Last summer a friend of mine gave me an old Boss DD3 digital delay pedal. I’d been looking to add a delay module to my modular synth and this guitar pedal fit the need pretty well. After playing with it for a few weeks I was wishing that it had some way to synchronize the delays with the beat of the synth. If you’ve ever used delay plug-ins with a DAW you know what I’m talking about. Most plugs that I’ve used allow one to choose delay times in milliseconds or in times related to the beat: quarters, eighths, dotted sixteenths, triplets, etc. Having some beat-synched delay taps hopping around the track really can add a lot in the way of syncopation. Having any delay, synched or not, is great. But that extra thing is what I was looking for.
I noticed that the several pedals have a tap tempo switch, which gets close but isn’t quite right for the synth. Tapping tempo is perfect for a guitar player who can subtly change speed to keep time with tapping a pedal. But the timing of a synth is much more machine-like in nature and would work best with the same clock as what’s timing the entire patch. If you’re running a sequencer, LFO, and envelope from a clock trigger, that same trigger could drive the taps of a delay and keep everything in time.
In an email to Navs, a musician in Germany, I happened to mention that a pedal with a trigger input would be a great thing. He replied with a link to a post he’d made on his own site about a year earlier. In this post, he writes about a musician, Rechner7, also in Germany, who had modified an Electro-Harmonix Stereo Memory Man with Hazarai (Hazarai is a Yiddish term meaning something along the lines of “everything and the kitchen sink”). Rechner7 had not just added a trigger jack, but he’d added three of them with a switch to choose between the 2nd and 3rd inputs, as well as a on/off switch for the loop button which would make that particular function much easier. I’d never soldered a thing in my life but onto Craigslist I went and a week or two later had a SMMH pedal.
Aftr studying Rechner7’s photos and a few emails back and forth, I understood a bit more of what was going on. Trigger/Gate input C on his plans is always on, and there’s an on/off/on switch that chooses to add input B or A to the signal at C. This allows a steady beat into C with odd or random beats into the other two inputs, which can add a lot of fun/chaos to the delay signal. The SMMH doesn’t repitch when the delay is sped up or slowed down (its only weak link in my opinion) so having these two inputs is terrific for quickly adding new taps or off-beat taps. He also added a little high-pass filter circuit (found about a third of the way down on Doepfer’s website here) which keeps a slow gate from inadvertently engaging the loop function. On the SMMH, the tap-tempo switch engages the loop if pushed for more than a half-second. What this means is that a long gate (half second or more) would do the same. So the high-pass filter only allows gates that are shorter. The exact length is decided by a capacitor and some math. (I apparently didn’t do the math correctly because mine still slips into loop mode now and then. I need to fix this.) There’s a switch that bypasses this filter for inputs B and A in case one wants to throw the thing into loop mode. Lastly, Rechner7 also suggested I add a transistor to the input circuits, which keeps unwanted voltage from traveling back to the trigger source on the modular.
I wired this all up on a breadboard before doing any permanent damage to my new pedal, and was quite surprised when it worked. Confidence flowing, I took the step of drilling six new holes into the aluminum case of the SMMH. This was rather thrilling in a DIY sort of way. There was no going back now.
It took the better part of the next day to get the wiring done and everything in place, and I’ll be the first to admit that my electronics work isn’t the prettiest. But the results are exactly what I wanted. The only change from Rechner7’s design was that I designanted the always-on jack as input ‘A’ rather than ‘C’ which just made more sense to me.
Here’s a short track where the different delay timings are really apparent.
One thing I’d not considered was that when the delay lands exactly on the beat, it’s not that interesting. So I find that using the Rotating Clock Divider from 4ms is necessary. A typical patch would be using the /3 output from the RCD as the main clock, and running the /1 and /2 into the inputs of the SMMH gives me triggers on the eighth-notes and triplets. Then I might have something more unusual running to my input C for some chaos tossed in.
Edit: I should probably mention that on the video up there, the same rather boring eight-step sequence is spit out by the synth throughout the entire video. All the syncopations and funny beats and extra rhythms are created entirely by the Stereo Memory Man being clocked by the µStep, a little trigger sequencer from Intellijel. The dry signal is on the left channel and the wet is on the right, so you can listen to just one or the other and hear the differences.
Since completing this mod, I noticed that Rechner 7 had done a similar modification to an EHX Deluxe Memory Boy as well. I’d been thinking about adding an analog delay pedal to my arsenal, and found a used one a few weeks ago. About the same time, Pittsburgh Modular announced an analog delay module for Eurorack that may end up being more what I’m looking for, even without tap tempo, so I’m holding off drilling the holes into the DMMB in case I need to let it go.