Real McTube build

[mac dillard]

Ijust finished building the Real McTube II and as we use to say back in the CB days, this thing really blows smoke. Got it connected to an AX84 P1 amp and they must be in love with each other. Glad I can't post pictures, this thing is ugly. I put in in an old Sears 200 amp inverter housing that I had. It measures 7 1/2 x 6 1/2 x 6 1/2. That is pretty big. Before it was over I was glad of ever cubic inch I had. I just don't have the knack of putting all of that into a little biddy box. The wiring is point to point using terminal strips.   Used two Radio Shack 450 ma 120 to 12 ct tranformers. The filament voltage is 9.3 vdc and the rail voltage (B+) is 150 vdc. Followed Paul's example and made both pots 1M and deleted R9. Plan on making it remote switchable in the future. It is running on a 12AX7 and I have a 12AU7 that I want to try but I can't get the kid off of it long enough to switch the tubes.( He is the guitar player, I just build the devices). This is my second pedal build and I have got to take my hat off to you that can work in the little boxes, I have a lot of trouble with it. Great forum here. Keep up the good work

[brett]

Hi
I agree that it is an amazing project.  A B+ of 150V sounds good.  I've built different versions with different B+ and I found the 150V to 250V range really nice.  The original 130V gives very heavy distortion.

The filament voltage is 9.3 vdc

You might want to reduce the 12 ohm 2W resistor to about 6 ohms.  The heaters want to run on 11 to 13.5V.

cheers

[mac dillard]

Thanks, I'll try changing the 12 ohm resistor..Tube seem to be running ok though. Have you experminted with the values of C6 and C8? i'm running .022 uf. Thinking about lowering them some. Don't know how much just yet. Have not done the math.