Mystery Circuits, LLC
By Mike Walters - Chapel Hill, North Carolina
Radio Ace
The Radio Ace is an AM/FM drum machine built for Mark Lewis in 2015. Using a late 1970s clock radio, the Radio Ace is a 3 x 8 programmable drum machine that has an analog bass drum, a gated input, and it uses the audio from the radio as the source for the snare drum noise. The snare (radio) and the line level input have individual sustain controls. The tempo goes from sloooow all the way up into the audio spectrum.
Built by Mike Walters Chapel Hill, NC 2015
Audio Samples
Audio Sample 1 - Tweaking the sustain of the Snare drum, and sweeping through FM stations
Audio Sample 3 - Running Minimoog through Radio Ace, sweeping Input sustain from open to choppy, then changing states of input steps from eighth notes to less.
Audio Sample 4 - Running Polymoog through Radio Ace, then turning up tempo all the way! Notice the subtle gallop at the beginning and towards the end.. This happens when the input sustain is turned all the way down, and the input is quiet. It's a "flaw", but I liked the effect, so I kept it.
How It Works
This is how it works... The clock is a 555, with variable frequency (tempo). The clock feeds a 4017 decade counter wired to repeat after 8 steps. On the front panel, there are 24 mechanical push on/push off latching switches, with LEDs wired above them that light when on. The output of these switches go to a bank of 3 input AND gates. The steps from the sequencer go to the other inputs, as does the pulse from the 555. If the switch is on, AND the sequence is on, the output of the gate goes hi when the 555 pulses. The 3 input with clock signal is necessary because the 4017 stays high the duration of the step. So if the very next step is programmed to trigger, the gate won't go low in between, and won't retrigger. I ran into this problem when I built the Trommemaskine, but on that I used differentiators.
The bass drum is analog, and is a modified version of the same circuit in a Korg Monotribe. The snare drum is audio directly from the built in AM/FM radio, which tunes via a knob on the side of the Radio Ace. A slider switch changes the band from AM to FM. The input takes any (hot) line level, and gates it according to the sequencer. Both sustain controls are identical. Turned all the way up, the snare or the input are legato, turned all the way down, they're staccato. There is a red LED glued to the bottom of the tuner bar that flashes on the 1 and 5 counts. I used a capacitor to make it fade.
The "Snoozer" button no longer gives you 10 more minutes of extra sleep. It now turns on and off the rhythm.
The Build
The radio is something I found at the thrift store. It's a SPARTUS brand. They made some very cool radios!
I removed the LED clock, and replaced it with the 24 matrix switches. Unfortunately, the overall depth of the radio was way too shallow to accommodate all of the circuits and power supplies, so I stretch-limoed it by building a new bottom. The top is transparent black plexiglass. I cut out a rectangle the right size with my CNC, and manually bent the sides using a heat gun and a metal bending brake. I got it right in two tries!
Radio Ace demo. Gating Yamaha CS01 II
Gotye demos Radio Ace in 2015
Songs By Mark Lewis using the Radio Ace
Mark Lewis owns the one-and-only Radio Ace, and here are some songs he recorded using it.