AES Paper Digest: Do Audio Op-amps Sound Different?

[oivavoi]

Earl found that one form of nonlinear distortion, crossover distortion in poorly designed class ab amplifiers that experience bias failure and slip into class b evidenced this problem. This problem is old news because it was experienced and documented long before electronic amplification was even possible. It reasserted itself in first generation SS amplifiers. By the third generation SS power amp biasing circuits in mainstream gear was pretty consistent and reliable, even in low priced amps.

Thanks! I have never experienced decent AB amplifiers as distorted myself, at least. All subjective, of course.

 

[Krunok]

This kind of response is kinda tedious. Applied psychoacoustics with regards to sound reproduction is a small, small, actually tiny scientific field, compared to most other fields. The number of replications of any of the existing studies are close to zero (with a couple of exceptions). Are you seriously claiming that every single post on this forum should have a reference to a peer-reviewed publication? In that case, the forum would die down very quickly.

Also, this kind of debate is actually how science is done. This is how scientists communicate between themselves. They mention possibilities and hypotheses, and take it from there (and ultimately try to measure and confirm/disconfirm). It is not against the spirit of science to say things one is not 100 sure about. Quite on the contrary, as long as one is clear about what the epistemic status of the claim is (in this case I was clear that I was not sure about the epistemic status of the claim).

A short google search led me to this interview though, where dr. Geddes says exactly what I said he said:



Searching a bit more, I found this AES convention paper written by Geddes and his wife: http://p3dal.com/Files/articles/AuditoryPerceptionNonlinearDistortion.pdf

But alas! It is only a convention paper, it has not been through peer review! So what does your rulebook say in this case, am I allowed to post it or not?

Let's take it slowly, shall we?

Look at the first sentence of what he said: "Our studies indicated that distortion in a loudspeaker is not likely to be a major factor as long as the loudspeaker is operated within its design limits. ". Ok, so he claims that distortion of the loudspeaker cannot really be heard as long as speaker is operated within its design limits. Now we should remember that even the very expensive speaker's THD is typically 50dB higher than THD of a very cheap DAC. And yet he made a research if differences between DACs can be heard after he found that speakers THD cannot? Huh..

P.S. I'm not the one to allow you or to forbid you to post, but I would really prefer that you rethink your posts before writing them.

 

[SIY]

Hahaha - no offense taken, I'm merely waiting for @SIY to post a link as he was the one who mentioned it. I think we should all be able to post a link to an article we're quoting otherwise it's hearsay..

A link to what? AJEV's website? Just grabbing the latest couple of issues (I did say random), see for example
Linking the Sensory Properties of Chardonnay Grape Vitis vinifera cv. Berries to Wine Characteristics
Jun Niimi, Paul K. Boss, David W. Jeffery, Susan E.P. Bastian
Evaluation of the Sensory Profiles of Texas High Plains Tempranillo and Cabernet Sauvignon Wines
Matthias Bougreau, Jean Guzzo, Patrice Arbault, Guy Loneragan
Reduction of Red Wine Astringency Perception Using Vegetable Protein Fining Agents
Wenyu Kang, Jun Niimi, Susan Elaine Putnam Bastian
Shiraz (Vitis vinifera L.) Berry and Wine Sensory Profiles and Composition Are Modulated by Rootstocks
Sandra M. Olarte Mantilla, Cassandra Collins, Patrick G. Iland, Catherine M. Kidman, Renata Ristic, Paul K. Boss, CharlotteJordans, Susan E.P. Bastian

If you don't do good controlled sensory analysis, you have as much chance of getting past the referees as someone trying to use phlogiston in a submission to Physical review. There's a difference between popular magazines and serious science journals.

 

[Jakob1863]

"Most likely"? Are you able or are you not able? How did you actually tested yourself so that you got the "most likely able" as a result?

Empirical tests are connected to probability . Do you know the nice aphorism "being a statistican means never to be sure" ?

I use controlled test setups in "sighted" and "blind" condition and i did quite often conduct controlled listening tests with other people as well.

 

[Wombat]

This kind of response is kinda tedious. Applied psychoacoustics with regards to sound reproduction is a small, small, actually tiny scientific field, compared to most other fields. The number of replications of any of the existing studies are close to zero (with a couple of exceptions). Are you seriously claiming that every single post on this forum should have a reference to a peer-reviewed publication? In that case, the forum would die down very quickly.

Also, this kind of debate is actually how science is done. This is how scientists communicate between themselves. They mention possibilities and hypotheses, and take it from there (and ultimately try to measure and confirm/disconfirm). It is not against the spirit of science to say things one is not 100 sure about. Quite on the contrary, as long as one is clear about what the epistemic status of the claim is (in this case I was clear that I was not sure about the epistemic status of the claim).

A short google search led me to this interview though, where dr. Geddes says exactly what I said he said:



Searching a bit more, I found this AES convention paper written by Geddes and his wife: http://p3dal.com/Files/articles/AuditoryPerceptionNonlinearDistortion.pdf

But alas! It is only a convention paper, it has not been through peer review! So what does your rulebook say in this case, am I allowed to post it or not?

Your post #228 was vacuous. This follow-up shows that the information was available and could have been presented then. I don't believe we are always conducting scientific procedure, here, we are not conducting experiments but rather presenting views and backing them up with credible information.

 

[oivavoi]

Let's take it slowly, shall we?

Look at the first sentence of what he said: "Our studies indicated that distortion in a loudspeaker is not likely to be a major factor as long as the loudspeaker is operated within its design limits. ". Ok, so he claims that distortion of the loudspeaker cannot really be heard as long as speaker is operated within its design limits. Now we should remember that even the very expensive speaker's THD is typically 50dB higher than THD of a very cheap DAC. And yet he made a research if differences between DACs can be heard after he found that speakers THD cannot? Huh..

P.S. I'm not the one to allow you or to forbid you to post, but I would really prefer that you rethink your posts before writing them.

Well, discussing the studies Geddes did is good. You may challenge it - perfect. I myself have some reservations - the claim that distortion isn't that audible goes against my intuitions, even though later research seems to confirm that THD is not a very good indicator of what may or may not be audible (take a look here for example http://www.aes.org/e-lib/browse.cfm?elib=19224 )

And frankly, the exasperation is becoming mutual, even though I have enjoyed many of your postings here so far. I would really prefer that you stop making such comments, and stick to just discussing the arguments I make. Ping @Thomas savage.

 

[Krunok]

A link to what? AJEV's website? Just grabbing the latest couple of issues (I did say random), see for example
Linking the Sensory Properties of Chardonnay Grape Vitis vinifera cv. Berries to Wine Characteristics
Jun Niimi, Paul K. Boss, David W. Jeffery, Susan E.P. Bastian
Evaluation of the Sensory Profiles of Texas High Plains Tempranillo and Cabernet Sauvignon Wines
Matthias Bougreau, Jean Guzzo, Patrice Arbault, Guy Loneragan
Reduction of Red Wine Astringency Perception Using Vegetable Protein Fining Agents
Wenyu Kang, Jun Niimi, Susan Elaine Putnam Bastian
Shiraz (Vitis vinifera L.) Berry and Wine Sensory Profiles and Composition Are Modulated by Rootstocks
Sandra M. Olarte Mantilla, Cassandra Collins, Patrick G. Iland, Catherine M. Kidman, Renata Ristic, Paul K. Boss, CharlotteJordans, Susan E.P. Bastian

If you don't do good controlled sensory analysis, you have as much chance of getting past the referees as someone trying to use phlogiston in a submission to Physical review. There's a difference between popular magazines and serious science journals.

Ok, I don't have time to read all of them, so let's concentrate on the 2nd: "Evaluation of the Sensory Profiles.."
Here I quote from the abstract: "The two varietal wines could not be significantly distinguished by their average sensory profiles, although butter, caramel and lavender were significantly stronger in Tempranillo and black currant in Cabernet Sauvignon. "

Hmm.. Differentiating between two such very different sorts of wines as are Tempranillo and CS isn't that much impressive, I can also do it without any trouble. But I believe we were talking about differentiating between 2 bottles of Tempranillo of which one costs say 20EUR and the other 100EUR.

 

[Krunok]

And frankly, the exasperation is becoming mutual, even though I have enjoyed many of your postings here so far. I would really prefer that you stop making such comments, and stick to just discussing the arguments I make. Ping @Thomas savage.

I was merely referring that you are mixing article about DACs distortions with the article about loudspeakers distortions without even thinking that one about the speakers proves the one about DACs impossible. That I see as a fact for which I have no intention to apologize for, no matter how offended you may be.

 

[Arnold Krueger]

Thanks! I have never experienced decent AB amplifiers as distorted myself, at least. All subjective, of course.

Besides all of the sighted and DBT listening tests I've been measuring audio gear for over 50 years. There was a time in the 60s where amps with failed or misadjusted bias were not uncommon. By the 80s the adjustments largely disappeared, and the parts devoted to the issue were a trivial expense in the amplifier BOM.

 

[oivavoi]

I was merely referring that you are mixing article about DACs distortions with the article about loudspeakers distortions without even thinking that one about the speakers proves the one about DACs impossible. That I see as a fact for which I have no intention to apologize for, no matter how offended you may be.

I have no problem with you challenging my arguments, as already stated - quite on the contrary, I very much enjoy being challenged. Thinking is fun, and being forced to rethink one's convictions is even more fun. But I do have a problem with the fact that you on two occassions within the last 20 minutes have asked me to stop posting the way I do.

ps: I am not offended, I am annoyed. And "getting annoyed" is not what keeps me coming back to this forum

 

[Krunok]

I use controlled test setups in "sighted" and "blind" condition and i did quite often conduct controlled listening tests with other people as well.

Well, in no way I want to criticize your tests, but my perception is that on a scientific forum like this we should state as facts only things that have been proven by independent parties in a scientific manner.

 

[Wombat]

I

I have no problem with you challenging my arguments, as already stated - quite on the contrary, I very much enjoy being challenged. Thinking is fun, and being forced to rethink one's convictions is even more fun. But I do have a problem with the fact that you on two occassions within the last 20 minutes have asked me to stop posting the way I do.

ps: I am not offended, I am annoyed. And "getting annoyed" is not what keeps me coming back to this forum

You suggest to others how they should/should not post. Just sayin'.

General comment: Make a point, support it credibly and discussion can flow more easily. Introducing hypotheticals and hearsay is a sure way of muddying a conversation.

 

[oivavoi]

I
You suggest to others how they should/should not post. Just sayin'.

No. I have never suggested to you how or what to post with the regards to factual matters. The only thing I expect is that people here refrain from focusing on the person making the argument in stead of the argument itself.

 

[Krunok]

I have no problem with you challenging my arguments, as already stated - quite on the contrary, I very much enjoy being challenged. Thinking is fun, and being forced to rethink one's convictions is even more fun. But I do have a problem with the fact that you on two occassions within the last 20 minutes have asked me to stop posting the way I do.

ps: I am not offended, I am annoyed. And "getting annoyed" is not what keeps me coming back to this forum

I can only repeat this: Make a point, support it credibly and discussion can flow more easily. Introducing hypotheticals and hearsay is a sure way of muddying a conversation.

P.S. Staying or not on this forum is your choice and you should make it as all of us adults do, no matter if you live with parents again.

 

[svart-hvitt]

I could pick up a journal of the homeopathy trade and find opinions that support the practise. Some credible supporting information would be more pertinent.

This is the kind of commentary we don’t need her. You cannot simply dismiss sources and references like this when you ask for evidence and sources.

By the way, this is Wilipedia’s description of The American Journal of Enology and Viticulture:

«The American Journal of Enology and Viticulture is a peer-reviewed scientific journal. It was established in 1950 and is published 4 times a year by the American Society for Enology and Viticulture. According to the Journal Citation Reports, the journal has a 2016 impact factor of 1.721.[1]»

And: «The American Society for Enology and Viticulture, founded in 1950, is a non-profit, scientific wine production industry organization headquartered in Davis, California.

Its membership of 2,400 includes professionals from wineries, vineyards, academic institutions and organizations. In addition, it has 120 Industrial Affiliates (companies).»

And: http://www.ajevonline.org/content/about-us

Seems like a good reference for wine research for me.

 

[Jakob1863]

May i suggest that we open a new thread where we discuss posting style issues?

 

[Krunok]

This is the kind of commentary we don’t need her.

And who are "we"? You and @oivavoi?

 

[Krunok]

May i suggest that we open a new thread where we discuss posting style issues?

And wines, as well!

 

[DonH56]

Wow, just wasted three pages of my life...

I think Arnie has delineated the problem well, and it aligns with the data from Geddes, concerning low-level amplifier distortion. Most things (amplifiers and speakers) have lower distortion as you reduce the signal level. For amplifiers, e.g. class-AB and push-pull types, there are low-level distortion mechanisms like crossover distortion that can inject fairly constant wideband distortion even at very low output levels. A known problem, a big deal in the 1960's and 1970's, but better device matching, faster driver and output transistors (allowing broader loop bandwidth and higher loop gain to provide better feedback), and improved circuit design and biasing essentially eliminated that as an issue by the early to late 1980's and things have continued to improve since then. It is a real thing, a real problem, really solved...

That said I am sure someone can find some poor designs that exhibit things like crossover distortion. The push to decrease power consumption in some cases led to very low output stage biasing that could bring an old problem back (measles no more, why vaccinate? duh...) and then marketing pushed amps with higher biasing that solved the problem they (re)created. Gotta' love it.

There are low-level things that can happen to speakers, too, but again by and large AFAIK they've been solved for a long time.

Whatever - Don

p.s. Obligatory credentials since that pissin' contest seems to have arisen again: hairy-knuckled low-brow eng-un-ear with ears of clay. Likes to blow own horn.

 

[oivavoi]

I can only repeat this: Make a point, support it credibly and discussion can flow more easily. Introducing hypotheticals and hearsay is a sure way of muddying a conversation.

P.S. Staying or not on this forum is your choice and you should make it as all of us adults do, no matter if you live with parents again.

Go play with your tubes, will you. I'm out of here for today.