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

Showing 14 responses by grannyring

Please share the QS models so I can be very specific. Need to see the space you have and what’s in there now. QS gear is a great brand to upgrade. They are built very well, point to point, simple circuits, and built with modest parts quality. I think QS gear would respond very favorable to some well thought out and executed upgrades. The same sort of upgrades the builder would do if not trying to sell at a given price point.


Sold every single piece of gear I ever upgraded/modified with no problem and happy buyers. Well done upgrades, professionally done, have a good sized market out there. I must have sold over 25 modified/upgraded pieces of gear. Always sold pretty fast.
As an example, if you have the standard QS Linestage, then the top two things you can do are:

- replace the Alps Blue pot with the same exact value TKD pot from Japan. Big jump in resolution and realism.
- replace the film coupling caps behind the tubes with Vcap Odams. The same value. 
Just these two things will make you smile big. These parts will fit. Top two things you should do. Yes you can do more, but these will have more impact than any other upgrade .
I would do what I said above with your preamp.  Replace the Alps Blue pot with the same value TKD. The potentiometer has a sticker on the back that tells you if it’s 25k, 50k, 100k etc…. Nice step up in resolution and realism. More than replacing a cap. This can be found at Parts Connextion or Hifi Collective. I think the TKD pot costs just under $100 shipped. 
Replace those white caps labeled QS behind the tubes, 2 of them, with Vcap Odam 2.2 uf.  600v. If too pricey for you use the Audience XO caps. The Odams are wonderful in every way and a nice step above the Audience. The Odam caps will cost around $100 each.  The Audience caps about 1/4 that.  
You could replace the 4 - 47uf 500v filter caps with Mundorf M-Lytic HV 500V 2-Lead Single Section Axial cap from Parts Connextion.  If the amp is 10 years or older, then consider this upgrade.  They cost some $11 each. 
Your amplifier has 4 coupling caps that can be improved on.  The two orange ones are .22uf and are Orange Drop brand. Replace with Vcap Odams if you can afford them. Audience Auricap XO if you need to spend less.  Both will fit.  
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. 
The bridge rectifier is soldered directly to that large blue electrolytic filtering cap mounted on top of the chassis. It can be upgraded to fast recovery type (Fred) if not already. Not sure what is in there now. 
Other stuff, but not sure you want or need to go that far. 
The Orange Drop caps are nowhere near the Vcap Odams in performance. The Odams are far more nuanced, resolving, dynamic and real sounding. Not close. However, neither is the price ☹️
Both the Audience XOs and Sonicaps are also a nice step up.


If you are close to Nashville, I could do the work for you. Important the work be done cleanly and right. My guess is you are out in the Northwest by looking at your username pic.  
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.
One last thing.  You could also upgrade the wires going from under the preamp mounting board to the RCAs. VH Audio Airlok silver 18 gauge is great.  The Airlok copper is much less and also good.  You only need a foot or two. 
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 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.
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.
That is funny. I dislike Miflex. Far too forward sounding to me. I replaced them in my integrated amp and past tube dac with Odams. The Odams were clearly better in every sonic parameter.  Now Vcaps do take awhile to burn in. Longer than Miflex. Wonder if he did not give them 150-200 hours! If not, that is why. The Odams can sound constipated and bass shy initially. 

I know the Miflex very well. Just can’t get past how pushed forward the stage is. I know two other builders who now offer Odams over Miflex based on listening tests.  
Go figure. 
Agreed. My point is vs Jupiter caps and those are not being carried for other reasons beyond what we want as I understand it.


Jeff at Sonic Craft is a great guy and I have learned a great deal from him. Big plus for the industry! I will try the other Miflex caps based on your comments here. I have only tried the KPCUs based on Jeff’s suggestion.
Wow. The Odams never sound congested in the over 20 units I placed them in. In audio it seems nothing is ever absolute. We get that. I know Jeff at Sonic Craft likes the Miflex. The Jupiter copper caps sound better, but he no longer sells them. He will push what he carries and that makes sense. He told me the Miflex sounded as good or better than the Jupiter copper foils for less money so I tried them. I just cannot agree. They are too forward sounding in the electronics and crossovers I placed them in. The Odams were the best of the lot. Just my opinion.

Some like that forward, front row perspective and that is a subjective preference for sure. This is why nothing is absolute. Builders have sonic preferences just like the rest of us.

The one thing I find strange however is the congested comment on the Odams. I have never heard it. No other comment I have heard or read suggests this either. This is an outlier opinion that has me scratching my head my a little 🤓. However, I greatly respect Aric and his builds.  He does great work and that is a fact! 
Yes Solen Fast caps are made in France. They could very well be used by QS. They are the very definition of modest quality…at best. Dull and flat sounding compared to the better ones mentioned here. Used by many builders because they are very low cost. Some builders do have real cost constraints to contend with.