I have to object. An amplifier that delivers a signal on the output that are indistinguishable from the signal on the input (as judged by a controlled blind listening test) is worthy of the title "accurate amplifier".
If you want to compensate for problems with your room or the recoprding engineers choice of microphones and their placement in the recording room/hall you are of course free to do so though.
The interaction between power amps and speakers makes this a bit more complicated of course and the (voltage) amp with the best linearity and lowest output impedance is not necessarily the one giving the best end results (technically speaking) with a given load (speaker) attached to its outputs.
The YBA, is a leach light.. Nothing wrong with that concept.
I use my own adaption of that kind of design... If you look around the forum I have even posted a picture or two of my take on that circuit.
BUT I also made a stand alone OPS with a gain of one, this could work with some kind of NON feed back Voltage stage.
With this combination I think feedback is used where its really needed as a control interface to the speaker, but not used where it's not needed (to create voltage gain) in order to have good distortion performance
I use my own adaption of that kind of design... If you look around the forum I have even posted a picture or two of my take on that circuit.
BUT I also made a stand alone OPS with a gain of one, this could work with some kind of NON feed back Voltage stage.
With this combination I think feedback is used where its really needed as a control interface to the speaker, but not used where it's not needed (to create voltage gain) in order to have good distortion performance
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I think it's a mistake to state that "tube amps sound wonderful with horrific levels at THD?".
There are all sorts of tube amps with performance levels/characteristics all over the map. Putting them in one group makes no sense.
I've certaily heard lower distortion SS amps side by side with respected slightly higher distortion tube amps feeling the SS amp sounding more "wonderful".
Tube amps with higher levels of distortion typically can sound good with easy program material (voice + solo instrument for example) but try that with a busy rock song or complex symphonic material. Listen to the signal before and after the amp and you'll probably learn that the amp is indeed acting as an effect box with very different results on different program material.
Very difficult being objective about the subjective........
Some of the best SETs are up around 1% THD at listening levels.
Hugh
Some of the best SETs are up around 1% THD at listening levels.
Hugh
Some of the preferred SETs are up around 1% THD at listening levels. 😱
By definition, if they are around 1%, they are not the best ....
Jan
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Yes and no. You can sort listening test data in various way. That's being done in all sorts of human testing. Be it perception (in audio engineering for example) or medicine.
Which means? And please define "best".. ;-)
Why does this have to be a fight between right and wrong. I think this could be a good thread about how to use feedback in sensible way, rather than is feed back good or bad... why do we need fractions..?? this is not politics.
It's like I know better than you, or mine is bigger than yours. (it probably is)
I hope that those playing around with this know better than most that there's not one single truth, it's an endless quest of bending something not straight into something close to straight.
There's No correct answer and No correct way of measuring and ranking the results. What is good in one respect may fail miserably in an other. An endless series of compromises.
It's like I know better than you, or mine is bigger than yours. (it probably is)
I hope that those playing around with this know better than most that there's not one single truth, it's an endless quest of bending something not straight into something close to straight.
There's No correct answer and No correct way of measuring and ranking the results. What is good in one respect may fail miserably in an other. An endless series of compromises.
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Although I am sure Hugh started this as a light hearted stirring it's interesting to see that people are as confused now about GNFB as they were in 1980. So this is a constant in the world of audio.
As Jan said very well preferences are exactly that and no one has an issue with them as long as you don't claim they are 'better' or 'more accurate'. Linn owners will not agree with me 🙂
As Jan said very well preferences are exactly that and no one has an issue with them as long as you don't claim they are 'better' or 'more accurate'. Linn owners will not agree with me 🙂
It's a paradox, but in my experience the amps that give the least satisfaction for users are expensive "technically correct" amps. Two things that are most commonly used to achieve technical correctness, VFA and high feedback factors, especially together, on average, sound worst. People often buy expensive amp of that kind and are surprised with the sound that does not satisfy them. I've seen many such people for whom listening to music is torture and frustration. Some of them avoid to admit that the money is thrown away and some simply curse HiFi as "the biggest fraud" ever. Many of them think that the sound is bad but since the spec says that distortion is 0,0000...%, it must be that something is wrong with them! It's necessary to free ourselves from dogmas of any kind. One of the dogmas is that global negative feedback is universal tool that always gives the best possible objective result which automatically means the best possible sound.
I think it terrifying that we still measure steady state one tone distortion....as our foremost qualifying parameter.
When did it become a fight and stop being a good thread?
Answer to which question?
Of course there are correct ways of measuring electronics and also ranking results.
The most widespread dogma in this debate I would say is that GNF sounds bad, period.
It's not true but this myth flourish in some audio circles.
I'm not familiar with "steady state one tone distortion....as our foremost qualifying parameter".
That said, if you know what to look for there's often a lot in a single sine analysis.
Just as a carpenter does not only bring a hammer to work, you use the tools necessary to find answers to the questions you have.
Nothing wrong with 0,000..% distortion.
We can not talk about accurate without reference. And audio measuring is not just THD at one frequency.
In my experiment, I change amplifier's compensation to get different slew rate. And slew rate does matter.
I found different topology sound different, although THD and slew rate almost same. I really want to know why they sound differently. IMD? Harmonic profile? S/N ratio? PSRR?
I think some people buy an amplifier to find sound that they like, not which accurate.
I take exception to that. I don't.
My hunch is that it is done so often because 1) it is relatively easy to do with a $ 100 sound card, a PC and limited knowledge, and b) it is a comfortable single number.
Professionals have moved on beyond that decades ago.
Jan
Some examples, preferably with the speakers being driven. As many have said other factors in design are audible...