You're far from alone, so do many others. That's why there's still people making a living at dowsing, astrology, faith healing, homeopathy, magnetic therapy, and polygraphy. To move ahead and not be mired in the errors of the past, one needs to verify hypotheses. Otherwise, no real progress is made, only the illusion of progress, and one ends up going in circles.
So far, no-one from Waterloo has asked to test my phono stage and I'm not holding my breath waiting for the call.
I would like to point out something to everyone about capacitors. About 50 years ago, Mylar caps came out into the marketplace. What did they use before? Well, WAX PAPER CAPS were in virtually everything consumer, with polystyrene used for special products, like analog computers. One of the design 'secrets' of the Marantz 7C was the MYLAR caps. Yes, it was a trade secret! Now we have polypropylene, more compact polystyrene, and even Teflon. We have gone that direction, and found further measurable and listening 'improvement'. However, please remember that Dielectric Absorption or DA in caps can sound 'better' to some people, as it adds an 'afterglow' to the sound. What do you find, SY?
The fashion now is to go back to paper. Those horrible old bumblebee caps are bringing big bucks these days.
What was that great old Joni Mitchell song?
We’re captive on the carousel of time
We can’t return we can only look behind
From where we came
And go round and round and round
In the circle game.
Regarding DA, 30 years ago I was designing fast HV dividers for transient voltage measurements, built also from small components in series, and series resistor damped. We were well aware of DA, and capacitors had to by bypassed by high value resistors. If not, you can imagine how capacitors connected in series would behave ....
PMA, I agree with you that engineers knew about DA in regard to sample and hold circuits, but AUDIO was ignored for the most part. I even ignored it, after getting a complete summary of DA from a colleague who did his masters thesis on DA in 1974. I had the equations, early articles from the Analog Computer days in the '50's, and the standard model for DA, BUT I just didn't put it together for audio, until Dick Marsh did some tests, after hours, at LBL, back in 1977 or so, and talked to me about it, along with Walt Jung. I concentrated on NONLINEAR distortion in caps from ceramics and tantalum caps in those days. Perhaps it was different in your country.
John, it was not any different in my country. But I graduated in electroacoustics, I was really engaged in it as a hobby as well, as many. And then, as a professional, I was engaged in measuring and transfer of fast transient signals small in level in an environment of high electromagnetic interference. And, maybe surprisingly maybe not, I found that audio issues and small signal transfer in EMI environment had a lot of common problems. Maybe for this reason, I have been and remained open for different than usual approach, not only in audio.
Going back to the issue of comparative testing, at least for a little while, let's assume that there are issues with the double blind tests that can mask the differences between amplifiers.
What can we do differently ?
John, how do you compare amplifiers in listening tests ? Do you avoid any ABX box ? Do you then move the cables from one amplifier to the other ? Do you do level equalization ?
I'm interested because I'm thinking of doing my own comparative listening tests and want to avoid any known pitfalls.
Others' advice would also be appreciated.
What can we do differently ?
John, how do you compare amplifiers in listening tests ? Do you avoid any ABX box ? Do you then move the cables from one amplifier to the other ? Do you do level equalization ?
I'm interested because I'm thinking of doing my own comparative listening tests and want to avoid any known pitfalls.
Others' advice would also be appreciated.
Fireworks, I appreciate your interest, but we rarely do direct comparison tests any more. Usually, we build on what we have learned over the years, trying not to make a serious error in judgement in any area, and test for any flaws that we can find. The idea that there ISN'T any difference between caps, has been buried for decades. What we concern ourselves with is: Which of the best of something is better? For example, this week, it was polystyrene vs Teflon from the SAME manufacturer. That is what I had an extensive discussion with the cap designer, himself, about, as well as noting what my competitors, who are as ruthless as me at 'getting it right' think about the very same caps. This AB testing of polypropylene vs Mylar, was done extensively by us, 30 years ago or more. We happen to trust our ears more than some, because it is in our interest to not fool ourselves, even though that is always a possibility. If we fool ourselves too often, then we will fail in the marketplace with independent reviewers and listeners. It HAS happened to me, when I once casually presumed that there was little difference between different brands of polystyrene and polypropylene, for example. Years before, I casually presumed that there was little difference between Mylar and polystyrene, and listening tests by others of my own designs, forced me to look at DA as important, as well as non-linear distortion.
Now where does this leave us? Regarding making a 'successful' audio design through measurements, topology considerations, and component selection?
This is important to me, because by 1980, most of us us have gotten to as far as we have discussed on this thread, recently, and little more 'research' appeared in the JAES that really gave us further insight.
This is where many of us started to try different cables, both interconnecting, and internal hook-up wire, with improved refining and better jacketing. Mogami became very popular in wire for a long time. Compared to 'hardware store' wire, it was better made, often more flexible, and more 'interesting' in its configurations. Improved RCA connectors became available, originally made by Japanese manufacturers for their own premium cables, were originally imported, and ultimately copied by American sources.
Rel. Caps were discovered, and were originally called 'Wonder Caps' and they were found to be subjectively better than typical Mylar, polycarbonate, etc. Experiments with circuit board materials going to something better were also going forward. Finally, servos were being used more and more in audio design, effectively removing coupling caps, as lower offset, fet input analog IC's such as the National LF411, became available.
For me, measurement was effectively standing still, EXCEPT for passive parts, such as Caps, Connectors, and Wire.
Connectors were studied by serious designers such as Walt Jung and Dick Marsh and a number of specialized papers were found promoting gold on gold connectors, if at all possible. Relay problems were also studied.
In caps, measurement of DA was still difficult, doing it the way similar to the way that Bob Pease had done in his paper, but a 'reasonable' solution was at hand by an analog differential test apparently developed by Walt Jung and Scott Wurcer.
This test used a quality, high common mode rejection, instrumentation IC op amp, or IN-AMP, designed by Scott Wurcer, making a differential subtraction of two caps, carefully matching their respective RC time constants to each other. Dick Marsh dropped out of this measurement effort, as it is only an approximation that shows differences, but does not show what the differences really are. However, it had the advantage of easy measurement setup and consistent results. Walt and I wrote a paper together on the results in the mid 1980's. more later
This is important to me, because by 1980, most of us us have gotten to as far as we have discussed on this thread, recently, and little more 'research' appeared in the JAES that really gave us further insight.
This is where many of us started to try different cables, both interconnecting, and internal hook-up wire, with improved refining and better jacketing. Mogami became very popular in wire for a long time. Compared to 'hardware store' wire, it was better made, often more flexible, and more 'interesting' in its configurations. Improved RCA connectors became available, originally made by Japanese manufacturers for their own premium cables, were originally imported, and ultimately copied by American sources.
Rel. Caps were discovered, and were originally called 'Wonder Caps' and they were found to be subjectively better than typical Mylar, polycarbonate, etc. Experiments with circuit board materials going to something better were also going forward. Finally, servos were being used more and more in audio design, effectively removing coupling caps, as lower offset, fet input analog IC's such as the National LF411, became available.
For me, measurement was effectively standing still, EXCEPT for passive parts, such as Caps, Connectors, and Wire.
Connectors were studied by serious designers such as Walt Jung and Dick Marsh and a number of specialized papers were found promoting gold on gold connectors, if at all possible. Relay problems were also studied.
In caps, measurement of DA was still difficult, doing it the way similar to the way that Bob Pease had done in his paper, but a 'reasonable' solution was at hand by an analog differential test apparently developed by Walt Jung and Scott Wurcer.
This test used a quality, high common mode rejection, instrumentation IC op amp, or IN-AMP, designed by Scott Wurcer, making a differential subtraction of two caps, carefully matching their respective RC time constants to each other. Dick Marsh dropped out of this measurement effort, as it is only an approximation that shows differences, but does not show what the differences really are. However, it had the advantage of easy measurement setup and consistent results. Walt and I wrote a paper together on the results in the mid 1980's. more later
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Another good source of cap measurements for audio was in a mid 1980's article by Martin Colloms in 'Hi Fi News' : 'Capacity to change'. The important cap articles are archived on Martin Colloms' website. If serious engineers would just look at these articles, many questions asked today would be answered.
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Martin Collums articles
John,
It appears as if the articles you refer to have been moved to the HIFICRITIC website:
HIFICRITIC, audio review magazine, hi fi critic
Good discussion!
Howard Hoyt
John,
It appears as if the articles you refer to have been moved to the HIFICRITIC website:
HIFICRITIC, audio review magazine, hi fi critic
Good discussion!
Howard Hoyt
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