The Owners Manual

Rebuilding the better beast's insides

I'm happy to say that I think I've figured out how to get my prototype to the check it and see if it makes any noise stage. (I knowingly although perhaps foolishly bought the proto in dissembled condition.) As a complete newbie tech-boi, I've traced the wiring down and think I know where the disconnected wires should be reattached. Two wriggling red wires flopping around inside the chassis connect to the power transformer, and I see a couple of 500 ohm resistors that need wires attached. The third red wire appears to connect to the output transformer and it appears the amp has no speaker output. I picked up a speaker jack and this weekend I'll pull out the solder gun and try not to damage anything. I'm still a bit confused about the self-shorting function on the speaker jack. One wire is current carrying, that would go to the output tranny, and the other goes to ground, so where's the third tab on the jack connect? If anyone out there with a clue dropped me a line I'd be a happy clam.

Be Afraid

The Hi-Mu Amplifier company produced approximately one hundred amplifiers for sale to the public in its six year history...
... and then there were the prototypes, the test amps, the experiments, and the wild hares.
Amp Maestro Barry Breisch built one very special amp for himself. Old school and too cool with Streamline Moderne styling stolen from the very best commercial industrial design, the Vaculator!

But let Barry tell the story:
"The base is a double coffee pot warmer unit that I got at a flea market for $2. I tore the guts out of it, fabricated a flat aluminum plate to replace the top, punched all the holes for the tube sockets and transformers and turned it into an amp. I had to do this because of the word VACULATOR stamped on the front of it..."



This one-off amp is simplicity itself. It has an on/off switch, volume and single tone control. Regarding the circuit inside, Barry went nearly medieval:
"I designed the circuit to be as 'old-time' as I could make it. It uses 6SJ6 pentode preamp tubes (not 12AX7's) and an active tone control circuit (totally non-Fender) that I lifted from a 1940's Motorola home stereo amplifier system."

The single ended 6V6 tube that drives this beauty (or is it beast?) is characteristic of most of the amps Barry built under the Hi-Mu marque.

Here's a picture of her backside.



"The output transformer is the first Air-Gap Prototype that I approved for production. It was hand wound by V&F Transformers in Illinois as part of the process of nailing the air-gap output transformer design.
"The rectifier is a 5Y3GT and the power transformer is my standard (custom) V&F Transformer.
"Despite the vintage pretensions, the amp also has an effect loop which is decidedly non-vintage. I honestly can't remember if the loop is 'active' or 'passive', but I'll guess passive since my goal on this design was a minimum parts count. I almost never use the loop.
"There is no question that I have played this amp more than any other amp that I've built."

I want to thank Barry for the photos and info that appears above,and the Vaculator's schematics posted below.


So check back, comment or shout out a hello. fred