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

Beware making changes in well designed gear.

I have seen both John Curl and David Berning deplore such 'improvements, saying that if they had wanted more expensive components in a given circuit they would have put them there - they designed for sound, not price.

And if you are talking about as market gear, I doubt that any substitution will make much improvement compared to buying a well designed piece of gear, even if it turns out to be pricy. (Sadly, there is lots of pricy gear that fails to give good sound too.....)

Had a few of coupling caps failed in a few tube amps, my current pre replaced all coupling and power supply caps with Vcaps, Mundorfs, and Jupiter.

Replaced IEC inlet with Furutec and went to Amperex tubes.

That said, things become more reliable but can change the sound for better or worse.

@wsphohn I appreciate your opinion. I’m not swayed. This gear, as Grannyring and decooney have pointed out, is clearly built to a price point. It is not in the league of better Curl or Berning gear. A $4 Orange cap as being intentionally part of an amp design? That does not strike me as plausible an explanation as the price point explanation. The preamp came with $13 tubes in it. Should I have left them alone? (I realize tubes may be a different thing...but still.)

The testimony of other owners of this gear is that it very much advances the gear into another level up -- so, rather than spending thousands more for another preamp and amp, I’ll spend hundreds. Everything is reversible if I don’t like it.

@terryakhan Things may get better. May get worse. I suppose that this is a level of risk I’m willing to take. That’s what this hobby means, for me at least.

Can be lower risk and higher reward when high quality-upgrade replacement parts of exact same specs are used and installed by a competent tech.  

Watch a Paul M video from PSAudio where they fully acknowledge even their higher end gear is all designed and built to a price point to control costs, keep pricing down, increase profitabilty, not using overly exotic parts.  And, then sharing in their other design lab they build and upgrade experimental prototypes built with the best parts available to help determine what is truly possible to achieve the best sound. "What is now proved was once only imagined" ― William Blake

How about upgrading transformers?

Do QuickSilver amps have high enough quality transformers and they don't need to be replaced?