Last fall I bought an old 1975 Hammond Organ. It had a transistor based sound generator (unfortunately, not tonewheel), and as I was experimenting circuit bending it, I short circuited the main sound generator. Tip for life; if it’s an analog signal, you probably shouldn’t attach random wires and expect positive results.
Anyways, this provided the opportunity to gutt the thing, and take out a few cool parts. The spoils from “organ harvesting” were the motor from the leslie speaker, a reverb unit, the power supply, the expression (volume) pedal, and the pedalboard. I moved twice in the winter, so I didn’t keep the rest.
What I really wanted, was to build a relatively portable instrument with the foot pedalboard. It wasn’t until I started practising for a jazz show, that I got to intentionally building a bass instrument.
So I made a couple schematics, at first I made a circuit similar to this, but the tone was higher, and more fitting for a keyboard. I needed a way to get really deep bass sound from a simple circuit. Then when shopping at Circuit City, I picked up a few 555 timers and started to play with them hooked up to a scope.
By attaching the switches from the foot pedal to an astable 555 circuit, I was able to get a consistent tone. The only way to get that tone deep enough was to use a 10uf capacitor on the trigger pin. To tune the tones I had to use very small values of resistance in series on the foot pedal. There’s 2 problems with using these values;
1. When a voltage that is not 9v is applied, the tone gets higher or lower, but is not the desired frequency.
2. It can’t be hooked up to a wall-wart transformer without the 60hz from the wall interfering with the sound, and kicking it out of tune.
With higher valued resistances and a lower valued capacitor, the tone wouldn’t be bassy enough to pass for a bass instrument. The 555 astable formula was unable to calculate the frequencies, so I used a guitar tuner and guesswork. This may just be because the timer is a HA1755, I don’t know.
With one 9v battery you’ll get somewhere between 10 and 15 hours of play. It will stay in tune even as the battery dies, only the volume gets weak when its nearing depletion. I’ve kept the circuit on a breadboard to continuously add modules to the circuit. So far, I’ve only added an expression pedal to a 2n3904 amplification circuit, with some clipping diodes on the emitter.
The case I used is from an old hi-fi stereo, with the foot pedal mounted inside with screws. Eventually, I’ll want to use a more sturdy case with rubber feet. But for the mean time, the temporary case works.
The BaceMaker gives a really deep bass sound, which compliments guitar or piano, or pretty well any other instrument very nicely. There’s a bit of a learning curve in playing the BaceMaker, it takes a bit of coordination to make it all work, and sound good. But it’s a great accessory for a one man band, or a band that lacks a bassist, or for a bass player who wants two basses at once!The name comes from Timer Chip / Pacemaker + Bass = Bacemaker
Here’s a video.