I've had a 74 Vibrolux for a while and I want it to perform at its best. When I first got it, it already had a three prong cable, but seemed otherwise mostly untouched. I changed out the filter caps that were blistering as a standard thing to do to old amps, and I made a minor (and reversible) 'blackface' mod by lifting the small treble caps on the 6L6 output tubes. What else should I do to get everything I can out of this amp while keeping its basic character? I'm thinking (in descending order) of some of the following ideas : - replacing the electrolytic cathode bypass caps - add a bias trim pot (see robrob's page) - add safety diodes to the rectifier tube (also robrob) - Replace the old and possibly tired GE 6L6 tubes (for example with russian 6p3se tubes because they're cheap...) - use the ground switch to mod the negative feedback (I'll let you guess where I got the idea... - changing the brown/navy 'turd' capacitors (some say they're not great, but I'm not too keen on changing them just for the sake of changing them) Any ideas on what would be worthwhile? Thanks!