Audioprism Mantissa tube preamp buzz

Hello everybody, I've just re-tubed this preamp and after hooking everything back up I have a loud buzzing coming from the speakers. I tried a different amp and putting the old tubes back in but I still have the buzz. I've narrowed it down to preamp being the source of the problem. This piece also has an outboard power supply. Is there anything that I might try to fix the problem or should I just take it to a tech. I appreciate any suggestions. THANKS
Try playing around with the input selector may not be seated properly. Or, try another input?

My Mantissa will buzz if the selector does not seat...a wiggle of the knob and it's gone. (the Mantissa are getting old)

Other than that...

good luck,

Is there a buzz coming from the outboard power supply? Perhaps there's a grounding issue there if it is (i.e. transformer hum).

Does it sound like a buzz or a hummmmm? In other words, did you perhaps disconnect a wire from the RCA's while you were in there? Check that all of the wires inside are connected at both ends and nothing is floating free.

Are the tube sockets solidly connected or did you perhaps loosen one up when pulling out a tube? Does the buzz switch from left to right when you swap tubes, or is it in both channels?

I would take it to a tech if the above mentioned fail
You probably have disconected something from the valve sockets,maybe a bad pin conection betwwen the valve socket and the board,could be a loose wire somewhere,as well...could be one of your interconects..check for shorts in the cabling, wishes Dan
Should a repair be required, you might want to contact Raptor Electronics. The owner, Brian Hawkins, was part of the original AudioPrism/Red Rose technical team. He can repair and make modifications/upgrades to electronics made by AudioPrism & Red Rose.

Raptor contact details:
Web site link