Sunday, 29 September 2019


My latest acquisition from Mutable Instruments is the Ripples filter.

Ripples unboxed.
With only one filter in my rack, it was not easy to have more than one interesting voice at a time. 
So I thought I needed another one to extend the capabilities of the synth.

Bob pushes modules around to make some room in the rack
For me Ripples has three main advantages :
  • I like the designs from Mutable Instruments;
  • it's a 4-pole 24 dB/oct filter and complements the 12dB/oct from the Doepfer DIY;
  •  it includes a VCA and it's a precious space saver in a small system like mine.

In the rack

There are 3 CV inputs : one for resonance and two for the frequency.
There are 3 filter outputs : 2-pole band-pass, 2-pole low-pass, and 4-pole low-pass.
The 4-pole low pass through the VCA is the latest output.

Getting Ripples and the Turing Machine change my initial plans a bit.
But that's the principle of having a modular synthesizer I guess.

It begins to take shape…

In the track below, hihat is white noise from the Random Module into the high-pass Doepfer fllter then on the VCA driven by the channel A of Rampage.
Kick and other percussions are from the same noise source into Ripples and on the VCA driven by channel B of Rampage.
Melodic lines are sine from Doepfer VCO into VCA driven by the envelope from Doepfer DIY, then passed through the phaser.
Sequencing wise, the first channel of the Korg SQ-1 triggers the hihats and serve as clock source for the Turing Machine.  CV out modifies the length of the rampage envelope to get longer hihats at times.
The second channel triggers kicks and other percussions.  Different percussions are obtained by modulating the frequency of Ripples.
Finally, driven by the clock from the first SQ-1 channel, Turing Machine provides gate and random notes CV (tuned by 2hp Tune) for the melodic lines.

DAW: Reaper
This is a single track from the synth plus a bit of chorus, delay and reverb.

Sunday, 8 September 2019

Turing Machine

The latest kit I built is the Music Thing Modular Turing Machine mkII

Turing Machine chilling on desk
Even if the boards are quite crowded, this is an easy build, thanks to the excellent documentation that comes with it.  The online build manual from Thonk is very well organized (smallest parts to tallest) and massively illustrated.  The fact that both value and component references are printed on the board is a real bonus.

Resistors first
Nothing special to tell, apart from the fact I soldered a 51k resistor instead of a 5.1k.  I simply misread and didn't double check.  Nothing serious : desoldering the wrong one, soldering the good one.

I used the documented trick to put some masking tape to align the diodes to the facade.  My diodes were well aligned but this left some greasy mark on the beautiful  facade.
Make sure your masking tape is not too old and will not leave marks by testing on the back side !

Finished boards

What is a Turing Machine ?

Bob calibrates the module
It is a pseudo random looping sequencer made from logic chips.  It is based around a shift register circuit.
You cannot program it or save sequences.  It produces clocked randomly changing control voltages.
The big knob controls how much randomness you put into it.  At noon, you're supposed to have a fully random sequence.  The more you go left or right, the more the loop is locked and stable, according to the length control.

Being fully made from logic chips with no software, the module can be clocked at audio rates to creates random wavetables as well.

Ready to assemble !

A word about the name by the designer, Tom Whitwell : "The Turing Machine is not a real Turing Machine the way Alan Turing explained it. The name is vaguely relevant because the module uses a loop of data being changed, but computer scientists find it very annoying. "

In the rack
Finally, here is a sonic example of a piece composed of 4 random tracks where the pulse output of the Turing Machine triggers an envelope and the output is passed through a quantizer to produce exact notes.  I added some pads and drums from software synths and voilà :