[dd3mon]

The spec for the MG Head OTL32 shows a pair of 12AU7 tubes.

Are 12AX7 variants (5751 specifically) interchangable with the 12AU7's in the MG Head OTL32? I've been under the impression that this would work, please correct me if this is not possible.

Thanks,

-dd3mon

 

[jpelg]

IIRC, there was a thread on this not too long ago. Say within the last three months or so. I believe Joe Lau even chimed in. Do a search.

 

[dd3mon]

I've seen a couple related threads, but nothing answering this question directly.

The closest I've seen is a thread about the regular MG Head OTL in which Joe says that 12AX7, 12AU7 and 12AT7 are all fine replacements for the signal tube in the MG Head. However, I know that design differences in amps can lead to a tube not being compatible in some designs, yet working fine in others.

-dd3mon

 

[mkyy]

Look here.
It's proabaly ok to go from 12ax7(higher gain) to 5751(lower gain). But it might not be a good idea to go from 12au7 to 12ax7 since it has a much higher gain. Just my guess.

 

[NotoriousBIG_PJ]

12ax7's are not substitues (or close substitutes) of 12au7's.

There are many other substitutes for the 12au7's however..

Biggie.

 

[usc goose]

Quote:

Originally posted by NotoriousBIG_PJ There are many other substitutes for the 12au7's however..

12AU7 ~ 5963, B749, ECC802S, ECC82, 7316, CV4003, 12AU7WA, 12AU7A, 6680, 6189, 6189W, CV491, 5814A, E82CC

or something...

 

[dd3mon]

I realize conventional wisdom here, however check out Joe Lau's response in this thread.

What I'm really looking for a response from Joe (who is the only one who could really say for sure

).

-dd3mon

 

[RulyS]

I tried something simillar, an 12AT7, and it seemed to work fine on my MG Head. I later asked Dianne at Divergent Tech. by email and she daid not to use the 12AT7 and just stick with the 12AX7.
She didn't go into any more detail though. You could call their number ask ask for Tash. I get the feeling he is the expert there for tech questions.

 

[RulyS]

Just gave a call to Tash at Divergent Technologies. Straight from him... "the 12AT7 is fine to use on the MG Head, it just has a different gain. As far as the 12AU7, no do not use it."
My feeling is that Tash is the best adviser on that subject.

 

[jpelg]

Quote:

Just gave a call to Tash at Divergent Technologies. Straight from him... "the 12AT7 is fine to use on the MG Head, it just has a different gain. As far as the 12AU7, no do not use it." My feeling is that Tash is the best adviser on that subject.

But we are talking about the OTL32, which uses the 12au7's as it's stock tubes. The question is can the OTL32 use 12a_7 variants, and/or which ones?

 

[RulyS]

My mistake...

 

[dd3mon]

Quote:

Originally posted by RulyS Just gave a call to Tash at Divergent Technologies. Straight from him... "the 12AT7 is fine to use on the MG Head, it just has a different gain. As far as the 12AU7, no do not use it." My feeling is that Tash is the best adviser on that subject.

As jpleg said, that's not exactly the purpose of this thread. However, if you click through on the link above (to this thread), you'll see that Joe Lau himself (the man who owns ASL, designs all the amps) states that a 12AU7 is fine in the MG Head. I suspect the gain would be low, but he states it will work, which again leads me back to my original question about the OTL32.

-dd3mon

 

[usc goose]

Quote:

Originally posted by dd3mon The spec for the MG Head OTL32 shows a pair of 12AU7 tubes. Are 12AX7 variants (5751 specifically) interchangable with the 12AU7's in the MG Head OTL32? I've been under the impression that this would work, please correct me if this is not possible. Thanks, -dd3mon

i'm guessing it might be a bad idea because every time i see someone switching out tubes for ones of a different type, they use tubes of a lower gain, not higher. and since going from 12au7 to 5751 is something like a doubling of the gain, i think bad things are too likely to happen for me to think it's a good idea.

edit: did i say double the gain? i looked it up and it's actually 3.5 times the gain.
http://www.rru.com/~meo/Guitar/Tubes....pl?sfkey=gain

 

[Joe Lau]

Just go 12AX7 if you need more gain. OTL32 had no feed back. It is no degrade sound when you use high gain tube.

 

[dd3mon]

Quote:

Originally posted by Joe Lau Just go 12AX7 if you need more gain. OTL32 had no feed back. It is no degrade sound when you use high gain tube.

Thanks Joe