Ive used them on bass, and guitars too.
It can be a CLEAN tube pre if you want. Provided the caps are still good.
(one of them is starting to hum a little. time to break out the soldering iron)
between the 3 of those, the two viking pres and the two akai/roberts tape pres I've got I am going to do my next session with the drums all hitting a tube stage and passing through tape on its way to the computer. see if I can get a mega distorto Boris-type vibe just for fun.
It shouldn't be too hard to find a stoner-sludge band around here