Hi there. I have a '77 JMP 50 watt. It is all original, verified to be cascading. My amp tech checked it thoroughly and said it is in perfect working order. It was re-tubed and biased back to the original 6550s and still no good. The problem is, the tone is flabby and the distortion is really gritty, not "nice" smooth distortion that I have heard from other amps of this ilk. Any ideas out there about why the amp sounds this way? Caps maybe? They are getting on 40 years old after all. Any other ideas (short of modding) on how to get this to sound how it should sound? Thanks in advance.