2. amps-preamps
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Ok to substitute 12AX7 for 5751 tubes in CJ Amp?

Hi Folks.

Despite having owned my Conrad Johnson Premier 12 tube monoblocks for over 20 years, I'm just starting to play around with tube rolling recently.  (Previously, when a tube got tired I'd just replace them with whatever CJ recommended at the time).

Playing around with the input tubes:   The CJs come with 5751s (I've been using GE), and as I understand it 12AX7 tubes are higher gain.   However, are they not interchangeable in most cases?  Just don't want to screw anything up in my amp.

Thanks.

 

prof
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facten
2,747 posts
 

Under what circumstances is a 12AU7 is a substitute for a 5751?

12AU7 substitutes are ECC82, 7316, 5814, CV491, 6189, E82CC, 5963, 6350, 6680 and a few others . Have never seen 5751 as one of them

thecarpathian
4,180 posts
 

Yes, I believe the 5751 is a compatible substitute for the 12ax7.

But, I’d confirm it with a call.

noromance's avatar
noromance
9,482 posts
 

12AU7 = 5751,

No. I think you mean 12AT7 with an amp factor of 60. The 12AU7 is much lower at around 17 at 250Vdc. 5751 is 70. 12AX7 is 100.

 

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