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Audio Notes…

January 12, 2012

I have been quite deeply into the world of vacuum tube audio in which some people are inclined to pillage Tektronix scopes for Amperex 6DJ8s not to mention the Holy Grail Telefunken 12AX7 to put into mostly desultory circuits. I flatter myself that my work has not been desultory and I have not pillaged equipment. The thing is, I found myself striving for something that most likely is delusory. Not that well designed vacuum tube audio equipment does not offer sound that simply is not available with commercial gear, simply that there was never any lasting sense of accomplishment. And, as good as the reproduction end can get, it is limited by one, the recording set-up which since solid state became prevalent is horrible, two my ears and three the room. The horribleness of the recording process stems not only from excessively complex solid state electronics but also from increasingly complex functionality. The recording engineers of the 50s and 60s had simple quality gear to work with, and knew how to use it musically. I don’t hear that so much these days.
Anyway, where am I going with this? When I was a kid, one of my father’s colleagues said to me “you do realise that you are listening to the power supply?” I sort of got what he meant but not really, however the question stuck with me. What I realised during my sojourn in this area is that the results are limited by the extent to which the signal can be isolated from the power supply. Commentary regarding the sonics of line cords and the sound of rectifiers puts blobs on me as my mother used to say. And, such commentary is irritatingly valid, I finally got what my father’s colleague meant. Consider that power mosfet technology can be used to significantly advance the separation of the signal from the power supply, providing the topology is Class A and I mean Class A, not Class AB described as Class A; these days since Class A was “discovered” many sellers describe Class AB push-pull amplifiers as Class A.
Western Electric actually did look at using constant current regulation to more effectively isolate the signal from the power supply than chokes can, however that was before the days of power mosfets and it was simply not practical using pentodes.
Actually, the power supply is just one area where solid state went WAY backwards, since there were and are no chokes and much deeper departure from Class A, the signal is forced to pass through large value electrolytic capacitors, this is a recipe for horrible sound. Truly, I cannot listen to music through such miserably inappropriate electronics; inappropriate because the designs were created to support marketable data for the punters, not beautiful sound. Another area is complex circuits combined with 40db or more negative feedback “correction”, after the horse has bolted, to accomplish the required marketing specification; apparently super-low harmonic distortion with P-O-W-E-R, resulting in the all-too-audible transient intermodulation or slewing distortion, that the simple valve amplifiers were relatively free of and the later zero feedback valve amplifiers are better still. And this to almost miss the resulting compression of the sound due to less and less efficient speakers dissipating all those W-A-T-T-S as thermal modulation of the voice coil resistance! And as the speaker became less efficient, so the P-O-W-E-R had to grow to compensate and we wind up with systems rated at over 1000W in cars!
I have written a paper about signal isolation that is available at www.richardsears1.wordpress.com
If I have contributed anything to the world of excellent audio this is it. However, people just don’t seem to get it and continue attempting to refine amplifier stages endlessly without taking care of the power supply first!
If, if you are interested, most of my work is published at www.triodeguy.com

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