I ended up ordering a batch of five DC-to-DC converter boards from JLCPCB. They take 9-36V in and gives +/-12V out, at 833mA per rail max. The voice cards draw 500mA per rail so that's about perfect.
To test everything, I found a 19V 2.4A power adapter from an old laptop. It measures 19.8V out which is fine.
To keep the output within range of my Logic2, I used a resistor voltage divider with 100k on top and 200k on bottom, which should give us 8V out.
The DC-to-DC converter has no trimming option, so we're stuck with whatever it outputs. My multimeter says 12.05 and 11.98V, which I think is good enough for Rock'n Roll.
I tried measuring the output, and while it's hard to know everything that affects the signal, here is my initial findings:
The output fluctuates between 7.797 and 7.807V, or 10mV. (or two steps on the Logic 2. The real fluctuation may be a bit higher).
It looks like the noise has a period of around 8uS, which means about 125kHz. Again, it's hard to tell if this is real and if it is caused by the converter itself, but this is what I got.
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| 10 cycles take 81uSlog |
I don't think I have any way of measuring ripple more closely than this, so next up is seeing if this is audible.
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