New ODS Build - Sounding WAY Better!... Little help please?

[keithrick]

I believe I read somewhere that the major difference (other then gain)between 12AT7's and 12AX7, 12AU and 12AY varieties (in the phase inverter position) is the transconductance and how this effects the power amp. It is also the reason why is is not a popular tube elsewhere. Maybe someone can shed some light on this?

FWIW-here are some values from the link RJ posted.

Transconductance:
12AT7 -4000 micro-ohms
12AX7 -1600 micro-ohms
12AY7 -1250 micro-ohms
12AU7 -3100 micro-ohms

[ic-racer]

micro-mho, right?

[v00d00blues79]

Thats why the 12AT7 makes a great reverb driver tube as well.

Andy

[Funkalicousgroove]

I think if you have one give it a try, you won't hurt anything- the PI is a Schmitt long tailed pair just like a BF Fender, Should work just fine.

[RJ Guitars]

So I came home for lunch and I did give it a try with a 12AT7 in the V3 spot. I think my ears / amp / guitar/ etc. are not tuned fine enough to hear the significance yet. I'm really pleased with the amp and this clearly didn't cause anything to go over the edge one way or the other. I don't have a scope but that may be what it takes to really understand the differences. I'll mess with it some more before I can say better or worse according to my ears.

I do have a question about the gain issue though. In a long tail pair there should be some gain in the phase inverter, right? So maybe if there are no other audible differences it might change the overall gain a bit... does that seem reasonable.

rj

[heisthl]

I think the 12AT7 sounds sterile compared to a 12AX7. Not drastically, but enough to not use one. JMHO