The assembled project, before knobs are added.

SparkPunk Project

It has been a while since I built something, so here’s a little project that was a lot of fun, and has opened up some new noise maker territory. Sparkfun is one of the top suppliers of parts and kits for the electronics hobbyist, and while I still prefer Adafruit for most things, Sparkfun has some unique items you won’t find elsewhere. One of them is the SparkPunk Sound Kit. The kit came with everything I needed, no missing parts, and the online instructions were spot on.

I chose to use IC sockets just in case I messed up.

I chose to use IC sockets just in case I messed up.

It took me about an hour and a half to build, which for me I think was just right.  The most difficult step had nothing to do with soldering or bad connections. The hardest part for me was the battery compartment, which required a multi-hand operation to get the part screwed onto the board.

Using hemostats to hold the nut for the battery compartment.

Using hemostats to hold the nut for the battery compartment.

The device worked the very first time, and was a lot of fun for annoying my wife. A little while later I returned to the project to make some of the modifications that Sparkfun documents. This included added photo resistors to manipulate the filter cutoff, and connections to make the CV inputs more usable. I went with a slightly different knob style, and found that some knobs use different set screw types. In this case I had a combination of flat head and Allen type, which was sort of annoying (why aren’t they the same??), but once they were on it was all good.

SparkPunk with photoresistors and CV cable (shorted).

SparkPunk with photoresistors and CV cable (shorted).

Shorting the CV inputs allows the unit to play without pushing down the button. The next step is to have something else provide CV to manipulate the device. Unfortunately I didn’t own any CV producing gear, as I am strictly in the MIDI and digital audio worlds, and never got into the old (but still thriving) modular CV world. So to really test out the SparkPunk for some ideas I wanted to carry out, I had to get something that produced CV. I already had my eyes on the Electro-Harmonix 8-Step pedal because I’ve got a few of their other pedals that can be used in combination with the 8 Step to manipulate expression pedal settings. With the SparkPunk, I had yet another device with which to experiment.

SparkPunk interfaced with the EHX 8 Step Sequencer.

SparkPunk interfaced with the EHX 8 Step Sequencer.

To use the two devices together, I needed a suitable cable. The EHX 8 Step comes with a stereo 1/4″ cable (TRS) for expression control, but the SparkPunk doesn’t have any such connections.  EHX recommends a TS 1/4″ connection for basic CV control. Making a cable was easy enough using some stranded wire and a 1/4 plug, but the connector on the SparkPunk side had to be improvised. My first attempt was using straight headers on the SparkPunk PCB (pictured above), but these got in the way of the knobs. Later I replaced this with some right angle headers – much better!

The EHX 8 Step puts out 0-5 volts, though when measured before posting this article, s a bit more than 5V:

2014-08-25 19.19.38 For now I just shorted the two CV inputs on the SparkPunk (connected to the center tip) and connected the Gate to ground. You might want to consult Sparkfun’s instructions on other wiring options. I was really just winging it here, and got it to work. The interaction between these devices can be a bit touchy.

A pulse from the Spark

An audio pulse from the SparkPunk, triggered by the 8 Step

The 8 Step has a lot of capabilities that I am not covering here. A little experimentation goes a long way, and it is even more fun once you add some effects after the SparkPunk signal, as you might with any other modular synth. In the videos below I give a brief demo of the SparkPunk, and the interaction with the EHX 8 Step Sequencer:   By itself, the SparkPunk may not be very exciting to some folks, and I found it really shines as part of a larger setup that includes some effects. I’ve already begun to utilize this setup in my audio experiments, and intend to use it in my next performance at electro-music.com’s annual festival. You can hear the device on this improv collaboration with fellow electro artist Clone 334: The funny part is… not long after I put all this together, Sparkfun came out with their very own sequencer, which is designed to work directly with the SparkPunk Sound Kit. So I envision an update to this post before too long! Well played Sparkfun! You can learn more about the SparkPunk kit on Sparkfun’s website. To learn more about the EHX 8 Step Sequencer, check out the EHX site.