Solid State Preamp to replace tube unit

@jimbones Not sure how far away you are to ship it in - I wonder why you might not consider sending in your current preamp to CJ for a checkover. Maybe they can test, check, make recommended updates?,

My main system is all tube preamp / mono tube amps. I had been searching past few years for a ClassA Pass/Forte’ F44 preamp to match my Pass/Forte 3/1A Class A amplifier in my other system. Found one, have been trying it on rotation this year. Sounds nice for sure. When I swap back in my all tube preamp with the Class A solid state amp there can be this added layering and 3D dimension effect that occurs. I credit the 6SN7 tube preamp. Has its own sound like your CJ gear. Swapping back and forth between the two different types of preamps helps to realize the differences. FYI, I’ve chatted with Nelson about this SS vs Tube preamp topic some a few years back. As I understand it, it’s one of the reasons he came up with the Korg B1 flat tube DIY preamp kit. It offers an option to explore for Pass amp owners. I’d be curious to know if CJ can help you or not to investigate more.

@jimbones do you have a copy of your original CJ owners manual for your version/series/serial numbers of the Premier 12 amps by chance? I’ve run across this same type of KT120/KT150/KT170 tube use confusion [with other manufacturers] about when you can/cannot run these larger output tubes where [for example] later versions might have had the larger power and output transformers to support the larger output tubes. Sure they might work and play, however is Jeff possibly referring to potential damage that might occur for your particular amps and serial numbers by chance - worth reconfirming. There may be a reason he said no.

Found this on the CJ forum, yes, some are running KT120s in their Premier 12s. A friend of mine has Premier 12s and still runs the 6550s in his fwiw. https://conradjohnsonowners.com/viewtopic.php?t=2320

@jimbones doing some quick checking over AudioAsylum and TubesAsylum to see if others with CJ Premier 12 and/or 6550s had tried others such as some of the better KT88s.  Also, located some comments indicating the Premier 12s are 650v at the plate. There is some mention, not a lot, but possibility of running good KT88s in place of 6550s maybe in your Premier 12s, worth checking more to see its a candidate. Seems the older discussions of running the Sventlana 6550s, led to others jumping over to KT88s.  But again, you may need to find multiple sources there to know for sure that its safe in your amps.

On a related note, I helped a friend and we upgraded his older Jolida amp, it use to run 6550s, and a few local friends and I suggested to the try the latest PSVane KT88 TII MKII tube in it. The result has been quite pleasing, less of a glassy modern sound, and more of a lush body/warmth to the amp now. Can be nice if that's what you like. Find a replutable tube reseller of KT88s if you try it.   Note: I run TS KT120s in my own QS Monoblock tube amps, and while I like the KT120 too vs. KT150s, if my amps had lower plate voltage, I'd be running really good KT88s as an alternate.  Long story, I cannot, i have the big amps with extra larger transformers and big plate voltage, will burn them up prematurely.   In your case, though - might be worth a nice try, and worth checking with peer P12 owners, and maybe CJ would advise you on this, worth asking. There are some big fans out here who prefer good KT88s over most of the othe TS KT series tubes fwiw.     

@jimbones that’s great, on a different path and price point - my local 55-year-in-business audio dealer has retired clients with upcoming birthdays and Christmas presents due -or- goals for their "bucket list" buys. He has ordered quad sets of E.A.T. KT88s. While they are quite pricey, if you want to splurge, I gather from people who purchased them, they were quite pleased. One other possible way to help squelch your TS KT120 desires, these might fill in nicely as another option. . I’ve never tried them but I might if my amps could run KT88s like yours can!

MFG and specs found here by European Audio Team

https://www.europeanaudioteam.com/en/eat-kt88-diamond-valve-wp000023.html

@jimbones I had the EH KT88s in my Cary SLI-80 stock, and never could get myself to warm up to those - at all. Kinda lean and non-engaging in that amp. Did not like then much at all for my amp at the time. Depends on the amp too, and how they are driven, biased, and of course how they work with the rest of your system of course. Your friend can probably tell you why they are available as loaners.  

I only kept them to give away with the amps as backup test tubes. When I upgraded the SLI-80 internally, the next tubes I tried was reissue new Genelex Gold Lyon KT88s. They were nice tubes (balanced top to bottom) for the quad price $ at the time.  My buddy did the PSVane KT88 MKIIs, and those had a little more body and warmth, slightly rolled off on top taking the etch off, and he's been running them 2yrs, loves. them, they did well in his amp.  

As for the overly pricey and limited availability EAT KT88s, maybe I spoke too soon, I noticed just now on a few sites they are unavailable, out of stock.  When I mentioned birthdays, christmas time, or bucket list buy - here is why. You could call TD and ask them about EATs, and they do sell other decent KT88s too.  Hold your breath now, LOL, seems they may not be available much right now anyhow...ugh. https://www.tubedepot.com/products/eat-kt88-diamond-power-vacuum-tube-matched-quad?srsltid=AfmBOoqggHuzJXgBXwvysqp1ORO7lRJ0AXCrUvY4B9PwrTacqQ-pyN2B

Heillo @jimbones after reading back through this thread and some of the steps you’ve taken so far, and about to take next, there are helpful suggestions by several members here.  

One is to ensure you have clean power at the outlet -or- your PS power conditioning unit. Whatever you use. The other is solving your curiosity about running a nice SS preamp, and seeing how that goes comparatively in terms of sound and presentation for you. Maybe there is a 30 day demo in our sights. 

While I’ve played with some older pass preamps, and after messing around myself, I don’t disagree with @skinzy - something like the XP-27 designed by Wayne Colburn would be nice to try for sure. It commands a real price. I’ve not tested one, yet I’ve chatted with Nelson a few years about the layering and presentation a really good tube amp brings. Comparing to this preamp, and Nelson’s DIY Korg flat tube preamp could be fun too. Nelson told me he has many SS amp customers using his amplifiers with tube preamps on the front end. I use both and rotate, yet always go back to the tube preamp for my own preferences, imaging, layering, etc. 

In a few cases i’m noting your comments about "tube noise", and your comments about buying some new (as in new re-issue) tubes and trying again. If you purchased tubes from Brent / Andy before, and the tubes tested well, something else comes to mind. Some times tubes get rattled and become compromised in shipping. Also wondering if you’ve tried the other "new" tubes you mentioned, has that helped at all?

Local Tech:

Re-test your tubes, all of them. Do you have a local tech you can go to around your area, bringing all of your small and large input/driver/output tubes and have them tested to possibly identify any culprits in the bunch contributing to your noted tube noise?

Local electrician:

If you’ve not already done this, do you have a local electrician who could come in and test your AC outlets to validate if there is noisy power?

I had something similar going on years back with my tube system and my other solid state system at the time. I ended up rewiring and replacing outlets, when with a Richard Gray power station for my amps and preamp and the issues disappered fwiw. Some other ideas for thought in finding the root cause, if possible. Best of Luck on the journey. 

@jimbones wow, sounds like you have all the bases covered and then some, and access to capable people around you to test things out. Very nice.

The only reason I commented was the original post was the possibility of a solid state preamp instead of tube. Last year I thought I’d try something similar, going in reverse of where I came from over a few decades. While it was in interesting exercise to re-validate history. and I enjoy a Class A preamp/amp periodically, I usually go back to my all tube preamp and tube amps system to experience what it does in its own unique way - for those more engaged listening sessions. 

Keep us posted on how the new tube testing goes and wether the original inquiry is solved yet or not.  I’ll be sharing this thread with a few friends doing something similar as you, going through all of the exact same checks and such. Enjoy!  

@jimbones does your Nad M23 amplifier mentioned in your original post hold up to that classical music challenge for you?