Slightly OT: volume problem with DS-1

[Bucksears]

When my DS-1's are ON, the volume control doesn't completely cut the volume off; there's still a decent amount of distorted signal being heard, and it sounds very much like a misbiased resistor until I turn it up.

The bypass works fine.

I had an older Alesis Quadraverb running in to the input of my SRRI for a day or two, and I also swapped out the p'ups on my Ibanez Artist; ever since, my two DS-1's volume stopped shutting all the way off and all of my distortions sound like crap.
Has anyone experienced anything like this before?
Should I replace the preamp tubes in my SRRI?

[Bucksears]

bump