What does it mean "SOUND"
Sound is perceived by our brain thru the ears, you should say: amplifiers do amplify the signal at input in the same exact way. At the output you'd find the same envelope with more amplitude. After trasduction from the speaker, the waves has to travel the air and then reach the ears, afterwards the brain generates an anticipation of the impulses generated by the ears to find if they respect the sequence of tones that is defined as music. If the expectation is satisfied, it's a musical sound.
Yes, without controlled test conditions and double-blind testing, our subjective experiences are extremely unreliable. There are days when the sight of a kitten moves you, and other days when you don't even notice it. The kitten hasn't changed, our state of mind has.
Years of experiments showed that most of it is THD and frequency response. If THD is low enough, and frequency response flat enough, the amp will have no "sound" of its own, i.e., it's a perfect amp. We're assuming basics such as the amplifier being kept out of clipping, the amp being stable, and the input signal being band-limited so that it doesn't contain any ultrasonic signals which might make the amp misbehave.
Conditions must be controlled for a valid comparison (for example, double-blind testing, loudness matched to within 0.1 dB for each amp, absolutely identical EQ for both amps, both amps switched into exactly the same speaker, et cetera.)
Simply walking into a room and listening to amp A, then amp B, is utterly useless, because all our subjective biases corrupt the result. It is well known, for example, that if you know that amp A is more expensive than amp B, and you can see which amp is switched in, that will immediately bias your perceptions, and the two amps will sound different to you.
That's not what decades of actual research and thousands of carefully controlled listening tests showed.
Since 1980 audio has mostly been in la-la land, based on subjective superstitious nonsense, and most of the actual science has been discarded by the supposed "golden ears" (who never have any objective hearing test data to back up their golden-eared claims.)
Basically, if it's about audio, unless it's found in a peer-reviewed scientific journal, disbelieve it; it's probably B.S.
-Gnobuddy
Whilst I accept most of what you say including the last paragraph there is no objective basis for claiming amps that achieve some level of distortion will all sound the same.
What if one is severely bandwidth limited, or has a skewed FR into real world loudspeakers due to poor design or high output impedance? The trouble with focusing on one ill defined metric is it ignores the multitude of other variables, and the actual constraints used in defining the metric. If you'd written all amplifiers with otherwise identical characteristics save their THD (at eg. 100/1kHz measured to 20kHz) I would accept that, but that's not what is written so I chipped in. I have no doubt the researchers in the 1960s will have controlled these other variables in their tests. Of course what was not open to them at that time was knowledge of the active and non-linear characteristic of auditory response and listening. Sadly underfunded now except in specific areas, a little effort in this 'soft science' arena would probably yield enough understanding to account for much of the golden eared wunderkinds enhanced hearing (where it is genuinely demonstrable).
What if one is severely bandwidth limited, or has a skewed FR into real world loudspeakers due to poor design or high output impedance? The trouble with focusing on one ill defined metric is it ignores the multitude of other variables, and the actual constraints used in defining the metric. If you'd written all amplifiers with otherwise identical characteristics save their THD (at eg. 100/1kHz measured to 20kHz) I would accept that, but that's not what is written so I chipped in. I have no doubt the researchers in the 1960s will have controlled these other variables in their tests. Of course what was not open to them at that time was knowledge of the active and non-linear characteristic of auditory response and listening. Sadly underfunded now except in specific areas, a little effort in this 'soft science' arena would probably yield enough understanding to account for much of the golden eared wunderkinds enhanced hearing (where it is genuinely demonstrable).
Nit-picking aside, I think we are essentially in agreement. Note that I wrote "most of it is THD and frequency response", which addresses both of your criticisms. I also mentioned some of the other conditions that need to be controlled.
Provided that level of distortion is well below the threshold of audibility (about 0.5%), and obvious other factors (already mentioned) are controlled, amps will have no sound of their own at all - they will be audibly transparent, essentially perfect, the "straight wire with gain" ideal audio amp.
Since amps that meet these conditions have no sound of their own, yes, they will all sound the same.
Such amps were challenging to build in the era of vacuum tubes or early semiconductor devices. That isn't the case any more, and now even cheap chip amps are frequently audibly perfect as long as you keep them out of clipping, and don't feed them out-of-band signals.
Now I'm off to buy some Mpingo discs, which apparently make everything sound better
: The Magic of Mpingo-Gnobuddy
I have been so lucky to get an old Audio Precision ATS-1 for nearly free
Do anyone know that unit?
Is an ATS-1 still usable?
The AST-1 has GPIB (IEEE-488.2), can I control it via an USB-GPIB and a program?
See post #14
LOL thanks, that does still not say anything about if anyone know the unit, I mean, have used the unit.
Or if it is still usable today with the today's amplifiers and there quality
Or if it can be controlled via USB-GPIB and what software
Hi dotneck335,
One thing I will say with conviction is that you can certainly hear differences between amplifiers that measure below 0.01%, forget about 0.1%! You may need to live with an amplifier for a few days to a week, but yes, you can hear a difference. Well, I should say that many could hear it, not everyone cares enough to pay attention and may therefore be happy with anything less than 1% distortion. We are lumping all types of distortion together of course.
All I can say is that today's instruments have been a massive aid in knowing what is going on and what kinds of things can cause distortion.
-Chris
At best you are creating a relational comparison without any standards based reference. Heck, no reference but the amp kept in a vault in France along with the Meter stick. All you really have is a conversation piece that would (maybe) be effective in identifying maybe the best amplifier that was dragged to the event. There is zero way to compare products without something that can be calibrated.
Actually, any modern Audio Precision, Keysight U8903x or the RTX-6001 are extremely powerful. The Keysight will reach 1.5 MHz (!) with that option. I would love one of these!! These analysers will all "see" below -120 dBu without any difficulty. Add the averaging power of DSP (which these all use) and you can average the noise (or grass) way down so you can easily see what is hidden underneath it all.
One thing I will say with conviction is that you can certainly hear differences between amplifiers that measure below 0.01%, forget about 0.1%! You may need to live with an amplifier for a few days to a week, but yes, you can hear a difference. Well, I should say that many could hear it, not everyone cares enough to pay attention and may therefore be happy with anything less than 1% distortion. We are lumping all types of distortion together of course.
All I can say is that today's instruments have been a massive aid in knowing what is going on and what kinds of things can cause distortion.
-Chris
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