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.
Takman resistors, film bypass caps on power supply electrolytics. Resistors have flavor, bypass caps tightened up bass.
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warning ...  as per @tvad's comments

rather treacherous, slippery slope here, with many bodies of regret-laden audiophiles littered about
@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!
The warnings are legitimate, reason you do homework prior to replacement parts. What is the sound quality you're looking for, is there some lacking in present state of equipment. Reading about other's experiences with particular boutique parts will give you idea of particular sound qualities.
And you can always reinstate original parts if you didn't damage them during removal. Not always possible because of issues with getting desoldering utensil where it needs to go, broken legs on removal of original parts happens. Its not risky replacing with boutique parts as long as you know voltage ratings, never replace with lesser voltage or temperature rated parts unless you understand the circuit.
I always figure the labor time and parts you invest in upgrades will never be accounted for, you're not doing this for the financial aspect, solely for sound quality. You may be able to get back what you paid for used items, I recently sold one of my modded amps for same price I paid originally, prior to mods. I've experienced a few buyers over the years attracted to modded units.

Just simply replacing original parts with upgrades is in no way hazardous to the health of unit unless you replaced with parts not up to spec or incorrect installation of those parts. I assume quality control is superior to generic parts, you can even get matched spec parts when requested.
If it does not have remote volume look into fitting a resistor loaded stepped volume pot.

Gold Point used to be recommended, but there are probably other current rec's.

Aside from my inexpensive Bottlehead I heard before/after with a Matantz 7 and it made a huge improvement (especially @ lower/mid volume levels).


@hilde45 you may have to go underground over to DIYAudio on this one to find the builders and mod-ers.:)  Not all, yet most here buy and try and rotate new $ amps to find the sound they are searching for instead.  I did high-end Mundorf caps only on my 120 monos. Super duper pleased with the results and would never swap back to the low grade stock caps. Voids warranty and not recommended per Mike at QS of course. Find a competent tech nearby who does this in their sleep if you proceed.
Call Mike at QS. He has a very good ear and can help your quest. Although he might say don't change anything. 
When I rebuilt my Dyna 70s into VTA 70s, I added the VTA board, new power supply caps, fresh tubes throughout, and premium caps in the audio stage.  The biggest changes since then have been from rolling tubes.   I settled on RCA clear top 12AU7 driver tubes, 12BH7 in the center and Gold Lion KT66 output tubes. 

Some vibration isolation can't hurt.
Some vibration isolation can't hurt.
Put springs under the amp. Plenty of threads here on the subject. 
how are your soldering and de-soldering skills @hilde45?  important question...
Thanks. Helpful advice regarding replacement parts and possible breakages.
"What is the sound quality you're looking for?" -- a good question. I'm not sure but I've heard that more air and detail are possible. Sort of like the question "Why would you want to try better beef?" Not easy to answer without experience. But you're right to look to other users.

@dekay I chose this pre because I didn't want a remote volume, so not going to alter that.

@decooney I have found an expert here in Colorado. No worries about his work.

@russ69  I suppose I could call Mike, but might he just defend his amp/preamp as built? I can understand that, but perhaps not objective enough?

@knotscott  -- I've been rolling tubes, too, and appreciate the KT66 mention. Want to try that; love the KT77s.

@jjss49  I would not do this myself. I'd pay to have it done and pay to have it reversed. Just like a vasectomy.
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@knotscott  -- I've been rolling tubes, too, and appreciate the KT66 mention. Want to try that; love the KT77s.

Be forewarned....burn in time for the GL KT66s is pretty long.  Bob Latino had suggested around 100 hours.  I think it took every minute of that.  I was honestly ready to give up on them and put them up for sale.  They were worth the wait.  Love them now.
What rectifier tubes do your quicksilvers use, and what are you planning on spending?
The biggest improvement in my tube system so far has been having a independent dedicated 20 amp circuit installed for my audio and video components. This immediately killed the slight crosstalk/ground noise I was getting in my audio and I listen to TV via cable via sound bar. No interconnect between my audio and video system now. The video/Comcast/interconnects between the preamp was the biggest source of noise. I helped the master electrician run the lines and install the lines as his helper didn't show. I learned a lot and would definitely recommend spending ($250-750 estimate) to have dedicated A/V lines as opposed to expensive Power Conditioner.
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.

Gosh hilde45 I must have mentioned this only about a hundred times by now- DIODES! Diodes were the first mod I did to my Aronov integrated back in the 90's. Big improvement in liquidity, layering, just a really nice upgrade and probably still to this day the biggest bang for the $8 they cost me.

Once that worked I went through and replaced all the caps. This was a long time ago, I think they were all Solen, not that great but a lot better than stock.

If doing something like this today I would do not just diodes, caps and (some) resistors, but also put fO.q tape around caps and on circuit boards. Of course before doing anything like this I would first have done all the easy stuff like QSA or SR fuse, Pods, SR ECT, and a good power cord. Then I would think long and hard about replacing electronic parts. All the really good ones are huge compared to what's in there now. It is a balancing act figuring out what to replace, what to spend, what to get and how to get it to fit. It is not just "oh I'll get Deulund". You will see.
@soniccsc1 I just installed 5 independent dedicated 20 amp circuits. So, I'm good there.
@invalid — yes, solid state rectifiers
@millercarbon Thank you for your suggestions! You sound much more comfortable doing the work than me! I'm going to hire someone who's done this a bunch. As for it being "a balancing act figuring out what to replace, what to spend, what to get and how to get it to fit. It is not just "oh I'll get Deulund". You will see."
I agree. If I was going to just resort to, "Oh I'll get Dueland," then this post wouldn't exist, n'est-ce pas?
Before changing the insides, put it on Nordost SortKones or Grand Prix Audio footers.

They made an improvement to every tube preamp I have owned, including a Quicksilver phono preamp
Before changing the insides, put it on Nordost SortKones or Grand Prix Audio footers.

Are you saying to do this because it might erase the desire to do other tweaks or because it is important as a preliminary step? I realize it's easier than making a change to the amp, but why "before"? Thank you.
I found that it made a significant reduction in the noise/distortion floor. 

If you do it "before" you can better understand the effect of future changes.
My rec does not add remote volume, just "likely better" sound by replacing the volume pot.

I have made a tremendous difference in sound by changing or altering my approach to my Cary tube amp by:
•adding a Schitt 4-knob equalizer • adding Sound Proof foam panels

add it is distanced enough to satisfy 
When I got my Primaluna Evo 400, I was left wanting more. I thought about capacitor upgrades in key locations. I upgraded my phono cartridge. That helped...up to a point.
I added an extra rug along the whole backwall. That helped too but not in the area I was seeking to improve (upper end detail). In the end, the best tweak was to buy the right speaker.

A more sensitive speaker took a ’good enough for me’ system into the realm of ’a whole lot better than I was hoping to get’ system.

Going from 88db Salk Songtowers to 93db Tannoy Turnberry GRs was a giant step in the right direction. Not only do I get detail in the up mids, I get detail in everything across the whole spectrum. It’s not perfect...but it’s definitely going in the right direction. 

The Songtowers were great speakers but simply need different electronics to meet them where they are.

When everything works together, lots can be gained. It's about synergy.

Now back to perfecting the room.

Well, there are external and external changes to consider. Much of above are good suggestions, I'd add ball bearing type footers, they always add air and spaciousness, however, may change timbre to some extent. But then timbre changes are concern with every isolation device, and I've tried every one of common designs, hanging your equipment from ceiling best, but of course that's silly suggestion in this instance.
In the end you could try every external change possible and may find same issues remain, and this is quite possible. Resistors, capacitors, diodes, voltage regulators, internal wiring, IEC receptacles, fuses, binding posts, I may be missing something. I've done everyone of these mods at one time or another, biggest bang for buck in general terms are capacitors, I'll put the rest in similar category, although some may have more effect than others in certain situations.
You're trying to gain more spaciousness, air. I've been in same position at another point in time. I'd start with coupling caps, may want to try something with silver, or combo silver/copper, Mundorf or Duelund here. This will most likely add exactly what you need on top. Resistors may be next move you'd make, depending on what QS is presently using, he may be using carbon comps, nice warm resistors, may be part of dark issue. Everything else would be of secondary importance.
I pretty much guarantee contact with OEM will not go well, they'll be offended you want to change what they consider optimal implementation of their design, you're trying to alter their child. I know this from experience, and this even if they later adopt your modification!

Also, do only one change at a time, do the caps, nothing else, listen for at least 200 hours, only make further changes based on what you're hearing at this point. You may not have to make any further changes.
Always remember that every single one of these changes may alter sound quality in ways you may not like. Change may also help in one area, not in another, so many parameters of sound to think about! For instance, you may get more air, spaciousness with certain capacitor, but it may alter overall timbre in ways you may not like. Changing out parts is like food recipe, a little of this or that may make all the difference, you need to be prepared to alter things as you go along.
All my warnings are just things to be aware of, parts changes can take a certain piece of equipment from temporary to permanent solution.
One time I had a Dynaco 70 redone and it was out so long that I forgot what it sounded like prior to the rehabilitation!

however when I re tubed a Primaluna amp and pre amp same day I could hear the difference!

Auditory memory!!!!
Major auditory gripe is that I listen to internet radio or Qobuz and the recording is what seems to change the listening experience!
ya can’t win!

My internet provider can only transmit what they get I assume! Mostly MP3 files!
besides I wonder if one can fully hear the difference between the various sample and bit rates ?????

I used to be v picky - loved the hi technology 

now , audio is a masker for tinnitus!

la vida es sueno!

Thanks folks for the suggestions for foam panels, equalizers, rugs, new speakers, etc. I'm sure there's a wine to drink along with the listening, too. Still, I'm really asking a very narrow question here.

That said, it is a free country and typing is therapeutic.

Thanks, SNS. Spaciousness…the final frontier. Yes! I will likely do only caps. Looking at used market, changing caps seems minimally controversial to buyers. That said, I'm looking on keeping these amps for quite a while.
yes, Davis Family vineyards, rotgut Syrah. Pinot for guests.
The Cardas binding posts are awesome and can provide gas tight connection…

I love the smell of solder in the morning 
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Think you may already be there but TUBES, TUBES, TUBES!
Great NOS tubes will radically improve the SQ. Maybe more than anything. Mike is a great guy. Call him and ask for his recommendations.
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 .
@grannyring Thanks for weighing in. Much appreciated. I've got some nice closeups of both the Line Stage and the Monoblock 60s on my system page, now:

I'm a noobie. I wonder what more experienced people think of the stock caps which came with my amp. My feelings won't be hurt and I know this is very affordable quality gear. But, getting down to the quality of the parts, what do you see in these photos?

Thank you, all.
I upgraded my input tubes on the phone and amp. The phono got a NOS Telefunken 12AX7 and the amp got 2 x 6922 NOS Siemens. Huge increase in soundstage and much more air around each instrument. Highs are crisp and clear, not sibilant. YMMV of course.
some of us remember swapping in Orange drops into a Hafler…because they were an…upgrade… it’s all relative….
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. 
@grannyring Thank you. This is all for the preamp. One thing -- the amp is not that old -- it was probably built in 2020 or 2019. Would you still replace those 4 - 47uf 500v filter caps? It sounds like you'd only do it if it was an older model. Thoughts?

Also, did I miss your thoughts on the mono block amps? 

@tomic601 I suppose it’s all relative. My amp is a 2020 model so I’m not sure how those orange drops stack up, relatively, *today.*
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. 
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.
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.  
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.