Aguilar DB750 buzzing

[fuzzylogic]

Hiya anyone who can put my mind at ease.

I was just moving some gear out of hallway and the DB750 which is in a rack case toppled over ( amp was on floor ). I set it up with my bass cab and when i plugged in my Fender Jazz bass it was, to my perception, making more of a buzzing noise than usual. This is especially true while standing fairly close to amp, but buzzing goes quieter when moving away from amp. I fear i may upset the tubes in the pre-amp section or maybe even the mosfets. Having said that when i unplugged my bass the amp was very quiet ( amp wasn't left on mute setting ). Can anybody advise as i'm sweating about it and don't now of any amp specialists in the West Midlands area who could be trusted to service my amp. The buzzing is similar to that of my Trace Elliot GP12 SMX combo. I have however worked out that the buzzing isn't there if i turn the dial for tube/solid state on pre-amp towards solid state giving me some indication that the premp tube ( 12ax7, i think ) might need replacing or there might be some loose soldering in the circuit perhaps.

I would be grateful for any advice,

Thanks Daz