Questions from a Tube Preamp newbie

@aberyclark   I only used one pair of JJs.  I abandoned them because of what I perceived to be a "hardness" to the sound.  The new production Gold Lions in my circuit yield an expansive soundscape, smooth textures and great dynamic swing.  This is referring to the Cryoset Gold Lions which are cryogenically treated.  I have no idea what the GL sound like without that treatment.  The JJs are inexpensive but when you have five figures in your system it seems foolhardy to cheap out on the tubes whose influence will be heard at all times.

@stereo5   Wow.  I'd have to check receipts but when I bought the CV 4003 about 15 or so years ago they were about $100.00 for a matched pair.  That was back in my early days with my tube line stage and just went with the advice I was given.  Perhaps I might have obtained better results with the Mullard 12AU7.

I never leave tube amps on when I'm not around as I've had small signal (preamp) tube commit "tubicide"…once in a guitar amp I left on after a rehearsal (for a week) and that amp never really recovered (sad), and another time a well regarded new-ish NOS Phillips AT7 killed itself right on front of me during a listening session…jumped up and shut down the amp before any damage happened. If tubes have a break-in period I'm not aware of that as they seem to display whatever their tonal characteristics are pretty much right off the bat, although the rest of the amp might need warm up. I noticed this when swapping out tubes having just shut an amp down to let it cool a bit…many many hours can be gleaned from a hard driven signal tube, proven by guitar players everywhere when you'd just forget about 'em until the amp starts to get weird…years...

I have a lot of the CV4003s from Upscale.  They used to be $35 each for the Platinum Grade.  These are the ones that I've had no problems with.  I've used them in DACs, preamps, phono stages, all over.

I also have several other types of Mullard 12AU7/equiv.