[Julz]

Hey guys 'n' gals

I understand that 5751's and CV4004's can be used in place of the 12AX7's, but what about the 12AU7's ? Are they compatible ?

J

 

[oldears]

I'm not sure I understand your question. However, 5751 and CV4004 are not generally considered to be substitutes for the 12AU7. The substitutes for 12AU7 would be 5814 and CV4003. The 12AU7 is not generally considered to be a substitute for the 12AX7, although it can be used as a substitute in some cases--it depends upon the circuit. Unless there is some specific reason why you would want to substitute a 12AU7 for a 12AX7, I would stick to the many generally recognized substitutes.

 

[jamato8]

The 12AU7 and 12AX7 draw different current have different gain and as a general rule, as stated wisely above, should not be subbed for each other. The 12AX7 has a gain of about 100 while the 12AU7 is around 20 so the aplification factor is different.

John

 

[Julz]

Quote:

Originally Posted by oldears I'm not sure I understand your question. However, 5751 and CV4004 are not generally considered to be substitutes for the 12AU7.

Thanks, all I needed to know !

 

[Hirsch]

Quote:

Originally Posted by Julz Thanks, all I needed to know !

Actually, there's more. The pin-outs of these tubes are the same, although the gain is different, as has been pointed out. I've had amps where cross-substitution was not possible. I've also had amps where any of these tubes could be used interchangeably (MG Head OTL comes to mind, as it will work with a 12AX7, 12AU7, 12AT7, or any of their close relations). Probably the best person to ask whether or not these tubes can be interchanged would be the manufacturer of the amp you're planning to use.

 

[oldears]

Hirsch and Jamato8 are both right (as am I for that matter

). The person to ask about an ASL would be Joseph Lau. But, there are quite a few 12AX7 subs to try if you want to tube-roll an ASL MG-Head (of whatever version). Lots of information/opinions on what's best too. So, I think that's the way to go. I've never seen anything to indicate that a 12AU7 is sonic nirvana in the ASL products.

 

[Hirsch]

Quote:

Originally Posted by oldears I've never seen anything to indicate that a 12AU7 is sonic nirvana in the ASL products.

Listen to an MG Head with a Telefunken ECC82 in front of a pair of Siemens EL84's driving an HD-650. Then report back...