I've just bought a 1988 JCM800 2x12 100w combo (not sure of the model number - it's got the horizontal inputs). Has anyone got experience of adding an fx loop to a JCM800? I asked my local amp tech about this and he said that he wouldn't recommend it because it will affect the tone. Given that there seems to be quite a few people like VoodooAmps offering various fx loop options I wondered how valid this really was. Can anyone recommend a UK-based amp tech who is into modding amps like this? I really want to be able to use this in conjunction with my Fender Twin, using the reverb on the Twin and a delay in a loop on the Marshall to get a really big sound.