How to setup DOS audiomixer levels
1) copy BTVMIX.EXE from my driverpack to root of boot disk in your system
2) add to autoexec.bat line like
btvmix.exe DV=4,4 MV=4,4 FM=4,4 CD=4,4 LM=4,4 MIC=0 INPUT=C
3) run once more btvmix.exe and adjust levels per channel as your like 😉

Ran across this and bought it. Looks to be the attachment for the Number 9 card shown in a previous post. Now if I could only find one of the cards... hah.
These are the seller's pics cropped: