hey I've searched pretty comprehensively and I havent found anyone with the same problem on a thread so I thought I would ask. I recently bought a jcm800 4010 blind off ebay (stupid i know and ive learnt my lesson!) and needed a $80 fix up job just to get it working. I got it back from the tech's repairshop today and although I'm no amp genius I think the preamp isn't doing it's job. On high sensitivity channel, moving the preamp knob from 1 through to 10 with master on about 1.5 -> 2 changes very little in terms of distortion and as an effect the most gain i can get is ACDC type crunch when i dig in as hard as i can. Having been a listener of Slash and Noodles from the Offspring I've heard it before and have deduced the amp is not working to it's full potential. I'm not too keen on taking it back to the tech as last time i was without the amp for a fortnight so it would be great if someone could help me out and explain what might be wrong ie tubes, transformer etc.