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.

Analogue-Systems-to-Doepfer Adaptors

Ever thought of installing Analogue Systems modules in your Doepfer Eurorack (or the other way around) without much trouble?

Tony from Synovatron came up with a few nifty solutions for that;
His latest 'inventions' are small adapters that allow you to simply plug directly into your  AS or Doepfer module, or that fit the connector on the module's PCB.

Installing is as easy as it looks;
 Note the red stripe - just line up the Doepfer cable's red stripe with it.
 The adaptors are also marked with pin 1 and have an orientation mark so pin 1 goes to the top (in fact to pin 1) and the red stripe goes at the bottom.

The order code for the socket-to-socket version (left) will be ASM2DB Adaptor (or Analogue Systems Module to Doepfer Bus Adaptor). The code for the plug-to-plug version (at the right) will be DM2ASB Adaptor (or Doepfer Module to Analogue Systems Bus Adaptor).

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

Blind Panels II

Beside for safety uses, as mentioned in one of my earlier posts, the blind-panels that Doepfer sells are also perfectly usable for all types of DIY-projects.
The 'standard' panels of 4,8,42 and 84 HP can be used for all types of original self-made modules or expanders. Sadly they don't have other sizes, but wouldn't it be nice if they had a 16HP and perhaps a 24HP to 'fill in the gaps'.

Drilling the metal plates is quite easy ( if you use the right tools ), and the panels come with pre-drilled mounting-holes.
If you don't like drilling, you can also order some pre-manufactured panels from the Doepfer A-100 specials list;


They still have many punched A-100 standard front panels of 4HP width, punched for 8 sockets, identical to A-180 front panel but without printing, very useful  for DIY or A-101-9 expansion  applications. You can save yourself some money by making your own A-180 multiple for almost half the price. (sockets can also be ordered at Doepfer )

Punched A-100 standard front panels of 8HP width are still available too. Punched for 5 potentiometers and 5 sockets (same as A-102, A-103, A-105, A-120, A-122, A-123, A-124, A-130, A-131, A-138), without silk screen printing.
They even  fit the Synovatron DIY1 and DIY2 kits. (*confirmed / ,but see feedback for remarks and more info)
Update March 3 2011: Synovatron now sells his own generic front panels for his DIY kits.

Doepfer also still has a few 14 HP front panels punched for 2 wheels and 4 sockets ( like A-174-2 ), without printing, that might useful e.g. for a DIY wheel module. Order it with two modulation wheels and you even get the front-plate for free...

Modifications I : A-156 Quantizer Follow

A-156 with modification

Yesterday i picked up the spare parts that i ordered from Doepfer; a few switches, 3.5 mm sockets, LEDs and blindplates of different types and sizes. Now that i have them i couldn't wait to start with my first project.

One of my personal little annoyances that i have with the A-100 system are the tiny internal jumpers inside of some modules. Behind these jumpers are sometimes great functions that make these modules a lot more flexible.

Where i can, i will try to replace the internal jumpers with switches on the front on more modules, but i started with the A-156 Dual Quantizer Module.

A-156 after removing all the knobs
and frontplate

This module has two separate Quantizers, one that only uses a semitone-scale and Quantizer 2 that has much more options like minor/major/chord/quint/6th and 7th scales. There is a way to let Quantizer 1 follow Quantizer number 2 by replacing an internal jumper, but why there? It is probably a cost-saving thing from Doepfer's side but there is enough room on the frontplate of the module to place a switch with the same function. You can find a neat step-by-step guide with pictures on how to do this HERE , but it is quite easy.

Wiring the new switch

After removing the frontplate and drilling a hole for the new switch ( there is enough room above or under the printed 'Options Quantizer 2' text ) i could fit a new Doepfer 1-0-1 (on-off-on) switch in the hole and mount it back together again.

A-156 detail close-up

The wiring was quite simple, so even with my mediocre soldering-skills this was a piece of cake for me. The result is a simple and invisible modification that works perfect. Switch down couples the 2 quantizers, switch up puts quantizer 1 in it's original mode.

Okay... a similar result can be obtained with the use of an extra multiplier, but i found this one more adventurous... and rackspace-saving.

Now its time to experiment with the new options that i have. I can think of some nice patches already, but there are also some good suggestions for the use of this module and this modification at Synovatron's blog.

SiteTip I : Tone's Analog Synthesizer Projects and Products

I stumbled upon this interesting site last week; Tone's Analog Synthesizer Projects and Products. You can find it at http://synovatron.blogspot.com/
The overall site looks like a good start for everyone who is busy with, or starting on eurorack synthesizer DIY-ing and is operated by Tony Steventon, a UK electronics design engineer with a long interest in synths.
"Like most ideas it came out of trying to solve problems..." he wrote to me "... I could not fit either the jack sockets or bracketed pots on to standard 0.1" perfboard and came up with this idea over a year ago".

He continues "...several people have expressed an interest in learning how to take an idea through to a design and onto a prototyped module which I am quite tempted to do as a future 'learning' page on my blog..." "...I am working on my CV Tools module at the moment, which I have prototyped using my kits, but when that is ready for manufacture I am happy to consider some more ideas, I already have four promising ideas which may get developed either on my own or in collaboration with the idea originators."

Along with selling different DIY sets and prototyping kits, you can also order additional components for reasonable prices here. Listed are various Control pots (50k linear supplied as standard but 10k linear, 100k linear, 1M logarithmic or a mixture are available upon request), Pot mounting brackets, Decoupling capacitors, 16-pin headers, 3.5mm jack sockets, Red/green 3mm 2mA LEDs, TL084 quad op-amps (DIL), 14-pin IC sockets, 16mm soft-touch knobs (red, grey, orange, green, white, blue, yellow pointers), 10uF 16V electrolytic capacitors, 100nF ceramic capacitors, Headers - single, double, straight, right-angle, DPDT toggle switches to fit DIY2,  ...and more on request.

The site has an interesting (and growing) support page with all the datasheets and other practical tips on synovatron products. More info and discussion is possible at his dedicated Forum.


For sales, support and combined shipping enquiries you can contact synovatron@btinternet.com
CAUTION: These kits are intended only for experienced experimenters and constructors to prototype their designs. It is possible for you to destroy components or damage your synth if you are not careful. It is recommended that you use a separate regulated ±12V power supply for experimentation.