February 2009

Alpo Can Ring Modulator

This is a ‘ring modulator’ similar to the one used in an ARP Odyssey… this version operates by the input of two square waves into a 4011 quad NAND gate. I didn’t have a 4011 available so in this version I use a 4001 quad 2-input NOR with two inputs wired to ground (low) instead of wiring the 4011 with two inputs wired to Vcc. If I did my logic correctly the 4001 works the same when wired this way. I included the logic tables on the schematic.

Ring Modulator Schematic

The two square wave tones passing into the gates are compliments of a simple op-amp square wave generator circuit. Information on how to wire one of these up is widely available on the web. Here’s one good resource. The original schematic and idea was found on simple-answer.com here. A brief reference to the ARP Odyssey and this ring modulator is mentioned on Wiki here.

Alpo Can Ring Modulator board top

Obviously this is in an Alpo Can. The circuit board can be viewed on Flickr (see link below) but it was pretty small so it had no trouble squeezing in there. The knobs were found on eBay for dirt cheap. The hardest part about modifying this can was getting the sharp edges off the holes drilled into the can. To get the top off without cracking open the dog food… and to be able to take the top on and off the can you’ll need one of these: Kuhn Rikon Safety Lid Lifter

More photos and comments can be found on Flickr here:

4001 Ring Modulator in an Alpo Can

Sound Samples:

Dry, without Effects

Wet, with effects

16 Step Analog Sequencer

A while back Gil Duross over at Philly Techno was talking to me and was thinking about coming up with a analog step sequencer which would cost less than $100. It got me thinking that this isn’t that crazy and it’s likely someone out there has already done something like this. As is it turns out that’s exactly the case. The following video is of my test circuit of a 16 step analog sequencer based on Mauno Tuominen’s schematic for an analog CMOS sequencer based around at 4067n multiplexer/demultiplexer. You can see a DIY version of the sequencer here at studiomanus.com. I had an old sn76477 which I had been planning on turning into something so I started with the basics… indicator lights, tempo, and a simple oscillator. The eventual plan is to expand this out into a large 16 step sequencer/synth based around the sn76477 allowing for extensive sound shaping of each step in the sequence. Although the sequencer is well under $100 by the time this is completely finished it will likely cost well over that but the result should be substantial. In the meantime, take a gander at the initial test circuit. The sounds aren’t the most musical at this time, but it’s function and simple design is more the point.

I’ve expanded on the original design using a simple 555 timer for the clock and the ability to control the number of steps in the sequence through use of the 4063N. This has not been tested… that’s on my to do list. If anyone who reads this is well versed in these components and circuit design I’d love to hear feedback.

sequncer step counter