[mevans]

  Its definitely something that a company would consider (the fact that some people might use measurements or blind tests as a way to perceive gear to be of low quality).
However, I feel like it cant be only it.
 
Measurements for example make sense not to be used as a sign on performance (because if you get a unit that does not fit to the supposed performance it might be a problem for the company in many aspects), however blind testing is, in essence, subjective objectivity.
 
What I am trying to say is that the blind test is objective for the tester, but it does not extend to other users.
 
In other words, what sounds objectively better (due to blind testing) to me, may not sound better objectively for you.

I think this problem of subjectivity can be avoided.  In a test of amps, for example, there is no need for the "blind" listener to determine which amp sounds better.  Instead, he would be asked to merely distinguish between one amp and another.  With amps of decent quality (ample power, negligible distortion) set to identical volumes, it is my supposition that such determinations could not be reliably made.  Further, I suspect that similar results would obtain with regard to cd players, converters and cables.  This would render the notions of synergy and scaling to be myths.  My concern is that an awful lot of money may be being spent by hobbyists chasing myths.   

 

[DavidA]

 
I think this problem of subjectivity can be avoided.  In a test of amps, for example, there is no need for the "blind" listener to determine which amp sounds better.  Instead, he would be asked to merely distinguish between one amp and another.  With amps of decent quality (ample power, negligible distortion) set to identical volumes, it is my supposition that such determinations could not be reliably made.  Further, I suspect that similar results would obtain with regard to cd players, converters and cables.  This would render the notions of synergy and scaling to be myths.  My concern is that an awful lot of money may be being spent by hobbyists chasing myths.   

I would have to disagree with your assumption that it would be hard to determine one amp from another doing blind testing.
 
The difference in the sound of my HD-650 from my Asgard2 and BH Crack is quite easy to notice, one of the reasons is the large difference in the output impedances of the amps.  A simple way to test this is use a amp from Garage 1217 that has adjustable output resistance/impedance, you can change the settings while the amp is on and if you adjust the volume to the same level using your ears you will notice a difference in the sound.
 
If you are comparing 2 solid state amps that have similar circuit designs and output impedances then I would say that it would be much harder or impossible to tell them apart

 

[cjl]

Well, since any decent amp should have an output impedance much, much lower than the impedance of the headphones it is driving (in order to provide audible transparency), that's not surprising. It just means that one of your amplifiers was not actually designed with optimal fidelity in mind.

 

[DavidA]

  Well, since any decent amp should have an output impedance much, much lower than the impedance of the headphones it is driving (in order to provide audible transparency), that's not surprising. It just means that one of your amplifiers was not actually designed with optimal fidelity in mind.

not sure if this was directed at me?
 
Most OTL amps have fairly high output impedances and are designed to be used with higher Z headphones.
 
What do you mean when you say "one of your amps was not actually designed with optimal fidelity in mind"?

 

[cjl]

It means that whoever designed the amp either did not design it to leave the signal as unaffected as possible, or they didn't use good engineering practices when designing it. That's abundantly clear from the fact that it's OTL though, since that's a very poor design for high fidelity reproduction, so it was obviously chosen because the designer liked the imperfections it caused.

 

[DavidA]

  It means that whoever designed the amp either did not design it to leave the signal as unaffected as possible, or they didn't use good engineering practices when designing it. That's abundantly clear from the fact that it's OTL though, since that's a very poor design for high fidelity reproduction, so it was obviously chosen because the designer liked the imperfections it caused.

Would you mind if I passed your post to the Bottlehead thread since I'm curious to see if the OTL design is a poor one? 
 
Its the first I've ever heard of OTL being a poor design for high fidelity reproduction, everything else I have read says its one of the best and simplest designs.

 

[cjl]

I suspect they won't agree, but go ahead if you want. In general though, if you're designing an amp with the intention of the cleanest possible signal for normal headphone use though, you really only have one choice these days: solid state with loads of negative feedback. Anything else is likely to perform worse at the same price point.

 

[jcx]

the 1st order difference between amps that do actually sound different in controlled listening is frequency response - both of the raw amp and as mentioned form higher output Z interacting with loads that aren't flat Z with frequency - like most headphones except Orthos
 
and a fact some may not like is that a cathode follower has 100% local negative feedback - with the consequent "harmonic multiplication" that goes with linear negative feedback around a slightly nonlinear gain block - simple circuit theory - easily seem distortion spectra
 
so if you intellectually bought into the common SET 'no feedback" "story" - you're not there with a follower (actually you're not there with a Triode either - the low mu is a consequence of internal plate V feedback inside the tube - early tube era patents used external positive feedback to cancel the internal feedback for more gain from Triodes)

 

[DavidA]

  I suspect they won't agree, but go ahead if you want. In general though, if you're designing an amp with the intention of the cleanest possible signal for normal headphone use though, you really only have one choice these days: solid state with loads of negative feedback. Anything else is likely to perform worse at the same price point.

Even with my very limited electrical engineering knowledge I would have to disagree with your assessment that OTL amps are a poor design, if they were a poor design why are there so many OTL amps out there?
 
As for the negative feedback, why are most high end amps zero feedback?
 
My experiences so far have been that OTL amps work best with high Z headphones, usually better than SS.
 
All high end amps have been zero feedback and have sounded wonderful.
 
Not saying you are wrong but these are my impressions and what my research has found.

 

[jcx]

 if they were a poor design why are there so many OTL amps out there?

really doesn't follow from any realistic understanding of the audio market - accurate amplification is way behind "story", "fashion", casework - bling connectors, knobs really are called "jewelry" by the industry insiders
 
the "zero feedback" is totally a product of marketing - as I mentioned above negative feedbak is happening in tubes: SET and Cathode Followers - the local/global distinction doesn't exist in the math, you fail your uni EE classes if you don't get this
 
 
I've been to several BAS presentations that discussed some audio businesses, an example is a US amp manufacturer who contemplated closing, as last gasp effort went from sheet metal to machined cases, careful matching anodize appearance, integral eye candy heatsink machining, heck even machined dovetails in the case' Al plate stock, "jewelry" connectors - and 3-5x price increases

in an hr presentation at BAS they never once mentioned actual circuit design changes - now a regular buyer of full page Stereophile ads - doing great business
 

 

[DavidA]

  really doesn't follow from any realistic understanding of the audio market - accurate amplification is way behind "story", "fashion", casework - bling connectors, knobs really are called "jewelry" by the industry insiders
 
the "zero feedback" is totally a product of marketing - as I mentioned above negative feedbak is happening in tubes: SET and Cathode Followers - the local/global distinction doesn't exist in the math, you fail your uni EE classes if you don't get this
 
 
I've been to several BAS presentations that discussed some audio businesses, an example is a US amp manufacturer who contemplated closing, as last gasp effort went from sheet metal to machined cases, careful matching anodize appearance, integral eye candy heatsink machining, heck even machined dovetails in the case' Al plate stock, "jewelry" connectors - and 3-5x price increases

in an hr presentation at BAS they never once mentioned actual circuit design changes - now a regular buyer of full page Stereophile ads - doing great business
 

we are getting way off topic here as my post was for using blind testing between two different types of amps

 

[krismusic]

we are getting way off topic here as my post was for using blind testing between two different types of amps

I don't agree it's way off topic. Perceived value is one of the variables that blind testing eliminates. It is interesting to hear how a manufacturer can deliberately use visual appeal to sell a product that was failing on its sonic performance.

 

[Ruben123]

I'd like to hear more about the feedback thing. The pono player is praised to heaven for its zero feedback.

 

[jcx]

actually my take is that there is little relation between "sonic performance" of amps and audiophile popularity - the company above had a long history of sales, good reputation in pro audio but needed to expand consumer sales to remain in business with their US manufacturing cost structure
 
so the over the top, heavy, expensive casework, even the fact of high "audiophile" pricing, became selling points that made the difference in sales without circuit changes
 
the other side of the question for audio electronics is that people apparently can also be talked into wanting, buying audio electronics with audibly differing frequency response, sometimes audible distortion if "the story" fits narratives that the audiophile press and marketing created, continue to promote despite the clear divergence from "hi-fidelity" taken as accuracy in known audible parameters
 
 
the no (global) feedback, "zero feedback" is such a guru/audiophile pundit driven narrative - very annoying to EE who realize it is practically impossible to build useful electronics without negative feedback
 
and have to deal with the misrepresentation that "local" is somehow different than "global" feedback - when one of the most pointed to "problems" of negative feedback is "harmonic multiplication" - which is trivially shown to apply to "local" negative feedback too
 
in fact the "low feedback" proponents are advocating circuits where the effect is most prominent, feedback factors ~=,< 20 dB give the biggest added new harmonic distortion components at levels still expected to be audible
 
a fun read on feedback - not that non EE types will get all of it:  http://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf
 
of course there are followers of every fashion in the recording/music production end of the business too, but the vast majority of commercial recorded music has passed through "high global feedback" op amps during the recording process
 
while there is now a audiophile push for the idea of a R-2R DAC "sound" difference from Delta-Sigma DAC, Delta Sigma ADC are used in the overwhelming majority of recording studios and Delta-Sigma internals use ridiculous high negative feedback internally to accomplish the noise shaping
 
 
a logical question to me is where are the (very short) lists of "acceptable", "zero feedback" production chains, "uncontaminated" commercial music releases that we could expect to hear the difference in the last few pieces of home audio electronics

 

[castleofargh]

we're going off topic, but then again, the motives to verify that something will result in audible difference with a blind test can go in all directions.
about feedback, the 2 links that convinced me it was not just a good thing, but something we can hardly avoid if we want stability/fidelity are the one jcx posted above, and the MIT videos that ab initio posted once http://ocw.mit.edu/resources/res-6-010-electronic-feedback-systems-spring-2013/course-videos/  
the vids are even "worst" than the PDF, with words like root locus(not a grasshopper that lives in roots), laplace, fourier or Z transform. stuff I personally remembered from gundam animes, and not at all from math courses. so if you didn't do math 2 years after high school(US model) there are chances you won't be able to follow all of it. I sure didn't.
but still many of the principles are explained with enough pedagogy and can be understood without the necessary education to follow the math explaining it(and google is a friend). a few examples talk about op amps and give some ideas of what it's all about when dealing with sine signals like music.