-
I was thinking more of the method that varies the rail voltage cleanly and efficiently
Should be easily achievable with a SMPS, you're effectively just looking for a 0-50V DC bench power supply, they can be had pretty cheap from China.
Not sure a PC PSU is clean enough for audio
Everything is powered by SMPSs now, obviously to drive just the logic in a class D amp you're looking at something more like the internal PSU of a phone rather than a 250W gaming PC PSU. The RFI issue is greatest at the high power end, and you have that problem from your class D output stage regardless of what you do with the logic PSU.
The alternative to messing with the rail voltage would be to mess with the pulse width, but I don't know whether you can get pulses down to narrow enough for the quiet passages if you also want the volume down to -40dB relative to full power. If your pulses get elongated due to finite rise time, you effectively have a compressor because the short pulses (low amplitude) have more excess area under the graph than long ones.
You are reading a single comment by @gbj_tester and its replies.
Click here to read the full conversation.
gbj_tester
I was thinking more of the method that varies the rail voltage cleanly and efficiently whilst allowing sufficient current. Need to do more reading!
Not sure a PC PSU is clean enough for audio without lots of RFI screening.