channel 3 feedback/squeal

[K-Roll]

Weird things started happening suddenly,

I get a loud feedback when playing staccato on channel 3 mark 4 mode when i push the gain and treble further than past 2 o'clock. on 2 it seems ok, but even if i raise it by a tiny hair, it starts squealing when playing palm mutes.. gets worse the louder i play i guess..even if I hold my strings with my right hand it's there like a sirene.

I bought 2 new 12ax7 from mesa, tried rolling each of those in different spots, the squeal remains there. I tried the pencil test on my power tubes too.. no microphonics, really weird. Ive got a BKP blackdog pickup in my 7string which is quite far from my strings, so i guess that's not the problem.
I tried using just the guitar/cable/amp and it's there. my NS2 does not kill that feedback when i switch it on.. any ideas what to look for?

 

[KH Guitar Freak]

Try a Mesa SPAX7 preamp in V1, unless they already come shipped with those...

 

[jb's 52]

Weird things started happening suddenly,

I get a loud feedback when playing staccato on channel 3 mark 4 mode when i push the gain and treble further than past 2 o'clock. on 2 it seems ok, but even if i raise it by a tiny hair, it starts squealing when playing palm mutes..

I've gotten this before even when standing roughly around 3 feet from the amp. There's a weird mix right there with the gain and treble past 2. But the last time this happened, I went from home to rehearsal. These settings worked at home...I think they were at 45W, master at 9, and the ch3 vol at 8' clock if I remember right. But, when I got to rehearsal I went jacked the master vol between 10 to noon and got this feedback/squeal. I typically go 90W with the band so, I just had to flip that switch and I'm sure I backed the gain down a bit...but all was better after that. I try to get a little feedback going, but yeah, not that much, that sudden...hehe...