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#1
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Best low cost hi-fi kit
Can I please have an up-to-date response for this perhaps frequently
asked question. In terms of overall performance, what is the best value 12-20W hi-fi stereo preamp/amp kit presently on the market? I am not concerned about the configuration, and will leave that to the experts. I am presently using a NAD 3020 (solid state) and like it's warm tones. I would like to move further in this direction, hence the tube amp. BTW I can build to moderate skill levels. Thank you for your reply. Ken Warren |
#2
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Best low cost hi-fi kit
Kenneth Warren wrote: In terms of overall performance, what is the best value 12-20W hi-fi stereo preamp/amp kit presently on the market? http://www.turneraudio.com.au/ Is a good place to start. I would suggest that rather than getting a full-blown "kit" and all the limitations that imposes these days that you research what is out there in the DIY world and make a choice from there. As you are looking in a very moderate power-range, it is possible that you could build a simple amp from scratch at a much lower cost than a kit. Just a thought. My next suggestion would be to look after any of several vintage units on the market that are amenable to after-market modifications, or might be suitable from the git-go. Such include, but are not limited to Dynaco, Eico, Scott, Fisher, Sherwood, Harmon Kardon and any of half-a-dozen non-US brands. Again, the bang-for-buck ratio can be quite substantial as you are already willing to investigate those modifications. I left Marantz & McIntosh out of the list above as those are mostly collectors' items and disproportionately costly. Peter Wieck Wyncote, PA |
#3
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Best low cost hi-fi kit
Kenneth Warren wrote
Can I please have an up-to-date response for this perhaps frequently asked question. In terms of overall performance, what is the best value 12-20W hi-fi stereo preamp/amp kit presently on the market? I am not concerned about the configuration, and will leave that to the experts. I am presently using a NAD 3020 (solid state) and like it's warm tones. I would like to move further in this direction, hence the tube amp. BTW I can build to moderate skill levels. Depends where you are, considering carriage costs. You will find few ppl who have experience or detailed knowledge of many kits, so the question is unlikely to elicit the kind of response you want. You must consider configuration, because it effects the outcome. You have to choose. An expert can't know which compromises you prefer. Low-budget valve amps mean cheap transformers. Not worth having in my view. In the UK, World Audio Design, attached to "Hi-Fi World" magazine, seems to be quite well respected and well documented. I think the transformers are too small, but they could be substituted if there is enough space on the chassis and if it can support extra weight. WAD seems flexible in offering part kits. An advantage of a good kit should be that the fine tuning of any feedback compensation and suppression of parasitics has been done for the particular transformer supplied. So if you substitute transformers this may have to be re-done. cheers, Ian |
#4
Posted to rec.audio.tubes
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Best low cost hi-fi kit
Kenneth Warren wrote:
Can I please have an up-to-date response for this perhaps frequently asked question. In terms of overall performance, what is the best value 12-20W hi-fi stereo preamp/amp kit presently on the market? I am not concerned about the configuration, and will leave that to the experts. I am presently using a NAD 3020 (solid state) and like it's warm tones. I would like to move further in this direction, hence the tube amp. BTW I can build to moderate skill levels. Thank you for your reply. Ken Warren I've built quite a few tube amp kits but mainly at the higher end of the market. However, besides your budget, it is useful to know which speakers you have, what their sensitivity is, and what sort of music you like playing. Some tube topologies, single-ended for instance, is economical only with highly sensitive speakers. SEX The outstanding low cost kit is the SEX, which stands for Single Ended Experimenter's Kit. I believe it is still sold in modified form. Back then for four hundred bucks you got two monoblocks in the form of laser cut plates and all components; you had to bring the wire and make the wooden box; for another thirty bucks you got four little ali drivers with enough sensitivity to build suitable speakers -- I had a lot of fun with those drivers in speakers made with carpet tubes and playing Gregorian chant with truly gothic bass. Super playing into regular (sensitive) speaks as well, a sound right out of its class. About 2W Class A from PSE 6DN7.Very developable, as the name tells you. See my review in Glass Audio about seven or eight years ago. The maker is Dan Schmalle of Electronic Tonalities of Poulsbo, WA; he also publishes VALVE magazine and you can find his enthusiasts at the Audio Asylum. ARION ADONIS The best of the reasonably priced European kits I built was the Arion Adonis, PP 5881 running in Class A for enough power to drive normal bookcase speaker. Everything about this amp was properly executed because the motivating force behind Arion was a Scot of truly driven cheapness (I know; he once sent me back to my drawing board for "wasting" a single milliamp in a design I made for him...) who expected exceptional value for every penny. You got a polished stainless chassis and transformers designed by the excellent Simon Shilton, and the very best parts within the price bracket. The Adonis was later sold by someone else, who may still be in business and selling it or its successor. I can't remember if I reviewed this one for Glass Audio or another magazine, but I liked it so much that I still have and play it occasionally many years later; I never fail to be surprised at the clarity and beauty of sound from an amp that cost only a few hundred pounds. STEIN PRE Another kit that is very reasonably priced for what its excellent quality, though probably outside your budget for just a pre-amp, is the Stein Audio pre with the 6DJ8. This is an introduction the very finest in design and component selection (glass capacitors!) backed by Holger Stein's experience, with a very seductive liquid sound that does well driving silicon amps, cutting their acid to bearable proportions. VELLEMAN K4000 This is PPP EL34 for 18W in Class A and near enough 1000W in Class B, an amp with oomph that really rocks. It's schizo of course, very sweet in Class A, a monster with full bass range in Class B. Pricey but good value for excellent professional design and good parts, backed by the Velleman completion guarantee (if it fails to work when you've soldered it, you return it to them and they fix your foulups). I built this for a review and still have it a decade later; the model number may now be different. Velleman gear is of the sturdiest: I have test gear I built from their kits fifteen years ago, including my everyday DMM and my handheld scope, that just work and keep working; Velleman is trustworthy. TRIODE SUPPLY JAPAN VPD-3000 "MIYABE" This was then and is today absolutely the best kit you can buy. It cost 1600 dollars back about eight years and was a bargain then. 300B PSE for about 16W, so I used it on my ESL63, so you can use it with any speakers except the most grotesquely insensitive. Another amp sold by a maniac who doesn't take "no" for an answer or any excuse at all when it comes to getting just the quality he wants. I priced up the parts and they came to twice the purchase price -- and a good bit besides. I still have this one too, and it is one of the amps I play most frequently. My review was in Glass Audio. **** Having mentioned some kitmakers I can recommend, let me give you a tip. A kit is an entertainment and an education in the building, a matter of pride once you have it up and working. But it won't save you money. The cheap way to get a tube amp is to buy Chinese. That solves your biggest problem in DIY, suitable casework, at a single stroke, and gives you a framework on which you try your own improvements. Buying Chinese is a twist on the good advice usually given here to buy an old amp and rebuild it; the cost of that advice is usually excessive -- I'm looking at the invoices for parts to rebuild a mostly good pair of Quad II as I write to you, and wondering if I shouldn't just have sold them on "as seen". If you're in the States, Dan Schmalle may be cheaper than the Chinese route. If you're in Europe, see if Arion is still offering kits (they are in Belfast). In Germany, besides Holger Stein (Stein Audio), you might try Allen Wright, who markets a modular PP kit with very flexible casework that you buy bit by bit as you need it; Allen knows what he's talking about (he's the guru of constant current loads). If you're in the Far East, shop the Triode Supply Japan catalogue; they make less expensive models than the flagship Miyabe. HTH. Good luck. Andre Jute Visit Jute on Amps at http://members.lycos.co.uk/fiultra/ "wonderfully well written and reasoned information for the tube audio constructor" John Broskie TubeCAD & GlassWare "an unbelievably comprehensive web site containing vital gems of wisdom" Stuart Perry Hi-Fi News & Record Review |
#5
Posted to rec.audio.tubes
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Best low cost hi-fi kit
Andre Jute wrote: Having mentioned some kitmakers I can recommend, let me give you a tip. A kit is an entertainment and an education in the building, a matter of pride once you have it up and working. But it won't save you money. The cheap way to get a tube amp is to buy Chinese. That solves your biggest problem in DIY, suitable casework, at a single stroke, and gives you a framework on which you try your own improvements. Buying Chinese is a twist on the good advice usually given here to buy an old amp and rebuild it; the cost of that advice is usually excessive -- I'm looking at the invoices for parts to rebuild a mostly good pair of Quad II as I write to you, and wondering if I shouldn't just have sold them on "as seen". This is where Andre is at a disadvantage. Here in the US, not only are vintage amps thick on the ground (at usually quite inexpensive prices), but many of the aftermarket suppliers are also a $4.50 priority-mail shipping box away over the cost of their parts. Avoid eBay unless you are in a hurry, get out, get around and you will find all sorts of stuff to trip over. I have done any number of kits over the last 46 years since I built my very first one (which did work, to this day I perceive that as a near-miracle). Put simply, I learned far more from trouble-shooting failed equipment than from any kit ever. Just in researching for making my one 'scratch-built' amp, I have learned more of what choices are out there than from much trouble-shooting. Kinda like the difference between reading lines from a set-piece, editing a set of bad directions for clarity and content and designing, specifying, building, trouble-shooting and then describing from scratch so the next person can do it without issue. New kits are good insasmuch as they get you there with a minimum of fuss-over-assembly. But as they more-or-less must be idiot-proof by design and execution (the set-piece, if you will), they do not offer much scope for experimentation beyond specifically designed-in options. Some of the vintage equipment has 40+ years of failure analysis, evolution and experimentation behind it. Picking the Dynaco ST-70 out of thin air (BE QUIET, BRET!), there are mods to that start with a single 10-ohm, 10 watt ceramic resistor and finish with a complete rebuild using only the tube sockets (and not all of them), the sheet-metal and the iron (The Turner Audio Rebuild). Figure you should be able to find a suitable, good quality vintage amp, do the mods and even replace the tubes in it with "new" for less than $500 if you are patient, $300 if you are both patient and lucky. With Chinese Junque, you get what you pay for. If the Iron is good, there may be hope for it with modifications. But I have not seen a Chinese amp at *retail* that delivers as well as the same $$ spent on either a DIY, or an upgraded vintage amp. I spent a few moments between calls today at a shop owned by a friend who has half-a-dozen Chinese amps lined up for his customers to test (where I found the McIntosh tuner). All I can say about them is 'eh'. He says that they sell like hot-cakes.... De gustibus and so forth. On the other hand, some of the kits do look intriguing, their greatest value would be in the building thereof, not necessarily the finished results. Lastly: Note that in DIY, expect that you are paying yourself $0.25/hour or less and the rest is the pleasure of doing it. This may be enough of a motive in itself. Peter Wieck Wyncote, PA |
#6
Posted to rec.audio.tubes
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Best low cost hi-fi kit
My suggestion is to go to triodeelectronics.com. You can build a classic
Dynaco Mk II (or is it III?) 60 W amplifier clone from all that Ned Carlson has to offer. A lot more expensive than the original $69.95-$79.95 of the original (but so is everything). If he can get a Dynaco PAS-3 (or 3X) cheap (not easy), it can be used as is or upgraded with what Triode Electronics has available. John "Peter Wieck" wrote in message ups.com... Kenneth Warren wrote: In terms of overall performance, what is the best value 12-20W hi-fi stereo preamp/amp kit presently on the market? http://www.turneraudio.com.au/ Is a good place to start. I would suggest that rather than getting a full-blown "kit" and all the limitations that imposes these days that you research what is out there in the DIY world and make a choice from there. As you are looking in a very moderate power-range, it is possible that you could build a simple amp from scratch at a much lower cost than a kit. Just a thought. My next suggestion would be to look after any of several vintage units on the market that are amenable to after-market modifications, or might be suitable from the git-go. Such include, but are not limited to Dynaco, Eico, Scott, Fisher, Sherwood, Harmon Kardon and any of half-a-dozen non-US brands. Again, the bang-for-buck ratio can be quite substantial as you are already willing to investigate those modifications. I left Marantz & McIntosh out of the list above as those are mostly collectors' items and disproportionately costly. Peter Wieck Wyncote, PA |
#7
Posted to rec.audio.tubes
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Best low cost hi-fi kit
Having mentioned some kitmakers I can recommend, let me give you a tip.
A kit is an entertainment and an education in the building, a matter of pride once you have it up and working. But it won't save you money. The cheap way to get a tube amp is to buy Chinese. That solves your biggest problem in DIY, suitable casework, at a single stroke, and gives you a framework on which you try your own improvements. Buying Chinese is a twist on the good advice usually given here to buy an old amp and rebuild it; the cost of that advice is usually excessive -- I'm looking at the invoices for parts to rebuild a mostly good pair of Quad II as I write to you, and wondering if I shouldn't just have sold them on "as seen". I know that Chinese amps are often ridiculised in this group. I can imagine that often it's with a reason. Now I had a very good experience just last week when I was on a business trip in Hong Kong: I heard the very well built Melody SP3 tube amp driving expensive Zu Definition speakers. There was absolutely nothing wrong with that sound. It must be said that the Zu's are enormously efficient, but with the SP3 delivering 38 watts it should be nicely useable with many loudspeakers. You can read a review about the SP3 on www.6moons.com . The price: in Hong Kong it was the equivalent an incredible ... wait for it ... 550 EUR. Considering the quality of sound I experienced and the very high standards of finish, this is a bargain. The price in the west is still not bad for what you get, but it's not such a bargain anymore. I was sorely tempted to carry one back to Europe... but I had a problem: I first had to take trip to Singapore, on an economy flight, hence that would give extra shipping costs, and I would need to pass customs twice. Perhaps, when I get to do another trip to only Hong Kong... cheers, Tom, who's meanwhile gathering parts to build an Aikido pre-amp (see www.tubecad.com) |
#8
Posted to rec.audio.tubes
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Best low cost hi-fi kit
Tom A. wrote: The price: in Hong Kong it was the equivalent an incredible ... wait for it ... 550 EUR. At present conversion values, that comes in at US$705.65 exclusive of shipping and various taxes. Even at that price and in the US, that is high for such an amp *IF* it is compared to readily available vintage amp upgrade/conversions (including the (in)famous VanAlstine ST-70). And in terms of what is available to the DIY, that is very high. But well-under exotic US-made *new* tube designs, of course. I have no argument that Chinese Junque can look mighty nice, bending sheet-metal and powder-coating is not rocket science by any means. But I tremble to see the fractured-english manuals and wonder whether as much care goes into the assembly as the translation. One would think that a manual would be written with _GREAT_ care as improper set-up could be spectacularly nasty. "Consumer-buyer is noted to be that maker may not warn of changes cannot guarantee accurate in future terms beware." is NOT comforting sentence, but one that I see on a schematic for an Antique Audio monoblock amp (made in China, of course). In this case, the phrase "time will tell" applies. How many Chinese amps sold today will still be singing in 40 years? Peter Wieck Wyncote, PA |
#9
Posted to rec.audio.tubes
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Best low cost hi-fi kit
Bret Ludwig wrote: Stuff.... You are very much like your Australian peer, Mr. Allison. Warped, prejudiced, angry and mostly absurd. But occasionally some truth escapes despite yourself. Peter Wieck Wyncote, PA |
#10
Posted to rec.audio.tubes
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Best low cost hi-fi kit
At present conversion values, that comes in at US$705.65 exclusive of
shipping and various taxes. Even at that price and in the US, that is high for such an amp *IF* it is compared to readily available vintage amp upgrade/conversions (including the (in)famous VanAlstine ST-70). And in terms of what is available to the DIY, that is very high. But well-under exotic US-made *new* tube designs, of course. It is true that the conversion to dollars is less atractive currently than the coversion to euro. I have no argument that Chinese Junque can look mighty nice, bending sheet-metal and powder-coating is not rocket science by any means. But I tremble to see the fractured-english manuals and wonder whether as much care goes into the assembly as the translation. One would think that a manual would be written with _GREAT_ care as improper set-up could be spectacularly nasty. "Consumer-buyer is noted to be that maker may not warn of changes cannot guarantee accurate in future terms beware." is NOT comforting sentence, but one that I see on a schematic for an Antique Audio monoblock amp (made in China, of course). I can only tell you that the SP3/Zu combination DID sound excellent. It is true that when connected to the 100db efficient Zu with active woofers, the amp didn't have to do any effort. I would like to hear it with 90db-ish speakers. It is also really well made. And I have yet to find a less than positive review anywhere on the net or in magazines. It seems that Melody is also one of the more serious Chinese brands, considering their other, more upmarket products. Building yourself will of course give the most satisfaction and you will know exactly what quality of OPTs go in there etc, but for those wjo don't want or can't take the DIY route this little amp is a nice, affordable gateway to the world of tubes. In this case, the phrase "time will tell" applies. How many Chinese amps sold today will still be singing in 40 years? I have no idea. But I also think that you're wrong in systematically declaring Chinese hifi brands as junk. After all, Quad products are now made in china too. If anything, we should be grateful that these brands lower the treshold. best regards, Tom |
#11
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Best low cost hi-fi kit
Tom A. wrote: .. After all, Quad products are now made in china too. If anything, we should be grateful that these brands lower the treshold. As are Zenith, Philco, Packard-Bell, Crosley, Sony, Marantz, KLH, Sherwood, Scott, and a whole bunch of others. Infinity, Advent & AR, even Thorens, Dual, Philips & Grundig in part. Lowering the threshold.... Possible in some cases. More likely a race for the bottom. Peter Wieck Wyncote, PA |
#12
Posted to rec.audio.tubes
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Best low cost hi-fi kit
Scratchbuildiong is the most educational and yet the least frustrating.
I'm totally with Bret here - if you have the courage, build from scratch. It's what you'll end up doing so you may want to cut out the intermediate step of rebuilding a Dynaco or Leak amp (interesting and instructive as it is - I think we've all been there). Before doing anything, buy "Valve Amplifiers" by Morgan Jones off Amazon (e.g.) and read it and use it as a reference all the way through your build. You want to make some basic decisions. These are the ones I recommend. a) Chassis. Think BIG, then BIGGER. If you are seriously going to carry on building you may like to start with two chassis - one power supply and one circuit. Your absolute minimum chassis size is a 2U 19" rackmount case - get a solid one, if possible with one side predrilled full of holes. You can use two of these - power supply and circuit. Your power supply should be approximately 300vDC for the HT at a minimum of 200mA. Feel free to chuck in as many chokes as you like - you can use 100mA ones and split the power supply into two channels. Use one set of chokes for the output and another for the input - four chokes of 100ma is nice. Forget electrolytics - buy ordinary motor run polypropylene caps, sizes 40uf are fine. Start with solid state rectification, but leave room for valve rectifiers which you may want to add later. For umbilical use 8 pin Neutrik Speakons or Amphenol sockets. b) Single ended or push pull. I'd suggest push pull - possibilities of many many circuits to copy and higher output. Can be as good as anything if you use DHTs (directly heated triodes). I'd go a step further and suggest balanced all the way through, with three stages. In Morgan's book you'll find some constant current sinks to build which you put under each of the first two stages (page 134). If you have a single ended input, normal phono plugs, ground the second grid of the first valve (again in the book). c) Get some decent output transformers. start with Hammond or something simple, but leave plenty of space to try something else. I'd suggest 5k to 6.6K in push-pull. d) Valves to use. If you want to aim for very good, use all octal sockets - don't even consider the smaller nine pins. If you want to aim for the best use all UX4. Plan your chassis layout for twelve UX4 sockets - big holes here. Get the right hole saw to put in your drill to drill out these holes, and imagine that each valve is 50mm across, so allow at least that plus another 15mm - 20mm space in between valves. This is why I'm talking big chassis. You are now ready for your super amp. The valves you can use go from 76 which is normal 6.3v heaters to fancy stuff like 26, a DHT, which will blow your mind away, but need special DC supplies. Get some cheap bench power supplies and use 26s - you'll just love them. They take 1amp on the heaters so any bench power supply that does 0-30 at 1amp is OK. Run the heaters in series in push pull. Or stay simple - one huge toroid at 6v will power a whole lot of valves. For output you can start with 807 in triode, using UX5 socket - same cutout as UX4 so you can swap later for a 2a3 or 300b. e) use a three stage circuit - plenty about. Go to www.audioasylum.com and hang out there and ask for suitable circuits, or work one out from Morgan's book. Look for circuits for a 6SN7 and substitute two 76 for one 6SN7. This may all be too advanced, but if you take the plunge and build big, you will eventually make your super amp using the same chassis and componants you started off with - nothing wasted, nothing to throw away. |
#13
Posted to rec.audio.tubes
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Scratch starter kit for DIY tubie, was Best low cost hi-fi kit
First Bret Ludwig wrote: Scratchbuildiong is the most educational and yet the least frustrating. Andy Evans wrote: I'm totally with Bret here - if you have the courage, build from scratch. This is true, in very limited circumstances. Ludwig is a technician who has long since forgotten how much time he spent learning the necessary electronics. Andy is, if I recollect correctly, a psychologist, as I am; he is such a longtime hobbyist that he too has forgotten when he learned his electronics and how hard it was. I am now in the same boat: it is no problem for me to design just the amp I want at any time, and to knock it up with chasses and parts I have, and to develop and tune it just so. But I think that, if I hadn't started with kits, I would have given up in frustration, trying to learn the basics of electronics and the ins and outs of components and construction all at the same time. A stepwise approach makes more sense; that is why so many people learned on secondhand gear and I now recommend starting with a kit or a cheap, developable Chinese amp. My own recipe for a starter kit is at the bottom. Meanwhile a few notes on the rest of Andy's post: It's what you'll end up doing so you may want to cut out the intermediate step of rebuilding a Dynaco or Leak amp (interesting and instructive as it is - I think we've all been there). Before doing anything, buy "Valve Amplifiers" by Morgan Jones off Amazon (e.g.) and read it and use it as a reference all the way through your build. You need two copies of each of Jones and the RDH so you can keep one in your lavatory or beside your bath or on your bedside table, wherever you do most of your reading. http://members.lycos.co.uk/fiultra/J...Bookshelf.html The kernel of Andy's advice is mad, magnificently mad but mad none the less. Since I'm an economist as well as a psychologist, you'll forgive me if I point out the obvious, which is that Mad Andy Evans wants you to build with tubes that are no longer made, in limited supply, already very expensive, likely to become more expensive. Nobody can accuse me of speaking up for anything less than excellence, or of being cheap but advising newbies to build with obsolete DHTs is one fast way to drive them screaming from the hobby. Still, big chasses and octals is good advice. Here is an amp for all of a third of a watt... http://members.lycos.co.uk/fiultra/K...0T68MZ417A.jpg You want to make some basic decisions. These are the ones I recommend. a) Chassis. Think BIG, then BIGGER. If you are seriously going to carry on building you may like to start with two chassis - one power supply and one circuit. Your absolute minimum chassis size is a 2U 19" rackmount case - get a solid one, if possible with one side predrilled full of holes. You can use two of these - power supply and circuit. Your power supply should be approximately 300vDC for the HT at a minimum of 200mA. Feel free to chuck in as many chokes as you like - you can use 100mA ones and split the power supply into two channels. Use one set of chokes for the output and another for the input - four chokes of 100ma is nice. Forget electrolytics - buy ordinary motor run polypropylene caps, sizes 40uf are fine. Start with solid state rectification, but leave room for valve rectifiers which you may want to add later. For umbilical use 8 pin Neutrik Speakons or Amphenol sockets. b) Single ended or push pull. I'd suggest push pull - possibilities of many many circuits to copy and higher output. Can be as good as anything if you use DHTs (directly heated triodes). I'd go a step further and suggest balanced all the way through, with three stages. In Morgan's book you'll find some constant current sinks to build which you put under each of the first two stages (page 134). If you have a single ended input, normal phono plugs, ground the second grid of the first valve (again in the book). c) Get some decent output transformers. start with Hammond or something simple, but leave plenty of space to try something else. I'd suggest 5k to 6.6K in push-pull. d) Valves to use. If you want to aim for very good, use all octal sockets - don't even consider the smaller nine pins. If you want to aim for the best use all UX4. Plan your chassis layout for twelve UX4 sockets - big holes here. Get the right hole saw to put in your drill to drill out these holes, and imagine that each valve is 50mm across, so allow at least that plus another 15mm - 20mm space in between valves. This is why I'm talking big chassis. You are now ready for your super amp. The valves you can use go from 76 which is normal 6.3v heaters to fancy stuff like 26, a DHT, which will blow your mind away, but need special DC supplies. Get some cheap bench power supplies and use 26s - you'll just love them. They take 1amp on the heaters so any bench power supply that does 0-30 at 1amp is OK. Run the heaters in series in push pull. Or stay simple - one huge toroid at 6v will power a whole lot of valves. For output you can start with 807 in triode, using UX5 socket - same cutout as UX4 so you can swap later for a 2a3 or 300b. e) use a three stage circuit - plenty about. Go to www.audioasylum.com and hang out there and ask for suitable circuits, or work one out from Morgan's book. Look for circuits for a 6SN7 and substitute two 76 for one 6SN7. This may all be too advanced, but if you take the plunge and build big, you will eventually make your super amp using the same chassis and componants you started off with - nothing wasted, nothing to throw away. Okay, here we go with a sensible, flexible setup for a starter kit for a beginning DIYer. First, decide on SE or PP. I suggest PP for the flexibility and slightly lower cost. (SE can be cheap too-- http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg --but unless you have a lot of money it can be very limiting.) Next buy two Hammond 17x10x4 inch ali boxes and six or so 17x10 covers and about a dozen each of 6x4 and 4x4 ali plates (they're covers for smaller boxes you won't buy). Buy some slotted 3/4 in angle ali. Brace the two flimsy Hammond boxes with the ali on all edges. Bolt ali angle strips across the width four inches apart. The less than an inch open at end will be to lead cables in while you do development work. Don't be tempted to buy steel cases; they'll just skin your knuckles and blunt your tools and discourage you before you even start work. These two boxes are in any event just covers for electronics. It is easier to build on the big flat coverplate stiffened by ply, and then just to bolt on the box as safety cover. But for the time being you will build on the little plates section by section and bolt them onto the framework. One box is your power supply, the other the amplifier. Decide to use only octal tubes. The 6SN7 is greatest signal tube and small power tube too that God ever made, and the 6SL7 the sweetest. The EL34 is the greatest power tube God ever made, and that includes the 300B. The 6SN7 is in production in Russia and China, and so is the EL34; the 5SL7 is in plentiful cheap supply and equivalents are also available. These are just samples: there are many more octal tubes worth your attention for one reason or another, like the KT88/6550 for more power, for instance. All the really desirable tube rectifiers are octal. A stereo PP amp needs a minimum of four octal sockets on the chassis (I will publish such a design in the next few weeks) but all you'll drive with it will be a pair of headphones or some small multimedia speakers. A realistic stereo PP amp needs at least input/gain, phase splitter and power tube sockets, which adds up to a minimum of six sockets for single-ended inputs. For balanced inputs, or at least long-tail pairs, which open the way to balanced input, and differential gain stages, you need two sections or one whole envelope per stage, so now you need eight sockets for the signal section. You might want a buffer or an extra gain stage for some reason, so add two more sockets for a grand total of ten. Unused sockets can just sit there. You fit these sockets two to a 4x4 ali plate (you clamp them all and drill them all five plates at once) or even six to a 6x4 ali plate -- it depends on what circuitry you want to attach to the socket pins and standoffs or component strips you also bolt to the same plate. Each stage or group of stages is built complete on the plate so that it has only wires leaving for signal in and out, power and earth (to a star ground near the mains input). The complete plate is bolted onto the angle ali over the open end of your cover box. Input and output and control circuitry also goes onto these or separate plates; you don't drill the main box for the RCA, five-way connectors, mains input, switches and volume pot until you have a humfree arrangement. The power supply needs four sockets in case you ever want to build a rectifier bridge. You won't. The Graetz bridge with one fullwave rectifier and two diodes that I show in many of my circuits-- http://members.lycos.co.uk/fiultra/T...trafi-crct.jpg --works indistinguishably from a full tube rectifier bridge, but the other sockets will be handy if you ever want to build a tube regulator, or for separate power takeoffs or for plugging in relays. You can buy plugs to fit octal sockets and they're well rated and cheap, an easy solution to a perennial problem. Some come with a big cover for building silicon electronics inside and I have used them for building constant current sinks. Next you need very, very flexible transformers. In the States UBT sells a universal transformer roughly equivalent to the old Tango 808 but of course vastly cheaper. In Europe it isn't really worth going for anything less than cut C-core Lundahl transformers, which are a couple of magnitudes up the scale from the UBT; Lundahls may seem a little pricey at first but they are the best-sounding transformers in the world, the top models are the most flexible, and in that light they are a stunning bargain. Buy the Lundahls with multiple windings on the secondaries which can be connected to reflect a vast range of primary impedances and connected to virtually any speaker impedance. Or, if you know you will stick with the stunning EL34 and its relatives, in the States you can buy Plitron transformers designed by Menno van der Veen; the same design is sold by Åmplimo in Europe. A pair of Lundahls or Plitron/Amplimo vanderVeens will last your lifetime. Menno has published some really good amp designs to use with these transformers; Plitron sells his book with these designs-- http://members.lycos.co.uk/fiultra/J...S%20T%26T.html --and also a PCB to speed your work if you're in too much of a hurry to hardwire. A Lundahl LL1651 power transformer is beefy, well-made, silent, and with four 3.1A filament supplies and a 250-0-250V supply of 430mA is very flexible. The Lundahl mains and output transformers all fit the same bolt footprint and their bases are tapped, so you just drill three 4x4 plates all at once. A choke is a really good piece of iron to have. The Lundahl LL1638 is very flexible since it is wound with two coils which can be used in series for 10H/200mA or in parallel for 2.5H/400mA; it can also be split across the positive and negative rails to give you a quieter amp-- http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm http://members.lycos.co.uk/fiultra/K...hn%20Byrns.htm Two chokes gives you the opportunity to investigate the attractions of choke input power filters, which changes the sound appreciably. The choke, or a pair, sits on a 6x4 plate together with holes for bolting down the associated caps. Now you're ready to design and build an amp. I suggest it be PP Class A1 trioded EL34. That's simple to design and build, and will give you a decent output. If it isn't enough power for your speakers, you can rewire for class A/B and get 24 clean watts. If you need more than 20W, you should build better speakers-- http://members.lycos.co.uk/fiultra/K...Impresario.jpg http://members.lycos.co.uk/fiultra/K...20T91HWAF3.jpg You will eventually get there anyway when your amp will be so much better than your current speakers that the speakers will become the bottleneck in your system. There's a lot of design information he http://members.lycos.co.uk/fiultra/T...mp%20INDEX.htm You might also want a root around in my general hi-fi design site: http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS.htm Good luck. Andre Jute Visit Andre Jute at http://members.lycos.co.uk/fiultra/ "wonderfully well written and reasoned information for the tube audio constructor" John Broskie TubeCAD & GlassWare "an unbelievably comprehensive web site containing vital gems of wisdom" Stuart Perry Hi-Fi News & Record Review |
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Scratch starter kit for DIY tubie, was Best low cost hi-fi kit
Andre Jute wrote: Lots-O-Stuff. Mostly on-target. Andre.... Be careful. That little dickens McCoy is poking its egotistical nose (and my goodness, but it is a long one) out from its cage. Try to keep the madness at bay. A couple of things to keep in mind however before advising anyone to leap full into tube-based scratch-building. A. Tube based systems, while not complex, can be rather dangerous. Between the lethal voltages in use, the potential for spectacular and expensive - and very simple - mistakes and the many thousands of choices, options and approaches available, some hands-on experience with well-established systems is advisable. B. Such well-established systems with many options and many years of research, failure-analysis and proven modifications surrounding them can be excellent learning experiences in both theory and practice. Furthermore and despite Bret's opinions, it can be done quite inexpensively. C. Working outside of a straightforward "kit" mode, but within such parameters as noted will not only help the autodidact but will establish connections between theory and practice such that the book-learning will be connected to reality. D. There is nothing like a few early successes right out of the gate to give one the confidence to go forward. This as compared to smelling and watching a set of output transformers giving up their magic smoke because an improper connection was made. Or some similar disaster. Peter Wieck Wyncote, PA |
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