Demeter VTBP-201S issue

[Spent]

Something weird is going on with my preamp. I use my Demeter VTBP-201S for gigs only, practice at home with a MatkBass CMD102P and use a GK 1001RB at band practice. Getting ready for a gig last night, I set up my rig for a quick check at home. I plugged in my Spector Legend (active) and it sounded horrible. Every time I slapped or popped a string, it sounded like a bad chorus pedal. This was the case straight in, through my pedalboard, two different DIs and in the active or passive input. I even opened the Demeter to adjust the output level. This bass sounds fine through every other amp mentioned and even directly into the sound board. And yes, the battery is fine and the preamp was on long enough for the tubes to warm up. Next, I plugged in my Fender Aerodyne (passive) and it sounds great with each of the above mentioned options. I am at a loss. I'm contacting Demeter, but in the mean time, has anyone else had this experience?

 

[Big String]

Maybe a tube gone micorphonic???

 

[Spent]

Maybe a tube gone micorphonic???

Maybe I don't know enough about tubes to be able to tell. They're cheap enough and I was planning on getting a couple to play with anyway. Just not sure why the two bases sound differently. One is active, but I'm running them through several pedals.

 

[Spent]

Just heard back from James Demeter, suggested I change tubes. I would really appreciate suggestions for replacements. I like a nice clean sound with plenty of headroom. The preamp does put out more than it needs to, I've actually used the internal trim pot to attenuate it a little at times. I'm not sure how much difference specific tubes make in this preamp.