor, I'm not ignoring anything and my referencing the classic equations should have given you a clue I'm including all of them. but also the coupling capacitor, the following grid resistor, the shunt and miller capacitances of the following tube, et al. They ain't there in the stand alone CPI test I ran. Nor does it make any difference to the question at hand because they're equal and covered by the caveat of equal load impedances. A theorem I verified by running both a 'whole amp' and standalone CPI simulation. Similarly when calculating the source impedance at the anode you must include the total cathode load in the calculations. Second, it isn't sufficient to calculate only the source impedances, you must also calculate the source voltages at the anode and cathode. The trick is that the anode and cathode source voltages vary with frequency in such a way that they cancel the effects of the differing source impedances driving the two loads, the result being that the two output voltages remain balanced even as frequency varies. Did you bother to read what I said? Because I said exactly that for the 'different impedance' model. However, the whole point to 'equivalent impedance' calculations is so the 'simplified' term can be used in subsequent calculations, like in the RIAA filter I mentioned above. But, in the special case of an equally loaded CPI, it doesn't provide any useful differentiation because, while you can argue all day long that the impedances are 'different', there is no difference in the behavior. As I said, and to which you decided to 'argue' with by saying the same thing, the 'trick' is "as cathode impedance drops anode gain increases in exact proportion to the drop across the 'larger' anode impedance." I.E. the 'source voltages' change. However, another way to look at it is, with equal load impedances, you have a local feedback loop that lowers the 'effective impedance' of the anode and that's not a particularly odd view as it's conceivably a similar mechanism to that used in lowering amplifier 'effective output impedance' with GNFB. Or, conversely (again), if one insists on saying the reflected pentode impedance 'is' the (actual) impedance (equivalent to arguing the CPI source impedances are, 'in fact', different) then the 'source voltage' is changing to compensate for the varying load impedance. The mechanism, in either case, falls apart if the load impedances are not the same, like if the following grid goes positive (since they don't do so at the same time) and then the 'different' source impedances becomes seemingly apparent. Or the feedback loop goes cockeyed (as does GNFB at clipping) because the special case it depends on is no longer valid. I say "seemingly" for the 'different impedance' model because, again, it does not behave as one would expect from a 'simplified' impedance calculation since, when the cathode goes +ve into the following grid, the anode signal changes dramatically even though there is no 'difference' in the load *it is seeing* (at that point in time). And, no, I'm not 'ignoring' that the anode source impedance has changed because of the change in cathode impedance, I'm simply saying that things fall apart so these 'simplified' equations (calculated for the equal load case) no longer hold. I'm not good enough to do the math but George E. Jones Jr did it in a 1951 paper on the subject. http://www.diybanter.com/attachment....2&d=1213179423 I will take a look at that article, does it come to the conclusion that the anode and source impedances are equal? He wasn't dealing with that 'argument', although the 'different source impedance' model would seem to clearly be what leads people to the erroneous 'imbalanced at HF' conclusion, but I suppose it depends on how you look at the results. The roll off can be approximated with cathode source impedance and the roll off is the same for the plate side so one might conclude it has the same effective impedance, because that is the apparent behavior. Flipper, you seem to be flopping all around, trying to walk both sides of the street, or perhaps trying to swim both sides of the pier would be more accurate. The anode and cathode source impedances are either the same or they aren't the same, you can't have it both ways, you have to pick one or the other, they can't both be true. Once you have made your choice, then you can work on trying to justify it. I still don't see how the fact that the two output voltages remain equal as the frequency is varied, in anyway implies that the anode and cathode source impedances are equal? Of course the effects of grid to anode and grid to cathode capacitance do unbalance the concertina at very high frequencies, but I leave that for Patrick to worry about, from my perspective it isn't a problem worth troubling over. Well, at very HF over say 50kHz, capacitances begin to lower the way the CPI is loaded at its anode and cathode. The cathode output tends to have a higher F pole than at the anode. There us *some* Miller C in the CPI, because the anode signal is inverted, and effectively, the C between g and a is more than between g and k. So the CPI becomes loaded with a lower load at the anode than cathodeand hence the difference in output levels at HF. Taken to extreme, consider what happens at 1MHz. If Cga was say 10pF, ZC = 16k, and so there is the V1 anode Rout in series with 16k in series with RLa of the CPI triode, and the Cgk is lower, but the cathode output is from "follower" action, and anode output falls before cathode output. The capacitances involved manage to become such low impedances as F rises they saturate the opeation of the tubes and the triodes clip. But for ordinary amp builders, they needn't be too worried and any old CPI works quite well as long as you don't expect too much voltage swing or you overload it or expect it to have F2 too high. I prefer having an SET input tube using a paralleled twin triode such as 6CG7 or 6DJ8 and then drive an LTP woth a pair of triodes such as two 6CG7 tubes, and have a CCS cathode sink. This is best set up so it makes 50% more voltage than needed for output stage clipping, and you'll find it overloads symetrically, or at + and - voltage peaks together. The Williamson done right sounds just great though. About the only improvements anyone needs to think about is adding a small C across the Rk of the CPI, and then having a long tail resistor from the balanced amp to say a -120V rail; about 13k is OK if the Ia in each 1/2 of the balanced amp = 5mA. This long tail makes the two phases of the balanced driver amp stay equal and ensures that much better cancelation of 2H occurs and stops 2H appearing at each anode of the balanced amp. The balanced amp creates the most distortion, and should be a small quantity of mainly 3H. Patrick Turner. -- Regards, John Byrns Surf my web pages at, http://fmamradios.com/ |
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