So long story short, I think I've made a costly mistake.
So I was messing with amps, pedalboards and all that good stuff. I was testing some sounds on my JVM410H and Peavey 6505. I sat both on top of a Marshall cab to do my fiddling.
Did my thing with the Peavey and went round the back to mess with the JVM to connect it up. So swap cables between the heads for the power, loops, etc.
In a nutshell, I brain farted and connected the JVM's 16 ohm out to the Peaveys 16 on output. So yes, both outputs connected together instead of plugging the Marshall into the cab. The Peavey was of course off, but fired up the JVM, spent a minute wondering why there was no sound and looking around the back fiddling with effect loop connections realised what I had done.
The aftermath is that the Peavey makes plenty sound on the clean channel, drive is extremely low volume and although it increases with the volume knob, the max sounds extremely low and fizzy.
The Marshall seems to operate OK but I would swear it now sounds a bit off. I can't decide if I'm imagining it or not.
While I'm familiar enough to do basic repairs, out of hand, how badly did I mess up? Whats in that pathway that I could have properly destroyed?
Yes, I'm a dumbass. Silly mistake.
So I was messing with amps, pedalboards and all that good stuff. I was testing some sounds on my JVM410H and Peavey 6505. I sat both on top of a Marshall cab to do my fiddling.
Did my thing with the Peavey and went round the back to mess with the JVM to connect it up. So swap cables between the heads for the power, loops, etc.
In a nutshell, I brain farted and connected the JVM's 16 ohm out to the Peaveys 16 on output. So yes, both outputs connected together instead of plugging the Marshall into the cab. The Peavey was of course off, but fired up the JVM, spent a minute wondering why there was no sound and looking around the back fiddling with effect loop connections realised what I had done.
The aftermath is that the Peavey makes plenty sound on the clean channel, drive is extremely low volume and although it increases with the volume knob, the max sounds extremely low and fizzy.
The Marshall seems to operate OK but I would swear it now sounds a bit off. I can't decide if I'm imagining it or not.
While I'm familiar enough to do basic repairs, out of hand, how badly did I mess up? Whats in that pathway that I could have properly destroyed?
Yes, I'm a dumbass. Silly mistake.
While I AM truly sad to hear of your plight, all may not be lost! 
If you closely follow the advice/instruction/guidance/tutelage of some of the brilliant techs around here, they may well be able to help you sort out the problems, without it costing you a fortune! 
Been There, Done That, Got The Tee Shirt! 
