A-178 Theremin Control Voltage Source

The Theremin, invented in the late 1920's by Léon Theremin was one of the earliest electronic instruments.
The instrument is known for it's distinctive ( spooky ) sound, but most of all for it's playing method; Instead of playing it with a keyboard, the Theremin has antennas that sense the movement of the players hand, without touching the instrument.
Best known for playing the Theremin is Clara Rockmore, one of Theremins finest students.

Most theremins use two antennas, usually one for pitch and one for volume, so with two Doepfer A-178 Theremin Voltage Source modules, an oscillator (VCO) and an amplifier (VCA) module, it is quite easy to re-create the sound of a 'real' Theremin. You can even easily extend that sound by patching in filters or other modules.

And again, that is what makes the A-100 modular so versatile. 

Instead of just recreating the original Theremin you can use the module as a control voltage source for other modules. 

The voltages can be used for controlling any voltage controlled parameter of the A-100, e.g. pitch or pulsewidth (VCO A-110/111), loudness (VCA A-130/131/132), panning (A-134), filter frequency or resonance from all of the filter modules, phasing (A-125), frequency shift (A-126), resonance peaks (A-127), envelope parameters (A-141/142), and tempo (A-147), to name just a few ;-)

The Gate-output with adjustable threshold (not available on the original Theremin) is a nice extra output. I often use this for (re-) triggering notes or filter effects, but it can also be used for starting sequences (A-155) or for reset or switching functions (A-152).

Doepfer recommends if two or more A-178 are used the distance between the modules/antennas should be at least 30 cm to avoid interference.

Booktip V - The A-Z of Analogue Synthesizers by Peter Forrest

This 'Encyclopaedia of all the great analogue synthesizers and keyboards' is written by Peter Forrest and is probably one of the most detailed analog synthesizers-catalogs out there.

The books list all analog synthesizers that were ever produced, and is spread across 2 parts with a total of 600 pages, filled with useful info about manufacturers, statistics and lots of pictures in black and white.
Both books also have a 16-page full-color-section, stuffed with cool pictures.

The first edition of Part One (A-M) was published in 1994, two years before Part Two (N-Z) arrived. The Revised version of Part One was published in 1998.
Although the layout of the books and some b/w pictures may look a bit cheap the books are highly informative if you are interested in analogue synthesizer history.

ISBN Part One A-M revised 0 9524377 2 4
ISBN Part Two N-Z              0 9524377 1 6
Susurreal Publishing: http://www.vemia.co.uk/susurreal/

Most wanted III - DIN Sync

The DIN Sync (or Sync24) standard, was introduced by Roland in the 80's for synchronizing sequencers, drummachines and (synth-) arpeggiators. The name Sync24 is derived from the frequency of the pulses, 24 pulses per quarter note (PPQN). A clock signal  of 2.51 V, at 24PPQN, defines the speed of the sequence or drum pattern. The start/stop signal defines if the sequence is running and has a voltage of 0 or +5 Volts. A lot of Roland's products were using this standard at the time, so some have sync-in, -out, or switchable sockets.

After the wide adaptation of the MIDI standard, the DIN sockets started to dissapear from most instruments. Syncing instruments via MIDI is now handled by the MIDI Beat Clock at a same 24 PPQN rate.

The SYNC plugs look the same as MIDI plugs ( DIN-standard, round with 5 pins ) ,but the pins have a different configuration as the MIDI plugs. The Din Sync standard can only handle clock signals (for tempo) and start/stop signal, so it sends no pitch-control. More info on Doepfer's SYNC FAQ page.

I know the DIN-Sync standard is now close to death. Only a few 'modern' drum-machines still have a SYNC In or Out, like for example the Novation Drumstation that i own.

The idea of a A-100 SYNC converter module doesn't sound bad in my opinion, perhaps a kind (extended) modular version of  MSY2 MIDI-to-SYNC Converter that Doepfer sells? ( A-190-X maybe? )

If i might suggest some extra features, why not add a 16 (or more) trigger outputs (A-160/A161-style) , SYNC-in possibility, reset output(s) and switches on the front for choosing dividing factors.

That, together with a set of MIDI In and Thru, or an internal link possibility  to the A-190, would make an awesome (and not too expensive) module that for example could be used for percussive effects like triggering drumsounds in Sync with your old equipment.

Gate vs Trigger

Both the terms Gate and Trigger are commonly used for a signal out event type, mostly generated by a keyboard or sequencer, to start the process of generating a note or sound.

A trigger is typically of short (fixed) duration, where a Gate is usually continuous and muted when a key is lifted.

Gate-times can often be altered, in fact an Envelope Generator is not much more than a trigger-to-gate converter, often with different kinds of variables.
Most commonly used types of EG's are from the ADSR type ( adjustable Attack, Decay, Sustain and Release time ), but you can also find simpler AR, AD or ADR modules in other analogue systems.

CD-Tip III : Analogklang - Modulsystem A-100 Demo CD

This CD was published by Doepfer in 1995 to show off their then brand new A-100 modular system. It has 29 tracks and a large, colorful, fold-out booklet (in German) with a description of most of their early modules.

All the basic modules are demonstrated on this CD, that was produced by Andreas Merz from Weltklang and  narrated in German by a vocoded voice. The tracks are short, between 25 seconds and 3½ minute, what brings the total length of the CD to just 30 minutes.
This CD itself must be a collector's item by now i guess, because the item isn't available anymore on Doepfer's website. I'm quite sure i won't sell my copy... ever. This CD still means something special to me, and i did listen a lot to it, even before i bought my first modules.

Although the CD isn't available anymore, all tracks ( and some other sound-examples ) are still available for download HERE ( ...sadly enough in a poor ( 16Kbps) quality due to file-size decisions, but if you really need better audio-files you can contact Doepfer for better ones )
A must-have /or at least must-listen CD for all the real A-100 geeks and you might even get some new, fresh ideas out of it.

Modifications III : A-127 Triple Resonance Filter Expander (part 2)

Hmmm... that went faster as i expected.
My brand new self-made A-127 Expander Module is now almost finished.
( Find part 1 HERE)
The switches are wired too, and the overall look of the module is even better as expected.

I did have some trouble with drilling holes through the aluminium front-plate at first, but it seems i aligned the sockets nice enough with the output sockets of the A-127 itself.
The switches work smoothly and the 'new' 12 dB filters sound sweeeeeet.

I'm very happy with this module, and glad that i went with this option instead of just putting switches on the A-127's front panel.


The wiring of the modules on the backside was quite simple. Red wires were used for switching between the different filter-modes, the blue ones the the audio-multipliers, and yellow ones (not visible in the picture) for the lower switch.
I did the soldering without removing anything from the module, but you might want to remove some components for easier access.

Instead of soldering you can also use small (0.1") wire-sockets at the board's jumper-spots. An example with detailed information of this can be found HERE

Update March 10, 2014
Doepfer announced an official Breakout Module for the A-127,
find out all about it at http://patchpierre.blogspot.nl/2014/03/doepfer-127-bom-filter-breakout-module.html

Modifications II : A-127 Triple Resonance Filter Expander

Now that i finished my first 'real' module-modification i couldn't wait to start with the next project.
At first i wanted to replace a red LED for a blue one on one of my modules myself, but i couldn't decide which module i should pick for this... and i'm still not sure, but that can wait....

Another plan that was in my head from the beginning was the placing of 3 switches on the front-plate of my A-127 Triple Resonance Filter. There are 3 jumpers inside this module that allow the user to switch the filter-type of each of the three channels between Band-Pass (standard) and 12 dB Low-Pass. I have seen some examples on the web of this modification, most of them just with the switches mounted on the A-127 itself, but unexperienced as i am, i was too afraid to damage the front-panel and went for an Expander Module design.

So that is why i am building it into an official 4HP blind-panel that i bought from Doepfer. Each of the three A-127 channels on my expander module design will have a switch to switch the channel's filter-mode and will also provide an extra (linked) audio output.
( mainly to fill up the space, but i aligned these with the A-127's original outputs to make it look more like an official Doepfer module ) .

To complete the expander module i also want to place a switch at the bottom that has the function of the J3 jumper that is inside the A-127 module on the mix circuit-board. This switch can put the module in a mode so that both levels of the filter and the original can be controlled with attenuator 1 ( audio level in )

I am not finished with the project yet, the mounting of the switches and extra outputs is done. Wiring is the next step, i'll write another post on that later this week...
Find Part 2 at http://patchpierre.blogspot.nl/2010/12/modifications-iii-127-triple-resonance.html


Update March 10, 2014
Doepfer announced an official Breakout Module for the A-127,
find out all about it at http://patchpierre.blogspot.nl/2014/03/doepfer-127-bom-filter-breakout-module.html