Herbert MKII feedback problems

[-Nox-]

Hey folks!

I had my brand new Herbert MKII in rehearsel yesterday - unexpectedly with enormous feedback problems. In addition to that, I have to say that our rehearsel room is quite small at the moment, because we're moving. My 6505+ runs quietly in the same setup.

Currently I'm playing an ESP Horizon NT II /w sh4+sh1 straight to the amp through an ENGL 412VS cabinet. The settings of the Diezel are nearly all about 12 o'clock, volume is moderate. To make a point, at CH3 the feedback drives me nuts. After 3-4 seconds the single notes feel like "dying" and slip into the feedback. wtf?
I recently played a studio session with the Herbie and I had no problems at all!

I'm desperated! Idea, anyone?
David

 

[MARK2C]

Try a new V1 and V2 preamp tube and see if that helps.

 

[RedB4Black]

sounds like a microphonic preamp tube.

 

[PaulyPanacea]

sounds like a bad preamp tube or 2 .... but those guys said that already

 

[King Crimson]

Yah, what PP said.

With the Herbert off standby and on CH1 tap each preamp tube with the eraser end of a pencil. Listen for any type of "bell" sound or anything unusual coming from each preamp tube.