Doepfer History: Doepfer MCV1 MIDI-to-CV Converter

In 1986 Doepfer introduced the first in a series of MIDI-to-CV interfaces, the MCV1.
The MCV1 was a monophonic MIDI-to-CV/GATE-Interface that could control other vintage analog synthesizers equipped with CV and Gate/Trigger inputs via MIDI.

MCV1 front (version 4 or 5)

MCV1 was equipped with MIDI in and Thru, one CV (control voltage) output to control the VCO's (Voltage Controlled Oscillator) and a Gate/Trigger output to control the Envelope Generators.
It was suitable for synthesizers using standardized V/Octave or Hz/V and gate voltages from +5V to +12V or switched trigger (S-Trig)

The factory setting and adjustment of the CV output was 1.00V/Octave. To change or re-adjust the scale you had to insert a small screw driver into the the hole labeled ADJUST/ or SCALE right of the CV jack and turn the potentiometer setting to the desired value.
The factory setting for the GATE output was +5V voltage gate, and if you wanted to change the setting you had to remove the cover plate.
On the PC board inside you could find a  jumper that could be set in 3 ways: +5V or +U voltage gate or SWITCH TRIGGER (S-TRIG. e.g. used by MOOG).

There was also the possibility of changing additional settings by Program Change control numbers.

The interface had no separate ON/OFF switch nor have a built-in power supply. Instead it used an external plug-in type.

Back side of the MCV1 plus external adapter

The pictures probably show version 4 or 5. 

Versions 1 and 2 were available only as kits and there was no suitable housing available (i.e. pcb only). 

Version 1 had no sockets on board. The MIDI and CV/Gate sockets had to be wired manually. 

Version 2 had MIDI and CV/Gate sockets on board. MIDI channel and other parameters were adjusted by means of a DIP switch. 

Version 3 was a redesign of version 2 so that a small standard case could be used (the case in the picture). 

As far as Dieter remembers the only difference between versions 3 and 4 was the non-volatile memory. Version 3 did not store the settings (i.e. after power off the settings for MIDI channel, reference note and other parameters were lost and the unit started with Midi channel 1 and reference note 36 after the next power on). 

Version 4 had a non-volatile memory for these parameters 

The price range of the MCV1 was from around Euro 50 (kit version without case) to about Euro 90 (ready built with case).
Approximately 500 units were sold (i.e. all versions together).

Another fun fact: The guy who programmed the firmware for the MCV1 about 30 years ago showed up at the Doepfer/Alex4 booth at MusikMesse in Frankfurt this year. They had not seen each other in more than 15 years...

Find more info at http://www.doepfer.de/alte_anl.txt/MCV1_V5E.txt

*Special thanks to Dieter Doepfer again for all additional info

Synovatron CVGT1 Eurorack-to-Buchla Converter

If you want to control a Buchla modular synthesizer with your Eurorack (or your Eurorack with a Buchla!) you should know that Buchla uses a different Volts-per-octave ratio as the Eurorack synthesizers, that work on a standard 1 Volts/Oct.
Buchla's pitch CV scaling conforms to neither the common 1V-per-octave or Volt-per-Hz (Roland) standards.

Buchlas generally conform to 1.2V/Octave (100mV/semitone) but older systems have 2V/octave scaling e.g. 258.

The other voltages lie in standard regions. 

Control voltages and timing pulses of the Buchla are +5V (signals with sustain) and +10V (transients only), and should be compatible with most other manufacturers' devices.
Besides that, Eurorack uses 3.5mm mini jack sockets and Buchla uses 4mm banana sockets.

Synovatron's latest module is a Eurorack format Eurorack/Buchla translator called CVGT1.
It was launched a few months ago at the Brighton Modular Meet at the University of Sussex just outside Brighton UK.

The 8 HP wide module allows Eurorack and Buchla synths to interact with each other, as the name suggest it provides a CV and a Gate/Trigger interface.

The module is an active module; The CV amplifiers use precision 0.1% resistors to set the scaling plus very fine adjustment by trim pots to achieve even better accuracy.
Trim pots (on the board) can be adjusted for trigger widths between 0.5ms and 5ms.

Not only does it provide the correct format connectors (and adheres to the Buchla color code) but it also deals with the CV scaling and offsetting and the gate/trigger and timing pulse conversion required to allow control in both directions.
CVGT1 can also be used to adapt to other banana connector synths e.g. Serge or Bugbrand which have 1V/octave using the "1" scale position.

More info at http://synovatron.blogspot.com

Watch the CVGT1 in action below (although it is hardly visible in the video, but i do like the soundscapes):

Video: Mutipatch 1 by Eldancer (Buchla and Eurorack)

mutipatch 1 from Eldancer on Vimeo.

Tony (from Synovatron) mailed me today that he can't make them fast enough, and that he's just over half way through my pre-order waiting list.
He underestimated the demand, initially he only bought enough components, pcbs and front panels for 20 modules (big mistake).
He will be building another ten or so but have negotiated with a local company to build the rest for him.

Volts per Octave

The Volts-per-Octave standard luckily turned out to be a quite good one.
A lot of (early) synthesizers manufacturers adapted this standard, 'invented' and popularized by Bob Moog.

Best known manufacturers of early products using the 1V/Oct standard are Roland, Moog, Sequential Circuits, Oberheim and ARP. The big benefit of standards like these is inter-compatibility between products of different manufacturers. It allowes them to communicate better.

The V/Oct standard was wider adapted as other standards, like for example Yamaha and Korg's Hertz-per-Volt standard, that  represented an octave of pitch by doubling the voltage. 
A few synths that use the Hz/V standard are:
Korg: 770, 900-PS Preset, M-500 Micro Preset, M-500SP Micro Preset, Mini Korg, MS-10, MS-20, MS-50, Synthe-Bass, X-911
Yamaha: CS5, CS10, CS15, CS15D, CS20M, CS30
Moog: Taurus I Bass Pedals
Paia: 2720, 4700 Series

The Hz/V standard was used before the log converter was used in VCO's and is essentially linear control as can be found on various signal generators and function generators like those used by the BBC Radiophonic Workshop before they got a VCS3*. There are/were solutions available that convert from  Hz/Volt to V/Oct and vice-versa.  ( like the Korg MS-02 ).

No wonder that the A-100 system uses the V/Oct. standard. You can easily synchronize your system with almost any (old) machine that you have lying around, and most MIDI-to-CV converters use the same standard too.

For example i love using the CV (and Gate) output of my Roland TB-303 to control my A-100 system. The signal arrives at my system via a  A-180 2x4 multiple, so i have 3 copies of both signals available at any time.
Sometimes i use the CV slightly detuned for an interesting effect, sometimes i put it through a voltage inverter first, something that doesn't work out with all your 303-lines because of tuning.

The Gate output (trigger) of the TB-303 can be sent through a delay for some more interesting echo-like effects.
There are so many possibilities for your other gear to communicate with your A-100 with the 1 V/Oct standard... just go ahead and try... and amaze yourself.

*thanks to Tony Steventon for additional info

Best Friends Forever III

My next unseparable combo is a threesome this time.

This is another essential combination for me, because i use my A-198 Trautonium/Ribbon Controller a lot to control my A-100 system.
The yellow patchcables between these modules always stay connected whenever i start a new patch.

The Voltage Control output ( pitch control ) of the Ribbon Controller goes straight into the A-156 Dual Quantizer.
This module divides the signal into various little steps that provides many different possibilities to scale the notes that are played, allowing the player to play more accurate notes and scales.

Note that I use the lower and more extended half of the Dual Quantizer.
The upper half has less functions and can only divide the signal into steps of 1 /12th Volt = 1 Volt per Octave


Last in the line is the A-170 Dual Slew limiter. With this one i can add a subtile portamento to the signal.

Again, only the lower half of the module is used in this patch, because this half has more possibilities.
The slewrates are adjustable from low to mid or high, and it has separate controls for rise and fall times.

This patch gives me all the control that i need, and i cannot do without any one of these in my live-setup.