Working on a build using a Panasonic SW-5582 Bluray drive that I have. The drive has the 2 pin digital audio interface which I hooked up to a Sound Blaster Audigy, but despite the drive playing music, the digital input seems to be dead.

I have confirmed that the drive works fine using the 4 pin analog interface, but due to quirks of the Audigy DOS driver I have that input hijacked for PC Speaker sound. So my intention is to use both CD inputs simultaneously to have both PC Speaker and CD audio routed through the card.

Swapping in an NEC ND-2500A instead and I can confirm that this setup works fine. Nothing is wrong with the card or the wire, and both inputs are active in DOS.

One possible solution I might be able to do is build a passive mixer to use the analog input for both sources, but was wondering if anyone knew anything about some kind of not well known setting to enable digital audio on optical drives? Searching has not proven very helpful since it seems most people went from 4 pin to just using audio through IDE, but obviously that's not a solution for DOS redbook audio games.

Given that this is a very late IDE drive it would not surprise me at all if the digital out was just non-functional (I was actually kind of surprised the analog output even worked). I do know the command for setting the CD drive volume has 4 channels, so one theory I have is that it's possible that the volume for the digital output is tied to the "rear" volume levels, but this doesn't make a whole lot of sense to me. Nor do I know of any easy way to try it.