ok here is my review.
In 2 identical power amps, one has the opa627 installed & the other has Burson inside. The one with the Burson outperformed the one with the well known 627 (which is still a good one). So just by pressing switches i have the chance for real time comparison. No placebo effect here, just changing from one amp to the other. The pre-amp used is a hybrid class-a one with 6922 tubes.
So for me outperform is :
With burson : tight & well controlled bass - you can define the notes. Natural mids with very good extension, you can hear the cymbals sound real, even the fingers that touch the strings.
with opa627 : good bass but a lot of bass notes sound the same, mids have a touch of darkness (like they are laid back a bit), highs are extended but sound unreal. That is my experience.
As you said you can have a placebo effect for a standalone device, but at this kind of comparison test, differences are there.
In 2 identical power amps, one has the opa627 installed & the other has Burson inside. The one with the Burson outperformed the one with the well known 627 (which is still a good one). So just by pressing switches i have the chance for real time comparison. No placebo effect here, just changing from one amp to the other. The pre-amp used is a hybrid class-a one with 6922 tubes.
So for me outperform is :
With burson : tight & well controlled bass - you can define the notes. Natural mids with very good extension, you can hear the cymbals sound real, even the fingers that touch the strings.
with opa627 : good bass but a lot of bass notes sound the same, mids have a touch of darkness (like they are laid back a bit), highs are extended but sound unreal. That is my experience.
As you said you can have a placebo effect for a standalone device, but at this kind of comparison test, differences are there.
To quote Inigo Montoya, "You keep using that word. I do not think it means what you think it means."
Even though I haven't 'heard' the burson discrete op-amps I seriously doubt the human ear would hear the tiny differences that it offers with all the other materials the signal has to travel through and things it's exposed to. I also learnt that this forum, great as it is, dosen't make sense. Physically better isn't always better here! I also learnt recently from one of my threads that tubes are hi-fi!
The Burson's have better RF induced noise resistance than do many of the monolithic types. The National LM4562 is particularly bad in this aspect. this is one of those parameters that is entirely off data sheet. (And for good reasons!)
The Chinese copy of the Burson is not the same, it has a different layout and a different number of parts.
If someone is happy to play plug and listen they can pick the sound they prefer. It may not be the lowest distortion, but it is their preference.
I don't think there is really a conspiracy against good perceptual test reporting here - it is just that there are minimum standards for valid perceptual comparison that most "subjectivists" are actively hostile too when not simply ignorant of them
if you "just listen" - you will "hear differences" - many will be "real" - because you haven't controlled for level and frequency response matching to within 0.1 dB ~ 1% matching
we do know from controlled double blind abx tests that people can resolve differences that small with statistical significance
1 dB is pretty much the limit of what can be judged by ear as loudness difference - thats ~10% V amplitude difference
so it simply isn't valid to say "I set the levels the same by ear" - you have use measurements to get better than 1%
aural "memory" is also proven to be poor - take minutes to swap out a part and you are no longer able to use short term memory - only a tiny fraction of our sensory input is surprisingly coarsely encoded in longer term memory - this is well explored perceptual psychology
reports of "I heard it with amp X at a show and ..." are likely pure "fabrication" by your unconscious processing, “reconstruction” going on in long term memory recall
and while some take "placebo" or "expectation" effect criticisms as "fighting words" – somehow an attack on honesty or mental capacity they are well established in psychology as well - it is only a comic book super hero conception to think as a human you can “overcome” unconscious bias mechanisms
our brains have evolved to use every “cheat”, short cut”, possible correlation and then hides all of this from our conscious awareness
in response perceptual psychologists, pyschoacoustics has developed minimum standards for valid listening tests to be considered reliable reflections of actual sound field differences
if you "just listen" - you will "hear differences" - many will be "real" - because you haven't controlled for level and frequency response matching to within 0.1 dB ~ 1% matching
we do know from controlled double blind abx tests that people can resolve differences that small with statistical significance
1 dB is pretty much the limit of what can be judged by ear as loudness difference - thats ~10% V amplitude difference
so it simply isn't valid to say "I set the levels the same by ear" - you have use measurements to get better than 1%
aural "memory" is also proven to be poor - take minutes to swap out a part and you are no longer able to use short term memory - only a tiny fraction of our sensory input is surprisingly coarsely encoded in longer term memory - this is well explored perceptual psychology
reports of "I heard it with amp X at a show and ..." are likely pure "fabrication" by your unconscious processing, “reconstruction” going on in long term memory recall
and while some take "placebo" or "expectation" effect criticisms as "fighting words" – somehow an attack on honesty or mental capacity they are well established in psychology as well - it is only a comic book super hero conception to think as a human you can “overcome” unconscious bias mechanisms
our brains have evolved to use every “cheat”, short cut”, possible correlation and then hides all of this from our conscious awareness
in response perceptual psychologists, pyschoacoustics has developed minimum standards for valid listening tests to be considered reliable reflections of actual sound field differences
Hmmm, I have seen the schematic of the Audiolab 8000P (to tell you the truth I do not know the serial number of it) and it uses bipolar transistors as the input diff. pair and one OP amplifier as the DC servo (TL071). From the pictures seen, this one can be one of the newer versions - possible 2SK389 as an input diff. pair. Do we realy know what is the use of the OP amplifier there? DC servo? Or something else? It would be funny if it is a DC servo. But, hey - if it makes you happy, why would we judge?! 
In any case OPA627s are relatively fast opamps reputed to require some attention to layout. I don't think an integrator as used in a DC servo would be very likely to oscillate, but still it's something to consider.
Evaluating things solely by ear isn't what I'd call a particularly good idea. For one thing, measurements tend to be an awful lot more reproducible. Try picking up low-level oscillation by ear, too... performance is not necessarily degraded enough for it to become plainly audible.
By comparison, listening tests done right are a real PAIN. It still isn't a bad idea to conduct them if measurements look good, though at this point I wouldn't expect anything unusual any more provided you've measured the right things (interpreting measurements is a bit of an art by itself, but one worth learning).
Evaluating things solely by ear isn't what I'd call a particularly good idea. For one thing, measurements tend to be an awful lot more reproducible. Try picking up low-level oscillation by ear, too... performance is not necessarily degraded enough for it to become plainly audible.
By comparison, listening tests done right are a real PAIN. It still isn't a bad idea to conduct them if measurements look good, though at this point I wouldn't expect anything unusual any more provided you've measured the right things (interpreting measurements is a bit of an art by itself, but one worth learning).
Yes that is true. I just don't think we'll reach a point where everyone has the equipment or knowledge to fulfil those requirements. Its one of those things where we have to let both camps be. It takes all sorts to make a community, some are here to learn while others only participate on a level that suits them.
Can't hear it. Might be more useful if you post up the waveforms so we can see what is going on.
I have the early schematics of the amp. Audio signal passes through the opamp. Otherwise i wouldn't buy the Burson. Also upgrade kits sold for this amp include changing the opamp.
Hmmm, I have seen the schematic of the Audiolab 8000P (to tell you the truth I do not know the serial number of it) and it uses bipolar transistors as the input diff. pair and one OP amplifier as the DC servo (TL071). From the pictures seen, this one can be one of the newer versions - possible 2SK389 as an input diff. pair. Do we realy know what is the use of the OP amplifier there? DC servo? Or something else? It would be funny if it is a DC servo. But, hey - if it makes you happy, why would we judge?!
hahaahhaaaa .... nice !!!
Can't hear it. Might be more useful if you post up the waveforms so we can see what is going on.
take a look
Since i shared my experience & had the luxury of direct comparison take a look here. You will get an idea of how good they are -->
Burson Audio Blog
And these are diyers that shared their projects, at least they were not attacked by extra terrestrials...
Since i shared my experience & had the luxury of direct comparison take a look here. You will get an idea of how good they are -->
Burson Audio Blog
And these are diyers that shared their projects, at least they were not attacked by extra terrestrials...
I stumbled across this thread last night, read some of it, usual naysayers that don't know what they are talking about if you ask me..
I was tipped off by 2 fellow ASR users, that Burson single op amp replacement in the Emitter 2 exclusive was a definite upgrade, I read into it as I usually do. My E2 had the later OPA 551 ic's fitted, so my first thing was to try the Ad843 that ASR originally used, and employ various bypass caps across 1&7. There were slight improvements, nothing major, but worth the time and little cost. I did then order the Bursons, and fitted them on the day of arrival, together with a .1uf Vishay Roderstein across 1&7. Yes, again a small improvement, but I had to let them settle for 100 hrs minimum. So, left system on for a week, then tried again.
To all of those that have not done the above, you are not in any position to debate on the benefit these Op amps provide. Looking at data tells us absolutely nothing I'm afraid, as much as I'd like these to 'test' better, they are average at best on paper. Which is fine if all you guys want to do is study specs, I personally would much rather listen to Music that is startlingly realistic at home, and that is helped no end by using the Burson Op amps.
And before anyone goes on about this dbx testing, you don't need to to hear the difference. Placebo? Give me a break, I don't give a s**t what option sounds better, as I have no affiliation to any if them. Would I swap them back to ic's? Er no, no way. Anyone want some ic's, I have some for sale.
I was tipped off by 2 fellow ASR users, that Burson single op amp replacement in the Emitter 2 exclusive was a definite upgrade, I read into it as I usually do. My E2 had the later OPA 551 ic's fitted, so my first thing was to try the Ad843 that ASR originally used, and employ various bypass caps across 1&7. There were slight improvements, nothing major, but worth the time and little cost. I did then order the Bursons, and fitted them on the day of arrival, together with a .1uf Vishay Roderstein across 1&7. Yes, again a small improvement, but I had to let them settle for 100 hrs minimum. So, left system on for a week, then tried again.
To all of those that have not done the above, you are not in any position to debate on the benefit these Op amps provide. Looking at data tells us absolutely nothing I'm afraid, as much as I'd like these to 'test' better, they are average at best on paper. Which is fine if all you guys want to do is study specs, I personally would much rather listen to Music that is startlingly realistic at home, and that is helped no end by using the Burson Op amps.
And before anyone goes on about this dbx testing, you don't need to to hear the difference. Placebo? Give me a break, I don't give a s**t what option sounds better, as I have no affiliation to any if them. Would I swap them back to ic's? Er no, no way. Anyone want some ic's, I have some for sale.
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