The ESL63 uses 2 identical C-cores with the secondaries in series to generate up to 5kVrms at any audio frequency.
Phil don't need no stinking anger management class, Phil just needs people to stop pissing him off! :-) Mikek
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A slight variant of this was demonstrated to me by Quad. (I organised the public lecture.) They used the Quad 405 amplifier, driving a dummy load which simulated the complex impedance of an electrostatic speaker. (It was inconvenient to have a real speaker in a separate room when this demo was being done in a lecture theatre.)
An attenuator reduced the output of the 405 amplifier to be exactly equal to the input. A differential amplifier then amplified the difference between the input and the attenuated output by about 60dB before feeding it into a power amp and loudspeaker.
When the setup was first activated there was some high- frequency sound audible. Their test rig had an air-spaced variable capacitor to allow the high frequency response of the input path to the differential amplifier to have its high-frequency rolloff exactly matched to that of the amplifier under test.
When this capacitor was tweaked the high frequency audio disappeared and all that was left was some very quiet white noise with no trace of residual audio, regardless of the audio input level up to the point of clipping - which made a spectacularly loud noise. As with the demo you described, when the difference amplifier was set to unity gain the result was silence - up to clipping point.
The source material was a good quality master tape played on a Revox at, I think, 30 inches per second to avoid any criticism that the bandwidth or slew-rate of the source material might be compromised.
This demonstration was utterly convincing to me and everyone else who heard it.
John
** But what exactly were you convinced of ?
That the 405 was a specially marvellous amplifier ?
The exact same test was applied to the 303 and others by Quad who said that most, well designed amps could pass the test.
... Phil
I was convinced that the 405 (and other good amplifiers) really did add nothing to the audio signal that could possibly be heard apart from a very small amount of noise.
I was consequently convinced that much of what was being written in the audio press at the time was nonsense.
John
** You have rather missed the point.
Was not me who claimed the Quad amp test unconvincing for audiophools and audio reviewers - it was the folk at Quad - who were able to judge people's reactions first hand.
I doubt you and your cronies at the demo needed much convincing in the first place. Room full of Quad owners and electronics types - right ?
Comprehending the reasoning behind the test requires a good understanding of and familiarity with audio signals and electronic test techniques - or a heck of a lot of lot of trust in Peter Walker.
Neither of which was possessed by your average audiophool - who generally owned Naim amplifiers and speakers and turntables made by Linn back in those days.
Julian Vereker and Ivor Tiefenbrun have a lot to answer for - anyone remember the latter's infamous "This is a lemon" advertisement in the Gramophone when CD players first appeared ?
... Phil
The first CD players weren't entirely perfect, though they didn't damage the media they were playing from, as even the best vinyl players did at that time.
They weren't too bad and they did get better fairly quickly ...
-- Bill Sloman, Sydney
** It was those damn rabbits.
A rabbit plague got into most of the early CD players back in 1982/3, buggered them right up. Eventually it was found the furry varmits just loved eating high inductance resistors.
Sony and Philips soon pissed those damn C&N pieces of shit off.
Bloody hare brained to have ever used them in the first place ....
... Phil
I heard about that. I was told that one manufacturer tried building a "fence" (out of stamped sheet metal) across the middle of the PC board
- all the way from the rear panel to the front panel - but the rabbits just dug under it.
Matt Roberds
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