Hi, I had been using my JMP-1 for over a decade - stock tubes, OD2 channel - with no issues until recently. There was this bad cable that kept producing loud spikes - although I'm not quite sure the JMP-1 wasn't adding up to these as well. After that the JMP-1 started sounding dull, one-dimensional, with poor note definition, and worst of all - with a subtle yet relentless flanger quality to the sound on all four channels. Swapping tubes (V1->V2) didn't help at all. Having googled extensively, I assume it's quite an uncommon issue. Any help much appreciated.