Since on your own words, you don t design for electrical
comparative measurements, all is left is to listen but then,
how do you know that an amplifier sound good if you don t
compare it with other ones ?....
The way I operate in development is to have two complete versions of an amplifer. I'll compare the amp with the latest mod against the unmodified amp - but this comparison isn't done double blind. If I prefer the modded amp, I'll apply the mod to the other amp and then move on to thinking about the next mod.
Well, that s a method that can be subject to some psychological
biaising since one will forcibly wants his latter design to be better
than the former...
Excellent technique. I have it down "pat" 🙂 I have 2 pair of my AX , GX , whatever.... I make the modification on just one pair and keep the "baseline" design to compare to. I can do a "swap" of the voltage stage in 1 minute flat , so what I heard last is still very "fresh" in the mind. Using the same exact current stage for all the voltage stages allows for a very objective judgement of just the input/voltage stage under test.
For initial tests , a small 2 device OP stage is used (PB60) , this allows one to run the "snot" out of the voltage board to avoid a more dangerous situation at higher power levels.
OS
Sure, it easily can. So to follow this route impartially, the designer must be self-aware enough to not want the mod to be an improvement. I do agree - if the designer has a belief in the mod, it will potentially impair his/her ability to listen impartially.
OTOH, you can design with THD solely in mind and somehow deal with the poor correlation between good sound and low THD?
What exactly is the correlation, Wahab, can you describe it usefully to me?
Hugh
What exactly is the correlation, Wahab, can you describe it usefully to me?
Hugh
Is Wahab on record here as saying there is a correlation? If so, I'd appreciate a heads up on where.🙂
Seeing as this question appears a little pointed (by being directed in particular at Wahab), has something Wahab said hit a raw nerve?
Abrax,
No raw nerve, just curious, but perhaps we should wait for Wahab to answer..... it was not directed at you!
It's not pointed, but my thoughts are that if we design for utterly clean sound, THD is probably relevant, but if we design for anything else (which could be euphonic sound, the tubey kind) then the jury is out. It might be possible to design for a particularly harmonic profile, too.
Wahab advocates measurement all the way through, which is fine as far as it goes, but I'm concerned about the customer, who only ever assesses by ear and appears often to come up with different conclusions from those which would follow from very low measured distortion.
The usual subjective v. objective stuff, you know how it is....
Hugh
No raw nerve, just curious, but perhaps we should wait for Wahab to answer..... it was not directed at you!
It's not pointed, but my thoughts are that if we design for utterly clean sound, THD is probably relevant, but if we design for anything else (which could be euphonic sound, the tubey kind) then the jury is out. It might be possible to design for a particularly harmonic profile, too.
Wahab advocates measurement all the way through, which is fine as far as it goes, but I'm concerned about the customer, who only ever assesses by ear and appears often to come up with different conclusions from those which would follow from very low measured distortion.
The usual subjective v. objective stuff, you know how it is....
Hugh
When I first read D. Selfs book I was enthralled. (Ill admit it was the first audio amp book I read and that helped ). I was impressed by the objectivism and still think there is little room for subjectivism (some room but not much) in a technical subject such as this. Heres my reason again, ( I apoligize to those who have already read similar posts I have submitted).
If you design an amp to suit a large number of peoples (best case, to suit yourself, worst case) subjective impressions, the design will evolve to "sound good" to those people. It will not evolve to be what I believe is the goal of an amp, uncolored sound (straight wire with gain). To reproduce the sound exactly as it was mastered (good or bad). Why? As I have learned from this forum, audiophiles like there sound colored (actually most people do) and this leads to disagreement. If its not colored its usually labeled "sterile" or "clinical". People like certain types of distortion: $200k tube amps with over 1% THD, Neve consoles from th 60s and 70s which run the signal thru dozens of transformers. Changing opamps in designs that are optimized for one type. Need I go on?
Just because one amp has a wider sound stage or deeper bass than another dosnt mean its better (you may think it sounds better, but if it becuase of phase anomalies or a freq response thats not flat than its distortion).
I keep hearing that you need to listen to a lot of live music to be able to tell what amps are better. Yes it helps, but moving from row 10 to row 20 will change the tone, soundstage and reverberation a lot more than switching between 2 competent amp designs. (any one whos recorded a group of musicians with a stereo mic will tell you even a few feet will make more diff than the amps).
Theres 1 word that sums up the subjective objective debate: EGO. The objectivists eliminate this from there designs. (To be the hypocrite, its my ego that tells me not to let other people decide what sounds goods) Ill admit the numbers game may not be the answer to everything, yet, but its a better answer than "it sounds better".
Whats wrong with less distortion? (not just THD and TIM but all the distortions) This is where Selfs book (if not there yet) is leading us. And this is why he deserves cudos.
If you design an amp to suit a large number of peoples (best case, to suit yourself, worst case) subjective impressions, the design will evolve to "sound good" to those people. It will not evolve to be what I believe is the goal of an amp, uncolored sound (straight wire with gain). To reproduce the sound exactly as it was mastered (good or bad). Why? As I have learned from this forum, audiophiles like there sound colored (actually most people do) and this leads to disagreement. If its not colored its usually labeled "sterile" or "clinical". People like certain types of distortion: $200k tube amps with over 1% THD, Neve consoles from th 60s and 70s which run the signal thru dozens of transformers. Changing opamps in designs that are optimized for one type. Need I go on?
Just because one amp has a wider sound stage or deeper bass than another dosnt mean its better (you may think it sounds better, but if it becuase of phase anomalies or a freq response thats not flat than its distortion).
I keep hearing that you need to listen to a lot of live music to be able to tell what amps are better. Yes it helps, but moving from row 10 to row 20 will change the tone, soundstage and reverberation a lot more than switching between 2 competent amp designs. (any one whos recorded a group of musicians with a stereo mic will tell you even a few feet will make more diff than the amps).
Theres 1 word that sums up the subjective objective debate: EGO. The objectivists eliminate this from there designs. (To be the hypocrite, its my ego that tells me not to let other people decide what sounds goods) Ill admit the numbers game may not be the answer to everything, yet, but its a better answer than "it sounds better".
Whats wrong with less distortion? (not just THD and TIM but all the distortions) This is where Selfs book (if not there yet) is leading us. And this is why he deserves cudos.
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How long did you think about this statement? Sound quality and music quality (art) are totaly unrelated and so is the way we percieve and enjoy them. (and probably use completely different parts of the brain ). You will remember a violin solo that that made you melancoly a lot longer than an amp that had a little more stage depth or slightly tighter bass.
Not only ear, but more often by review, friend or heaven forbid, salesman.Then it becomes fashion: SS last year tubes this year SS next year.
I raised the issue of whether THD is a particular good measure to use on another forum - it ended up in my getting banned so its obviously an excellent topic.😀 Doug Self says this:
It is acknowledged that THD ... [is] of limited use in predicting the subjective impairment produced by an imperfect audio path. With music etc., intermodulation effects are demonstrably more important than harmonics.
So my question is - is it sheer laziness that leads to designers to concentrate their attention on THD measurements, and not intermodulation? Is it the absence of standardisation in intermod tests (should there be two or three tones, or a multiplicity)? Is there a common belief that THD performance will accurately predict intermod performance and therefore intermod tests are essentially redundant? Doug Self's view seems to me to lean towards this last one, though its merely an impression that I get, he does not state this explicitly.
Yes, agree totally. But you focus your own efforts apparently on distortion harmonic profiles - measured with a single tone. Am I correct in that perception? What has led you to the notion that distortion profile is a determinant of perceived sound quality, or is it primarily a marketing position to give you a USP? Why wouldn't you focus on intermodulation performance, just to offer one alternative?
No time at all, I post entirely from the hip😀
The basis of this statement is?
And this one is founded on what neuroscience?
Irrelevant, violin solos don't make me melancholy. But an amp with a better stage depth will tend to give a sound which is more easy to recognise as a violin.
Perhaps you were being confrontational? The topic is harmless enough....
It could be many things. People love numbers, that is certain; marketing departments use numbers as statistics to impress. Intermodulation is certainly more difficult to measure, yes, but then so is image depth, or 'timbre', whatever that is. If it's an orchestra we are attempting to reproduce, then clearly we should use as many notes as possible, perhaps four, or five, or ten. In the absence of a properly engineered standard it's difficult to know. I think it's true that because THD and IMD contain the word 'distortion' the consensus amongst laymen would be that, right or wrong, they are very similar. This could be easily exploited by an astute marketing department, keen to prove superiority with numbers alone.
This is a generic discussion rather than a personal or marketing crusade. If you want answers to these questions, email me. I will be more than courteous.
Cheers,
Hugh
Actually I have found that musicians generally aren't even interested in high end audio.
More often than not they have crappy, sub $1K systems which would make audiophiles blanch....
Yet they are quite happy, and miss very little of the performance.
Why is that?
More often than not they have crappy, sub $1K systems which would make audiophiles blanch....
Yet they are quite happy, and miss very little of the performance.
Why is that?
Do continue. No of course I'm not serious - audio is my hobby. I do have a life as well... Or did you mean did I intend to ask the question I asked? Yes, for sure. So you're going on to say that sound quality is not art? If so please unpack that further.
This movie producer is a neuroscientist then? I asked about neuroscience, not the economics of movies.
Probably they won't know if its a real violin or a synthesized one in that situation. I'm interested in hearing such distinctions myself.
And so? I do understand emotion, probably better than you. But you might be able to convince me I'm wrong...😛
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