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

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.

I'll need to confer with him. Doing caps with exact value matches and not much else would be a decent upgrade and would minimize risk. The preamppot seems very doable We'll find a happy consensus, I'm sure.

just a few additional thoughts for your consideration @hilde45 as you explore this element of hifi-nerd-geekdom :)

in my experience, by far the best context in which to mod high end gear is if -- a) you are committed to keeping the piece of gear for the long term, and b) you yourself are quite experienced in disassembling, reassembling gear, soldering, desoldering, and choosing components - second best way is to have a well trusted, highly cost effective local tech to do the skilled labor

reasons being
-- it costs something non trivial to ship/ship back a stereo component, with attendant damage risk in shipping
-- when soldering in even passive components, there is some risk of damaging the pc board or making other internal connections frail, with unforeseen issues, thus the skill, diligence and experience of the tech is absoutely crucial here
-- trading away a modded piece can be problematic (not always, but sometimes) ... even if you ’restore it back to stock’ to resell, that should be disclosed, and then the market for such a unit will be reduced compared to honestly saying a piece is ’factory original, never altered’
-- there is indeed a market for modded units by well-known modders - dan wright, smc/mccormack, vsei, great northern, and so on from yesteryear -- perhaps bill/grannyring has achieved that level of ’celebrity’ for his mhdt dac mods, but in my experience specific modders become well known for specific modded units, that experienced buyers will honor by paying top dollar prices upon resale
-- of course, modding a name brand component invariably voids any factory warranty, to state the obvious

with the above, i have always been very cautious and reticent about undertaking mods on well known, high value units (i know i don’t solder well, i don’t trust myself to do it to a ’pro’ quality and problem solve issues that may arise) - in fact, i greatly prefer to buy them at a signfiicant discount used rather than pay for the mods to be done, and in the rare instance where i have changed things ’under the hood’, i pretty much resign myself to treating the unit as a ’its mine forever’ unit, or a throwaway if things don’t go 100% right

i know my approach above is rather conservative, and may well elicit ’ aww c’mon man!!’ responses from others who are much more into modding gear, but i just wanted to share my own perspective and experience

i know this is all a fun, and exploratory journey for you -- i hope this helps you and others to hear a perspective from one dedicated enthusiast who has been at it for some time  ...

@jjss49 9

(a) I am committed to keeping this gear.

(b) I would look to a local tech, highly recommended. I wouldn't trust myself to do it anymore than I would trust myself to pick out carpeting on my wife's behalf!

Agree about the ship/ship cost and risk concern.

Good point about the re-sale; Tvad was saying that earlier. My sense is that this unit has really, really good fundamentals and I'd likely be nipping an upgrade bug early if I just take it to a better level, now. Judgement call. I'd rather experiment with speakers and Dacs, etc., down the road, knowing that my tube gear was batting .450

Violating the warranty is a concern, but there's only a little bit more than a year left on it. I could wait, but a caps change seems low risk. I suppose I'm tired of being risk-averse. Could it be the age we live in?

I hear you about the conservatism — I think we're alike. A couple of things are swinging me in this direction:

* Experienced opinion: QS owners who have done these mods are unequivocal in praising the results
* Reality check: This QS gear is not on the level of, say, others — Atmasphere; lots of room to improve; a quick look at some of the parts costs quickly confirms
* Plan B: My solid state can carry me pretty well, if necessary (assuming my preamp is ok)
* Settling the issue: I think it's in my head to do this and I have the time to enjoy the process right now.

All your caveats make a lot of sense — thank you for writing them out.

Sometimes I approach these questions as if they were serious medical procedures; they're not! This is a hobby and I'm trying to slide into the greater ease I see in other hobbyists with, well, trying sh*t!

@grannyring 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……

Yes, agree. Modest at best on the stock caps in the amps and preamp. Studying a bit inside, maybe Solen or Sonicap ? is OEM with the odd .27uf on the amp IT side and 2.0uf in the preamp. The mfg owner-designer shared he likes aluminum foil caps. There are four $4 715P Orange Drops in these amps on the OT side. Replaced those on mine after year one, along with a five+ others who followed here on A'gon. Yep, a no-brainer.  I was astonished at the results, making the simple cap upgrades for these very solid amps which already have good bones. 

grannyring has good advice above.  I like the VCap Odams much.  They are also easy to work with size wise. But you'll need to tell your tech that their bodies are somewhat conductive. I wrap them in silicone tape prior to install.    I would simply start with the coupling caps and output caps (typically located right before the lines running to RCA outputs).   If it's a preamp you are upgrading, you can match your output cap better to your amp if they are of different brands.  There's a nice calculator on the VCap website for this purpose. 

I was never able to find a tech that wanted to assist with modifications.  It's kind of like taking your car to a service place and asking them to install specialty muffler, brakes, etc.  They typically aren't jazzed to do it and they look at the vehicle as if it were an appliance--not to be touched from the engineer's design. 

I've experienced far more meaningful results upgrading caps/resistors than I have playing with hookup cables/power cords (I do that too but I just hear more of an improvement from the other stuff).  

One warning you didn't get yet---It's slightly addictive.  I spent $900 upgrading my crossovers on my loudspeakers.  I bought Cornwall IVs but would have loved Volti speakers (didn't want to spend $10k).  The crossover upgrade got me where I wanted to be.  

Modifications can keep me from upgrading by allowing me to get more out of a design I already love.  A Ford Mustang or even Chevrolet Corvette are built to a price point--they are not a Rolls Royce. So there's a good foundation to make improvements to your specialized taste.  Enjoy your journey!