McTube using 12au7

[bagudan]

HI! I built the Real McTube using two 240/12 transformers. The only tube I had lying around was a 12ua7. The result is a very nice sounding booster...not much overdrive/distortion. Will a 12ax7 make much of a difference, or has my choice of transformers made it more of a cleanish pre-amp than an averdrive?
Thanks

[Ripthorn]

Compared to a 12ax7, the 12au7 is extremely low gain (12au7 has a mu of 20, 12ax7 has a mu of 100).  Those voltages should make it so that putting in a 12ax7 would make a world of difference.

[sean k]

That said it has to be remebered that the 12AU7 is much more useful for the amount of current push it has as opposed to the 12AX7. 12AU7's make beautiful low impedance microphone preamps because they are a low impedance tube. The 12AX7 is a high impedance tube so it's suited to the multiply windings of a guitar pickup.

The 12AU7 has even been used as a power tube for a watt or two as output so it's a completely different kettle of fish than a 12AX7 and
you're kind of using a tow truck as a race car. It will go fast and will be fun but it ain't a racecar!

[Paul Marossy]

You'll definitely have a lot more gain with the 12AX7.

[bagudan]

Thanks, I´ll go get one then