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Many have heard these at my place or at CAF in '15. Here's the schematic and a few pictures (with the smaller 24VCT transformers I used to use). If you want to build a stereo version, you'll need to substitute a 36VCT/3A transformer....

Everything except the power supply:


Interior view:


External, they're mirror images:


Schematic:


Roscoe

Why the 1875?

Best sounding one I tried....

Roscoe

If someone needs some LM1875T's let me know.

Probably have 10 new in a tube from Digikey. Should be latest production.

I already ordered some and hopefully they are on the way

heatsinks will be a problem though
going through parts shelf, I have most everything else

You don't need much, an old CPU cooler would probably be enough.... I've never noticed mine being more than barley warmer than room temperature... The 47labs GainCard just used the chassis, without any real heat sinks...

Roscoe

Are both of the caps on the chip 0.1uF? Did you reverse signal connection to get polarity corrected?

Yeah, both. Value here isn't critical, that's the local PS bypass right at the chip pins. When I originally built these amps, they were non-inverting, so the output is inverting, I just flip the output connections. Feel free to hook up your output to the black binding post & the red one to ground, then you won't have to think about it when they got hooked up...

Roscoe

maybe a noob question but....
are the chips insulated from heatsink/ground. I see the thermo paste but curious it there is a piece of mica in there also