8 responses Add your response
CMII owner here. First I tried new Genelex Gold Lion 12AU7's and 12AX7's in all five slots. A little bit better, but not night and day. So then I got an Amperex Bugle Boy 12AU7 from Andy Bowman at Vintage Tube Services, and that also is better. But I'm now still hankering to try a vintage Mullard in the pre-amp position, as stereo5 did.
I also splurged on new Genelex Golden Lion KT-88s to see how they sounded in comparison to the KT-120s, and after a week the 120s are back in the sockets. More impact, more bass extension, and only very very slightly less sweet. No reason (now, I discover) to change these.
So, my experience to date: the stock JJ's are not such underachievers as they are sometimes made out to be. But with some expensive NOS small-signal tubes you can certainly improve and tweak the sound.
It may be aging, or it may not measure well. Do you know any of history on it? For $10 more, Upscale sells a specially tested one for CJ and Rogue preamps.
Also, has anybody tried using a Brimar instead of a Mullard on the pre-amp socket? I keep hearing that they're pretty good, but the Mullard seems tried and tested.
@twoleftears The new production Gold Lions respond well to cryogenic treatment. I use GL 12AU7s in my line stage on an ongoing basis and replaced the stock Sovtek 5AR4 rectifier in my SACD player power supply with a Gold Lion GZ34. I always source my GL’s from Cryoset. Ron Sheldon’s tubes are quiet, neutral and seem to last forever...they just don’t get noisy.
One more tweak that really makes a difference is using Herbie’s Audio Labs tube dampers on ALL tubes. I just got an all titanium damper for my very hot running GZ34. It fits tight as can be and as crazy as it sounds all images since installing it are rock solid. Greater air to soundscape and improved dynamics!