I've seen this before, a long time ago, where a Voyetra Turtle Beach Sound Card failed, but I don't know what kind of failure it was. I only mention it because the Turtle Bay and Audigy were around the same time period of production, same style of sound card, but different manufacturers.

The problem I'm having with my SB Audigy is that the left MIDI channel has failed, and adjusting the left-right balance does nothing.

I replaced all the capacitors on my SB Audigy (Wasn't easy), because it seems like various electronics were failing around this period as well due to bad cap formulas. (I'd be testing the card, but my main motherboard, a 22 year old system, started showing them too on the CPU vCore line! So now I have to wait until Wednesday for replacement capacitors.)