Can I do that subs 12ax7 with 12at7

[tony Ma]

Hi all,

can I exchange for Pre-amp 12ax7 with 12at7?

tks

[Oscar2]

The two tubes have the same pinout and can be freely swapped in that sense.
However the gain of a 12ax7 is 100 whereas a 12at is spec'd as 60.
Also a 12ax drives about 1 ma whereas a 12at drives 10mA.

So put in an ax if you need more gain, an at if you need more current drive capability.

[SY]

Here's a crazy idea: if the circuit calls for a 12AX7, use a 12AX7. They aren't exactly hard to find, and excellent versions are relatively inexpensive.

[DF96]

Now you are being boring!

[SY]

That is indeed my curse.

[Oscar2]

Originally Posted by SY

Here's a crazy idea: if the circuit calls for a 12AX7, use a 12AX7. They aren't exactly hard to find, and excellent versions are relatively inexpensive.

Of course one of the very nice aspects of playing with tubes is that you can do stuff like that and its ok.
In the transistor world, not so much.

[DF96]

OK if you want an FX box, or the original design was wrong and just happens to better suit the 'wrong' triode. If the original design was correctly optimised for one triode, then putting another one in with completely different characteristics will give poorer performance.

Alternatively, just add a pot to fiddle with the bias and dial in whatever amount of distortion you prefer.