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

@grannyring rannyring Thanks for all the thought you’re putting into this question. I’m in Denver, so I’ll go with a good local tech on this.

A couple follow ups if you don’t mind:

First, about the amp: you wrote,

It also has 2 white QS branded caps that are an odd value .27 uf.  Most all caps come in .22uf. Don’t just replace with .22uf.  You want to match the .27uf value. Both Audience XO and Sonicap Gen 1 from Sonic Craft have .22uf and .047uf value caps that can be combined in parallel for the .27uf value. They are both not expensive.

You mention the odd value .27 uF. That struck me, too. 

QUESTION: But if  the combination you mention (Audience XO and Sonicap Gen 1) to equal that value is as you put it, “not expensive,” would the upgrade be worth the surgery?  You did say that “Both the Audience XOs and Sonicaps are also a nice step up” — so perhaps you’ve addressed this concern in your later post?

Second, when you say,

I would replace with the Mundorf caps. They will improve sonics a little. Better bass and a touch more clarity. Not expensive and easy to do since the preamp is already disassembled. I would add one bypass film cap to each Mundorf electrolytic. A bypass cap is simply one cap soldered in parallel. Use a .22 uf to .47uf Audience XO or Sonicap Gen 1.

QUESTION: …are you talking about the black caps in the preamp, again? You had suggested that I “replace the [black] 4 - 47uf 500v filter caps with Mundorf M-Lytic HV 500V 2-Lead Single Section Axial cap from Parts Connextion.” So,  are you now amending this to reaffirm that suggestion but adding another cap along with it?

I’m sorry to not be following easily. We're got two different units here (preamp and amp) and various caps and parts. I'm compiling a table to order correctly. I need to instruct the tech who will be doing the work and so if I’m not clear on it, he won’t know what I need.   

Yes on the .27uf combo from Audience or Sonicap. Both should be a step up. I am basing this on the parts quality used throughout the amp which are modest. Someone is making the QS caps, but I am fairly certain they are not quite up to the Audience XO level of quality.
Yes on the 47uf preamp caps. I added the bypass idea which is a no brainer and will yield sonic improvement. Look up the dimensions of this Mundorf cap and be sure they will fit. Just make sure. I bet they do, but……

I swapped out Gold Lion 6SN7's for NOS Ken-Rad's in an amp and got more bass definition and depth, which I liked in my system. The Gold Lions might be smoother on higher frequencies.  Not cheap on a per-tube basis, but no big deal in the overall allotment of audio funds.

@grannyring Thank you. I'll communicate with my tech on this. The additional bypass cap is not something I anticipated and we'll discuss. 

Do grannyring's suggestions, these may be end game pieces for you then. While I've not yet tried the ODAM, I will drop them in my phono pre in a bit. Reportedly right up there in sound quality with best, and their relatively smaller size vs. film caps makes them better, easier fit. Other parts he mentioned I've heard or modded with, all good. I'm using the Airlock for all my diy power cords, better than Duelund here.

I'm using combo of silver litz and Duelund copper internal wire, Duelund silver bypass cap on power supply in my custom 300b monoblocks. Flavor wise, wonderful timbre, extension on top, controlled bass. I know the silver internal wire and Duelund silver bypass has much to do with attainment of this sound quality. I'd presume the ODAM with Airlock silver would be avenue for you.


I'm not sure all techs will take on custom work, many frown on customer spec'd parts substitution. Don't want the liability if you're not happy with sound and/or don't trust you're substitutions are correct for circuit.