emulate 12ay7 using 12ax7?

[Groover]

I notice that many Tweed Fender circuits use 12ay7 for the first stage, which I understand has lower gain than the 12ax7.
Can one triode of a 12ax7 be made to perform more like a 12ay7 for the first stage by using different values of plate and/or cathode resistors?

Is there a tube made with one AY triode and one AX triode?

[trevorus]

A 12wd7 is half a 12ax7, and half a 12au7, if I remember right. Only one of that type that I know of.

[Bruce / Mission Amps]

I notice that many Tweed Fender circuits use 12ay7 for the first stage, which I understand has lower gain than the 12ax7.
Can one triode of a 12ax7 be made to perform more like a 12ay7 for the first stage by using different values of plate and/or cathode resistors?

Is there a tube made with one AY triode and one AX triode?

Yes.. experiment with a split load resistor pair on the triode you want less gain.

[Groover]

Yes.. experiment with a split load resistor pair on the triode you want less gain.

Does that mean using two resistors in series as a voltage divider in the plate circuit?

Never mind, I found the answer to my question here: http://music-electronics-forum.com/t15765/

and some extra info here: http://music-electronics-forum.com/t11984/

[Groover]

from the above-referenced 12ax7 & 12ay7 in harmony thread:

Or you can add a resistor or two between stages to reduce the signal level some, this is done all the time. If we make them variable, we call it a volume control.

So would reducing the signal level after a 12ax7 gain stage give substantially the same result as using a 12ay7 stage, or are there other characteristics of the 12ay7 that would make doing it that way a not-so-close approximation?

What about attenuating the input side (assuming we are talking about the first stage) with a larger grid-stopper? (Or using input 2 given a standard Fender input configuration?)

[Bruce / Mission Amps]

from the above-referenced 12ax7 & 12ay7 in harmony thread:



So would reducing the signal level after a 12ax7 gain stage give substantially the same result as using a 12ay7 stage, or are there other characteristics of the 12ay7 that would make doing it that way a not-so-close approximation?

What about attenuating the input side (assuming we are talking about the first stage) with a larger grid-stopper? (Or using input 2 given a standard Fender input configuration?)

Well, I've been doing this for years with excellent results but the 12AY7 does seem to draw more idle current then the 12AX7... the split load sounds really good with the 12AX7 anyhow and there will be a nice reduction of output signal with a little taming of the shrill top end.
You can drop the cathode biasing resistor down on that triode to 820 - 1K for another very very mild tonal tweak. That has nothing to do with the current threads found about increasing gain by changing the ratio of plate to cathode resistors. It is only for a tiny bit more idle current through that triode.
What I do is use two 47K to 56K resistors and bring the signal out with the coupling cap at the junction of the two.... it sometimes sounds better to use a slightly larger value cap... like if it was a .022uF, I'd use a .033uF or .047uF.
This is not written in stone and sometimes it sounds better to go smaller anyhow.
You can drop the cathode biasing resistor down to 1K too for another very very mild tonal tweak.

[Wombaticus]

A 12wd7 is half a 12ax7, and half a 12au7, if I remember right. Only one of that type that I know of.

The JJ ECC832 is the current production version of this.