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#81
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift: The executive summary
Phil Allison wrote: "Andre Jute" Dr Otala is a distinguished scholar and designer of highly rated audio gear. ** Completely false. Here is the man's CV. http://www.kauppakorkea.fi/tutu/FUTU...nglCVotala.htm " His specialities are Management of Change, Business Process Re-Engineering, International Competitivity, total Quality Management, total Quality Management, and Learning Organisations. " The amp designs attributed to him ( for marketing purposes) were the work of many people, unfortunately, none of them were competent audio designers. ....... Phil That's a pretty impressive CV Otala sports, Phil. But no, I'm not defending either Phil T's misinterpretations or even the points where he hit the mark. I never thought he had a case, but I wanted to see his argument in case there was something I missed or misunderstood when I first came across these matters about 12 years ago. In fact, my opinion has now moved on from the "amazing" in my post which set up this collection of threads to "incredible". I'm just kicking the usual diplomaed quarterwits in the teeth for being netbullies and netscum, and for disgracefully failing to explain why Phil is wrong. Andre Jute Visit Jute on Amps at http://members.lycos.co.uk/fiultra/ "wonderfully well written and reasoned information for the tube audio constructor" John Broskie TubeCAD & GlassWare "an unbelievably comprehensive web site containing vital gems of wisdom" Stuart Perry Hi-Fi News & Record Review THIS IS MY TEXT PHIL ALLISON IS REFERRING TO Andre Jute wrote: Phil wrote: We're not talking about "-30 degrees at 20 KHz," we're talking *dynamic* phase shifting, the kind that makes a Crown preamp bite your ears off, while testing at 0.0001% THD. Let's hear some more about this dynamic phase shift that pours a pint of vinegar into a Crown preamp. I'm not overimpressed with vanishign THD but this is an amazing explanation for why so many silicon amps, and not a few tube amps, sound like ****. Andre Jute Visit Jute on Amps at http://members.lycos.co.uk/fiultra/ "wonderfully well written and reasoned information for the tube audio constructor" John Broskie TubeCAD & GlassWare "an unbelievably comprehensive web site containing vital gems of wisdom" Stuart Perry Hi-Fi News & Record Review On the one side of this argument we have Dr Otala and Phil "Toob". Dr Otala is a distinguished scholar and designer of highly rated audio gear. Phil T is an earnest student who in the manner of earnest students occasionally overstates his case. On the other side of the argument we have Arny "I spoke in error" Krueger and Graham "Poopie" Stevenson. Arny Krueger assembles computers for a living and had a part in creating a now superceded and never very useful ABX test to determine which computer sound cards did the least damage to the sound; he pretends to be a recording engineer. Graham Stevenson's employment appears to be writing to the Usenet about politics and boasting about his self-proclaimed part in the design of the least well-reputed Neve deck; when that wears thin he brags about his education a generation ago. From the violent attacks "I spoke in error" Krueger and Poopie Stevenson have made on Phil T, one would be justified in concluding that these minor players and permanent losers claim Dr Otala is simply wrong. In fact, careful reading reveals that their entire argument is that components have improved so much in the intervening generation as to obviate Dr Otala's important point. The subtext of their manner of stating this weak case is that these two loud fools are smarter than Otala. It is not difficult for the rest of us to decide who in a crunch we will believe, the distinguished Dr Otala and a cross section of spec sheets of modern components showing the problem has moved on, or the hysterical screechings of the self-important "I spoke in error" Krueger and his limp sidekick Poopie Stevenson. This entire long thread has done little to illuminate my main question, so I put it again in different form in another thread. Andre Jute Our legislators managed to criminalize fox-hunting and smoking; when they will get off their collective fat arse and criminalize negative feedback? It is clearly consumed only by undesirables. |
#82
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Phil" wrote in message
The "almost" part comes from something I believe to be true, namely that the dynamic phase shifting and other possible abuses of signals 80 dB below the main signal in high feedback amps are *reduced* as the speed of the closed loop increases, This makes about as much sense as believing in the Easter Bunny. |
#83
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift: The executive summary
"Andre Jute" Dr Otala is a distinguished scholar and designer of highly rated audio gear. ** Completely false. Here is the man's CV. http://www.kauppakorkea.fi/tutu/FUTU...nglCVotala.htm " His specialities are Management of Change, Business Process Re-Engineering, International Competitivity, total Quality Management, total Quality Management, and Learning Organisations. " The amp designs attributed to him ( for marketing purposes) were the work of many people, unfortunately, none of them were competent audio designers. That's a pretty impressive CV Otala sports, Phil. ** It is a totally **apalling CV** - if the criterion is demonstrated, audio design expertise. Reads more like the CV for that internationally notorious audio charlatan / con artist - Dr Amar Bose. Otala is nothing but a pseudo-academic prick who did enormous harm with his erroneous bunk. I'm just kicking the usual diplomaed quarterwits in the teeth for being netbullies and netscum, and for disgracefully failing to explain why Phil is wrong. ** Phil T never supplied actual reasons for his wild assertions. Only when those reasons are supplied, in sufficient detail, can they possibly be refuted with facts. Unsupported assertions NEED NO REFUTATION - as nothing is holding then up. Quoting the absent expert is a popular debating cheat, as you must be well aware . Phil T went several stages beyond that, with blatantly fake quotes and alarming fallacies of his own invention. The man is clearly a mental case. If he were not such a conceited and malicious ASS - I might just feel sorry for him. ........ Phil |
#84
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Arny Krueger wrote:
"Phil" wrote in message The "almost" part comes from something I believe to be true, namely that the dynamic phase shifting and other possible abuses of signals 80 dB below the main signal in high feedback amps are *reduced* as the speed of the closed loop increases, This makes about as much sense as believing in the Easter Bunny. I am truly impressed at your complete, 100% level of dishonesty. I certainly hope anyone thinking about doing business with you takes a look at these threads, and sees you in action. Unless they're complete idiots, they will immediately realize that they need to do business with almost anyone else. Your statement above implies that you believe that higher speed devices have no advantage when it comes to feedback problems. Right. As always, you make a general criticism with no specifics, no references, no examples. You really are a one-note type of guy, aren't you? The same boring debating tactic, over, and over, and over again. Why don't you try to come up with a new form of criticism. It can still be useless, just make it different. Have you ever noticed that ALL the people that everyone admires have personalities that match their true selves like a glove? And did it ever occur to you that if you constantly treat others in ways that you cannot stand for others to treat you, that your personality does not match your true self (almost by definition)? People whom others admire, Arny, WORK ON THEIR CHARACTER, every day. That means, in case you're too stupid to get it, that they see to it that their actions toward others do not contradict how they wish others to treat them. And now you know why you have so few, if any, real friends, or at least, none worth having. Phil |
#85
Posted to rec.audio.tubes,rec.audio.opinion
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The awful truth of Kroofulness
Phil said: People whom others admire, Arny, WORK ON THEIR CHARACTER, every day. That means, in case you're too stupid to get it, that they see to it that their actions toward others do not contradict how they wish others to treat them. And now you know why you have so few, if any, real friends, or at least, none worth having. Irrelevant. Arnii is doing "God's work" on Usenet. Mr. ****'s "Usenet career" is his pride and joy, his life's achievement, his contribution to history. Obviously Phil you're jealous Phil of something you can never hope to equal Phil. -- "Christians have to ... work to make the world as loving, just, and supportive as is possible." A. Krooger, Aug. 2006 |
#86
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Phil" wrote in message
Arny Krueger wrote: "Phil" wrote in message The "almost" part comes from something I believe to be true, namely that the dynamic phase shifting and other possible abuses of signals 80 dB below the main signal in high feedback amps are *reduced* as the speed of the closed loop increases, This makes about as much sense as believing in the Easter Bunny. I am truly impressed at your complete, 100% level of dishonesty. Wrong, I'm being completely honesy about my feelings in this matter. |
#87
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
On Sun, 10 Sep 2006 13:13:05 GMT, Phil
wrote: This makes about as much sense as believing in the Easter Bunny. I am truly impressed at your complete, 100% level of dishonesty. I certainly hope anyone thinking about doing business with you takes a look at these threads, and sees you in action. Unless they're complete idiots, they will immediately realize that they need to do business with almost anyone else. Your statement above implies that you believe that higher speed devices have no advantage when it comes to feedback problems. Right. As always, you make a general criticism with no specifics, no references, no examples. You really are a one-note type of guy, aren't you? The same boring debating tactic, over, and over, and over again. Why don't you try to come up with a new form of criticism. It can still be useless, just make it different. Have you ever noticed that ALL the people that everyone admires have personalities that match their true selves like a glove? And did it ever occur to you that if you constantly treat others in ways that you cannot stand for others to treat you, that your personality does not match your true self (almost by definition)? People whom others admire, Arny, WORK ON THEIR CHARACTER, every day. That means, in case you're too stupid to get it, that they see to it that their actions toward others do not contradict how they wish others to treat them. And now you know why you have so few, if any, real friends, or at least, none worth having. Phil Wise words indeed, Phil, in every way. |
#88
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"paul packer" wrote in message
On Sun, 10 Sep 2006 13:13:05 GMT, Phil wrote: This makes about as much sense as believing in the Easter Bunny. I am truly impressed at your complete, 100% level of dishonesty. I certainly hope anyone thinking about doing business with you takes a look at these threads, and sees you in action. Unless they're complete idiots, they will immediately realize that they need to do business with almost anyone else. Your statement above implies that you believe that higher speed devices have no advantage when it comes to feedback problems. Right. As always, you make a general criticism with no specifics, no references, no examples. You really are a one-note type of guy, aren't you? The same boring debating tactic, over, and over, and over again. Why don't you try to come up with a new form of criticism. It can still be useless, just make it different. Have you ever noticed that ALL the people that everyone admires have personalities that match their true selves like a glove? And did it ever occur to you that if you constantly treat others in ways that you cannot stand for others to treat you, that your personality does not match your true self (almost by definition)? People whom others admire, Arny, WORK ON THEIR CHARACTER, every day. That means, in case you're too stupid to get it, that they see to it that their actions toward others do not contradict how they wish others to treat them. And now you know why you have so few, if any, real friends, or at least, none worth having. Wise words indeed, Phil, in every way. More evidence that Phil has one small strength - he has studied and understood how to apply the life of P. T. Barnum. |
#89
Posted to rec.audio.tubes
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Dynamic phase shift
"Chris Hornbeck" wrote in
message Right. Maybe a better way for the OP to approach this is to begin with a true step input (a signal with *zero* risetime) beginning at very small levels, then increasing levels until slewing is observed. Which may never happen. There will be a threshold level where even an amplifier without feedback will slew. Not necessarily. It is entirely feasible to build an amp that never limits due to slew rate limiting. Just limit its bandwidth. There will also be a threshold where an amplifier *with* feedback will slew. Again, not necessarily. If there are no other differences between the amplifiers, these two levels will be *the same*. Or, non-existent. For the second case, as you've said, clipping may already have occurred. In a modern amplifier this *must* be the case; it's too easy to get right. Agreed. The issue of slew-limiting in amplifiers arose because amplifiers with feedback must sacrifice some slewing ability to the altar of stability. Again, not necessarily. Classic, circa-70s slew rate limiting came about because of a dynamic range limitation that was hidden until appropriate tests and analysis were done. Feedback didn't cause it, it only made it more apparent if it existed. (Many, many qualifiers need be inserted here; whole 'nother can 'a worms. But we're talking about a thirty year gone issue.) Agreed. In the early dark days of semiconductor amplifiers, compromises for stability were so demanding as to damage signal in the passband at ordinary levels. AFAIK, slew rate limiting was not a universal problem, even in the early days. And, FWIW, the highest rise-time possible in a band-limited signal is a square wave of just under bandpass frequency run through the bandpass filter. IOW, a sinewave of the highest frequency within the bandpass. Agreed. This is 101 stuff and the OP really should bone up as possible. Also, there's *zero, none, nada* correlation between feedback and anything remotely approaching "dynamic phase shift". Agreed. Phil is just stringing together words that he doesn't seem to understand. The term itself is snake oil of the highest grade. I'll argue against whether it is really high grade. ;-) |
#90
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Phil wrote: Arny Krueger wrote: "Ian Iveson" wrote in message k Phil wrote: Well, remember, the maximum slew rate found in audio signals is much greater than what a theoretical 20 KHz signal is going to supply, Yes and no, Phil. Take 20kHz at full amplitude to define the required slew rate. Add another identical signal, in phase. You now have twice the slew rate, as you think. But the signal is also twice full amplitude, so it is not comparable. To make it comparable, you must reduce it to full amplitude. In so doing, you halve the slew rate, returning it to its original value. Hence adding these signals together doesn't alter the slew rate, as long as the total signal remains within the defined full amplitude. Agreed. Does this logic hold for the sum of a full amplitude 20kHz and some other, lower frequency? Intuitively yes, to me. A bit of simple trig would confirm. The math supports your intuition. What about smaller signals? Well, they will never have a higher slew rate than the 20kHz at full amplitude, surely? As long as they are band-limited to 20 KHz. The agenda that seems to be hidden from Phil relates to the vast improvement in the bandwidth of power transistors over the years. In the 60s and early, large power devices used in power amps usually ran out of gas below 1 MHz. Today for about the last 20 years, parts that beat that by a factor of 10 or more are plentiful and inexpensive. It is not hidden from me, and I have mentioned the same thing somewhere in this thread, but since I was never claiming (as implied by PA) that modern amps produce TIM, it is *almost* irrelevant. The "almost" part comes from something I believe to be true, namely that the dynamic phase shifting and other possible abuses of signals 80 dB below the main signal in high feedback amps are *reduced* as the speed of the closed loop increases, something that has indeed improved greatly not just since the 60's, but since Otala wrote his papers in the 70's. However, "improved" does not equal "perfect," or even "adequate," and since any SS amp short of a Krell (if that) still is sonically challenged -- *especially* when it comes to the really low-level information -- compared to the best low or zero feedback triode amps, one has to suspect that it is a problem that has only been reduced, not eliminated. Given that there is room for improvement, it would be helpful if we could figure out what is wrong. Here you have not only my theory as to what is wrong (based mainly on Otala's paper) -- problems caused by the higher feedback of SS amps, among other SS problems -- but also a basic outline for a possible solution. By all means, if you are aware of someone else who has pursued my line of reasoning, and proved with actual experiments that it is useless, post the information here (but don't waste our time with TIM papers, since that is *not* what either I or Otala am/were talking about). I will then publicly state, here, that you were RIGHT, and that both my theory about one of the diseases of SS amps, and therefore my proposed cures, were WRONG, and we can all move on in an attempt to figure out the true reasons why all but the best SS amps suck when compared to even very good tube amps, let alone the best ones. Pragmatic Phil I am still waiting for someone to define just what is the problem of dynamic phase shift in amplifiers. Is it a phase shift of high frequencies caused by AMPLITUDE changes of lower frequencies rather like the "doppler" effect in a speaker where the frequency of a 10kHz wave will slightly change 50 times a second if there is a 50Hz tone also present? I see no evidence of any doppler effects in an amplifier. So just what is the problem we need to consider or fix???? Patrick Turner. |
#91
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Patrick Turner" wrote in message
.. So just what is the problem we need to consider or fix???? Finding a cork for Phil so as to stop the flow of weirdness. |
#92
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Phil Allison" said:
"Phil" toob-headman " You know, I have terminal cancer, and maybe heart problems (waiting for the results), " ** Don't be so modest with your medical boasting - you also have terminal autism and bi-polar disorder. " .... but I would rather be me, and dead soon, " ** Then we all have something to look forward to. Now THIS is cute! Impressed Phil ** To save everyone further grief - drop dead now. ........ Phil A close DIY friend of mine recently died of cancer, I witnessed the process closely. I sincerely hope you won't ever have to face such a situation, or even suffer from such a disease yourself, Phil. It's horrible. -- "Due knot trussed yore spell chequer two fined awl miss steaks." |
#93
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Phil wrote: Joseph Meditz wrote: Phil Allison wrote: "Andre Jute" Let's hear some more about this dynamic phase shift that pours a pint of vinegar into a Crown preamp. ** Dynamic phase shifting of audio signals is all around us, all the time. The fact that cones move, continuously alters the origin and hence time of arrival of any higher frequencies being simultaneously radiated. Phase shift in degrees ( at any point in time) is simply 360 x cone excursion / wavelength of the high frequency. Some call this effect " Doppler Distortion" - a misnomer. Hi Phil, Here's my take on this interesting topic. I say that this is precisely an acoustical frequency modulator. If you input two sinusoids, one low and one high, then the spectrum of the upper one will be spread out about its center. And the greater the amplitude of the bass signal, the greater the modulation index. From the modulation index one could predict what the side bands will look like. I found the term "Doppler Distortion" helpful. The situation here is not exactly like the sound of the horn of a train passing a station. Rather, it is the sound of the horn of a crazy train oscillating back and forth across the station. Joe So, is an acoustical frequency modulator some type of equipment? It does sound like what I *think* Otala is saying happens when a feedback amp gets hold of two sinusoids, as you say. What is a good methos for seeing this spread? Someone suggested (oh hell, I think it was Arny; a USEFUL idea???) using a spectrum analyzer, maybe it's that simple? By the way, I *think* PA is wrong, in a way. It may be that a cone moving forward at a bass frequency can Doppler shift a high frequency signal, but doesn't the mic that recorded the two frequncies to begin with invert this process, thereby cancelling it out? Just thinking ... Phil Hi Phil, I tried to respond to your email, but it bounced back twice. Anyway, it looks as though your questions have been answered. Regarding cancellation, I think that, even if you could use the very same loudspeaker that generates the sound as a microphone to pick up the sound, it would still not cancel the effect of the moving cone because the sound reaching the "microphone" will be weaker than the transmitted signal. Hence it would not move the "microphone" cone as much, and its resulting rate of change of phase will be less than that of the transmitting speaker. Joe |
#94
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Sander deWaal wrote:
"Phil Allison" said: "Phil" toob-headman " You know, I have terminal cancer, and maybe heart problems (waiting for the results), " ** Don't be so modest with your medical boasting - you also have terminal autism and bi-polar disorder. " .... but I would rather be me, and dead soon, " ** Then we all have something to look forward to. Now THIS is cute! Impressed Phil ** To save everyone further grief - drop dead now. ........ Phil A close DIY friend of mine recently died of cancer, I witnessed the process closely. I sincerely hope you won't ever have to face such a situation, or even suffer from such a disease yourself, Phil. It's horrible. Thank you for the hopeful wishes! I am trying to find ways to at least delay that horrible ending, although f-NHL (follicular non-hidgkin's lymphoma) has, I believe, an ending that is better, on average, than some of the more ruthless cancers. The main drawback to the indolent lymphomas in general is that they are 100% incurable, although f-NHL folks have an average life expectency of 7 years (I've had mine 6-1/2), so at least you usually get some time. Phil |
#95
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Patrick Turner wrote:
Phil wrote: Arny Krueger wrote: "Ian Iveson" wrote in message k Phil wrote: Well, remember, the maximum slew rate found in audio signals is much greater than what a theoretical 20 KHz signal is going to supply, Yes and no, Phil. Take 20kHz at full amplitude to define the required slew rate. Add another identical signal, in phase. You now have twice the slew rate, as you think. But the signal is also twice full amplitude, so it is not comparable. To make it comparable, you must reduce it to full amplitude. In so doing, you halve the slew rate, returning it to its original value. Hence adding these signals together doesn't alter the slew rate, as long as the total signal remains within the defined full amplitude. Agreed. Does this logic hold for the sum of a full amplitude 20kHz and some other, lower frequency? Intuitively yes, to me. A bit of simple trig would confirm. The math supports your intuition. What about smaller signals? Well, they will never have a higher slew rate than the 20kHz at full amplitude, surely? As long as they are band-limited to 20 KHz. The agenda that seems to be hidden from Phil relates to the vast improvement in the bandwidth of power transistors over the years. In the 60s and early, large power devices used in power amps usually ran out of gas below 1 MHz. Today for about the last 20 years, parts that beat that by a factor of 10 or more are plentiful and inexpensive. It is not hidden from me, and I have mentioned the same thing somewhere in this thread, but since I was never claiming (as implied by PA) that modern amps produce TIM, it is *almost* irrelevant. The "almost" part comes from something I believe to be true, namely that the dynamic phase shifting and other possible abuses of signals 80 dB below the main signal in high feedback amps are *reduced* as the speed of the closed loop increases, something that has indeed improved greatly not just since the 60's, but since Otala wrote his papers in the 70's. However, "improved" does not equal "perfect," or even "adequate," and since any SS amp short of a Krell (if that) still is sonically challenged -- *especially* when it comes to the really low-level information -- compared to the best low or zero feedback triode amps, one has to suspect that it is a problem that has only been reduced, not eliminated. Given that there is room for improvement, it would be helpful if we could figure out what is wrong. Here you have not only my theory as to what is wrong (based mainly on Otala's paper) -- problems caused by the higher feedback of SS amps, among other SS problems -- but also a basic outline for a possible solution. By all means, if you are aware of someone else who has pursued my line of reasoning, and proved with actual experiments that it is useless, post the information here (but don't waste our time with TIM papers, since that is *not* what either I or Otala am/were talking about). I will then publicly state, here, that you were RIGHT, and that both my theory about one of the diseases of SS amps, and therefore my proposed cures, were WRONG, and we can all move on in an attempt to figure out the true reasons why all but the best SS amps suck when compared to even very good tube amps, let alone the best ones. Pragmatic Phil I am still waiting for someone to define just what is the problem of dynamic phase shift in amplifiers. Is it a phase shift of high frequencies caused by AMPLITUDE changes of lower frequencies rather like the "doppler" effect in a speaker where the frequency of a 10kHz wave will slightly change 50 times a second if there is a 50Hz tone also present? I see no evidence of any doppler effects in an amplifier. So just what is the problem we need to consider or fix???? Patrick Turner. Patrick, in some ways I am completely with you, and in some ways not. I don't have, nor have I been able to find (so far), Otala's paper on the conversion by feedback of amplitude distortion into phase distortion, although I may be able to obtain Greiner's (sp?) paper. For obvious reasons, it would be nice to have it/them. However, although many here have pointed out that TIM is a non-issue, that is not what Otala was talking about in this paper. Remember, his investigation into the fundamental nature of feedback came after a BS session with several other people in The Audio Critic (Stew Hegeman, Bruce Zadye, Mitch Cotter, etc.), in which the basic nature of feedback was extensively discussed. I have seen no references, other than the one by Greiner, that *might* suggest there is even a limitation, let alone a flaw, in Otala's mathematical proof regarding feedback. According to Aczel, he incorporated ways of reducing feedback's negative effects in his design for Harmon-Kardon's Citation XX, so if I/we could find a paper by Otala on the Citation XX, even that might provide the answers! On the other hand, I *think* you'll agree that high feedback amps very often are sonically challenged, so a mechanism for problems does exist. Therefore, even if we figure out exactly what feedback screws up, we still have to figure out how to avoid those problems. This might be easier if we could find the papers, but even the somewhat cryptic description, "converts amplitude distortion into phase distortion" *may* give us the information we need, assuming this description is correct. To partially answer your question, therefore, the problem is probably not one of amplitude, but amplitude *distortions*. Unfortunately, I believe this refers to any "correction" of the signal by the feedback loop, which would certainly appear to include the excess gain of the open loop that is normally used to obtain the feedback, meaning that high feedback amps constantly convert the excess gain of the open loop, even if the amplifying devices are perfectly linear, into *some* type of phase distortion. The human ear no doubt has a threshold below which it cannot detect phase distortion, so for a while you truly get "free lunch," an improvement in amplitude distortions, with no detectable phase distortions. This is probably also aided by using very fast devices. In that BS session in TAC, they said the following: [p 22, Cotter] "A loudspeaker contains a system that stores energy ... we store energy in a loudspeaker and ... we release it backwards [into the power amp]. [Otala] We measured about 50% of the energy coming back during the next 50 milliseconds. [Cotter] Which is a hell of a long time compared to the dimensions of most rooms -- or the dimensions of time for most musically important events. The basic problem is, what happens to that energy?" They then addressed the issue of what happens to the energy from the loudspeaker in the Bell Labs triode amps: [p 23, Cotter] "But the thing that's interesting about these systems is not only did they share this very low time dispersal, very low delay property, but in effect, you had this terribly inefficient plate resistance of the tube, which in the case of the 300B was a very linear resistor ... what you had was an amplifier that could be envisioned analytically as essentially a current source, shunted by a fairly fat resistor, a fairly power-grabbing resistor, in parallel with whatever the load was." They also said (in various places) that a feedback amp must handle the energy from the speaker by generating an error signal and putting it back through the amp. It must correct the amplitude distortions generated from the energy coming back from the speaker by using the feedback loop, since there is no low impedance plate resistor, like you find in a triode, to absorb this energy. Otala then commented -- and this is before his paper on feedback -- about a feedback problem he had seen in an amp: [p 23 Otala] I recently discovered a unit which did not produce TIM at all, although it was described as producing lots of TIM-like distortion. The effect was very simple. It was namely so, that since the poles of the transfer function just moved up and down with current excitation, so when used with a large amount of feedback, its phase margin was going up and down. The frequency response varied, depending on the signal level. Therefore it created very much this kind of time effects, phase modulation or time modulation, whatever you wish. But here the important thing is, once again, that effects like TIM, or this phase margin shifting or whatever, are not related to the basic concept of feedback, but a very poor application of the principles." My impression is that after his more thorough, mathematical analysis later, Otala found that actually, "this phase margin shifting," is indeed related to the basic concept of feedback. And when you add both the energy from the speaker and the (possibly) constant error of the open loop, you have a lot of amplitude distortions that can be converted into phase distortions in a feedback amp, assuming that phase shifting IS a problem. And although the "what else can it be" form of reasoning is not my favorite, since it is so unreliable, in this case, if feedback "Doesn't either have problems Otala said it does!", as some here want to believe, then what else is there that could possibly explain the fact that high feedback amps DO SUCK? It turns out that my initial thoughts on an alternative method of feedback, one which only applies an error signal when there is actually an error -- meaning that the high gain, which is moved to the feedback loop, is no longer seen as an error -- is NOT equivalent to Black's feedforward scheme, although it's very, very close. It is in fact equivalent to the "Active-Error Feedback" described by J. R. MacDonald in "Proc. IRE," vol 43, pp 808-813, July 1955, and for that matter several other references that were printed both before and after MacDonald's. Phil |
#96
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Phil said:
Sander deWaal wrote: "Phil Allison" said: "Phil" toob-headman wrote: " You know, I have terminal cancer, and maybe heart problems (waiting for the results), " ** Don't be so modest with your medical boasting - you also have terminal autism and bi-polar disorder. " .... but I would rather be me, and dead soon, " ** Then we all have something to look forward to. Now THIS is cute! Impressed Phil ** To save everyone further grief - drop dead now. ........ Phil A close DIY friend of mine recently died of cancer, I witnessed the process closely. I sincerely hope you won't ever have to face such a situation, or even suffer from such a disease yourself, Phil. It's horrible. Thank you for the hopeful wishes! I am trying to find ways to at least delay that horrible ending, although f-NHL (follicular non-hidgkin's lymphoma) has, I believe, an ending that is better, on average, than some of the more ruthless cancers. The main drawback to the indolent lymphomas in general is that they are 100% incurable, although f-NHL folks have an average life expectency of 7 years (I've had mine 6-1/2), so at least you usually get some time. Ummm........I was addressing Phil Allison, not you. I'm sorry if it looked that way. Phil A.'s quoting abilities leave somewhat to be desired, hence the confusion. FWIW, my friend died within 2 months of the dicovery. In the process, they amputated his arm and part of his shoulder, since the cancer was in there. A very aggressive form of cancer it was. It already spread across his chest, and he chose not to be radiation-treated, but to spend his last says with his family. At 35 years, he left a mother and 2 kids behind. -- "Due knot trussed yore spell chequer two fined awl miss steaks." |
#97
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Dynamic phase shift
On Mon, 11 Sep 2006 21:50:29 GMT, Phil
wrote: [p 23 Otala] I recently discovered a unit which did not produce TIM at all, although it was described as producing lots of TIM-like distortion. The effect was very simple. It was namely so, that since the poles of the transfer function just moved up and down with current excitation, so when used with a large amount of feedback, its phase margin was going up and down. The frequency response varied, depending on the signal level. Therefore it created very much this kind of time effects, phase modulation or time modulation, whatever you wish. But here the important thing is, once again, that effects like TIM, or this phase margin shifting or whatever, are not related to the basic concept of feedback, but a very poor application of the principles." Ah, I'm beginning to see the source of the confusion. Otala is describing an extremely non-linear amplifier, an abberation. There are some monolythic op-amps made this way deliberately, to optimize some other characteristics. This shouldn't, however, be conflated with a conventional linear amplifier. Whole different critter. My impression is that after his more thorough, mathematical analysis later, Otala found that actually, "this phase margin shifting," is indeed related to the basic concept of feedback. It's certainly not evident from the quotation above. And I'd be really astonished if true; he's not a quack. The rest of the stuff quoted is marginal to bogus. All good fortune, Chris Hornbeck "You have to have an idea of what you are going to do, but it should be a vague idea." - Pablo Picasso, 1946 |
#98
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
On Sun, 10 Sep 2006 13:13:05 GMT, Phil
wrote: in case you're too stupid to get it He's too stupid to get it. |
#99
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Dynamic phase shift
On Tue, 12 Sep 2006 00:01:28 +0200, Sander deWaal
wrote: Thank you for the hopeful wishes! I am trying to find ways to at least delay that horrible ending, although f-NHL (follicular non-hidgkin's lymphoma) has, I believe, an ending that is better, on average, than some of the more ruthless cancers. The main drawback to the indolent lymphomas in general is that they are 100% incurable, although f-NHL folks have an average life expectency of 7 years (I've had mine 6-1/2), so at least you usually get some time. Ummm........I was addressing Phil Allison, not you. I'm sorry if it looked that way. That's a relief, Sander. I thought you'd suddenly lost all sensitivity! |
#100
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Dynamic phase shift
paul packer wrote:
On Sun, 10 Sep 2006 13:13:05 GMT, Phil wrote: in case you're too stupid to get it He's too stupid to get it. So it would appear! That's all right, I'm sure he thinks he's much smarter and more clever than you and me put together. He's a winner! The fact that he forget to check which race he is winning, versus the race he should be winning, will never seriously occur to him. Phil |
#101
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Dynamic phase shift
Chris Hornbeck wrote:
On Mon, 11 Sep 2006 21:50:29 GMT, Phil wrote: [p 23 Otala] I recently discovered a unit which did not produce TIM at all, although it was described as producing lots of TIM-like distortion. The effect was very simple. It was namely so, that since the poles of the transfer function just moved up and down with current excitation, so when used with a large amount of feedback, its phase margin was going up and down. The frequency response varied, depending on the signal level. Therefore it created very much this kind of time effects, phase modulation or time modulation, whatever you wish. But here the important thing is, once again, that effects like TIM, or this phase margin shifting or whatever, are not related to the basic concept of feedback, but a very poor application of the principles." Ah, I'm beginning to see the source of the confusion. Otala is describing an extremely non-linear amplifier, an abberation. There are some monolythic op-amps made this way deliberately, to optimize some other characteristics. This shouldn't, however, be conflated with a conventional linear amplifier. Whole different critter. My impression is that after his more thorough, mathematical analysis later, Otala found that actually, "this phase margin shifting," is indeed related to the basic concept of feedback. It's certainly not evident from the quotation above. And I'd be really astonished if true; he's not a quack. The rest of the stuff quoted is marginal to bogus. All good fortune, Chris Hornbeck "You have to have an idea of what you are going to do, but it should be a vague idea." - Pablo Picasso, 1946 Could be ... of course, then we really are back to square one as to what the heck does cause high feedback amps, meaning the linear amps, to sound so bad. Maybe it's actually the fact that along with the high feedback that came with solid state, we used "devices with silicon capacitances," instead of "devices with vacuum capacitances," to obtain the error signal, thereby polluting the signal with garbage from the silicon capacitors. My *guess*, however, is that feedback itself is causing a problem, and I still hope to see the papers for and against the idea of feedback converting amplitude into phase distortion before I give up on the idea. Phil |
#102
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Sander deWaal wrote:
Phil said: Sander deWaal wrote: "Phil Allison" said: "Phil" toob-headman wrote: " You know, I have terminal cancer, and maybe heart problems (waiting for the results), " ** Don't be so modest with your medical boasting - you also have terminal autism and bi-polar disorder. " .... but I would rather be me, and dead soon, " ** Then we all have something to look forward to. Now THIS is cute! Impressed Phil ** To save everyone further grief - drop dead now. ........ Phil A close DIY friend of mine recently died of cancer, I witnessed the process closely. I sincerely hope you won't ever have to face such a situation, or even suffer from such a disease yourself, Phil. It's horrible. Thank you for the hopeful wishes! I am trying to find ways to at least delay that horrible ending, although f-NHL (follicular non-hidgkin's lymphoma) has, I believe, an ending that is better, on average, than some of the more ruthless cancers. The main drawback to the indolent lymphomas in general is that they are 100% incurable, although f-NHL folks have an average life expectency of 7 years (I've had mine 6-1/2), so at least you usually get some time. Ummm........I was addressing Phil Allison, not you. I'm sorry if it looked that way. Phil A.'s quoting abilities leave somewhat to be desired, hence the confusion. FWIW, my friend died within 2 months of the dicovery. In the process, they amputated his arm and part of his shoulder, since the cancer was in there. A very aggressive form of cancer it was. It already spread across his chest, and he chose not to be radiation-treated, but to spend his last says with his family. At 35 years, he left a mother and 2 kids behind. Oops! He so needs to change his name ... The Real Phil |
#103
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Dynamic phase shift
On Tue, 12 Sep 2006 00:57:40 GMT, Phil
wrote: Could be ... of course, then we really are back to square one as to what the heck does cause high feedback amps, meaning the linear amps, to sound so bad. Well, this part is really a stretch for most, including me. "So bad"? What does this even mean? Maybe it's actually the fact that along with the high feedback that came with solid state, we used "devices with silicon capacitances," instead of "devices with vacuum capacitances," to obtain the error signal, thereby polluting the signal with garbage from the silicon capacitors. The "error signal" in linear feedback is just a notion; no such thing exists. Output signal is fed back to an input terminal and compared *within the amplifier* to input signal. There is no error signal in ordinary linear feedback. This holds true independent of device construction and method of employment. There's only input and output. My *guess*, however, is that feedback itself is causing a problem, and I still hope to see the papers for and against the idea of feedback converting amplitude into phase distortion before I give up on the idea. I'll get Otala's original paper out to ya tomorrow morning, and it might provide a little historical framework. Please beware of stuff like _The Audio Critic_; it's whack. All good fortune, Chris Hornbeck "You have to have an idea of what you are going to do, but it should be a vague idea." - Pablo Picasso, 1946 |
#104
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Dynamic phase shift
On Tue, 12 Sep 2006 00:50:13 GMT, Phil
wrote: paul packer wrote: On Sun, 10 Sep 2006 13:13:05 GMT, Phil wrote: in case you're too stupid to get it He's too stupid to get it. So it would appear! That's all right, I'm sure he thinks he's much smarter and more clever than you and me put together. He's a winner! The fact that he forget to check which race he is winning, versus the race he should be winning, will never seriously occur to him. Phil It might now. Then again.... |
#105
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Dynamic phase shift
Chris Hornbeck wrote: On Tue, 12 Sep 2006 00:57:40 GMT, Phil wrote: Could be ... of course, then we really are back to square one as to what the heck does cause high feedback amps, meaning the linear amps, to sound so bad. Well, this part is really a stretch for most, including me. "So bad"? What does this even mean? Maybe it's actually the fact that along with the high feedback that came with solid state, we used "devices with silicon capacitances," instead of "devices with vacuum capacitances," to obtain the error signal, thereby polluting the signal with garbage from the silicon capacitors. The "error signal" in linear feedback is just a notion; no such thing exists. Output signal is fed back to an input terminal and compared *within the amplifier* to input signal. The input signal is compared to a fraction of the output signal by means of a single tube acting as a differential amp or a pair of differential tubes in an LTP. Only the difference between the signal fed back is amplified by the amp. This difference signal will contain the non-linearities, ie artifacts not present in the input signal and be amplified to oppose their own production, so the error signal which is defined as the signal within the amp after the summing/comparing process does contain non linearities. There is no error signal in ordinary linear feedback. This holds true independent of device construction and method of employment. There's only input and output. But what is ordinary linear feedback? no feedback path is perfectly always linear. There are always TWO inputs and ONE output in the simplest NFB amplifier, unless its a balanced input and output and then there may be more input/output ports. My *guess*, however, is that feedback itself is causing a problem, and I still hope to see the papers for and against the idea of feedback converting amplitude into phase distortion before I give up on the idea. I'll get Otala's original paper out to ya tomorrow morning, and it might provide a little historical framework. Please beware of stuff like _The Audio Critic_; it's whack. All good fortune, Chris Hornbeck "You have to have an idea of what you are going to do, but it should be a vague idea." - Pablo Picasso, 1946 I'm ignoring most pots on dynamic phase shift because nobody has bothered to define what the **** it actually is. So like a flock of chooks you can all cluck onwards to cluckdom which is largely free of any wisdom about dynamic phase shift IMHO. Patrick Turner. |
#106
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Dynamic phase shift
Patrick Turner wrote: I'm ignoring most posts on dynamic phase shift because nobody has bothered to define what the **** it actually is. Don't be ridiculous, Patrick. You can't define something which never existed and, if it did, is confined to temporary importance (and excused by) the fact that transistors back a generation ago were even more dire than they are now. In these emotive surroundings, with the silicon brigade taking the slightest slur on their fave as an attack on their mother's honour, it is perhaps not surprising that it took 105 messages to decide ... what I knew when I mailed the first post in the thread, and signalled loud and clear by "amazing". So like a flock of chooks you can all cluck onwards to cluckdom which is largely free of any wisdom about dynamic phase shift IMHO. Hey, the silicon slime has rights too. In particular, they insist on their right to beat up on an earnest innocent. See, it "proves" they are "engineers". Patrick Turner. "Incredible" hardly describes this thread. And it leaves us with no answers about why excessive NFB sounds like ****. Andre Jute "You can wait 'til more important things get taken care of." -- Ned Carlson of TubeZone to a Customer who already waited *14 weeks* for his tubes. |
#107
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Phil" wrote in message
On the other hand, I *think* you'll agree that high feedback amps very often are sonically challenged, so a mechanism for problems does exist. Addressing a tube advocate, this is both a sure thing and pretty much meaningless. It's like asking a member of the New York Yankees baseball team whether or not they like baseball. Therefore, even if we figure out exactly what feedback screws up, we still have to figure out how to avoid those problems. Figuring out what feedback screws up (in well-designed systems) is very difficult. No matter what all the trolls and tubies say, NASA is still going to use feedback control systems to send man into space. Nuclear power plants are still going use loop feedback no matter what Phil or Pat agree on. No matter how many OCD-ridden audiophiles buy into this weirdness, just about every piece of audio gear in the world, including virtually all of the production gear, is going to based on the effectiveness of loop feedback. And here is the irony, just about every recording that Phil and Pat have ever played on an audio system was produced using high-feedback amplfiers. Phil and Pat can agree on what they like, but just about every extant piece of vinyl they've ever played was made using a cutter head with loop feedback, and/or driven by power amps with loop feedback. This might be easier if we could find the papers, but even the somewhat cryptic description, "converts amplitude distortion into phase distortion" *may* give us the information we need, assuming this description is correct. Contrary to popular belief among our local paranoids, phase distortion can be readily measured if you have the right equipment. The margins for audibility or inaudibility of phase distortrion are known to people who study psychoacoustics. The world is full of audio gear that simply has no audible phase distortion, their heavy use of loop feedback notwithstanding. To partially answer your question, therefore, the problem is probably not one of amplitude, but amplitude *distortions*. Yet another one of those things that is readily measured, and which the ear has well-known tolerance. Unfortunately, I believe this refers to any "correction" of the signal by the feedback loop, which would certainly appear to include the excess gain of the open loop that is normally used to obtain the feedback, meaning that high feedback amps constantly convert the excess gain of the open loop, even if the amplifying devices are perfectly linear, into *some* type of phase distortion. High feedback amps do not necessarily do any such thing. This one of those things that needs a sighted listening test to "find". Hence all of Phil's phobias and false claims about bias-controlled listening tests. The human ear no doubt has a threshold below which it cannot detect phase distortion, so for a while you truly get "free lunch," an improvement in amplitude distortions, with no detectable phase distortions. And these thresholds are far higher than the levels of any such distortions in a wide range of conventially-designed audio gear. BTW much of this audio gear is present in the signal chain used to produce the recordings that Phil uses when he psych's himself up to *hear* them. Odd that he can't hear them, eh? |
#108
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Dynamic phase shift
"Phil" wrote in message
Could be ... of course, then we really are back to square one as to what the heck does cause high feedback amps, meaning the linear amps, to sound so bad. Listener bias. That's why DBT's don't confirm the existence of this so-called problem. |
#109
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Dynamic phase shift
"Arny Krueger" And here is the irony, just about every recording that Phil and Pat have ever played on an audio system was produced using high-feedback amplfiers. Phil and Pat can agree on what they like, but just about every extant piece of vinyl they've ever played was made using a cutter head with loop feedback, and/or driven by power amps with loop feedback. ** The famous Crown DC300A model was popular as a stereo LP cutter head amp. It's got a primitive uA739 dual op-amp at the input. It's got oodles of loop NFB. Mediocre slew rate, by some estimates. Contemporary alternatives were all inferior. LOL ! ......... Phil |
#110
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Phil Allison" wrote in message
"Arny Krueger" And here is the irony, just about every recording that Phil and Pat have ever played on an audio system was produced using high-feedback amplfiers. Phil and Pat can agree on what they like, but just about every extant piece of vinyl they've ever played was made using a cutter head with loop feedback, and/or driven by power amps with loop feedback. ** The famous Crown DC300A model was popular as a stereo LP cutter head amp. It's got a primitive uA739 dual op-amp at the input. It's got oodles of loop NFB. Mediocre slew rate, by some estimates. Contemporary alternatives were all inferior. LOL ! The predecessor tubed amps were often MacIntosh 300-watters that had plenty of local and loop feedback, as well. It's been a long time since I've seen the schematic for a MC300, but I believe that it followed the pattern of the 275. http://www.drtube.com |
#111
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Arny Krueger" "Phil Allison" And here is the irony, just about every recording that Phil and Pat have ever played on an audio system was produced using high-feedback amplfiers. Phil and Pat can agree on what they like, but just about every extant piece of vinyl they've ever played was made using a cutter head with loop feedback, and/or driven by power amps with loop feedback. ** The famous Crown DC300A model was popular as a stereo LP cutter head amp. It's got a primitive uA739 dual op-amp at the input. It's got oodles of loop NFB. Mediocre slew rate, by some estimates. Contemporary alternatives were all inferior. LOL ! The predecessor tubed amps were often MacIntosh 300-watters that had plenty of local and loop feedback, as well. It's been a long time since I've seen the schematic for a MC300, but I believe that it followed the pattern of the 275. http://www.drtube.com ** Tube amps are just so compromised by that damn great lump of iron hanging off the output. You would not believe the massive phase shift these boat anchors exhibit at both ends of the audio band. Totally prevents using a **decent amount** of loop feedback or the whole amp becomes HORRIBLY unstable. ........ Phil |
#112
Posted to rec.audio.tubes
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Dynamic phase shift
Andre Jute wrote: Patrick Turner wrote: I'm ignoring most posts on dynamic phase shift because nobody has bothered to define what the **** it actually is. Don't be ridiculous, Patrick. You can't define something which never existed and, if it did, is confined to temporary importance (and excused by) the fact that transistors back a generation ago were even more dire than they are now. In these emotive surroundings, with the silicon brigade taking the slightest slur on their fave as an attack on their mother's honour, it is perhaps not surprising that it took 105 messages to decide ... what I knew when I mailed the first post in the thread, and signalled loud and clear by "amazing". So like a flock of chooks you can all cluck onwards to cluckdom which is largely free of any wisdom about dynamic phase shift IMHO. Hey, the silicon slime has rights too. In particular, they insist on their right to beat up on an earnest innocent. See, it "proves" they are "engineers". Patrick Turner. "Incredible" hardly describes this thread. And it leaves us with no answers about why excessive NFB sounds like ****. Andre Jute "You can wait 'til more important things get taken care of." -- Ned Carlson of TubeZone to a Customer who already waited *14 weeks* for his tubes. Some things go better with NFB. This week I had the irksome job for a day and a half to re-engineer a 1965 Phillips "Music Theatre" concoction of gram with ceramic cart and truly awful SS AM radio. Half but not all the transistors were germanium. Some had become so noisy that all the applied NFB couldn't cure it at all. I replaced all the germanium except the outputs which have survived OK and of course the bipolar silicon types in the two stage preamp and driver stage of the power amps had more gain so hence more applied NFB. I re-did the attrocious circuitry by Phillips; and if anyone deserves to be hung, drawn and quartered for giving solid state a terrible reputation, it has to be the ****ed up thinking of the guys who worked in companies like Phillips ( and many of the other companies ) at that time. The idea of a flat response, absense of do-das and simplicity is totally absent and their efforts sounded far worse than the tube gear that the SS had begun to replace. Even the AM radio tuner which is a module the size of a matchbox with 3 IF single tuned coils at 3 slightly different frequencies is a ******* of the thing to tune well by ear and gives no better AF bandwidth than the critically double tuned IFTs in a tube set, with switchable selectrivity for wide bw for locals, and low distortion due to wide dynamic range of the tubes. Solid state really was NO Improvement where it should have been in a radio had the designers used the right sort of double tuned IFTs but these were deemed too expensive to make and deploy. It's possible to make an exceptional radio with all SS but the human temptation to dumb everything down by arsoles in Phillips was triumph of gross mediocrity. The power amps are complementary pair germanium AD161 and AD162 coupled via 1,000 uF to the speakers. One rail of +27V is used and one driver NPN transistor and one PNP silicon input transistor is used. About 8 watts or as much as a 300B is available to the listener. Such a simple amp. And after replacing the ge driver transistor with a BD139, the gain went up hugely and distortion went low and bandwidth was from 30Hz to 800kHz, ( yes, 800kHz ). I tamed the bw with passive cap at the input rather than have a massive amount of C across the FB resistor from the output to Q1 emitter. I altered a few other C values to get the LF pole down from the initial 70Hz and to stop leak through from the preamp to power amp driver via the common rail filtering. I lost count of the faults in the engineering. The high impedance volume control with built in variable loudness networks had a terrible effect on the sound. The tone controls were anything but flat when in the flat position. Bass and treble rolled off before they should but were peaked badly. All the choices of compensation all over the circuits and evidence of silly *******s applying stupid silly pet theories about audio abounded, and THIS was what went a long way to give SS a rotten name, rather than the actual use of silicon or even the worse germanium itself. But once rewiring was completed the preamp amd power amps were sounding acceptable as long as the source wasn't the radio within the set or the TT and ceramic cart. In this case the cart and the radio determine the crumminess of the sound with the typical brashy hashy sandpapery top end so typical of budget SS **** of the 1960s and 70s; basically it is lots of IMD in the sources. 1/2 the cart does not work and I have to replace the cart from a place in Holland if the client chooses that path but I reckon any budget modern TT with built in magnetic phono amp using FB around an op-amp will sound better than the original ceramic cart and high impedance feed to the preamp, and the gord-knows-what downforce of such a cart on the records. If I can talk the client into chucking out the Phillips 1965 idea of what a TT should have been then the whole set will begin to actually sound reasonable rather than remain faulty but nevertheless a heck of a lot better than what it was when it came home from the shop in 1965. For 40 years this **** of a **** box has been filling someone's lounge with music that was ghastly and yet these ppl happily put up with it and wanted a repair rather than want to retire the crap to a dumpster bin where a very large proportion of early SS gear belongs. And not necessarily because of the silicon itself, but because of the severe limitations of the mental capacities of the company design department. What a bunch of nerds they truly were!!!!! I drive a 1986 Ford Laser with the original AM/FM radio supplied by Ford when motor car companies began to fit radios to cars they sold as a standard item. The car radio provided by Ford I have is another ode to the crappiness of SS ****ological inventiveness of would be nerds who must have been the next generation of such like after the first lot who gained employment under false pretences at Phillips and other companies 20 years before....... Meanwhile I see you think that dynamic phase shift of part or all of the signal content by amplitude changes to part or all of the signal does not exist because of some reason why it should not be able to exist. Fair enough, and if something like doppler distortions did occur in a power or preamp you'd think someone would have spotted it by now, and written reams about it in concise easy to undertsand terms. Meanwhile, my expereince at building NEW SS power amps using quite large amounts of NFB has never proved to me that high NFB are ALWAYS bad sounding, and I have on occasions demonstrated to gathered ppl on musical evenings that a high NFB SS amp could sound identical, or at least just as well as a tube amp with mild NFB. However some of the budget Creeks and Cambridge amps were quite awful as well as a range of other amps and receivers I have repaired over the years, and often I have worked on a few SS amps and had them running as perfectly as i could in the technical sense and thought not bad until I switched to something with bottles again and then heard my brain's sigh of relief.... So my own humble explanation about SS gear I have made which doesn't sound to bad despite all the bagfuls of NFB is that I made it with some regard to power supply quality and rail regulation of input stages rather than rely on NFB to reduce the noise as well as the THD and IMD and Rout. The SS power amps I have made could all actually be tested without the global NFB connected, so that full power of 30Vrms into the load could be examined with only 2 mV of input, and without the output signal being a mass of noise and poor bandwidth like many SS amps with their global NFB disconnected. The schematics of several SS amps all with varying amounts of NFB are explained at my website. I will say that class A SS amps simply don't need much NFB, and need no more than a pentode amp which must have at least 20dB to reduce its Rout to acceptable and usable levels. Everyone should know that triode amps don't necessarily need any NFB because of the local NFB within the triode and the resulting low Ra compared to any load driven. So if anyone wanted to make a simple PP class A SS amp they could do worse than have a complementary pair of emitter followers with darlington bjts or source follower mosfets and a linear drive amp using the usual class A ziclai pnp/npn array of two transistors set up to have excessive dynamic range compared to what is actually used. I'll still prefer tubes. Patrick Turner. |
#113
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Phil Allison" wrote in message ... : : : ** Tube amps are just so compromised by that damn great lump of iron hanging : off the output. : : You would not believe the massive phase shift these boat anchors exhibit at : both ends of the audio band. : : Totally prevents using a **decent amount** of loop feedback or the whole : amp becomes HORRIBLY unstable. : : ....... Phil : i'd call that a massive generalisation. exibit A sowter U 061, leakage inductance 86 dB below inductance, - 0.5 dB 10Hz 42 kHz controlled hf roll off from 100 kHz 0.05 % THD at 100W, 1kHz, 0.5 % at 22Hz 100W can you give us the ^massive^ numbers ? Rudy |
#114
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
Phil Allison wrote: "Arny Krueger" "Phil Allison" And here is the irony, just about every recording that Phil and Pat have ever played on an audio system was produced using high-feedback amplfiers. Phil and Pat can agree on what they like, but just about every extant piece of vinyl they've ever played was made using a cutter head with loop feedback, and/or driven by power amps with loop feedback. ** The famous Crown DC300A model was popular as a stereo LP cutter head amp. It's got a primitive uA739 dual op-amp at the input. It's got oodles of loop NFB. Mediocre slew rate, by some estimates. Contemporary alternatives were all inferior. LOL ! The predecessor tubed amps were often MacIntosh 300-watters that had plenty of local and loop feedback, as well. It's been a long time since I've seen the schematic for a MC300, but I believe that it followed the pattern of the 275. http://www.drtube.com ** Tube amps are just so compromised by that damn great lump of iron hanging off the output. You would not believe the massive phase shift these boat anchors exhibit at both ends of the audio band. Totally prevents using a **decent amount** of loop feedback or the whole amp becomes HORRIBLY unstable. ....... Phil Phil, I do beg to differ. The OPT when it is well made can be a superb coupling device over a bandwidth which extends from 15Hz to 300kHz at full power and from 3Hz to 300kHz at low power used for average listening. I have wound plenty of wide BW OPTs. Because the amps work with so much class A more than a total of 16dB of local and global NFB is not needed. Quad II is an example of adequate NFB and they are stable even though the OPT is a toy compared to what might have been made if Mr Walker and the guys surrounding him had seen fit to produce all those years ago. The problem isn't with the iron, its with the guys who design the gear, and the limitations imposed by bean counters. McIntosh have a fair amount of local NFB in their output stages and then apply much additional NFB globally; EAR509 is another amp which does a similar thing to make a class B amp perform well technically. The McI amps were renowned for their low thd and Rout and stablity. Whether or not they sound terrible is something I leave the audiophiles to argue about, but after listening to music through a McI powered system I cannot agree they sound awful. For the doubters about McI and high NFB, they can be arranged to run in class A and with less NFB and internal gain, and who is to say they'd be worse sounding then? And with such a mod they'd even be more stable than they are already... Patrick Turner. |
#115
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Ruud Broens" wrote in message
"Phil Allison" wrote in message ... ** Tube amps are just so compromised by that damn great lump of iron hanging off the output. You would not believe the massive phase shift these boat anchors exhibit at both ends of the audio band. Totally prevents using a **decent amount** of loop feedback or the whole amp becomes HORRIBLY unstable. ....... Phil i'd call that a massive generalisation. exibit A sowter U 061, leakage inductance 86 dB below inductance, - 0.5 dB 10Hz 42 kHz controlled hf roll off from 100 kHz 0.05 % THD at 100W, 1kHz, 0.5 % at 22Hz 100W can you give us the ^massive^ numbers ? You gave us a good one: "0.5 % at 22Hz 100W" ....and that's just the output transformer. It doesn't include the thermionic noise and distortion generator(s) that go with it. |
#116
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Arny Krueger" wrote in message . .. : "Ruud Broens" wrote in message : : "Phil Allison" wrote in message : ... : : : ** Tube amps are just so compromised by that damn great : lump of iron hanging off the output. : : You would not believe the massive phase shift these boat : anchors exhibit at both ends of the audio band. : : Totally prevents using a **decent amount** of loop : feedback or the whole amp becomes HORRIBLY unstable. : : ....... Phil : : i'd call that a massive generalisation. : exibit A sowter U 061, : leakage inductance 86 dB below inductance, : - 0.5 dB 10Hz 42 kHz : controlled hf roll off from 100 kHz : 0.05 % THD at 100W, 1kHz, 0.5 % at 22Hz 100W : : can you give us the ^massive^ numbers ? : : You gave us a good one: : : "0.5 % at 22Hz 100W" : : ...and that's just the output transformer. It doesn't include the thermionic : noise and distortion generator(s) that go with it. : Ahh, Arny likes numbers, eh ? OK, bet you a 1000000 dollars, your speakers won't even come near 0.5 % with a 100 W input at 22 Hz.... 10 % would be a more like it ~just your speakers we're talking about~ so, if you're obsessed with being right, why not get much, much better speakers hehe R. (or use mfb) |
#117
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Ruud Broens" wrote in message
"Arny Krueger" wrote in message . .. "Ruud Broens" wrote in message "Phil Allison" wrote in message ... ** Tube amps are just so compromised by that damn great lump of iron hanging off the output. You would not believe the massive phase shift these boat anchors exhibit at both ends of the audio band. Totally prevents using a **decent amount** of loop feedback or the whole amp becomes HORRIBLY unstable. ....... Phil i'd call that a massive generalisation. exibit A sowter U 061, leakage inductance 86 dB below inductance, - 0.5 dB 10Hz 42 kHz controlled hf roll off from 100 kHz 0.05 % THD at 100W, 1kHz, 0.5 % at 22Hz 100W can you give us the ^massive^ numbers ? You gave us a good one: "0.5 % at 22Hz 100W" ...and that's just the output transformer. It doesn't include the thermionic noise and distortion generator(s) that go with it. Ahh, Arny likes numbers, eh ? Hmm, another guy who likes to externalize rather than take responsbility for issues that he has raised. Ruud, you're the guy who brought these numbers up, now stand behind them or quit. OK, bet you a 1000000 dollars, your speakers won't even come near 0.5 % with a 100 W input at 22 Hz.... 10 % would be a more like it ~just your speakers we're talking about~ Hmm, tubed equipment - what you buy to match the quality of the other worst part of your audio system. so, if you're obsessed with being right, why not get much, much better speakers As if speakers were all that there is to listen to. As if we buy stereo equipment to match the weakest link in our systems. |
#118
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Arny Krueger" wrote in message . .. : "Ruud Broens" wrote in message : : ** Tube amps are just so compromised by that damn great : lump of iron hanging off the output. : : You would not believe the massive phase shift these : boat anchors exhibit at both ends of the audio band. : : Totally prevents using a **decent amount** of loop : feedback or the whole amp becomes HORRIBLY unstable. : : ....... Phil : : i'd call that a massive generalisation. : exibit A sowter U 061, : leakage inductance 86 dB below inductance, : - 0.5 dB 10Hz 42 kHz : controlled hf roll off from 100 kHz : 0.05 % THD at 100W, 1kHz, 0.5 % at 22Hz 100W : : can you give us the ^massive^ numbers ? : : You gave us a good one: : : "0.5 % at 22Hz 100W" : : ...and that's just the output transformer. It doesn't : include the thermionic noise and distortion generator(s) : that go with it. : : Ahh, Arny likes numbers, eh ? : : Hmm, another guy who likes to externalize rather than take responsbility : for issues that he has raised. : : Ruud, you're the guy who brought these numbers up, now stand behind them or : quit. uhmm, right, the issue i raised being, no such thing as *massive* faults necessarily connected with OT's - raised & not been refuted as far as i can c : : OK, bet you a 1000000 dollars, your speakers won't even : come near 0.5 % with a 100 W input at 22 Hz.... : 10 % would be a more like it : ~just your speakers we're talking about~ : : Hmm, tubed equipment - what you buy to match the quality of the other worst : part of your audio system. hmm, dodging the issue would be an understatement here, eh ? : : so, if you're obsessed with being right, : why not get much, much better speakers : : As if speakers were all that there is to listen to. : true but you gotta start somewhere (or work on your personality : As if we buy stereo equipment to match the weakest link in our systems. : : ?no secret door |
#119
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Patrick Turner" ** Tube amps are just so compromised by that damn great lump of iron hanging off the output. You would not believe the massive phase shift these boat anchors exhibit at both ends of the audio band. Totally prevents using a **decent amount** of loop feedback or the whole amp becomes HORRIBLY unstable. Phil, I do beg to differ. ** Like the true ****head you are. Because the amps work with so much class A more than a total of 16dB of local and global NFB is not needed. ** 16 dB of loop NFB is all that can be applied. At mid band frequencies. Backs up what I said completely. ........ Phil |
#120
Posted to rec.audio.tubes,rec.audio.opinion
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Dynamic phase shift
"Ruud Broens" : : ** Tube amps are just so compromised by that damn great lump of iron hanging : off the output. : : You would not believe the massive phase shift these boat anchors exhibit at : both ends of the audio band. : : Totally prevents using a **decent amount** of loop feedback or the whole : amp becomes HORRIBLY unstable. : : i'd call that a massive generalisation. ** I'd call YOU a massive ****WIT !!! exibit A sowter U 061, leakage inductance 86 dB below inductance, - 0.5 dB 10Hz 42 kHz controlled hf roll off from 100 kHz 0.05 % THD at 100W, 1kHz, 0.5 % at 22Hz 100W can you give us the ^massive^ numbers ? ** Where are the * phase shift * numbers - ****wit ?? Lets see them for various load conditions too. Even the best tube amp designs have only 20 dB of loop NFB. ........ Phil |
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