Monday, October 10, 2016

Great American Sound

One of my best friends worked at G.A.S. for awhile, he introduced me to James Bongiorno in 1975 (I also met him later a few times) and Andy Hefley (who became one of the principals after James left).  All very interesting experiences.  I never bought a G.A.S. product new, I was a student at the time and they seemed too expensive, but later I did buy a second hand Son which developed an RFI problem I never fixed.  Having seen my own GAS unit have troubles, and other troubled units, I often wonder whether reliability was the actual issue which brought them down, not one of many others which have been alleged.  But the split between the founder and the remainder certainly didn't help either.  At the time of my last visit to the GAS company in Chatsworth, only a few miles from where I had attended all my primary and secondary schools, James had already left the company and GAS had installed Wave Soldering machines all over (this led to their debt problem I suspect).  Wave soldering was a very new thing at the time, and can itself lead to unreliable construction if not done correctly--which may not be easy.  OTOH, I suspect they went to Wave Soldering after the regular soldering wasn't going very well either.  Andy was doing the final feedback loop adjustments on his prototype Godzilla, which that evening we played at his beach house...

Given the charismatic James, it's no wonder every G.A.S. product was iconic and worth learning about even if his associations or companies didn't last long.  The first amplifier, Ampzilla, has been said to be one of the most copied transistor amplifier designs.  James seemed equally proud of the Thedra preamplifier, which near the time of his death he said there had never been anything like it before or since and he'd never use anything else (he did also create a new generation Thedra, much different, during the 2000's).


So what's special about this?  Many things have been widely copied, others not.

1) Separate MC and MM phono stages (no transformers!)
2) MC stage has servo loop (uniquely so as far as I know)
3) Line (tone) amp also has servo loop
4) DC coupling enabled by servo loops (no coupling caps!, except in phono)
5) Tone Controls with far-out hinge points (160Hz and 4kHz)
6) Tone and Volume controls use stepped attenuators using sealed metal film construction.
7) Low filter is Bessel type with 5 positions.
8) Very low impedance line outputs

Like many before his time, James insisted that preamps should have tone controls.  His final redesign of the Thaedra had the most flexible controls he had ever done (though still not quite what the Cello Pallete offered).

That's very interesting I think now.  Personally, no gear that I have owned has had easily accessible tone controls (I'm not counting fancy DSP) since 1979, about the time JB left GAS.  Before that time, I had been using a Marantz 2270 receiver which did have tone controls which I never used, and it especially irked me that the "stepped" controls were not stepped at all, they were using ordinary pots with a mechanism which made it seem like the controls were stepped.  Indeed when set to "flat" the Marantz 2270 controls were not exactly flat, as you could easily see on a square wave.  And there was no tone defeat switch.  I couldn't wait to ditch the Marantz once I discovered this.  Actually this kicked off a year of experimentation as I tried different IC op amps to replace the line amp in the Marantz.

If only I had bought a Thedra preamp, it might have been all different.







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