Hotbox III w/Pedal Power

[kkillebrew]

Just finished building this Hotbox clone and I wish I had done it years ago.  Incredible box - gets me the tone from my cranked DC 30 clone in half power mode.  With the addition of full bypass it gives you a great clean boost along with preset distortion and whatever sound you have dialed in on bypass.  Very versatile.

I fussed with the tone controls trying a more conventional fender style, and a Marshall stack, but the Matchless design is somewhat parametric and offers a wide range of sounds and I went back to it exactly.  In the end I used the original Matchless design changing only the plate resistor in the first overdrive stage from 220k to 100k. 

I tried three different power transformers before I found one I could mount inside the Hammond steel enclosure and still keep things quiet. I finally used an old Heathkit preamp transformer with nice copper shielding. With a voltage doubler circuit and increased Pi resistor values I am getting the exact HT voltages and I notice it sounds MUCH better at these voltages than anything else I tried.  I am using AC on the filaments, and it's all very quiet.  This transformer has two 1 amp filament windings and I was able to use the second winding to create an isolated 9V tip neg pedal supply which seems to work fine up to about 400ma.  It's operating my Eventide Rose with no problem.

Definitely my current overdrive/distortion box of choice, but tastes and styles will vary. Attached is the schematic specific to my build.