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Questions from a Tube Preamp newbie

I have my Rogue RP-5 back from warranty repair and I am loving how it sounds. While at Rogue, they installed 4new JJ 12au7-s tubes. Sounds great. I have some questions.

1. with about 2 hours daily playing, how long do typical preamp tubes last (I have heard Rogue's, like CJ, can be hard on tubes)

2. Do new tubes need broken in? if so, what is normal time frame?

3. Does tube rolling really make a difference on a preamp vs power amp?

4. What is the general concensus on JJ tubes for a preamp? Again, I am really happy with the sound, so I probably won't change. However, I will eventually probably get the itch.

Thanks
aberyclark
hifiman5's avatar
hifiman5
1,832 posts
 
@stereo5   My previous post should have been stated more accurately.  The NOS Mullards I used were 4003s not 12AU7.  They were recommended by Upscale for my line stage.  Glad to hear you're having good luck with your NOS Mullards.  The 4003s I used yielded an amazingly smooth texture to the music.
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hifiman5
1,832 posts
 
@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.
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stereo5
6,430 posts
 

The CV 4003 are around 100.00 each at Upscale which is too rich for my measly pension as I wanted 5 of them.  According to Uncle Kevin, the 12au7 have the same sound as the CV4003, but were manufactured in Mullard's plant in India instead of England.  They are also a little more robust than the CV4003.


I tried the CV4003 in my older Cronus Magnum integrated and it lasted less than 6 months as it got quite noisy, so I see where you are coming from

hifiman5's avatar
hifiman5
1,832 posts
 
@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.
wolf_garcia
6,719 posts
 
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...
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