There is a small but vocal community of people who geek out over "heritage" capacitors, and transistors and even op amps. There are a couple on this site. But since it requires opening up your amp and using a soldering iron and is even potentially dangerous the appeal is considerably more limited than rolling tubes, that are designed to be user replaced.

As for your SS amp specifically, if you care I don't see any down side to asking the question. I sent my Pass Aleph (SS) amps back for an overhaul after about 20 years and they were quite keen to discuss all the parts they were replacing, although I didn't really have any option as to the new parts they used, many of which were NOS. But I think in general shops that do this kind of work are more concerned with availability and reliability than absolute performance. Also, SS amps tend to have more complicated circuits than tube amps so the individual parts don't have as big an impact on the sound. There are some people that will modify gear (often classic stuff like old Marantz or Dynaco) with something like "anniversary mods" but they are few and getting fewer I think.

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It may. It may also take weeks. YMMV.

1958 Harmony Stratotone still rocking with Sprague Atoms on a cupcake Stacked tone/volume

I think asking someone to upgrade your amp spec is complicated by the fact that most all parts have some sonic differences, for better or worse. And one good cap might work really well in one position in a given amp, and another equally good cap might not be so synergistic. So changing coupling caps to V-Caps, or To Miflex Copper Foil, to Miflex Copper Foil in Oil.... these can all sound really good in the right settings, but they sound different enough from each other that their individual characters could be used as notable tuning tools in mods.

I guess I have done hundreds of experiments with caps, resistors, wires, pots, connectors, etc, mostly in Decware. From this clean beginning, with a system set up for resolution and spaciousness, I can hear every change. Even changing about any 1/2 watt resistor in there, testing two of the same type (say metal film), but different makes, you can get a sonic choice. Both resistors being to Spec, one will usually fit the whole better. And they add up... 10 resistor improvements will refine the whole sound more than a few. Or adding very small 0.001 bypass caps to help pull the very finest information from a bypass set....even with these really little caps, the cap sounds from two companies will almost always make real enough differences for sonic choices. And a lot of more subtle choices that are meaningful, can become far from subtle if they are all working together.... each choice making the others better.

So in a transparent and resolving component, with a lot of changes together, you can quite notably change the amp. I prefer holding close to the same basic signature, and refining complexity, space and speed by ear. And when it works, that signature becomes more musically complete, more and more fine information present while increasing space... the same basic signature can grow more complete. Or, you could change the whole signature, but it is not too hard with these simple designs to go "off," especially considering mods working across recordings is really important to me.

I started bypassing the Power supplies of my Torii and CSP3 in later 2016... Plugging along, usually a part or two at a time over many years... still at it now some. So over time, I guess I tried 5-10 different bypass caps in some PS positions, as well as 2-3 different values of caps combined together to fulfill a given electronic and sound need, the two completely interrelated. I had done a lot of cable experiments, a fair bit of speaker crossover experimenting, as well as simple mods in amps, like replacing coupling caps. But I was watching VyoKyong's mods on his Mystery amp and this gave me some nerve over time to dig in further. He had not done a whole lot with cap bypasses, but a lot of work overall, and I was inspired.

I knew from all my speaker explorations that small bypass caps can be really powerful for refining sound values. And looking around the web, I saw a few folks out there for whom bypassing was a big deal. Also several folks and threads covered trying and commenting on a lot of caps... the foundations for the caps I got for speaker explorations. So once I got going in the amps, I was primed to start with Power Supply bypasses since I had a bunch of small caps I had used in Crossover bypass experiments.

The first pair I put in the Power Supply blew me away. A little 0.22 uF cap on top of a 47uF electrolytic was a big step in open speed and clarity. And trying more, little value differences in these bypass caps could change the tone, speed, depth.... Also, the same value of say an Obligato Premium and a Mundorf Zn sounded notably different as power supply bypasses... Then I noticed combining different bypass caps sounds can help the whole of the Power Supply sound, when complimentary, each helping one another. But I also noticed some caps, including these two I first explored, can sound great with some recordings, and not great with some recordings.... so the need for complexity in the balancing act got clearer, leading to more refined cap choices and combinations that could support more latitude across recordings with relative finesse.

So I ended up "making caps," combining them toward a needed value, multiple lower value caps added together potentially adding nice complexly when tuned well. So say a 0.22 uF cap would be about right for a specific power supply bypass, this value giving good spectral and speed balances. But I found that making the caps with two 0.1 uF caps, and one 0.022, each cap focussed on its specific frequency and speed areas, and having its own special sound qualities... together you can get more than the sum of the parts when really right, combinations so complimentary that they can be as good or better than 0.22 caps that cost a lot more.


So, with caps I have explored more in depth, I often end up with different combinations in different positions, helping me gradually refine the overall sound balance with more pleasing speed and complexity. I think so far, I have always preferred a nice blend of good caps over a single cap, but this can take some time to "get right," and guessing this is part of why you don't see a lot of this. And change up the sonic or electronic values of those combinations a little, you change the sound for better or worse.

I guess all this is pointing to how big a deal really good modifications can be... and if you want mods that might "upgrade" your amp spec.... it could be pretty important that the person has really good ears and skill levels, and perhaps a good familiarity with the sound of your amp. For such complex balances, it would probably be wise to trust the sonic tastes, objectives, and experiences of the modifier....because if parts change, the sound changes.

Yes, this should be interesting and fun. I was sort of hoping it was a Pass and that the work might be done by them, or by a Pass aficionado who has dug in!

FWIW my experience with Pass was exemplary. But to your OP, I think as a practical matter Pass is going to use they parts they think are best. Also, FWIW, I loved my Pass amps but my UFOs (with Omega speakers) are an improvement in every way.

It makes a great amp stand as well:

Hey, Meester- I have a few thoughts, none probably at the philosophical level you are looking for, but thoughts just the same….
1. $8 is a lot for a 22k pf cap. These little bumps are usually a few cents each.
2. I’ve been having this same general experience elsewhere in this forum that I believe goes mostly unseen b/c it’s not in the general section. FWIW, the zkit is a really inexpensive way to try out the Decware sound with the cheapest components possible and upgrade piece by piece over time listening to each and every change along the way and understanding what affects what, the trade offs, the benefits, etc.
3. Will makes some good points earlier in this thread. Unintentionally putting my words into his mouth, there is a lot of user preference involved and that’s just something you have to learn and experience for yourself. The more I do it the more I hear diminishing returns. Every tweak gets “different” but “better” is highly subjective.
A humble man once said, “if you can’t be happy with what you got you’ll never be happy with anything else.”

I guess it is all relative. But if Pass believes those cap upgrades make the older amp optimal, that seems a good sign they have not come up with better for their tastes and pricing preferences, etc,. And I guess that could be a good thing, Pass amps still a doorway to the beauty for many.

Also, I agree that a cap does not necessarily need to be costly to help with exotic, complexly musical sound. And how long a cap lasts in electronics is likely a consideration for Pass also.

As many as I tried, my favorite very small bypasses, the ones I use a lot for bypassing bypasses , these caps 0.01uF down to 0.001, are between $1-2 each, polyester Mallory M150s. I have tried a fair number of 0.01s for comparison, but mainly cheaper ones under $10 for these small/small caps, with a few more costly, and Duelund 0.01s being the only "boutique" caps I have tried in this small cap area.

To me there is no denying impressive sound from Duelund caps, but here, none are in use just now. So far (over several years of intermittent attempts) I still find the Duelund bypasses seductive at first, but finally a little overstated in the applications I have tried. That said, obviously many, many audiophiles love them, and I hear from reliable sources that crossovers are where they can really shine. But to me the little ones I have tried are "too good." This setup super resolving, I hear everything pretty clearly, and I find them to be "very intelligently" voiced, intellectually getting it really pretty "right" by most audiophile standards. A big part of this being nicely translucent and low on smearing while remaining musical. So they seem quite clear in "what they have to say," and here, they say it so clearly that I hear them as a little "too intellectual" and a little "forceful" sounding. And I most definitely want similarly open, resolving, unsmeared beauty, but only if it mixes with the rest as natural sounding, and in ways that I am not able to "hear" a part, while loving how engaging resolving beauty can be.

So, in my "mind," most decisions for that "house sound" make total sense, and they do it all really well, but in this setting, they tend to a little strongly stated and "too right" sounding. I really have wanted to love these caps, and almost do every time I retry them somewhere. They sound great in most capacities in my "mind," but not quite to my "heart," so they don't stay in. But I have gotten what I think it is a more real seeming window into a similar open, resolving, clarified musicality that is less "obvious" by mixing other caps carefully, something I have enjoyed playing with. So my guess is that I already am getting most of what Duelunds offer from a lot of things combined, which likely makes adding them a little forceful for me. And though I have tried these smallish bypasses in lots of places, it is still limited exposure, and my specific exposure, so......

Different end-sound, but I have a similar feeling from the Mundorf Supreme line. Silver oils are the highest I went up this range, a nice cap designed to fit Mundorf's idea of complete sound, but also having a "feeling" of intellectual affect, voiced to tick all the audiophile boxes in a little different ways. But, for me, they too are a little too "made rather than born" sounding.

So here are two "boutique caps" I have tried in many places, electronics and speakers. And especially after these and similar experiences, I have not tried soniccraft's high cost teflon very small bypasses or VHAudio's. Part of this is that those are pretty costly to try, and part is that the Mallorys are relatively speaking subtly good (to me) for these very fine detail and speed supplementations, the right values in the right positions gently giving the sound refinement I am after. In combination with my other larger preferred bypass caps, it can be right enough feeling that I "don't hear" the caps...just music.

My bigger bypasses (0.022-0.22, most core bypasses combinations of around 0.1) are mainly Milfex Copper Oil, Miflex Copper Foil (in combination these 2 Miflex are most present), along with some recycled Jupiter HTs in several positions, and a few nicer poly caps for solid flavor in specific amp/sound areas. So I am a more middle of the roader cost-wise, and could care less if it is "boutique sound," my big concern extraordinarily real feeling sound and relative synergy across most recordings styles. Though admittedly my financial risk meter is an influential bias from the above experiences and similar. And for smaller value caps particularly, Miflex are to me a real value cap. I prefer my Miflex Copper Oil and Mallory blends over the above mentioned "high dollar" caps, and more costly midrange 0.1 caps, for which I have quite a few that are well respected.

And this does not mean these caps would make your Pass amp more refined and resolving in musical ways... I am not familiar with the insides of them so can't speculate on how you might benefit from more complete sounding caps well placed. But I also would not be surprised if it could be artfully tuned to sound more complete with carefully chosen and implemented mods.

Also the system/room we are listening to obviously matters in how we hear or don't hear subtle things that can make the music real when right. So when folks who have used Pass and gotten Decware don't look back, it may be more spacial resolution and harmonic lift is a "grabber," and that this may be based a lot on a simple point-to-point design arrived at by tech, but mostly sound finally, with few parts, and decent tubes being such a big part of those sound designs. So the Decware "flavoring" from Steve's voicing includes being transparent enough to hear small changes in a resolving system/room.

Don't know where this is going, but hopefully some more helpful things to consider as you evolve with "having thoughts."

Do I recall correctly Burgermeester that you are in Japan? If so, one thought came to mind as I was reading your recent post as a possible exploration that could possibly help move in a direction intersting to you??? Are you familiar with Jeff Day and his writings? Not that I necessarily agree with some of his findings, but as we have learned, how things mix can be as important as what we are trying to mix, and he is no doubt an avid and considered explorer. If I am recalling correctly, his Japanese freind/mentor loves to fix up vintage amps??? Don't know details, but it might be worth checking Jeff's post index and perhaps search WE wire (NOS Western Electric) and Arizona Cactus capacitors, two things I think I recall this Japanese man bringing to Jeff's attention as worth exploring. I wonder if you could find him, and with luck in proximity, see if you like his sound preferences. Then, if so, see if he might be up for tuning up your amp some? Maybe start small and see if you agree with his choices and go from there???

Right, so those must be electrolytic caps, and different ones do effect the sound differently, but they are common in part because they are comparatively cheap and a lot smaller sized relative to film caps of similar values. Bypassing electrolytics with good film caps is where I started, and it really matters with Steve's designs, hearing pretty much the same sonic influences of the bypass cap as you would if it were in the signal path. Still a little tricky to get the just so values, and more complete sonic enhancements from specific cap sound, while also integrating with all else for optimal speed and without changing the spectral balance adversely. But a pretty straight forward experiment in Steve's designs. Then there are the more commonly played with signal caps, like coupling caps that can really matter too, not to mention wires, resistors, connectors... it all matters with revealing gear. Good luck in the search!