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current feedback electrostatic amp


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Another electrostat CFA lives. This one born on the 4th of July? The PCB is congo5's layout. The amps is powered by my GRHV PSU with ~405VDC rails.  Many thanks to Kevin for another wonderfu

Finally cased my ES CFA amp.  Returned the bias resistors to 1M with the larger heatsinks. Running 20mA bias for the output sections.

build it, put it in a super fancy box, and sell it for $37k betcha it sounds better than the high priced spread, at least no stupidly expensive and useless input transformers. its a push pul

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listening / measuring again.

on startup the outputs are positive, which is safe, good.

I added a fan to my heatsink plate, lowered temp = lower bias.

on start bias is ~13ma and climbs as it warms up. if my fan lets it.

which may be why offset is different today. and also running on mains instead of variac.

rails at +-394v, outputs to ground are all positive, 10v  and under.

no adjustment needed here.

I call this a Big Win   :D

Its to cold to feed ducks, glad I made this.

Thanks

cfbastat2.jpg

 

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Bias current seems to have positive correlation with temperature. That means this amp may blow itself without adequate heat sink? Also, the performance will be different in winter or summer.

Please describe the sound.

Anyway, nice job. It's time for some fancy casework.:D

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these are positive tempco devices, as are most things.

it does seem more sensitive to rail voltages.

Could that be a way to autobias the thing?

Do think it sounds better warm

I am in awe of the simplicity of the circuit vrs SQ

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I'm intrigued by this design. Have to think about how to absolutely minimize chassis size with some small external heatsinks, and maybe use split GRHV PSU boards (not that there's anything wrong with the mini-BH, and it might win out for me in the end).

(Not that I need to make yet another electrostatic amplifier...)

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