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[nekonoko]

I have a Lisa 2/5 with a VintageMicros DAC card installed. In my system the card does operate, but seems overly loud and distorted with persistent hum/background noise once initialized.

I was wondering if this is just how these cards are or if there is a slight incompatibility  - perhaps the VIA clock difference between 2/5 and 2/10 I/O boards or an improper resistor value (or other defect). Not having encountered another of these I have a sample size of one to compare it with.

[sigma7]

DAC card ... seems overly loud and distorted

IIRC, the distortion is common for a lot of the sound output, here is an example: YouTube: New DAC Sound Card for Apple Lisa

The pixel tracks on the screen is an indication of incompatibility... those bits are supposed to go into sound hardware locations.

However, I believe there were a few applications that had good sound with it; I think Dafax published a list of those.

Earlier in the video there are some MacinTalk examples that have pretty good quality.

As for too loud, that may be a hardware problem which may be adding further distortion.
You could compare your board with the one shown here: LisaDAC Sound Card

[nekonoko]

That's exactly what I was looking for; mine sounds pretty much the same. I'll go over the board just to make certain but based on that video it seems to be expected behavior. Thanks for the info!