12BH7 in place of 12AU7...

[tubedood]

… In an upcoming build of RR's JCM Micro (RR800M). Would one simply replace the 12AU7 with the BH or would we use a different grid leak/stopper divider?
A few of the 12BH7 Push Pull type schematics I have glossed over show a 22k stopper and 220k grid leak.

Thoughts?

Thanks as always for your suggestions!

Dale

 

[tubedood]

Also any other suggestions on different small wattage power tubes to try in these micro builds?

 

[dan40]

I use the 12bh7 in mine because it sounds slightly fuller and tighter than the 12au7. I didn't make any changes from the schematic and the 12bh7 seems to be doing just fine. I did decide to raise the cathode resistor value slightly to allow the power tube to run a bit cooler but it seems to do just fine with the recommended value.

 

[tubedood]

Thank you dan40!
Trying to get my ducks in a row on this next build and wasn't too sure on the grid resistors for the 12BH7. Nice to hear that your build benefited from the BH7.

 

[JeffBlue]

I have changed out 12AX7s with 12AU7s in many of my tube based pedals. Then trying 12BH7s works well with many of them, if they can fit.

Have you ever tried a 12BZ7? It's like a taller 12AX7 and I am currently using a 12BZ7 in my Fuchs Plush Valve Job pedal with outstanding results.

 

[tubedood]

JeffBlue I cant say I have ever tried that 12BZ7 but I will sure check into them.

RobRobs circuit is using the 12AU7 as a power tube in push pull configuration.
I am always up to ideas and suggestions!