Thanks for the reply. Turns out all the valves were crap!!
The pre amp valves were all below 50% efficient (even the new ones that I had put in!), and all the kt66's were losing their vacuum pretty badly.
I've just put new Gold Lion KT66's in it and Sovtek 12ax7's, which has improved it a bit, but not loads.

The glassy tone seems to be there when the master vol is full (and therefore out of the circuit) but not had anywhere suitable to get any overdriven tones like that as its way too loud!!!
It's on eBay and Music Radar classifieds at the moment as I'm not sure I can be bothered to mod it until I get what I want, as I can't do the work myself.

Hi, I'm new here, but thought this would be the best place to get advice about my jtm45/100.

I bought the amp already built from its original owner a few months back and am not happy with the sound. For a start the bass has a flubby/farty sound that I've heard described here, so I know the possible mods for that. But on listening to YouTube demos of other jtm45/100's, and in particular those from the guy I bought it from, realise that my amp has none of the 'glassy' or chimey sound that all the others have. The original owner was in an AC/DC band and there's no way I can get the amp to sound a bit like AC/DC!!!
Can anyone suggest what may be wrong???
I'm taking it to my amp tech next week to check valves, bias and voltage etc but any suggestions are welcome.