Tube Amp, Preamp upgrades -- what did you do that improved your units?


Hi folks,
If you upgraded a point-to-point wired tube amp or preamp, what did you upgrade?
I assume capacitors, but was there anything else which you upgraded that made a genuine difference for the sound?
I am looking into improving the caps in my Quicksilver stuff, but before doing that, I am curious if there's anything in addition to caps which I should consider.
Thanks.
128x128hilde45
@tvad  Good points. Regarding (1), if the alteration is not preferred, then I can put the older caps back in, right?  Regarding (2) noted. I think that the QS gear may really be my main rig for at least 5 years and likely much longer. Upgrading it with beneficial effect would solidify the choice. Otherwise, I suppose, I'd be willing to lose some resale value.

@jjss49 Your warning is appreciated. I assume that I might hedge my bets about the risk taken with the modications if I did a simpler upgrade that would be easier to reverse. Because I don't know electrical engineering I don't know where the line between relatively safe vs. risky upgrades are.

@sns Thanks for the list!
warning ...  as per @tvad's comments

rather treacherous, slippery slope here, with many bodies of regret-laden audiophiles littered about
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Takman resistors, film bypass caps on power supply electrolytics. Resistors have flavor, bypass caps tightened up bass.