I got it going Saturday night. It's an inverting 1875 amp
using Scott Nixon's boards. I made it in a dual mono
configuration with two 36.5 volt CT transformers from
James Electronics (under $10 each). They are rated at 1.5
amps, which seems light, but they sound fine on my sacrificial
startup speakers (Radio Shack Minimus 7's) and then later on
my old main speakers (first generation B&W 802s). On the latter,
there is obvious compression at high volumes, but no tonal
distortion. So for 20 watts and a non-beefy power supply,
I'm pleased. They are, thus far, as promised, very clean and
dynamic, but not cold. While playing, the rails are at 25.7 volts(+/-) and the offset
into 23.5 ohm resistors is 13 millivolts, both channels the
same. The only somewhat unusual pieces are the GE motor-run
capacitors as input blockers. These are 6 uF paper-in-oils. I
will experiment with a foreplay that already has caps on the
output to hear how it sounds with those caps bypassed.
That's it for now, many experiments with speakers (Lowthers,
Studio 1 and 2 Pi Speakers), preamps, cables, etc. ahead.
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