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#121
Posted to rec.audio.tubes
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pentode amplifiers
Andre Jute wrote: On Nov 8, 6:32 am, Patrick Turner wrote: Andre Jute wrote: ,,,but decided not to complicate what I wrote with qualifications (no doubt Trevor Wilson will next accuse me of *lying*!). Shock, Horror, will someone tell you if you lied? how awful.... I don't mind if I'm wrong on some statement I made being corrected, preferably politely of course. But Wilson accuses people of lying if they don't include his fave Blow Jobs for Transvestites when they talk about tubes; I just don't see how such an omission is a lie. If I want to talk about BJTs, I can go to the alt.perverts.ss.gruppenfuhrer newsgroup. But jokes aside, if we once open the door to a single mad obsessive like Trevor Wilson, soon we'll have one-string ramkiekie players around here demanding to know why they aren't mentioned every time we mention a favourite recording of say, a Bach Cantata. The Wilson Road runs from madness to madness. But its become very well known amoung those of us who live nearer to TW to keep blood off the wattle by simply not taking what he says about tube amps too seriously. He does tolerate the better measuring large output power ARCs and the like, when they are properly biased and working well, which seems to be a rare event for many american amps I find due to their generally very poor biasing arrangements. ((I now have a McIntosh re-issue MC275 in for damage appraisal which is spitting out KT88 and blowing fuses, and it was only purchased 4 months ago. Can't the yanks get ANYTHING right?)) TW has no time for SE amps with a lone 300B. He's not alone, and a whole army of knockers loathe any 8 watt wanabe amps.... But the 8 watts is fine for any speakers with high enough sensitivity to allow the corresponding wanted output levels. One has to fumble through life accompanied or surrounded by ppl who are addicted to some view or other which to us is a complete nonsense; perhaps their religious belief, political belief, financial habits, historical views, sexual habits et all. Even amplifier habits as well. Hence sex, politics and religion are forbidden to be discussed at polite dinner parties, and if amps are mentioned, hardly anyone will understand what is said just like nobody can decipher the gobbledegook political speaches being made right now by Labour and Liberal leaders in the last 3 weeks before our Federal Election. Put simply, our Liberal Johnny Bloward is saying "I've raised prices and lowered wages, and you'll get more of that if you vote for me like youse did last time", and the wannabe Prime Minister contestant from Labour, Kevin Dudd is saying, "yeah, that's maybe roughly about what i say too." Labour Midnight Oil singer Peter Guardrat, wanabe environment minister say "we'll change it all when we get voted in..." Dudd was quite miffed. Well, we all know they ALL goner do that anyway, but the truth wasn't appreciated.... Look at what's been said here about pearl Harbour, and behaviour of the German ppl with regard to jews in WW2. Sure is plenty to disagree with. But my world won't disintegrate if I simply don't bother to join in these OT discussions very much. So whatever is said about tubes or all this OT politico/socio crap won't change my faith in using tubes. I am secure in my beliefs, welcoming any challenge to them but they do need to be VERY convincing challenges if I am to change seriously. And I have limited time. I'd rather spend 4 hours doing a 100k bike ride or concentrating more fully on the numerous tube projects required by my clients and friends. Its better than spending 4 hours so easily arguing and typing counter BS with ppl on OT subjects where the resulting net effect is a negative outcome; ie, a completely wasted effort, and a clutter of the archives which no ******* ever reads, and nothing done to further enhance anyone's existance. I would rather leave a tangible legacy appreciated right now than watch TV all night or type BS. And Cantata 199 to every cyclist: "My heart pumps a whole lotta blood", freely translated (very) from the Cherman "Mein Herze swimt im Blut." Hubert Opperman once said at maybe my age that older cyclists are like old tyres. They may have been designed to take high pressure, but sometimes they blow up. I regard myself as extremely fortunate to be able to ride 108k in 4.5 hours on truly difficult and hilly country roads in the hills and valleys at the back of Canberra at my age. I don't plan to heed the advice of others who'd say i should buy a motorcycle. I am criticized for taking so long to do things. But I am very good at doing things that take a long time to get right. During the little 108km ride organised by Pedal Power here, it seems I did no damage to my knees despite the condition of pain I had 3 years ago and despite doctors having diagnosed that a pair of titanium knee joints was what i really needed. Doctors, like many experts, can be incorrect. Those of us like TW, and myself, and Andre and all of us here can also be wrong. Its something worth remembering all the time. For those who do tolerate cyclist matters being discussed, the Pedal Power event called Fitz's Challenge attracted about 450 riders spread over 4 distances, 210km with 3,500metres of steep climbing, 160km with 2,200m of climbing, 108km with 1,200m of climbing, and 50km with maybe 500m of climbing. 20 years ago I did the inaugural 147km ride, a slightly different route, but very hard, and rode from home to the course start/finish and then home which made 177km for the day. I do not want to be able to finish this distance at 60. Enough is enough. I like the speed of a good ride, but not to spend too long in agony, and its impossible for me to just amble along slowly. In 20 years i have slowed considerably and was just wize enough to select a lower range of gears appropriate to my age. My lowest was 39 chain ring, 27 cog at the rear wheel. At 40 I managed the same hills on 42 x 23, and some elite lightweight young riders would use 42 x 17 or even higher lowest gear. Last fortnight one fellow of 29 covered the 210km course in about 7.3 hours, and he's done this october ride about 9 times. Many others DNF. Unlike last year, nobody died on the course during a rapid dangerous descent this year. Nobody has ever suffered heart failure. I'm sure many have worse hearts than I have. Such "randoneur" events are not bad to ride in because its not a race, but you are out on roads with many cyclists about, and the occasional car drivers on the sunday morning get reminded to take care. I treated my distance like a race as many others of all ages did, and I started 1/2 an hour before the official start time for my distance group at 8.30. I was passed by only 2 young fellows under 35 who eventually caught me. I wondered what took them so darn long, I had only taken for myself a 1/2 hour start ahead of them while giving them a 25 year start on me..... There were quite a few ppl who appeared to be my age who did the 160km course. I didn't see the group who attempted the 210km, because they started at about 6.30am. Tonight my resting heart rate is 48 beats per minute. 3 years ago I was 20Kg heavier, and HR was 65bpm. I am at peace, and I don't give a **** if I die in 5 minutes time. Patrick Turner. Andre Jute No real corpses were harmed in the assembly of my golem Worthless Wieckless. I made him by stuffing a cow's bladder with pig offal. -- Creepy Mike LaFevre, Magnequest Transformers, Philadelphia |
#122
Posted to rec.audio.tubes
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pentode amplifiers
"Andre Jute" wrote in message ups.com... On Nov 2, 5:22 pm, John Byrns wrote: In article , "Arny Krueger" wrote: "Dave" wrote in message news:CfGWi.1359$8S5.242@edtnps82... "Andre Jute" wrote in message oups.com... I know for a fact that people cannot hear as much as 3/4 per cent second harmonic but can hear that much odd harmonic very clearly, and many people can hear or are made uncomfortable by 0.3 per cent odd harmonics. This order of harmonics issue is way overblown. Doesn't matter whether it is odd or even order nonlinearity, it all makes IM. IM is generally aharmonic and it all sounds bad. But even order IM is much more obvious and annoying in listening tests, although I suppose others may find odd order IM more annoying, its probably partly a matter of personal preference. Arny is trolling. It is widely known that second harmonic is euphonious whereas third and higher harmonics are disturbing. 2H is an exact octave of the fundamental, and so in reasonable amounts, may be considered benign. 3H is an octave and a fifth above the findamental. That might seem OK on the face of it. But consider a chord that has no fifth (the thirteenth is a good example) Here is another aural perception experiment which most students find of interest: Ask a section of five saxophones to play that chord. If the amplifier is adding a fifth to each of the five instruments, then you have another 13th chord set one and a half octaves above what they are actually playing. That's horrific! Iain |
#123
Posted to rec.audio.tubes
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pentode amplifiers
On Nov 8, 4:38 pm, "Iain Churches" wrote:
"Andre Jute" wrote in message ups.com... On Nov 2, 5:22 pm, John Byrns wrote: In article , "Arny Krueger" wrote: "Dave" wrote in message news:CfGWi.1359$8S5.242@edtnps82... "Andre Jute" wrote in message oups.com... I know for a fact that people cannot hear as much as 3/4 per cent second harmonic but can hear that much odd harmonic very clearly, and many people can hear or are made uncomfortable by 0.3 per cent odd harmonics. This order of harmonics issue is way overblown. Doesn't matter whether it is odd or even order nonlinearity, it all makes IM. IM is generally aharmonic and it all sounds bad. But even order IM is much more obvious and annoying in listening tests, although I suppose others may find odd order IM more annoying, its probably partly a matter of personal preference. Arny is trolling. It is widely known that second harmonic is euphonious whereas third and higher harmonics are disturbing. 2H is an exact octave of the fundamental, and so in reasonable amounts, may be considered benign. 3H is an octave and a fifth above the findamental. That might seem OK on the face of it. But consider a chord that has no fifth (the thirteenth is a good example) Here is another aural perception experiment which most students find of interest: Ask a section of five saxophones to play that chord. If the amplifier is adding a fifth to each of the five instruments, then you have another 13th chord set one and a half octaves above what they are actually playing. That's horrific! Oh, I doubt Krueger will even hear there is something wrong... Iain Andre Jute Perception is a skill that requires study and careful development over along period of time. Few have it as a natural gift. -- Iain Churches |
#124
Posted to rec.audio.tubes
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Stagione to Stax, "The 400" in instalments pentode amplifiers
On Nov 8, 11:22 am, RdM wrote:
Patrick Turner writes, inter alia, in . au: How many recordings of Vivaldi's Four Seasons does the world really need? Oh, well over 400, I should think ...http://svalander.se/vivaldi.htm His wife is probably glad it keeps him out of the pub, judging by the romantic photo she took of him. In June 2002 I sent him details of one I had that he hadn't; not even on his wanted list, so probably not known to him; Quattro Stagioni by the Kammerensemble Cologne, on the Swiss Kutlu label; the lead violinist played a 1724 Stradivarius; Never heard of the label, but I too have heard the KEC. I looked into my catalogue and I have, in a collection of 6000 discs, three versions of the Four Seasons, all the of them listed by your chum. I bought the CD after the concert at the church they played in here; I miss it very much, it having been left at a friends place which was like a railway station with regular weekly music nights, and vanished ... A close friend is one who can "borrow" your books and CDs permanently without being struck off your Christmas card list. I'd very much like a copy again, if anybody ever sees one:http://i17.tinypic.com/6ypj5zm.jpg And perhaps some of the recording quality had to do with the equipment used:http://i11.tinypic.com/8evj28x.jpg(trimmed, much reduced quality of scan!) (I had thought I might see if I could sneak a 40kb jpg into a text attachment to the end of this message, re recent discussions, but nah, can't be bothered) AJ may NB the Stax SR-Lambda Pro used for monitoring. My ad agency owned a recording studio, which we bought in an (idle) quest to give me more control over the quality of our advertisements. There a set of Stax headphones was kept for me in a locked wooden box, to which my boxers'n'sox dolly (the assistant who carried clean panties for the girl and me so that we didn't smell too bad after four days on my little plane), carried the key. I can't remember now what model it was but, given the time, the late 1960s, it was probably electret. I'm not into Stax history, which is pretty convoluted. But I can say that a modern fixed bias Stax sounds just like the real deal of ESL-63, whereas the electret of all those years ago didn't come to within a mile of ESL-57. My Stax are absolutely amazing loudspeakers compared to, for instance, the Senheisers I also have, but then they should be, considering the price difference. But the Stax also leave my old Bang & Olufsen dynamic headphones in the shade, and B&O don't have the excuse that their product is cheaper. Not sure if the comment on "transformerless" will win PT's heart, though! One wonders if they mean "windingless" or if this is a mistranslation for "not processed in any way". An absolute proscription on transformers would be a new audiophool obsession you have discovered, if true. [No "tubes", either!] -- Ross Matheson (in nz, not zz...) Andre Jute "I was at a board meeting for the LA Chapter of the Audio Engineering Society last night on XM Satellite radio audio and data transmission. Sadly, we missed you there, and at the SMPTE and Acoustical Society recent meetings as well. Everyone was asking, 'Where is that wonderful Andre Jute? The world just doesn't rotate without him...'" -- John Mayberry, Emmaco |
#125
Posted to rec.audio.tubes
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pentode amplifiers
"Iain Churches" "Arny Krueger" John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. ** That is not "acoustic" ie the science of sound. That is a defect in human hearing that varies from one individual tt another. The fact effect it goes away when listeners are at a greater distance ( ie listening to a lower SPL version of the same sound ) proves the point. ........ Phil |
#126
Posted to rec.audio.tubes
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pentode amplifiers
John Byrns wrote: In article , "Arny Krueger" wrote: "Patrick Turner" wrote in message And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. What about the ear of the listener, isn't IMD produced there that mixes the whole acoustic output of the musicians? Indeed ears create artifacts, and as we age the dynamic range of ears to cope with wide dynamic range is seriously reduced. Everything one does at 25 becomes restricted or down graded as we age, except perhaps becomeing wize, which requires accumulated experience. But in a simple guitar, bass string tension at the bridge pulls the bridge and other string tensions are altered slightly, and some IMD must result. I don't know how linear the stop start air flow in organ pipes or trumpets might be, or in bows on violins, but surely they ain't perfectly linear, and some IMD products are produced. Arny suggests there are no non-linearities in musical instruments, and none in the air, or caused by the room, so its only the microphone of other electronics that can create it. I'm not talking about huge amounts as Arny think I am either. No use talking to Arny, one gets Kroogerated. Patrick Turner. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#127
Posted to rec.audio.tubes
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pentode amplifiers
Andre Jute wrote: On Nov 8, 3:23 pm, "Arny Krueger" wrote: "Iain Churches" wrote in message i.fi "Andre Jute" wrote in message oups.com... Dave wrote: "Andre Jute" wrote in message roups.com... The explanation is simple. Loop NFB causes artifacts of ever lower magnitude but higher order. Good example of majoring in the minors. Loop NFB drops nonlinearity by 20 dB or more. The equipment in question was not entirely free of higher order nonliner distortion, and the secondary effect being obsessed over here typically adds far less distortion than was already there.OTOH, the loop feedback drops all nonlinear distortion by 20 dB. The net higher order distortion is thus dramatically reduced. We're not talking about the net number, Krueger. We're talking about the effect of the composition of the residual distortion. Well yes, but with music this is an extremely complex mix of dynamically changing frequencies, and listened to alone separated from the undistorted signal, sounds like noise and range of harmonically and unharmonically related tones; bloody awful sounding, worse than pink noise or any real music. Its the aim of every tube amp maker to reduce this to below audible levels without applying too many tricks. These high order distortions, even at 60dB below conscious perception are very, very disturbing, If they are so disturbing, why aren't the SET owners running out of the room screaming every time they turn their MI amps on? Repeat, its not like SET amps are free of higher order distoriton.They are based on tubes and tubes are exponentially-based devices. The expansion of their theoretical amplitude transfer function includes signficant higher-order terms, loop feedback or not! A conservatively designed and well-developed 300B amp can easily get the third and higher harmonics down to 0.03 per cent without any loop or stage feedback. I don't see how that is "significant" at all. Hmm, most SET amps with 300B need to be powering horns so THD/IMD is less than 0.2 watts and then you might get down to 0.03%. But with ordinary speakers of 88dB/W/M, the SE amp with one little 300B will have at least 3% at 5 watts with a highish RL, and at 0.5W average power for such insentive speakers the output voltage is about 1/3 that for 5 watts, and THD is 0.75%, mainly all 2H, but way above 0.03%, which is only realizable if you have lots more 300B in parallel or you have a PP pair, and powered by a balanced PP input stage to avoid the 2H made in so many half baked designs for PP where the 2H of the single lousy driver is way above the mainly 3H of the PP output stage THD. If the output SE stage's 2H is cancelled by the driver stage's 2H then its possible to very much reduce 2H down to less than the 0.03% at up to a few watts, but then that's only for one value of load, as the amount of 2H changes with load on the output tube. Natural cancelling of 2H by *VOLTAGE* cancelation in SE amps instead of *CURRENT* cancelations in PP stages actually makes tube sound better, so my clients tell me. In a generic SET amp with 300B, it is thus possible to make a triode driver stage which makes 0.75% of 2H at the 0.75W output level, but its also not wise, since at that low output level most well designed driver stages won't make that much 2H to cancel anything much. A driver stage naking such a lot of 2H will struggle at higher levels, and maybe clip earlier than the output stage. IMD produced in the driver get passed on and muddy the output spectra. Hence my solution is to use local CFB from the OPT around tetrodes/pentodes, and reduce max output stage THD to say 2% at 20 watts, abd then the driver stage when loaded with an RL 10Ra will never struggle or muddy up the sound, and what little 2H it makes willo nicely cancel the output stage 2H....and presumably most other even order products. The result is beautiful un-muddied SE sound, and because the amps I make have over 20 watt capability, there is enough headroom for most ppl and perhaps 1/10 of the THD/IMD as one may hear with a lone 300B with average power at 1W. The odd order junk isn't thus cancelled, but will be a vile residue. But its at such a low level below what would otherwise be a large 2H amount, it matter not, even if you weighted the audibility acording to the Nsquared/4 rule. So in fact in my amps I *actually do achieve* your quoted 0.03%, but nobody else seems to. Most SET amps I have to rewire or teach how to sing and how to behave are travesties of engineering because the makers fail so dismally with basic loadings on tubes, and thd and noise is way above what is possible. Because all amps I make have wide bad OPTs giving over 50khz of bandwidth WITHOUT dependance on global NFB, when I do apply a bit of NFB, say 9dB, to ensure Rout of the amp is at least 1/5 of RL, and preferably 1/10 RL, then the THD and IMD is further reduced and the net residual artifacts no matter what they are would be much lower level and far less unpleasant if sent to the speakers without the music signal present compared to the rubbish and junk which exists in an average low power SET amp signal if played a little too loud and without distortion cancelling schemes either bt way of clever driver or PP design, and without loop NFB. Audio is a gentle low level energy in the air and excites our fabulously sensitive ears which have evolved over millions of years. But folks seem hell bent on owning insensitive speakers, and sometimes will aquire low power SET amps. If they listen up close to the speakers at low level, fine, and I know guys who do this, but filling a large hall sized lounge with high level is impossible and silly. Its not easy to accurately reproduce the sound of a loud trombone player right in front of you without clipping anything. Ditto someone pounding away on a grand piano, lid up, facing towards you. Horns come to mind. And lotsa watts. whereas second harmonic up to three-quarter per cent cannot even be distinguished by professional musicians. It is a subliminal effect, and of course in pentode mode it is exaggerated. People look at the total harmonic distortion but in fact the higher harmonics must be weighted much more heavily than the second harmonic to account for its extraordinary subliminal effect, often described as "edgineess" by professional musicians. This was the explanation I was looking for. thank you. Yes. That seems to be a good description of what is going on, and explains why two similar tubes/valves of the same type but by different makers may sound different. They usually have the same or very similar THD but the distortion spectra are sometimes surprisingly different. 2H is exactly an octave of the fundamental, and so, in "trace" amounts may be regarded as benign. 3H, 5H, 7H and 9H, even at much lower levels are considerably more disturbing. Same mythical thinking, repeated. All right, Krueger, so you don't like psycho-acoustic truths observable in repeatable tests disturbing your fauz certainties. So, slumber on. Repeat again, its not like SET amps are free of higher order distortion.They are based on tubes and tubes are exponentially-based devices. The expansion of their theoretical amplitude transfer function of a tubed amp includes signficant higher-order terms, loop feedback or not! So you keep saying, Krueger, but so far you have provided no proof of your contention, which those of who bulld SETs know is untrue. I have heard many excellent sounding systems with 8W SET amps with a lone 300B. The best had either professional horn speakers made by JBL or Altec, or large sensitive Tannoys in huge bins for great bass. Average power was miniscule, and issues of audible THD/IMD are not worth discussion, because the levels are so low. It so happens that at a watt, 2H from a 300B or other tride such as trioded KT88, 6550, or KT90 etc is often 20 times the level of any other H. Pentodes and beam tubes are not so benign, and produce varying amounts of many harmonics and 2H will be high like in a triode with too low a load when it is loaded low, then fall to zero at some critical medium load value, and then rise again as RL is increased, but the phase of the 2H is opposite below and above the critical RL. The odd numbered H are many and varied with pentodes and beam tubes and the best way of dealing with them is NFB, and this is achieved in every triode because of the electrtostatic NFB acting between anode and space charge summing point between cathode and grid. The triode NFB does a pretty good job at odd order H reduction. But if a similar amount of local CFB from an OPT is applied then the H reduction is similar to triode. So to shoehorn a beam or pentode tube into low THD production, the open loop gain must be well reduced to about the same as low µ triodes. So in my latest work with 13E1, the open loop gain is 16, but reduced to 2.5 only with the local NFB from OPT CFB and THD becomes benign. The tube sound IS THERE, but not muddied by anything very much. The baby is retained, only the bath water is thrown out. With BJTs, the effort to make them tolerable to listen to always requires lotsa NFB as with pentodes or beam tubes. Arny doesn't take in the variety and differences in tubes; triodes are infinitely more tolerable sonically than pentodes or beam tubes or BJTs or mosfets when used *WITHOUT* any NFB. That mantle radio set with a lone 6V6 is a HORRID little audio crapper if ever there was one, but generally has no GNFB or local NFB. Any single BJT used similarly would even be worse.. Some years ago, the technical director of Svetlana sent me the findings of a listening group with whom he had been working. Their task was to evaluate 6CG7 tubes by different makers, and put them in order of preference, so that they could be measured and analysed. Although I was not able to obtain all twelve makes on the list, with some colleagues, I repeated the experiment.The differences were most interesting. The interpretation of which is "better" must be left to individual taste, but in general terms, we ranked the tubes in roughly the same order as the Svetlana listeners. In case you are wondering, the RCA cleartop was the best sounding. It also had the lowest odd order harmonics when measured in a mu follower circuit. Yet another anecdote with questionable relevance. Well here I have to agree that sonic differences in preamp tubes can be heard. Even when THD and IMD measures below 0.01%, a typical value where you have a line stage preamp with volume pot before a generic gain stage using a 6CG7. I have, with 4 other guys spent an afternoon tube rolling with 6CG7 samples. We agreed the NOS Seimans were best, then made in Oz Miniwatts, then Mullard, and then very much last were recent Sovtek versions. SNIP,,, Right now I'm running a solid state amp which is rated at 50W RMS with THD of 0.08%. I guess this isn't a reasonable target for a tube amp unless I run multiple parallel UL PP pairs per channel... A while ago, I built a push pull parallel EL34 amp, with two parallel pairs per channel. It can achieve 0.08% THD at full power. http://www.kolumbus.fi/iain.churches...em/C50_002.jpg I don't know whether to laugh or cry. Ah well, decisions, decisions. But the SS amp that makes 0.08% at a dB below 50W clip could make 0.08% at 1/2 a Watt if not carefully designed because of crossover thd. The tube amp which makes 0.08% at 50W will have smoothly decreasing THD as output voltage is reduced, so that at 5W, THD will be perhaps 0.03%, and at 0.5W its 0.01%, and utterly inaudible no matter what the harmonics are. If the amp moves from class AB to class A at the low PO level there is ZERO crossover H generated at low levels, because all is handled by devices in their linear regions. Patrick Turner. Snip more... |
#128
Posted to rec.audio.tubes
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pentode amplifiers
"Patrick Turner" wrote in message ... John Byrns wrote: In article , "Arny Krueger" wrote: "Patrick Turner" wrote in message And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. What about the ear of the listener, isn't IMD produced there that mixes the whole acoustic output of the musicians? But in a simple guitar, bass string tension at the bridge pulls the bridge and other string tensions are altered slightly, and some IMD must result. And when one uses two or more strings, IMD is also created. My example of a French horn section is the best example which one can demonstrate to students, and be heard by all. Arny suggests there are no non-linearities in musical instruments, and none in the air, or caused by the room, so its only the microphone of other electronics that can create it. Arny should listen carefully, from a well-chosen position from within the orchestra. I'm not talking about huge amounts as Arny think I am either. The amounts do not have to be large to be easily heard. Horns seem to be the worst offenders (and so make a good example) No use talking to Arny, one gets Kroogerated. ;:-) Iain |
#129
Posted to rec.audio.tubes
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pentode amplifiers
"Andre Jute" wrote in message ups.com... On Nov 7, 7:34 am, "Iain Churches" wrote: Take a look at the signal envelope of a typical pop-chart CD. In many cases you will find severe compression and clipping. I know from my close connections with record labels that CD returns for technical reasons are very low indeed. I have asked the children of friends who buy this kind of music whether or not they find this clipping disturbing. Usually the reply is, "it sounds good and loud in the car" Uh-huh. I wondered if I should mention what you describe: " levels of expectation have fallen considerably, (and with it the standard reference by which we all make our evalöuations)" but decided not to complicate what I wrote with qualifications (no doubt Trevor Wilson will next accuse me of *lying*!). Quite possibly:-)) It seems to me that somewhere around or perhaps after 1990 there was a turning point at which quantity replaced quality (in a strictly technical sense: the quality of the content of of the best classical recordings, which is what I know about, in the 80s and 90s was extraordinary). It coincided with MP3, miniaturized personal players and so on. But there were still audiophiles among the higheer socioeconomic groups. Fortunately this is a problem that is extremely rare in both classical and jazz recordings, where the brief for the mastering engineer is now, just as it was back in the vinyl days; "Make a 1:1 of this please! I have a number of pop CDs that were mastered in the mid 80's and then re-mastered (awful term!) some ten years later. It is interesting to compare them. Evaluation on a digital audio workstation provides some tell-tale statistics. Identical peak level on both early and later CDs - no surprise there, but the signal reached 0 FS about 12 times more often on the later remaster. The average level is increased by some 5dB. (!!) The original CD has no instances of clipping, the second CD had many hundreds per track. The dynamic of the music hafd suffered considerably, but yes, "It sounded good and loud in the car" This is a clear case of giving the public what they think they want. The killer -- where I think futureaudio-historians will point the finger -- was the rise home cinema, which took the attention and disposable income previously spent on music-audio and on music, and took it in precisely the key market niche. That also accounts for why the hi-fi industry so easily sashayed itself into the home video industry: they were dealing with the same customers. Yes this may well be the case, although I do know plenty of people who still have a dedicated music room separate from the living room in which they watch HT. You know that joke Patrick tells against Halcro, about the time the Hong Kong Audio Club tested one? To a lateral thinker it is instant proof of not only this contention of mine but another more controversial matter on which you and I also agree, that the mix of artifacts in THD is as important as its level. My good friend Peter Lewis, put me on to this, many years ago. It is only fairly recently that I have access to the equipment to confirm what he told me. When I mentioned it to the former technical director Svetlana, he replied "I thought you would have known about that" Iain |
#130
Posted to rec.audio.tubes
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pentode amplifiers
In article ,
Patrick Turner wrote: Hmm, most SET amps with 300B need to be powering horns so THD/IMD is less than 0.2 watts and then you might get down to 0.03%. But with ordinary speakers of 88dB/W/M, the SE amp with one little 300B will have at least 3% at 5 watts with a highish RL, and at 0.5W average power for such insentive speakers the output voltage is about 1/3 that for 5 watts, and THD is 0.75%, mainly all 2H, but way above 0.03%, which is only realizable if you have lots more 300B in parallel or you have a PP pair, and powered by a balanced PP input stage to avoid the 2H made in so many half baked designs for PP where the 2H of the single lousy driver is way above the mainly 3H of the PP output stage THD. If the output SE stage's 2H is cancelled by the driver stage's 2H then its possible to very much reduce 2H down to less than the 0.03% at up to a few watts, but then that's only for one value of load, as the amount of 2H changes with load on the output tube. Natural cancelling of 2H by *VOLTAGE* cancelation in SE amps instead of *CURRENT* cancelations in PP stages actually makes tube sound better, so my clients tell me. In a generic SET amp with 300B, it is thus possible to make a triode driver stage which makes 0.75% of 2H at the 0.75W output level, but its also not wise, since at that low output level most well designed driver stages won't make that much 2H to cancel anything much. A driver stage naking such a lot of 2H will struggle at higher levels, and maybe clip earlier than the output stage. IMD produced in the driver get passed on and muddy the output spectra. Why not build a blameless driver stage, and then create the desired 2H to cancel the output stage 2H by using a pre-distorter network? A single vacuum diode like half of a 6AL5 and a couple of resistors could be used to create a pre-distorter that would cancel all the 2H at full output, as well as at one lower level, without greatly increasing 2H at the lowest levels. I haven't done the math, but I assume the downside of this scheme is that it probably increases the amount of odd harmonics present at higher levels. A simple pre-distorter that wouldn't create additional odd harmonics could be built, but it would only cancel 2H at one output level and would increase the 2H at lower levels, although maybe that would be a feature, creating a euphonious sound. I suppose the ultimate would be a more complex pre-distorter, probably silicon based, that would exactly complement the transfer function of the output stage, eliminating all distortion below clipping, at least into a fixed resistive load. Hence my solution is to use local CFB from the OPT around tetrodes/pentodes, and reduce max output stage THD to say 2% at 20 watts, abd then the driver stage when loaded with an RL 10Ra will never struggle or muddy up the sound, and what little 2H it makes willo nicely cancel the output stage 2H....and presumably most other even order products. The result is beautiful un-muddied SE sound, and because the amps I make have over 20 watt capability, there is enough headroom for most ppl and perhaps 1/10 of the THD/IMD as one may hear with a lone 300B with average power at 1W. The odd order junk isn't thus cancelled, but will be a vile residue. But its at such a low level below what would otherwise be a large 2H amount, it matter not, even if you weighted the audibility acording to the Nsquared/4 rule. So in fact in my amps I *actually do achieve* your quoted 0.03%, but nobody else seems to. Most SET amps I have to rewire or teach how to sing and how to behave are travesties of engineering because the makers fail so dismally with basic loadings on tubes, and thd and noise is way above what is possible. Because all amps I make have wide bad OPTs giving over 50khz of bandwidth WITHOUT dependance on global NFB, when I do apply a bit of NFB, say 9dB, to ensure Rout of the amp is at least 1/5 of RL, and preferably 1/10 RL, then the THD and IMD is further reduced and the net residual artifacts no matter what they are would be much lower level and far less unpleasant if sent to the speakers without the music signal present compared to the rubbish and junk which exists in an average low power SET amp signal if played a little too loud and without distortion cancelling schemes either bt way of clever driver or PP design, and without loop NFB. Couldn't you easily meet your 1/5 of RL goal for Rout with only CFB and a moderately efficient OPT, without resorting to global NFB? I would think you might even be able to meet 1/10 of RL with an aggressive OPT design and perhaps a touch more CFB. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#131
Posted to rec.audio.tubes
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pentode amplifiers
"Patrick Turner" wrote in message ... Well here I have to agree that sonic differences in preamp tubes can be heard. Even when THD and IMD measures below 0.01%, a typical value where you have a line stage preamp with volume pot before a generic gain stage using a 6CG7. I have, with 4 other guys spent an afternoon tube rolling with 6CG7 samples. We agreed the NOS Seimans were best, then made in Oz Miniwatts, then Mullard, and then very much last were recent Sovtek versions. Nice to find that (unlike Arny) others also take the trouble to listen, and evaluate. RCA cleartop came at the top of our list then Siemens and Westnghouse close behind. A while ago, I built a push pull parallel EL34 amp, with two parallel pairs per channel. It can achieve 0.08% THD at full power. I don't know whether to laugh or cry. Ah well, decisions, decisions. To build something better in tubes would be a good project for Arny. It would also keep him away from RAT for a *very* long time :-)) The tube amp which makes 0.08% at 50W will have smoothly decreasing THD as output voltage is reduced, so that at 5W, THD will be perhaps 0.03%, and at 0.5W its 0.01%, and utterly inaudible no matter what the harmonics are. Indeed. Iain |
#132
Posted to rec.audio.tubes
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pentode amplifiers
"Arny Krueger" wrote in message . .. Iain wrote: Some years ago, the technical director of Svetlana sent me the findings of a listening group with whom he had been working. Their task was to evaluate 6CG7 tubes by different makers, and put them in order of preference, so that they could be measured and analysed. Although I was not able to obtain all twelve makes on the list, with some colleagues, I repeated the experiment.The differences were most interesting. The interpretation of which is "better" must be left to individual taste, but in general terms, we ranked the tubes in roughly the same order as the Svetlana listeners. In case you are wondering, the RCA cleartop was the best sounding. It also had the lowest odd order harmonics when measured in a mu follower circuit. Yet another anecdote with questionable relevance. Have you made the comparison, Arny? I have been involved in experiments on which panels of listeners have been asked to differentiate between two identical amplifiers, one set up to have 0.05% and the other 0.5% THD. This is a difference of 20dB. No one, even the professionals on the panel, could tell which was which. Probably not a well-run test. Orhanised by a broadcast studio (EBU) Participants were recording professionals and musicians. A better-run test is hard to imagine. Tests like this are strongly depenendent on the choice of program material. Most audiophile self-select program material that sounds good on their home systems. There were no "audiophiles" present. If the person doing the selecting has a system at home with relatively high nonlinear distortion, he's going to pick recordings that are tolerant of relatively high nonlinear distortion. So, they unconsciously desensitize the experiment because of their preferences. A shortlist of material was drawn up several weeks before the listening sessions. There were some ten titles in all, ranging from Baroque to voice and piano. All were chosen as clean sources. No rock'n'roll:-) It is a long time since I have read the book, but IIRC Olson states that listeners could not detect distortion levels up to 1% on a music signal. Again, that depends on context. How many CDs had Olson listened to by the time he made that claim? Do you have evidence that Olson's statement is incorrect? A while ago, I built a push pull parallel EL34 amp, with two parallel pairs per channel. It can achieve 0.08% THD at full power. http://www.kolumbus.fi/iain.churches...em/C50_002.jpg I don't know whether to laugh or cry. Don't do either. Just post a pic of your tube amplifiers. Iain |
#133
Posted to rec.audio.tubes
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pentode amplifiers
John Byrns wrote: In article , Patrick Turner wrote: Hmm, most SET amps with 300B need to be powering horns so THD/IMD is less than 0.2 watts and then you might get down to 0.03%. But with ordinary speakers of 88dB/W/M, the SE amp with one little 300B will have at least 3% at 5 watts with a highish RL, and at 0.5W average power for such insentive speakers the output voltage is about 1/3 that for 5 watts, and THD is 0.75%, mainly all 2H, but way above 0.03%, which is only realizable if you have lots more 300B in parallel or you have a PP pair, and powered by a balanced PP input stage to avoid the 2H made in so many half baked designs for PP where the 2H of the single lousy driver is way above the mainly 3H of the PP output stage THD. If the output SE stage's 2H is cancelled by the driver stage's 2H then its possible to very much reduce 2H down to less than the 0.03% at up to a few watts, but then that's only for one value of load, as the amount of 2H changes with load on the output tube. Natural cancelling of 2H by *VOLTAGE* cancelation in SE amps instead of *CURRENT* cancelations in PP stages actually makes tube sound better, so my clients tell me. In a generic SET amp with 300B, it is thus possible to make a triode driver stage which makes 0.75% of 2H at the 0.75W output level, but its also not wise, since at that low output level most well designed driver stages won't make that much 2H to cancel anything much. A driver stage naking such a lot of 2H will struggle at higher levels, and maybe clip earlier than the output stage. IMD produced in the driver get passed on and muddy the output spectra. Why not build a blameless driver stage, and then create the desired 2H to cancel the output stage 2H by using a pre-distorter network? A single vacuum diode like half of a 6AL5 and a couple of resistors could be used to create a pre-distorter that would cancel all the 2H at full output, as well as at one lower level, without greatly increasing 2H at the lowest levels. I haven't done the math, but I assume the downside of this scheme is that it probably increases the amount of odd harmonics present at higher levels. A simple pre-distorter that wouldn't create additional odd harmonics could be built, but it would only cancel 2H at one output level and would increase the 2H at lower levels, although maybe that would be a feature, creating a euphonious sound. I suppose the ultimate would be a more complex pre-distorter, probably silicon based, that would exactly complement the transfer function of the output stage, eliminating all distortion below clipping, at least into a fixed resistive load. Any deliberate attempt to create distortion with diodes is doomed to failure IMHO. and perhaps if you tried what you said you'd see what a dismal rewsult you'd get. My idea is to linearize the output pentode or tetrode with local CFB from the OPT so that its THD at the wanted nominal load for max power, ie, 0.9 x Ea/Ia reduces to about between 1% to 2%. The Ra will also fall to less than the Ra if the tube were triode connected. Final gain is thus usually less than triode. THEN one concentrates on a driver triode with resistance load which is say 10 x Ra and arranged so it is as linear as can be naturally expected with RL = 10Ra. So with EL34, and with 125Vrms output with 22k RL due to dc carrying RL and ac coupled bias R, the driver THD will cancel the output tube THD because both produce around say 1.5% and hence the cancelation of even order products. At ALL levels of output, the THD cancells well if this regime is followed. At low levels, order is very low, and typically the the THD at 5 watts in an SE pentode amp made for 35 watts at clip is similar to low levels found in PP amps. And we have not applied any global NFB. Hence my solution is to use local CFB from the OPT around tetrodes/pentodes, and reduce max output stage THD to say 2% at 20 watts, abd then the driver stage when loaded with an RL 10Ra will never struggle or muddy up the sound, and what little 2H it makes willo nicely cancel the output stage 2H....and presumably most other even order products. The result is beautiful un-muddied SE sound, and because the amps I make have over 20 watt capability, there is enough headroom for most ppl and perhaps 1/10 of the THD/IMD as one may hear with a lone 300B with average power at 1W. The odd order junk isn't thus cancelled, but will be a vile residue. But its at such a low level below what would otherwise be a large 2H amount, it matter not, even if you weighted the audibility acording to the Nsquared/4 rule. So in fact in my amps I *actually do achieve* your quoted 0.03%, but nobody else seems to. Most SET amps I have to rewire or teach how to sing and how to behave are travesties of engineering because the makers fail so dismally with basic loadings on tubes, and thd and noise is way above what is possible. Because all amps I make have wide bad OPTs giving over 50khz of bandwidth WITHOUT dependance on global NFB, when I do apply a bit of NFB, say 9dB, to ensure Rout of the amp is at least 1/5 of RL, and preferably 1/10 RL, then the THD and IMD is further reduced and the net residual artifacts no matter what they are would be much lower level and far less unpleasant if sent to the speakers without the music signal present compared to the rubbish and junk which exists in an average low power SET amp signal if played a little too loud and without distortion cancelling schemes either bt way of clever driver or PP design, and without loop NFB. Couldn't you easily meet your 1/5 of RL goal for Rout with only CFB and a moderately efficient OPT, without resorting to global NFB? I would think you might even be able to meet 1/10 of RL with an aggressive OPT design and perhaps a touch more CFB. The 13E1 with 33% of its primary devoted to a cathode winding with an OPT for 2.7k:5 ohms has Rout = 0.7 ohms without GNFB. The 9dB of the GNF reduces all THD and further flattens response and reduces Rout to 0.26ohms, which is a DF = 19 approx. There was no choice for the amount of CFB in the case of my 13E1 amps. 1/3 or one entire P section between two of the four S sections is devoted to CFB so that all the winding is at 0V potential. The other 2 anode sections are at +510V. But in the SE35cfb amps seen at my website the amount of CFB is much less and the result witha quad of 6CA7 is very nice if you read the page. http://www.turneraudio.com.au/se35cfbmonobloc.html In my PP 8585 amps, CFB = 12.5% of P windings, and now in my 300W amps its 20%. I am designing a 13E1 PP amp for a colleage to build for a client with Quad 2805 ESL. Power will be 100W class AB1 into 5k, about 16.6% CFB, Ea = 550V, Eg2 = 200V approx, Ia per tube = 100mA, and class A content = 25 watts. OPT is a 62mm stack 51 tongue GOSS, and losses less than 5%, BW 100k without NFB, ,Fsat at 16Hz, full power. We think this will be a masterpiece amplifier. My colleague isn't so hot with calculations, but does a great job on chassis, finish, and general construction, and I design all his OPT, and I get to know how they all work. Its possible to get maybe 200W class AB from a pair of 13E1. But these will be limited to making about 150W with 4 ohms connected to the 8 ohm outlet match. But class A content is low, and distortions are higher. With the right load of 8 ohms, there is 100W AB with 25W of class A, and if the 8 ohms is connected to the 3.6 ohm OPT config, you get 50W+ of pure class A, because Pda total at idle with two tubes is 110W. With each at 55W Pda, they should last very well and never thermal out, because the anodes won't glow red until Pda = a continuous 85W. The performance is similar to a six pack of EL34, or a quad of KT90. Its not wise to run such tubes in ordinary UL because the screen voltage should be well below the anode supply voltage for the 13E1. One could have Ea = 800V, Eg2 at +150V only, and RL about 6ka-a, and get some serious PO, like when one uses 800V for KT88, and get 140W. TT21 is better in this role because then the top cap anode connection allows the HV, and the screen voltage for such tubes is happy being only 300V to 400V, OK in an octal socket. 13E1 has a socket unlikely to arc with HV. Such amps usually sound very well. Using 6 x EL84 in parallel PP like Baird amps will give 60W AB, and a nice 30W in pure class A. Because the anode to cathode voltage isn't much more than 210Vrms, one may simply use a circlotron design or McIntosh, so 105Vrms is at anode and cathode, and grid drive is maybe 115Vrms, and and as long as the drive voltage is not distorted, Rout is very low. 6 x EL84 in SE parallel pentode will give 30 watts in pure class A. Pda = 72 watts, like a single 13E1, and gm = 60mA/V total which is more than twice 13E1. The first amp I made which sounded really well with some sensitive speakers was EL84 in SE pentode mode with about 10% CFB, because the gm and µ of this tube is so high, you don't need much CFB to perform wonders with distortion, and it sings. Grand piano sounded fabulous. Patrick Turner. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#134
Posted to rec.audio.tubes
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pentode amplifiers
In article ,
Patrick Turner wrote: John Byrns wrote: In article , Patrick Turner wrote: [Snip] In a generic SET amp with 300B, it is thus possible to make a triode driver stage which makes 0.75% of 2H at the 0.75W output level, but its also not wise, since at that low output level most well designed driver stages won't make that much 2H to cancel anything much. A driver stage naking such a lot of 2H will struggle at higher levels, and maybe clip earlier than the output stage. IMD produced in the driver get passed on and muddy the output spectra. Why not build a blameless driver stage, and then create the desired 2H to cancel the output stage 2H by using a pre-distorter network? A single vacuum diode like half of a 6AL5 and a couple of resistors could be used to create a pre-distorter that would cancel all the 2H at full output, as well as at one lower level, without greatly increasing 2H at the lowest levels. I haven't done the math, but I assume the downside of this scheme is that it probably increases the amount of odd harmonics present at higher levels. A simple pre-distorter that wouldn't create additional odd harmonics could be built, but it would only cancel 2H at one output level and would increase the 2H at lower levels, although maybe that would be a feature, creating a euphonious sound. I suppose the ultimate would be a more complex pre-distorter, probably silicon based, that would exactly complement the transfer function of the output stage, eliminating all distortion below clipping, at least into a fixed resistive load. Any deliberate attempt to create distortion with diodes is doomed to failure IMHO. and perhaps if you tried what you said you'd see what a dismal rewsult you'd get. Exactly, I am no fan of such a scheme, which is better reserved for Television transmitters and the like, my point was to parody the notion of using driver stage distortion to cancel output stage distortion. I fail to see a substantive difference between the two schemes, they both seem like bad ideas to me. In your third paragraph below you seem to endorse the notion of using driver stage distortion to cancel output stage distortion, can you explain why you think this scheme is any better than the "diode" idea? What criteria would you use to compare the performance of the two schemes? One problem with both ideas is that the impedance of real life loudspeakers varies with frequency, which causes the output stage distortion to vary with frequency whereas the driver stage distortion doesn't vary with audio frequency, hence you may get good cancellation at one frequency, but not at others. Personally I would focus on making the distortion of the separate stages as low as possible individually, as you describe in the following paragraph, before you go off the rails and opt for including a distortion cancellation scheme. My idea is to linearize the output pentode or tetrode with local CFB from the OPT so that its THD at the wanted nominal load for max power, ie, 0.9 x Ea/Ia reduces to about between 1% to 2%. The Ra will also fall to less than the Ra if the tube were triode connected. Final gain is thus usually less than triode. THEN one concentrates on a driver triode with resistance load which is say 10 x Ra and arranged so it is as linear as can be naturally expected with RL = 10Ra. So with EL34, and with 125Vrms output with 22k RL due to dc carrying RL and ac coupled bias R, the driver THD will cancel the output tube THD because both produce around say 1.5% and hence the cancelation of even order products. At ALL levels of output, the THD cancells well if this regime is followed. At low levels, order is very low, and typically the the THD at 5 watts in an SE pentode amp made for 35 watts at clip is similar to low levels found in PP amps. And we have not applied any global NFB. Hence my solution is to use local CFB from the OPT around tetrodes/pentodes, and reduce max output stage THD to say 2% at 20 watts, abd then the driver stage when loaded with an RL 10Ra will never struggle or muddy up the sound, and what little 2H it makes willo nicely cancel the output stage 2H....and presumably most other even order products. The result is beautiful un-muddied SE sound, and because the amps I make have over 20 watt capability, there is enough headroom for most ppl and perhaps 1/10 of the THD/IMD as one may hear with a lone 300B with average power at 1W. The odd order junk isn't thus cancelled, but will be a vile residue. But its at such a low level below what would otherwise be a large 2H amount, it matter not, even if you weighted the audibility acording to the Nsquared/4 rule. So in fact in my amps I *actually do achieve* your quoted 0.03%, but nobody else seems to. Most SET amps I have to rewire or teach how to sing and how to behave are travesties of engineering because the makers fail so dismally with basic loadings on tubes, and thd and noise is way above what is possible. Because all amps I make have wide bad OPTs giving over 50khz of bandwidth WITHOUT dependance on global NFB, when I do apply a bit of NFB, say 9dB, to ensure Rout of the amp is at least 1/5 of RL, and preferably 1/10 RL, then the THD and IMD is further reduced and the net residual artifacts no matter what they are would be much lower level and far less unpleasant if sent to the speakers without the music signal present compared to the rubbish and junk which exists in an average low power SET amp signal if played a little too loud and without distortion cancelling schemes either bt way of clever driver or PP design, and without loop NFB. Couldn't you easily meet your 1/5 of RL goal for Rout with only CFB and a moderately efficient OPT, without resorting to global NFB? I would think you might even be able to meet 1/10 of RL with an aggressive OPT design and perhaps a touch more CFB. The 13E1 with 33% of its primary devoted to a cathode winding with an OPT for 2.7k:5 ohms has Rout = 0.7 ohms without GNFB. So the answer appears to be yes, with a well designed output transformer, CFB alone will meet the 1/5 of RL goal for Rout, giving a DF greater than 7 without the need to apply overall loop feedback. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#135
Posted to rec.audio.tubes
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pentode amplifiers
John Byrns wrote: In article , Patrick Turner wrote: John Byrns wrote: In article , Patrick Turner wrote: [Snip] In a generic SET amp with 300B, it is thus possible to make a triode driver stage which makes 0.75% of 2H at the 0.75W output level, but its also not wise, since at that low output level most well designed driver stages won't make that much 2H to cancel anything much. A driver stage naking such a lot of 2H will struggle at higher levels, and maybe clip earlier than the output stage. IMD produced in the driver get passed on and muddy the output spectra. Why not build a blameless driver stage, and then create the desired 2H to cancel the output stage 2H by using a pre-distorter network? A single vacuum diode like half of a 6AL5 and a couple of resistors could be used to create a pre-distorter that would cancel all the 2H at full output, as well as at one lower level, without greatly increasing 2H at the lowest levels. I haven't done the math, but I assume the downside of this scheme is that it probably increases the amount of odd harmonics present at higher levels. A simple pre-distorter that wouldn't create additional odd harmonics could be built, but it would only cancel 2H at one output level and would increase the 2H at lower levels, although maybe that would be a feature, creating a euphonious sound. I suppose the ultimate would be a more complex pre-distorter, probably silicon based, that would exactly complement the transfer function of the output stage, eliminating all distortion below clipping, at least into a fixed resistive load. Any deliberate attempt to create distortion with diodes is doomed to failure IMHO. and perhaps if you tried what you said you'd see what a dismal rewsult you'd get. Exactly, I am no fan of such a scheme, which is better reserved for Television transmitters and the like, my point was to parody the notion of using driver stage distortion to cancel output stage distortion. I fail to see a substantive difference between the two schemes, they both seem like bad ideas to me. In your third paragraph below you seem to endorse the notion of using driver stage distortion to cancel output stage distortion, can you explain why you think this scheme is any better than the "diode" idea? One CANNOT escape from using distortion cancelling between any two consecutive triode casaded amplifier stages. The use of diodes and deliberate distortion creation in the driving triode to match the higher distortion of the following triode ( or pentode/beam tube) is not a good idea, because the IMD isn't cancelled, and nor is the inevitable small amount of odd order crap accompanying the even order crap. What criteria would you use to compare the performance of the two schemes? One problem with both ideas is that the impedance of real life loudspeakers varies with frequency, which causes the output stage distortion to vary with frequency whereas the driver stage distortion doesn't vary with audio frequency, hence you may get good cancellation at one frequency, but not at others. Indeed I have pointed out in numerous postings that the load affects the spectra of a beam or pentode tube. At low RL, even order 2H, 4H is high and like triode, but this falls to zero at some critical load value, then rises again but with an opposite phase to triode. But as load rises, the gain also rises, since beam and pentode tubes have gain = gm x RL approx. Without any NFB, and with very high RL the pentode&beam tube gain becomes very high, approaching µ, or gm x Ra. And the distortion is utterly horrendous. If you have CFB from the OPT, applied series voltage NFB becomes greater as load increases and the gain increases, so the increasing distortion with high RL is reduced. Where you have a beam or pentode tube connected in UL, the NFB is applied to the tube via the screen. But THD in any SEUL with a UL % tap to give neam beam power but a triode's spectra will just about always give 5% THD, mainly 2H at clipping. Where you have a driving triode its impossible to cancel this THD because the driving triode's THD is always well under 5% at the grid driving voltage needed for the UL or triode output tube. It surely is with a pentode or beam tube, which need only a low voltage drive. So there are at least three fundemental approaches to reduce distortions. One is to apply NFB from anode of the output tube to cathode of driver tube. This always has limitations, and the R needed to transfer enough current to driver tube Rk unecessarily loads the output tube. Its difficult to get a sufficiently effective amount of NFB. Two is to have a pentode drive tube, and arrange the circuit for shunt NFB where the Ra of the driver is the first arm of the R+R shunt NFB network. See my website for balanced shunt NFB in a power amp, see my schematics pages. or read RDH4 on this. Three is to use regular series voltage NFB applied from the low Z secondary of OPT back to an input tube cathode circuit. All these schemes involve feeding back a large fraction of output voltage to an input and generating a fair sized error signal which gives rise to a lot of second order IMD products unless large amount of NFB is used. Four is to have CFB applied from the OPT to output tube cathode and then have minimal GNFB. This way the CFB reduces the THD of the output tube without applying the distortion around at least a two tube network. The result is that you get a beam or pentode tube where the THD at any load of level up to clip is limited to under about 2%, yet the closed loop gain is about equal to a low µ triode, and Rout is even lower than the triode. Now the biggest problem with driving speakers is where the Z falls to below the rated nominal value, often in the critical band between bass and midrange where often the crossover filters pass wasted current in second order CL and LC networks at the Xover F. Where Z is low, the pentode/beam tube produces its highest and worst distortion. Fortunately, this very distortion at lowish load values is what we wish to cancel simply by having a triode driver stage set up for linear operation, ie, say making 2% mainly 2H when the amplifier clips. Its a doddle to therefore get nearly all the 2H to cancel with a 5 ohm load, and THD will measure very low. There is a very useful range of cancelling between 3 and 6 ohms available if you want it. The THD will be far lower at all levels for these load values compared to a triode or UL stage, or other straight pentode or beam tube with other types of NFB loops other than the local CFB. The odd numbered H are insignificant. Personally I would focus on making the distortion of the separate stages as low as possible individually, as you describe in the following paragraph, before you go off the rails and opt for including a distortion cancellation scheme. I have pointed out for the umpteenth time that it IS IMPORTANT to linearize ALL stages where possible without GNFB applied. But I have outlined above that UL, triode is prone to 5% at clipping, and beam/pentode is prone to far greater THD and complex spectra. See RDH4 for more info on comparisons between beam&pentodes and triodes. The CFB I am using linearizes the output tube very nicely so that the unavoidable distortions of the stage are less than 2%, and the unavoidable 2% from most driver triodes WILL NATURALLY CANCEL the distortions of the output tube without any "artificial circuitry" to make sure sufficient 2H is made in a driver stage to cancel that in an outpuit stage. There is a catch in tis natural order of things. The 2H of a drive triode will cancel the 2H of an outut beam or pentode tube with a low RL, but not when RL becomes high, and in fact the triode driver tube 2H becomes additive to the output tube 2H when the output tube is loaded with a high RL, because of the phase reversal of 2H that occurs above the critical load value which produces zero 2H. But the critical RL is a high RL anyway, above the nominal load value for maximum power. The additive effects of 2H at high values of RL will still give a THD result which is no worse than a UL or triode stage. My idea is to linearize the output pentode or tetrode with local CFB from the OPT so that its THD at the wanted nominal load for max power, ie, 0.9 x Ea/Ia reduces to about between 1% to 2%. The Ra will also fall to less than the Ra if the tube were triode connected. Final gain is thus usually less than triode. THEN one concentrates on a driver triode with resistance load which is say 10 x Ra and arranged so it is as linear as can be naturally expected with RL = 10Ra. So with EL34, and with 125Vrms output with 22k RL due to dc carrying RL and ac coupled bias R, the driver THD will cancel the output tube THD because both produce around say 1.5% and hence the cancelation of even order products. At ALL levels of output, the THD cancells well if this regime is followed. At low levels, order is very low, and typically the the THD at 5 watts in an SE pentode amp made for 35 watts at clip is similar to low levels found in PP amps. And we have not applied any global NFB. Hence my solution is to use local CFB from the OPT around tetrodes/pentodes, and reduce max output stage THD to say 2% at 20 watts, abd then the driver stage when loaded with an RL 10Ra will never struggle or muddy up the sound, and what little 2H it makes willo nicely cancel the output stage 2H....and presumably most other even order products. The result is beautiful un-muddied SE sound, and because the amps I make have over 20 watt capability, there is enough headroom for most ppl and perhaps 1/10 of the THD/IMD as one may hear with a lone 300B with average power at 1W. The odd order junk isn't thus cancelled, but will be a vile residue. But its at such a low level below what would otherwise be a large 2H amount, it matter not, even if you weighted the audibility acording to the Nsquared/4 rule. So in fact in my amps I *actually do achieve* your quoted 0.03%, but nobody else seems to. Most SET amps I have to rewire or teach how to sing and how to behave are travesties of engineering because the makers fail so dismally with basic loadings on tubes, and thd and noise is way above what is possible. Because all amps I make have wide bad OPTs giving over 50khz of bandwidth WITHOUT dependance on global NFB, when I do apply a bit of NFB, say 9dB, to ensure Rout of the amp is at least 1/5 of RL, and preferably 1/10 RL, then the THD and IMD is further reduced and the net residual artifacts no matter what they are would be much lower level and far less unpleasant if sent to the speakers without the music signal present compared to the rubbish and junk which exists in an average low power SET amp signal if played a little too loud and without distortion cancelling schemes either bt way of clever driver or PP design, and without loop NFB. Couldn't you easily meet your 1/5 of RL goal for Rout with only CFB and a moderately efficient OPT, without resorting to global NFB? I would think you might even be able to meet 1/10 of RL with an aggressive OPT design and perhaps a touch more CFB. The 13E1 with 33% of its primary devoted to a cathode winding with an OPT for 2.7k:5 ohms has Rout = 0.7 ohms without GNFB. So the answer appears to be yes, with a well designed output transformer, CFB alone will meet the 1/5 of RL goal for Rout, giving a DF greater than 7 without the need to apply overall loop feedback. One does not need to have GNFB with a pentode output tube and the final Rout at the OPT sec can be much lower than a triode. The working of the beam or pentode with CFB and screen bypassed to cathode needs to be mentioned. In effct, this case is one of real beam/pentode operation with one loop of pure series voltage NFB. Say distortion voltage at cathode = +Vd, and pentode open loop gain = -30. ( gain is negative, because of the inverting of phase between grid and anode ). Then in effect, -Vd is being applied to the grid, and appears as -Vd x -30 at between anode and cathode so +20Vd error correction signal exists at anode, and -10Vd at cathode. This opposes the natural open loop THD of -21Vd and +11Vd at cathode that would exist if there was no NFB. The +Vd appearing at cathode with CFB is also applied to the screen directly via the bypass cap and is a loop of positive feedback according to the screen gain, approx screen gm x RL, and much lower than control grid gain. Where the screen is bypassed to ground at ac, the cathode signal +Vd appears at the screen effectively as -Vd, and becomes a NFB causing applied voltage. One must take care that at no part of the wave cycle does the cathode voltage rise above the static Vdc of a screen bypassed to ground, or else the tube cuts off. In my case with SE 13E1 CFB, the 33% CFB winding has a CT, which is 16.5% of the primary. Bypassing the screen to 0V gave cut off behaviour. But with screen bypassed to the 16.5% CT of cathode winding there is effectively SOME NFB applied in the screen circuit which gives better spectra than with bypassing screen to cathode for maximal positive FB. One might be tempted to have equal anode and cathode windings as I have mentioned in another post re using EL84 where Va and Vk would be quite low, and hence Vg would be easy to arrange. Just how and where one bypasses the screen and at what Vdc you run the screen at becomes a critically important issue. Most folks find all this a pile of BS and all too hard to ever get right, and simply settle for triode or plain old UL. But I know what I'm doing, and my customers hear that the CFB sounds better. Patrick Turner. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#136
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pentode amplifiers
"Iain Churches" wrote in message
i.fi "John Byrns" wrote in message ... In article , "Arny Krueger" wrote: "Patrick Turner" wrote in message And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. What about the ear of the listener, isn't IMD produced there that mixes the whole acoustic output of the musicians? Yes indeed. I have experienced this many times. It is not audible from the audience seats. See my reply to Arny. Au contraire. If you're talking about the nonlinearity of the human ear above about 85 dB SPL, its audible everywhere. You just have to know how to make it audible. |
#137
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pentode amplifiers
"Patrick Turner" wrote in message
John Byrns wrote: In article , "Arny Krueger" wrote: "Patrick Turner" wrote in message And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. What about the ear of the listener, isn't IMD produced there that mixes the whole acoustic output of the musicians? At reasonable listening levels normal ears are reasonably nonlinear. To wit, we are indeed able to hear the effects of as little as 0.1% nonlinearity. Indeed ears create artifacts, and as we age the dynamic range of ears to cope with wide dynamic range is seriously reduced. Agreed, but normal ears aren't strongly nonlinear at normal listening levels. But in a simple guitar, bass string tension at the bridge pulls the bridge and other string tensions are altered slightly, and some IMD must result. I'm getting impatient who seem to need a Doctoral thesis written on the meaning of "strongly nonlinear" in order that they not confuse it with "a little bit nonlinear". I don't know how linear the stop start air flow in organ pipes or trumpets might be, or in bows on violins, but surely they ain't perfectly linear, and some IMD products are produced. The word some admits any finite artifact. We would probably interpret it today as being any measurable artifact. Given that we can easily measure nonlinearities below 0.001 %... Arny suggests there are no non-linearities in musical instruments, and none in the air, or caused by the room, so its only the microphone of other electronics that can create it. Arny seriously hoped that people could distinguish between "strongly onlinear" and "less than 0.001%". I'm not talking about huge amounts as Arny think I am either. No use talking to Arny, one gets Kroogerated. I'm getting my stomach Turnered. |
#138
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pentode amplifiers
"Iain Churches" wrote in message
.fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) |
#139
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pentode amplifiers
"Andre Jute" wrote in message
ups.com On Nov 8, 3:23 pm, "Arny Krueger" wrote: "Iain Churches" wrote in message i.fi "Andre Jute" wrote in message ups.com... Dave wrote: "Andre Jute" wrote in message ps.com... The explanation is simple. Loop NFB causes artifacts of ever lower magnitude but higher order. Good example of majoring in the minors. Loop NFB drops nonlinearity by 20 dB or more. The equipment in question was not entirely free of higher order nonliner distortion, and the secondary effect being obsessed over here typically adds far less distortion than was already there.OTOH, the loop feedback drops all nonlinear distortion by 20 dB. The net higher order distortion is thus dramatically reduced. We're not talking about the net number, Krueger. We're talking about the effect of the composition of the residual distortion. Well that's *your* problem, Andre. The net number matters, because its the difference between 10% ("Strongly nonlinear') and 0.001%. |
#140
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pentode amplifiers
"Iain Churches" wrote in message
.fi "Patrick Turner" wrote in message ... Well here I have to agree that sonic differences in preamp tubes can be heard. Even when THD and IMD measures below 0.01%, a typical value where you have a line stage preamp with volume pot before a generic gain stage using a 6CG7. I have, with 4 other guys spent an afternoon tube rolling with 6CG7 samples. We agreed the NOS Seimans were best, then made in Oz Miniwatts, then Mullard, and then very much last were recent Sovtek versions. Sighted evaluation. :-( Nice to find that (unlike Arny) others also take the trouble to listen, and evaluate. Libel. To build something better in tubes would be a good project for Arny. It would also keep him away from RAT for a *very* long time :-)) I don't even have time to build SS amps - I just buy them. The tube amp which makes 0.08% at 50W will have smoothly decreasing THD as output voltage is reduced, so that at 5W, THD will be perhaps 0.03%, and at 0.5W its 0.01%, and utterly inaudible no matter what the harmonics are. Indeed. Any half-ways decent SS amp will have 0.05% at any power level that is a dB below clipping. Crossover distortion hasn't been a problem with good SS amps for at least 35 years - its just a red herring that people who circulate old wive's tales like to trot out to scale small boys. |
#141
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pentode amplifiers
"Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Iain |
#142
Posted to rec.audio.tubes
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pentode amplifiers
"Iain Churches" wrote in message
ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( |
#143
Posted to rec.audio.tubes
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pentode amplifiers
"Arny Krueger" wrote in message . .. "Iain Churches" wrote in message ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. And you did not learn anything? Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( You miss the point entirely. When the horns are playing mezzo-piano the effect is clearly audible. Refer to the full-score. Iain |
#144
Posted to rec.audio.tubes
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pentode amplifiers
"Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Patrick Turner" wrote in message ... Well here I have to agree that sonic differences in preamp tubes can be heard. Even when THD and IMD measures below 0.01%, a typical value where you have a line stage preamp with volume pot before a generic gain stage using a 6CG7. I have, with 4 other guys spent an afternoon tube rolling with 6CG7 samples. We agreed the NOS Seimans were best, then made in Oz Miniwatts, then Mullard, and then very much last were recent Sovtek versions. Sighted evaluation. :-( Certainly not in the documented Svetlana tests or the ones in which I was involved. Patrick can describe his own experiences. To build something better in tubes would be a good project for Arny. It would also keep him away from RAT for a *very* long time :-)) I don't even have time to build SS amps - I just buy them. But this is RAT, a tube audio hobby group concerned with tube-craft - building, evaluation, listening and enjoyment. Why do you come here to talk about SS amplifiers? I was hoping you would build a better tube amp than I have done, and then start a thread about its concept, the chassis construction, the topology, the choice of input and driver tubes, the output pair. the OPT, tube voicing, test bench results and listening tests etc. It is pretty easy just to ridicule the efforts of others and do nothing yourself. Perhaps such a project is beyond you? If so there are plenty of people here who would be pleased to guide you:-) At least you still have a very long way to go before you reach the skill level of your hero Pinky, who could predict the performance of a tube amplifier by looking at the schematic of another (totally different) amp by the same maker:-) Iain |
#145
Posted to rec.audio.tubes
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pentode amplifiers
"Iain Churches" wrote in message
news "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. And you did not learn anything? Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( You miss the point entirely. When the horns are playing mezzo-piano the effect is clearly audible. Refer to the full-score. Just because the horns are playing mezzo-piano doesn't mean that the level is insufficient to cause certain ears to be nonlinear. If the effect is independent of level, then show me a modern commercial digital recording that demonstrates the same effect. |
#146
Posted to rec.audio.tubes
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pentode amplifiers
"Iain Churches" wrote in message
.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Patrick Turner" wrote in message ... Well here I have to agree that sonic differences in preamp tubes can be heard. Even when THD and IMD measures below 0.01%, a typical value where you have a line stage preamp with volume pot before a generic gain stage using a 6CG7. I have, with 4 other guys spent an afternoon tube rolling with 6CG7 samples. We agreed the NOS Seimans were best, then made in Oz Miniwatts, then Mullard, and then very much last were recent Sovtek versions. Sighted evaluation. :-( Certainly not in the documented Svetlana tests or the ones in which I was involved. Patrick can describe his own experiences. To build something better in tubes would be a good project for Arny. It would also keep him away from RAT for a *very* long time :-)) I don't even have time to build SS amps - I just buy them. But this is RAT, a tube audio hobby group concerned with tube-craft - building, evaluation, listening and enjoyment. Why do you come here to talk about SS amplifiers? Oh come on Iain. I only mentioned SS amplifiers in passing. If you are that hypersensitive to the mere mention of SS amplifiers, how do you survive in the real world? |
#147
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pentode amplifiers
"Arny Krueger" wrote in message ... "Iain Churches" wrote in message news "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. And you did not learn anything? Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( You miss the point entirely. When the horns are playing mezzo-piano the effect is clearly audible. Refer to the full-score. Just because the horns are playing mezzo-piano doesn't mean that the level is insufficient to cause certain ears to be nonlinear. Arny. What the experiment illustrates is the acoustic IMD produced by four or in this case five French horns, even at low levels. If you cannot even be bothered to do the test, I don't see how you can be in a position to question the results. Iain |
#148
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pentode amplifiers
"Iain Churches" wrote in message
i.fi "Arny Krueger" wrote in message ... "Iain Churches" wrote in message news "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. And you did not learn anything? Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( You miss the point entirely. When the horns are playing mezzo-piano the effect is clearly audible. Refer to the full-score. Just because the horns are playing mezzo-piano doesn't mean that the level is insufficient to cause certain ears to be nonlinear. Arny. What the experiment illustrates is the acoustic IMD produced by four or in this case five French horns, even at low levels. If you cannot even be bothered to do the test, I don't see how you can be in a position to question the results. I don't have to do the test today Iain, because I recorded a bunch of French horns about this time last year. I stood right in front of them during rehearsal. No IM. |
#149
Posted to rec.audio.tubes
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pentode amplifiers
"Arny Krueger" wrote in message . .. "Iain Churches" wrote in message i.fi "Arny Krueger" wrote in message ... "Iain Churches" wrote in message news "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. And you did not learn anything? Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( You miss the point entirely. When the horns are playing mezzo-piano the effect is clearly audible. Refer to the full-score. Just because the horns are playing mezzo-piano doesn't mean that the level is insufficient to cause certain ears to be nonlinear. Arny. What the experiment illustrates is the acoustic IMD produced by four or in this case five French horns, even at low levels. If you cannot even be bothered to do the test, I don't see how you can be in a position to question the results. I don't have to do the test today Iain, because I recorded a bunch of French horns about this time last year. I stood right in front of them during rehearsal. No IM. A bunch? Are you sure they were French horns and not bananas? :-) The Frech horn is a left-handed rear-firing instrument. So you need to stand to the rear and to the right of the section (in the very place one would put a mic in a multi-mic orchestral set up) just as I mentioned initially. I had an e-mail from one of your fellow countrymen, a student from Berklee College, Sherman Oaks,LA, a woodwind player who has been following this thread, and also the discussion with Andre about aural perception. He was interested to try the experiment I recommended to you, and states also that he can hear what he calls "mid notes" (IMD) between two Bb clarinets, the first playing Eb and the second playing B natural, with softish reeds at low volume. I shall be interested to give this a listen next time I have the opportunity. Iain |
#150
Posted to rec.audio.tubes
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pentode amplifiers
"Iain Churches" wrote in message
i.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message i.fi "Arny Krueger" wrote in message ... "Iain Churches" wrote in message news "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. And you did not learn anything? Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( You miss the point entirely. When the horns are playing mezzo-piano the effect is clearly audible. Refer to the full-score. Just because the horns are playing mezzo-piano doesn't mean that the level is insufficient to cause certain ears to be nonlinear. Arny. What the experiment illustrates is the acoustic IMD produced by four or in this case five French horns, even at low levels. If you cannot even be bothered to do the test, I don't see how you can be in a position to question the results. I don't have to do the test today Iain, because I recorded a bunch of French horns about this time last year. I stood right in front of them during rehearsal. No IM. A bunch? Are you sure they were French horns and not bananas? :-) The Frech horn is a left-handed rear-firing instrument. So you need to stand to the rear and to the right of the section (in the very place one would put a mic in a multi-mic orchestral set up) just as I mentioned initially. I was there too. Still no problems. |
#151
Posted to rec.audio.tubes
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pentode amplifiers
"Arny Krueger" wrote in message . .. "Iain Churches" wrote in message i.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message i.fi "Arny Krueger" wrote in message ... "Iain Churches" wrote in message news "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message ti.fi "Arny Krueger" wrote in message . .. "Iain Churches" wrote in message .fi "Arny Krueger" wrote in message . .. John wrote: And then there is ordinary real music from instruments. Presumably a fair amount of IMD is included. Wrong, because in a live performance there is very little that mixes the whole acoustic output of the musicians into a single signal and then puts that single signal through a strongly nonlinear process. Arny, Try this experiment. Sit amongst an orchestra during rehearsals or recording. Place your chair at the back and to the right of the French horn section, where the microphone would be on a multi-mic setup. Four horns are good, five horns are better. Sibelius 5, Op 82 Eb is a perfect example. Then tell me there is no acoustic IMD. Cordially, Iain, as soon as you start signing your little tirades with something that fits like: "With utter disrespect for common sense", I might consider responding to them. ;-) I repeat my request for you to do the experiment. Been there, done that, the first time about 50 years ago, more or less. And you did not learn anything? Iain if you think you're being terribly clever by pointing out that if you overdrive your ears with excessively loud noises they become nonlinear, then you are even more arrogant and stupid than I used to think. :-( You miss the point entirely. When the horns are playing mezzo-piano the effect is clearly audible. Refer to the full-score. Just because the horns are playing mezzo-piano doesn't mean that the level is insufficient to cause certain ears to be nonlinear. Arny. What the experiment illustrates is the acoustic IMD produced by four or in this case five French horns, even at low levels. If you cannot even be bothered to do the test, I don't see how you can be in a position to question the results. I don't have to do the test today Iain, because I recorded a bunch of French horns about this time last year. I stood right in front of them during rehearsal. No IM. A bunch? Are you sure they were French horns and not bananas? :-) The Frech horn is a left-handed rear-firing instrument. So you need to stand to the rear and to the right of the section (in the very place one would put a mic in a multi-mic orchestral set up) just as I mentioned initially. I was there too. Still no problems. It is not a problem, just an interesting, widely-known phenomenon. Iain |
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