I worked in an engineering building where 90+ percent of the engineers were in the 20 to 35 year old group. Many walked around with white wires sticking out of their ears. I and maybe three others out of over 1000 technical people built tube stuff, and two of them built guitar amps.
I built a simple triode wired KT88 push pull amp of about 35 WPC. It had an unnamed control on the front marked only with the numbers 0-10. It applied more GNFB and simultaneously increased the gain such that the overall output level stayed relatively constant. I loaned that amp out to maybe 20 people over the course of more than a year, only asking people to play with the knob and tell me their favorite setting. I did this twice in two different Motorola electronics plants since I changed facilities in the middle of the test.
No accurate scientific data on what speakers, musical tastes or volume levels were taken, but the results were not what I would have predicted. Most of the respondents liked the extremes, with very few in the middle. I needed a mid level of feedback on that amp to keep my Yamaha NS-10M's in line.
Of those, the zero feedback people would be the crowd that eventually wanted their own tube amp. Some people bought an amp, but most people built their amps........This is how Tubelab got started, but that is a different story.
I built a simple triode wired KT88 push pull amp of about 35 WPC. It had an unnamed control on the front marked only with the numbers 0-10. It applied more GNFB and simultaneously increased the gain such that the overall output level stayed relatively constant. I loaned that amp out to maybe 20 people over the course of more than a year, only asking people to play with the knob and tell me their favorite setting. I did this twice in two different Motorola electronics plants since I changed facilities in the middle of the test.
No accurate scientific data on what speakers, musical tastes or volume levels were taken, but the results were not what I would have predicted. Most of the respondents liked the extremes, with very few in the middle. I needed a mid level of feedback on that amp to keep my Yamaha NS-10M's in line.
Of those, the zero feedback people would be the crowd that eventually wanted their own tube amp. Some people bought an amp, but most people built their amps........This is how Tubelab got started, but that is a different story.
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That sounds like Nelson Pass’s SIT amplifier with the knob on the front of it, where he asked people to play with it and report their favorite position. ( I don’t remember off the top of my head exactly what it was doing but it changed the overall relationship of the dominant distortion between 2h and 3h as well as it’s phase compared to the fundamental) The information gleaned from those amps helped shape the overall distortion spectra of the following amps across the Pass Labs lineup.
It's on the Stereophile website.
Here in Europe we have this thing called 'Google'- finds everything you want! You should get it too!
LMGTFY: The Carver Challenge | Stereophile.com
Jan
i like tubes, i am a tubehead......but i am open to the idea that solid state amps can be fun too....
after all there is no perfect amplifier......ever....otherwise, we would have stopped looking for new amps...
i get my kicks out of making amps more than listening to a finished one...
after all there is no perfect amplifier......ever....otherwise, we would have stopped looking for new amps...
i get my kicks out of making amps more than listening to a finished one...
watched Nelson's 2016 burning amp lecture, i remembered the difference between output mosfets with and without 0.47 ohm degeneration resistors,
one had higher 2H and low 3H without degeneration, with the resistor degenerations in the 2H got lower but the 3H got higher a bit.....so here you have a choice, if you can hear it...
Once more into the breach!
I feel that this is, perhaps, the most important topic regarding the furture of home music entertainment. I say, entertainment, because saying reproduction inevitably leads one to concluding that faithful reproduction of the signal is the ultimate goal of amplifier design. That, however, ignores whether the signal itself is conveying the sound of the sonic experience of the original event. Questioning whether the signal conveys the sound of the live session may, at first, seem an odd notion. However, there is an sort of implicit assumption that the signal has captured the heard experience of an live event. When, actually, it only captures the microphone's 'experience' at the live event. However, is something important lost or not properly/effectively captured by the microphone, and therefore, not conveyed by the signal? If so, then no matter how faithful the reproduction of the signal, the sonic experience cannot be reproduced.
I agree with Vladimir Lamm. The ear depends on a certain dynamic behavior of the sound in order to sound real or live. My conjecture is, that for whatever reason, that dynamic distortion behavior is not fully or properly conveyed by a typical signal. What many tube amplifiers, and some solid-state, may do is to artificailly add the missing behavior. I suspect that dynamic distortion behavior is the elephant in the listening room. So, while artificially added by some 'musical' sounding amplifiers, and therefore less faithful, the net result sounds more real/live to the human ear.
I feel that this is, perhaps, the most important topic regarding the furture of home music entertainment. I say, entertainment, because saying reproduction inevitably leads one to concluding that faithful reproduction of the signal is the ultimate goal of amplifier design. That, however, ignores whether the signal itself is conveying the sound of the sonic experience of the original event. Questioning whether the signal conveys the sound of the live session may, at first, seem an odd notion. However, there is an sort of implicit assumption that the signal has captured the heard experience of an live event. When, actually, it only captures the microphone's 'experience' at the live event. However, is something important lost or not properly/effectively captured by the microphone, and therefore, not conveyed by the signal? If so, then no matter how faithful the reproduction of the signal, the sonic experience cannot be reproduced.
I agree with Vladimir Lamm. The ear depends on a certain dynamic behavior of the sound in order to sound real or live. My conjecture is, that for whatever reason, that dynamic distortion behavior is not fully or properly conveyed by a typical signal. What many tube amplifiers, and some solid-state, may do is to artificailly add the missing behavior. I suspect that dynamic distortion behavior is the elephant in the listening room. So, while artificially added by some 'musical' sounding amplifiers, and therefore less faithful, the net result sounds more real/live to the human ear.
Nelson Pass put it correctly when he said, the amplifier business is entertainment business, i agree....
I am still unsure what "warm" or "tubey" is supposed to mean and how this is a good thing but when my idea is right then yeah, get whatever power opamp, route the input signal through a lossy capacitor (paper dielectric, steel can) and feed that to a 2 way speaker with an 85dB/W 8" midwoofer and some cloth dome tweeter and you'll have a reasonably priced system that will make everything sound pretty mellow and unoffensive.
Remember to mount said input cap visibly to the top of the amplifier for maximum effect.
Remember to mount said input cap visibly to the top of the amplifier for maximum effect.
The effects of what you call dynamic distortion are fully understood.
What it does is make the difference between loud and soft sounds, less. This means that soft sounds that were unaudible before can become audible, resulting in a sence of more low level detail. On top of that, it's not a linear thing, it actually changes with level. So loud sounds, like a snare drum, seem to have more impact.
So more impact and more low level detail can be very useful for the listening experience. I fact it is one of the most used tools in the box for sound engineers, they call it compression. Tape, vinyl and some recording studio equipment have audible amounts of it. So do some amps and other audio stuff.
There was an excellent "Compression" demonstration seminar put on at VSAC 2008, in Vancouver, Washington. They had the compressed and un-compressed music files on their laptop computer, but they did not have speakers and amplifiers to play it back (except on the laptop).
They asked me if I could provide some speakers and amplifiers for the listening demonstration. I provided a modest set of 2-way speakers, and low power single ended amplifiers for that. As far as I remember, most of the listeners went away with a conclusion: Compressed was Dead! Un-compressed was Live! Not a very scientific study, but I bet all who attended remembered the results they heard of what compression did to the same music selections.
They also had voltage/time oscillograms of portions of the compressed and uncompressed selections that they projected, so you could see the relative dynamic ranges, on the white board. Remember, for example, if the voltage is 4:1, the power is 16:1.
One reason they gave for doing compression was to make it sound better in a car that was going down the freeway at 60MPH, into a headwind. For any recording, there is a reason why it is modified, or not.
Tube_Lab,
Thanks for your writeup about the Adjustable NFB Carver Amp, and the listeners thereof.
They asked me if I could provide some speakers and amplifiers for the listening demonstration. I provided a modest set of 2-way speakers, and low power single ended amplifiers for that. As far as I remember, most of the listeners went away with a conclusion: Compressed was Dead! Un-compressed was Live! Not a very scientific study, but I bet all who attended remembered the results they heard of what compression did to the same music selections.
They also had voltage/time oscillograms of portions of the compressed and uncompressed selections that they projected, so you could see the relative dynamic ranges, on the white board. Remember, for example, if the voltage is 4:1, the power is 16:1.
One reason they gave for doing compression was to make it sound better in a car that was going down the freeway at 60MPH, into a headwind. For any recording, there is a reason why it is modified, or not.
Tube_Lab,
Thanks for your writeup about the Adjustable NFB Carver Amp, and the listeners thereof.
Finally! I do tubes because I can still see the parts. Not because I "think" they sound better.
Thank you. I get so tired of people describing tube sound as mushy, overly warm and distorted. That is how bad tube amps sound. Cheap, worn out or poorly designed amps may have those characteristics but not good ones. Even my simple DIY SE amp can make me jump when it goes from a silent portion of the recording to a voice. For decades I kept trying to listen to classical music but never could get into it. Live performances were great but listening at home was never enjoyable; until I built my tube amp.
There's compression and there's compression. It's easy to over do it. The loudness war is an example of how things can get out of control fast.
But there are no commercial recordings, that I know of, available that have no added compression or distortion on them. All the usual mics used in a recording studio add audible distortion. The only mics, that I know of, that don't add audible distortion are specialized noise measuring mics with very high voltage power supplies.
Bill Coltrane,
All mechanical systems have distortion. Microphones, Loudspeakers, Servo Systems, our Ears, etc. How much distortion is the question. And remember, "All Generalizations Have Exceptions". Oh, was that a Generalization?
And now I am so glad to know that No commercial recording was ever done without using compression, right? Whatever happened to some of the recording marketing group's claims? Oh, I was a Marketeer for 5 years.
I often look at oscilloscope time domain views. I often see clipping on the output from the CD player (no, not full scale DAC 1111...s and 0000...s), just some lack of care on the recording engineer's part. Distortion, indeed.
All mechanical systems have distortion. Microphones, Loudspeakers, Servo Systems, our Ears, etc. How much distortion is the question. And remember, "All Generalizations Have Exceptions". Oh, was that a Generalization?
And now I am so glad to know that No commercial recording was ever done without using compression, right? Whatever happened to some of the recording marketing group's claims? Oh, I was a Marketeer for 5 years.
I often look at oscilloscope time domain views. I often see clipping on the output from the CD player (no, not full scale DAC 1111...s and 0000...s), just some lack of care on the recording engineer's part. Distortion, indeed.
Has anybody on this forum ever heard a microphone that did not add audible distortion (but that is: not a specialized noise measuring mics with very high voltage power supplies)? I hope so. Let us know. Otherwise, I may have to only listen to live music; and give up on any recording and playback system. My enjoyment has been badly compromised.
The reason I sometimes discover clipping in the recording, is because I hear distortion, and then I trouble shoot it, only to find that it is in the recording, not my system. And yes, sometimes (often) my system distorts (turned up too high, to low of a frequency for my speakers, etc.).
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😀 You act like all audible distortion is bad, it's not. Proof is in every commercial audio recording.
Edit: As I've mentioned here before, audible distortion adds more low level detail and gives percussion more impact, if done right. That's why it's on every commercial audio recording. Embrace the distortion, it's a good thing.
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OK. Point understood.
No, I do not think all audible distortion is bad. Some distortion does not sound like normal or natural instruments; that often bugs me. But there are some distortion effects that I do like, like some recordings of Carmen McRae; or an upright bass when the string is pulled away from the neck and allowed to snap back to the neck; or a Michael Hedges recording that makes me think he is going to snap the string(s). But I would not like someone to do a recording of a Franz List trick, and break the piano.
And I do not like a lot of electric guitar fuzz recordings. But I do like the 1959 recording of Marty Robbins singing "Don't Worry Bout Me". The Fuzz Bass on that is wonderful (but the cause of that distortion is another story).
No, I do not think all audible distortion is bad. Some distortion does not sound like normal or natural instruments; that often bugs me. But there are some distortion effects that I do like, like some recordings of Carmen McRae; or an upright bass when the string is pulled away from the neck and allowed to snap back to the neck; or a Michael Hedges recording that makes me think he is going to snap the string(s). But I would not like someone to do a recording of a Franz List trick, and break the piano.
And I do not like a lot of electric guitar fuzz recordings. But I do like the 1959 recording of Marty Robbins singing "Don't Worry Bout Me". The Fuzz Bass on that is wonderful (but the cause of that distortion is another story).
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The thing that bothers me the most in most modern classical recordings is the thousands of edits. Your not listening to the recording of the artist on the cover, your listening to the mixing engineers.