Tube rolling with Quicksilver Mono 60s -- from KT77 to KT88? KT 120? etc.

@yogiboy
@decooney My friend has the QS 120 amps and he has used KT88 tubes with those amps. It states this in the QS M120 manual!
Mono 120 for web (quicksilveraudio.com)

@yogiboy
IF they are the latest Mono 120s with the large transformers, have your friend call or email Mike Sanders at Quicksilver asap, and ask again, directly. Believe me, I’ve pushed it with him multiple times, fwiw. Other info...

Originally, I tried to order my Mono 120s with GL KT88s. Nope. Talked to Mike 3 separate times pushing him to share more, he keeps telling me "NO", no KT88s in my Mono 120s. I took his advice, fwiw. Says they will burn up, prematurely.

Tuning with KT150s:
And, once I got the right mid-1960s vintage dual triode Mullard "blackburn" factory 12AU7 and 12AT7 input/driver tubes, the KT150s sing now. More like a smooth KT88 sound with more depth in the sound stage and more power, dynamics.  Also tried the latest PSVANE small tubes too, a bit more midrange forward compare to the vintage Mullards.  The new Mono 120s needed a better pair of small tubes up front to precede the KT150s. Now I would not go to KT88s anyhow for the latest Mono 120s amps, even if Mike would permit it. . Once I changed coupling caps to high end Mundorf Silver-Golds, the synergy was amazing with the KT150s and Mullard small tubes up front. Super nice now.

Preamp:
They deserve a really good preamp. Now running a 6SN7 full Triode Cary SLP-98 preamp in front of the Mono 120s.  The updates to the Mono 120s and a good preamp in front of them brings them to an entirely new level. 
With the updates, I'd now put them up against the $20K KT150 Conrad Johnson monos all day long.  

The new Mono 120s have huge transformers, look for the big transformers, larger than prior version QS amps. fyi.

hilde45
No one has said a word about KT90s....

Bleh.  Stay with GL KT77s or for your upgrade, go with GL KT88s or TS KT120s instead vs. KT90 IMO.   

@decooney
Thanks for the information. I wonder why the manual says that the KT88 can be used? BTW, I use the KT88 with my QS Silver 70 amps and Mike told me that can also use the KT 150 if I wanted to give them a try. This is from the M120 manual! 
Tube Complement 1 - 12AU7, 1 - 12AT7 2 - KT88 or KT150

Watch the highs on the GL KT88s.  The bass is good, but really tiring, harsh highs.  I tried them for close to 100 hours and gave up,  IMO they were never going to change enough to be keepers. My small tubes include many of the vintage ones mentioned above, for power tubes I roll el34s, kt 77 and TS 7581a. If you’re amp can use the 7581a give them a try first. Bargain price and an excellent overall power tube. Worth a try for a minimal investment.  Great base and mid-range, with highs that are extended without the harshness of the 88. 

@decooney
Thanks for the information. I wonder why the manual says that the KT88 can be used? BTW, I use the KT88 with my QS Silver 70 amps and Mike told me that can also use the KT 150 if I wanted to give them a try. This is from the M120 manual! Tube Complement 1 - 12AU7, 1 - 12AT7 2 - KT88 or KT150

@yogiboy
Not sure I’ve helped. Re-check with Mike for sure with your friend’s 120 amps. This is why I say to contact him, have your friend give him the serial# on the amps and ask again. I’m not sure if he tweaked the plate voltage up on mine at some point for the KT150s. Maybe your friend’s amps are okay with 88s. Yes, the "120" manual shows KT88s in two places, and I challenged him on that too. Note: check the front of the web page on the Mono 120s shows only this now "2 KT120 or KT150 outputs". KT88s are no longer listed there for Mono 120s. Manual needs updating, I don't know - better to ask mike on your buddy's version of the Mono 120s, mine are 2019 version. 

Yes, the older Silver 70, 80s, 100 amps seem to be fine to run the KT88s as I understand it, smaller transformers, likely lower plate voltage (supposedly). Same with hilde45s Mono 60s, ideal for KT88s, the sweet spot. I’d also buy a quad of KT88s right now if he’d say it’s okay for my specific mono 120 amps. I won't ask him a 4th time :)