Patch Tips #21 - Getting Animated

Doepfer's A-137-2 'Wave Multiplier II' does more than just super-saw.



This module uses a set of comparators to generate four 'fake' phase-shifted versions of the input material. The offset of each saw can be modulated, generating a large sound from a single oscillator. As the module is DC-coupled, it can also be used to process CVs.

When I first got the A-137-2, I considered building an expander to gain access to its pulse outputs and avoid having to unscrew the module from the system to remove stages from its output. Two discoveries I've made this week happily mean this isn't necessary.

The first relates to the manual shift knobs: when set at zero, a stage is effectively removed from the output. This is great news if, for example, you only want one additional animated saw. It also has implications when using the A-137-2 as a comparator-based timing delay.

Secondly, the A-137-2 will function without the usual input. Activate a stage by setting its manual shift to something other than zero and feed your signal to its CV input. The result: those hidden pulses! With some careful setting, you can get some mad waveforms:



I'm not sure if this is a bug or a feature - a comparator needs two signals - but, as you can hear from today's Patch of the Day, it offers an additional palette of sounds.



To use the A-137-2 as a shonky beat machine à la A-143-1, feed it a ramp LFO. I've found using a positive-only CV from Maths works best as the comparators switch on both the rising (on) and falling edges (off) of a wave. Patch its output to an A-162 or similar to get clean pulses.

The A-137-2 is another Doepfer gem, offering several uses for not much money. If you want to learn more about the workings of this module, read the ETI article on the Digisound Waveform Multiplier or, if your French is up to it, the Elektor article linked at the bottom of the Doepfer product page.

Audio files not playing

Having moved my content to the cloud, my audio files are once again not playing.

Sugarsync used to allow direct access to files, meaning I could stream my MP3s via the Google reader player. They've now added an intermediary page which means this no longer works. Looks like I'll have to pony-up for a dedicated server after all.

In the meantime, here is a workaround: on Safari, go to a blog post, click play on the player, open up the 'Activity' page (under the 'Window' menu) and look for the Sugarsync URL. Double-click this and it should take you to the download. On Firefox, right-click to 'View Page Source', then search for the Sugarsync link.

Patch of the Day - Highly Strung

Kicking off the new year with the rediscovery of the Doepfer A-137-2 Wave Multiplier and a frenzied take on a duet for two acoustic guitars:



I bought this module when it first came out, then sold it two years ago because I'd run out of space. I've been working on a track that needs a big fuzzy, 'super-saw' bass but wasn't getting the right sound with multiple VCOs and wondered if the A-137-2 might fit the bill. As you can hear from today's PotD, that's not what I ended up using it for: the A-137-2 will do phasing saw sounds, bar the subtle detuning, but I found it's also great for EML-sytle abrasive tones that can then be tamed with a filter.

The patch involves CV-ing the WM II at audio rate, LP filtering the result with the Cwejman MMF-1 and then accentuating various frequencies with a low-bandwidth setting RES-4. Gordon Reid goes into much detail about how to achieve this in his synth secrets, but I just used my ears. A Wiard/ Make Noise Wogglebug generated the timing and note information. It was kicked about by one channel of Maths, which received a mult of the stepped output, thus varying the pace and intensity of the ratchets and completing a timing feedback loop. I recorded two passes of the result, varying the patch by hand.

LeafAudio Noisefoc Samples

A free library of sounds for Ableton's Simpler made with LeafAudio's Noisefoc synth.



From Manu: "We created a free library for Ableton 8 based on sounds of the NOISEFOC Synth - a 3-oscillator synth that can be built in our workshops as a diy-machine. The library includes 16 Simpler-Instruments that show the possibilities of combining diy-machines and professional production. It doesn't sound like that but yes, you can do electro pop with the sounds ;-) All sounds in this song except the drums are made with the Noisefoc library."

Noisefoc Ableton-Library Demosong by LeafAudio

The library is available here. Look out for LeafAudio workshops in Spring 2012 where you can build your own Noisefoc, Fuzz-O-Mat or Bumsss.

4ms PEG Demo

Audio examples of the 4ms Pingable Envelope Generator. An update to this post.



Perfect for synced modulations, the PEG generates LFOs and envelopes which can be locked to a master clock. Once 'pinged', its variable slopes run at either the base time or are stretched/ shrunk to a divided/ multiplied rate. Here it is in action:

4ms PEG demo by navs

The PEG offers voltage control over most of its parameters, various trigger outputs, an analogue OR and a variety of triggering options. The toggle function can be a creative source of surprise, as it flips the activity of the two envelope generators. The curves can be extreme, especially when the skew is maxed in one or the other direction, so you might want to use a linear VCA. That said, a 'whiplash' setting is great with low pass gates.

I've only scratched the surface with this demo: you could try the PEG on drones, slow pans or feeding it to a quantizer for synced, stepped CVs. QNT trig mode allows gated repeats or trills like the Plan B Model 10 or Cwejman CTG-VC. When used with a sequencer, you could set different length envelopes per note, or use the toggle jack to combine the two.

The PEG is rich in possibilities, so make sure you read the extensive manual. Once you've grasped the concept, it's easy to use. If you've ever wanted to keep your wobbles in time, the PEG might be what you've been looking for.

PT #20 - Hutchins' Anti-Glide Patch

How to compensate for frequency shift in exponential FM. Bernie Hutchins' Electronotes patch quoted in and cribbed from Allen Strange.



Exponential audio-rate FM is great for klangorous tones. Unlike linear FM, however, it's hard to patch dynamically. Changing the index results in a churning sound. The more you modulate the carrier, the greater the pitch shift.

Bernie Hutchins' patch counteracts this detuning by simultaneously pulling the frequency of the carrier down with an inverse envelope:

The modulator is patched to the carrier via a VCA. An envelope opens the VCA. The envelope is multed to a second VCA or ring modulator and multiplied by itself. The result is inverted and patched to the carrier.

Here's how it sounds:



With and without the compensation CV:



I'd tried this previously, as a work-around for my VCOs which don't have linear FM capability, but didn't get it to work satisfactorily. My mistake was to send the full inverted envelope to the carrier - it needs tweaking to find the right level. Don't expect to be able to set high indices. I found I couldn't push the envelope much above 2-3 volts, before the compensation CV itself became apparent. Similarly, short envelopes seem to work better than e.g. joystick sweeps.

Despite its limitations, this patch offers a method for dynamic timbal control of VCOs that aren't capable of linear FM. It's a bit fiddly, but as Allen Strange writes, it's certainly worth a try.

Mystery Beatbox

Spotted at Schneidersladen. One of five, custom-built, apparently based on a Hohner drum machine, master clock operation only, price unknown. Sadly, couldn't hear it in action.







Full-size pictures are here. Thanks to Moondust for the loan of the camera and the delicious Swiss chocolate!