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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
mofimadness's avatar
mofimadness
4,993 posts
 
1. Most preamp tubes will last 3000-5000 hours. Some are speced out to 10,000 hours, so there are exceptions.

2. 40-50 hours, there are exceptions.

3. Depends on how the circuit is designed and how the tube(s) are implemented within that circuit. Tube rolling can make a huge difference or none at all.

4. Never been a fan of the JJ tubes.

I have quite a few of the Mullards and have never experienced a premature failure or an increase in noise?  Excellent tube.  The Pvsane tubes are also very, very good.
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.
stereo5's avatar
stereo5
6,409 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.
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