I wanted to cure intermittent (seemingly unprovoked) rumbling noise in the reverb signal of my pal’s 77 Princeton Reverb. So I swapped the two old CC plate resistors in the reverb circuit for new metal film ones. The noise was gone (perhaps due to my tightening the nuts of the reverb jacks as well) and I returned the amp. Soon my buddy rang me up and told me that all vividness and deepness of his beloved amp has gone away. I said it cannot be so he played it for a couple of days but the negative impression stayed/hardened. Today I put back in the old resistors and even my old ears could immediatly (without letting the PR warming up) hear that the amp ‚has come back to life’. How can that be???????? The difference in tone was profound! Many reasonable / credible articles deny the impact on tone by the types of resistors in that particular position. Or am I wrong?? On my Fluke I could read that all 4 resistors where very close to 100K (+- 2%). Any thoughts?