This is a question for the sound card gurus out there. I have a PC where I get distortion on the Left channel for every Creative card that I put in. Here are the details:

- FIC 486-VIP-IO2 Motherboard running an AMD 5x86-P75 CPU overclocked to 150MHz, following this guide: https://www.dosdays.co.uk/topics/review_fic_4 … vip-io2_pt3.php. System is running pure DOS (the version that comes with Windows 95).
- Sound cards (used one at a time, of course 😉 ): Vibra 16, SB16PnP, AWE32, AWE64 value. No other cards in the system except for the PCI video card.
- Distortion only occurs when playing sound effects in games and only on the Left channel. The Descent setup program is a great way to test this. FM/AWE32 music works flawlessly. The cards sound and test perfect when used with the Creative diagnostic tool (diagnose.exe).
- Initializing the cards using Unisound does not make any difference.
- The problem does not change if the cards are inserted in a different ISA slot.
- Power supply readings (under normal use, with everything connected): 5V -> 5.1, -5V -> -5.2, 12V -> 11.8, -12V -> -11.3. I can't measure the ripple because I don't have an oscilloscope at home. My basic multimeter shows AC voltages in the millivolts for all of the rails.
- The distortion is the same when using Line OUT or Speaker OUT.
- It's not the speakers 😀

Unfortunately I don't have another power supply or motherboard to swap in, so I can only test using the current hardware. Any ideas are welcome.