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

I would not use Mundorf film caps for your amps. They are rather tipped up in the upper midrange and can sound a tad too brilliant and artificial. This is compared to the better sounding caps like Vcap Odam, Jupiter copper foil, Jupiter HT and others. These other caps are more coherent top to bottom. I am referring to the Supreme silver/oil and silver/gold/oil caps. I am not referring to their line of electrolytic capacitors.
My experience after using them several years ago.
If you are looking for some tipped up energy in the brilliance area, then the Mundorfs may be a good choice.

The  film caps I pointed earlier are all coupling David. The 2.0 uf white caps in your preamp are output caps sometimes called output coupling. You can use the Odam 2.2 uf there. In this output position 2.2uf is perfectly fine. This position is not the same as the stage coupling caps we discussed not changing the value of.

Re: Mundorf EVO Silver-Gold (non-oil) version sku #80510 is smoother, .22uF 1000vdc, and is not "tipped up". Actually,  the non-oiler version caps are better sounding than the Silver Gold Oil (SGO) version with oil in amps.  Yes, the opposite of what most might think about adding "oil". I learned this from an amp designer colleague when using them in my larger Cary amps, Cary preamps, and now using them again in my Quicksilver Mono 120s with KT150 tubes. 

>>They DO sound more pronounced until fully settled in. Easy to get impatient<<

Kinda discovered this by accident after not wanting "oil" caps that dry out in my prior big amps that get hot. 200hr burn-in required on the non-oiler version cap too, and it is an aggravating roller coaster ride before the EVO silver-gold non oil caps truly form and stabilize to their final set point. Sounds nice when they do.  

Yes, the EVO line is not as tipped up. Agreed.  I have used them in crossovers where I needed larger values and had little space.

Look at Miflex films as a competitive alternative to Jupiter/Dueland. 

"@grannyring ...You can use the Odam 2.2 uf there. In this output position 2.2uf is perfectly fine. This position is not the same as the stage coupling caps we discussed not changing the value of."

grannyring, interesting, I wanted to ask you about this for hilde45 if you felt jumping from 2.0 to 2.2uf was okay or not for the QS LS. Not seeing a lot of 2.0uFs out there any more like the old vintage stuff.  Good to know. 2.2 it is!