VXP1 Voyager Output Expander for Eurorack

(BLOG UPDATED 3rd August 2018)

News

VXP1 and VXP1-OS are no longer available from Synovatron for £180.00 GBP. 

Preliminary user manuals can be downloaded from these links:
VXP1 Handbook Rev 1.0 
VXP1-OS Hand Book Rev1.3

Back Story

A few years ago I designed and built a Eurorack interface for my Moog Voyager. I built it in a week to take to the Brighton Modular meet to see if there was any interest in such a module.

I have a Moog VX-351 which is a perfectly lovely bit of kit but I wanted something that had 3.5mm minijacks to make it easier to use with my Eurorack and Roland 100m modulars. The module I built was a simple breakout panel that had one jack per signal available on the Voyager's Accessory Port (a 25 pin D connector). Most signals were wired straight through but one or two included active electronics to provide scaling to give a more useful 5V range, in particular Keyboard Pitch had a scaling amplifier and a trimmer to set it exactly to 1V/octave. LEDs with driver circuits were also added to the LFO and the two gate signals.

Prototype Voyager Output Expander

Most modular users don't have a Voyager (and sadly it's now out of production) so I didn't get too much interest at the Brighton meet but I did get some interest on Twitter and Muffwiggler and in particular from one wiggler whose frequent enquiries about its development has spurred me on to develop it. It has been very slow going due to a number of reasons (not all connected to the module itself, the real world has a way of changing one's focus!).

Output Adaptor Retrofit

One reason for procrastination was due to an error in Moog's design of the Voyager's Accessory Port which was not suitably buffered; which means that when a cable is connected to the port some of the signals become unstable and oscillate. Moog's remedy for this was to use a small adaptor board that has to be retrofitted inside the Voyager between the main circuit board and the Accessory Port's ribbon cable (this just affects backlit types, not the Old School version).

The Output Adaptor is a small circuit board that adds a 330 Ohm resistor in series with many of the signals; here is a link to an installation guide. The 330 Ohm resistance is enough to isolate the capacitance of the extra cable length which maintains amplifier stability (ED Note: If you want to understand about amplifier stability then this series of 5 short videos by Analogue Devices is the perfect intro, in particular video 4 which describes this problem nicely. Ideal for anyone designing with op-amps).

As you will see from the installation guide that fitting the adaptor is a bit much for some people to take on and I didn't want to encourage inexperienced Voyager owners to open up their expensive synth and potentially damage it or harm themselves (there is an AC mains hazard around the power inlet if you don't disconnect from the mains). Unfortunately there is no other solution other than to use an Output Adaptor (like that supplied with the VX-351) so fit it if you are confident or get a music shop tech to fit it for you. You might already have one fitted if your Voyager has been used with the Moog VX-351. I tried to find a source of Moog Output Adaptors but alas no joy so I designed one from scratch; problem solved! Here it is:

Smaller, Better

Another reason for delay is that I increased the scope of what the VXP1 can do; I didn't want this to be a Eurorack rip-off of the VX-351. Rather than just a simple breakout panel it now handles each signal with active electronics as follows:

• All signals are filtered, buffered and have the necessary gain and drive to give more Eurorack-friendly output levels.
• The smooth and step Sample and Hold outputs are replaced by just one output and a variable control to give an adjustable slew to Sample and Hold.
• There are more LFO waveforms: ramp, saw and 10V clock.
• There are more noise options: white, red and random pulses.
• The panel is narrower than the first prototype: 16HP down to 14HP.

Here is the second prototype panel I have used during my development (a simple but mechanically accurate panel with engraved text made by Schaeffer):

Here is the panel design:

 

For Old School Voyagers which don't have a touch panel the VXP1-OS has repurposed the redundant TOUCH sockets to become a 3-input gate combiner. 

VXP1 Module, Cable and Adaptor | VXP1-OS Front Panel

New Euro to Buchla CV Translator - CV1.2

The CV1.2, one of the cvgtElements range of DIY circuits, is available and its data pack is ready to view/download on the support page. CV1.2 is ready built and tested, you have to DIY them into your own modules/panels.

CV1.2 takes a Euro 1V/octave CV and translates it into a Buchla 1.2V/octave CV - ideal if you want to take a Euro pitch CV into the Music Easel's pitch KEYBOARD CONNECTION

The GTPulse datapack is also available to view/download on the support page.

cvgt MM Buchla Translator ModuleModules

The first cvgt MM modules have started shipping to clients at the top of the pre-order list. If you want to be added to the list then please make contact on synovatron@btinternet.com

I will build in small batches and work through the list in chronological order and will then contact you when your order is ready to ship. Only at that point will I request payment (see prices below). Please note that this does not form any contract between us and you are not in any way commiting yourself to making a purchase until such a time that you make a payment.

 

Initially the cvgt MM will be only available directly from me but if there is enough demand then it is possible they will become available at all the usual distributors in due course. 

The current variants are:-

• Buchla-Euro (round or hex nuts on 3.5mm jacks; please select)
• Buchla-Serge*
• Buchla-BugBrand*
• Buchla-Fenix*

*These are banana socketed variants and only the colour of the banana sockets is different (to match the target system); All are variants (inc. Euro) are to translate from Buchla to 1V/octave systems.

The User Manual is being worked on and will be ready very soon and will posted here in an update. Please checkout the Eardrill website for more info on the ModuleModule concept and other great products from Chris Muir.

Euro variant

Serge variant

Euro (top), Serge (bottom)

Another custom built Euro to Buchla Translator module

I was recently commissioned by a client to build a custom Euro Buchla interface module, similar to the two I previously built, but with offset switching. The previous two designs both had fixed offset and gain and were intended for use with envelopes, LFOs etc. In other words there was no 1V/octave to 1.2V/octave scaling required just offsetting to ensure the Euro signals stayed in the 0-10V range of the Buchla (you can refer back to my earlier post here).

This module is intended to be used alongside my client's CVGT1 module (which provides the ground reference connection) and adds more CV channels. My client uses Expert Sleepers' SilentWay software for pitch sensitive CV and was not interested in scale conversion as the software does the necessary recalibration however he also wanted the flexibility to be able to interface envelopes, transients and LFOs and so wanted to be able to DC shift signals when he needed to.

The spec was 4 channels of Euro to Buchla (scale of 1, 0V or +5V offset) and 1 channel of Buchla to Euro (scale of 1, 0V or -5V offset); so 10 connectors a 5 switches in 8HP.  

My 8HP prototyping panels proved to be difficult as the existing hole positions meant that the connectors and switches would have been too close to each other plus I only had a few left and found they were scratched; they got binned. I used Schaeffer for a quick-turnaround panel; not cheap but very well made. In a moment of madness I got 5 panels made, including engraving (which the original 2 modules didn't have).

Some Preliminary Work on a ModuleModule Design

ModuleModule CV and gate/trigger translator

This is just a quick post to show what I have been doing with regard to the ModuleModule design I mentioned in my last blog post. More info will unfold over the next weeks but this is just to let several Muffwigglers know that I am progressing their ideas (albeit a bit slowly). These are just a first draft and the design will change. The idea is that there will be a common design that supports either Buchla/Euro or Buchla/Serge; the only difference being the connectors used. It's difficult fitting all I want in the smaller ModuleModule format - perhaps the trim pots will come out and I'll add scale switches as per the CVGT1 - your feedback would be valuable!

CV2 - a sister module for the CVGT1

This is another idea I've been mulling over which will complement the CVGT1 and is intended for non-pitch critical CVs and for audio level translation. Again it's just a preliminary idea and feedback is welcomed.

Euro and Buchla working together

Here's a short video by Eldancer showing the buchla and Euro systems workng together. Both the CVGT1 and a custom euro Buchla interface module I made a while back are in use here (top right hand corner). They don't get the limelight, they just allow the conversation to occur, working quitely in the background :)



mutipatch 1 from Eldancer on Vimeo.

A quick update on CVGT1 Modules

About half of my pre-order list for CVGT1 modules have been delivered and the rest will go out within the next month. Within a couple of months they will appear with distributers but I am having to look at relaying the boards for surface mount to keep assembly costs down - I don't want the price to go up and I cannot keep building them myself - after building 60 CV Tools and 20 CVGT1 modules (220 circuit boards in all) I am all soldered out. CV Tools will also get relaid for surface mount but I will still keep a through hole stock (currently sold out) for DIY kits.  Watch out for my next update in a month.

Announcing Synovatron's second module CVGT1

Sneak preview

The new module is a Eurorack format Eurorack/Buchla translator called CVGT1. It allows Eurorack and Buchla synths to interact with each other, as the name suggest it provides a CV and a Gate/Trigger interface. 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.

The module is in final stages of build and will need to undergo design proving tests before I release it into the world. So far the front panels are complete and all the components are in stock except for the slightly important PCBs which are due in tomorrow (18th July 2012). The intended launch date is Saturday 21st July at the Brighton Modular Meet at the University of Sussex just outside Brighton UK. 

Here are some quick photos of the panels and partial assembly.  I will follow up in a few days with better photos of the fully assembled module, further details and User Manual download link.

1200HP Monster Synth

I met with Gregg Wilson at the last Brighton Modular Meet. We had talked about the possibilities of this project prior to the meet as he had bought a CV Tools from me. Anyway I ended up building the power supply and Trunk-line modules for his brainchild 1200HP wall mounted synth over the ensuing months so thanks Gregg for placing your trust in me. It is not only amazing as an instrument but also also as a visual feast - a fine piece of active wall art - well conceived and nicely built. The surrounding backlighting sets it off a treat.

The fantastic Wenge wood case was made and installed by Ross Lamond of Lamond Design; This guy rocks!.

Here are a couple of videos of what any synth does best - being used! Enjoy.



Modular Synth Live Performance 1 from Gregg Wilson on Vimeo.

Modular Synth Live Performance 2 from Gregg Wilson on Vimeo.

I Dream of Wires 2: A documentary

A very inspirational video; certainly from my perspective as a small manufacturer of synth modules. Modcan's Bruce Duncan and Intellijel's Danjel Van Tijn give the low-down on their synth building ethos. I have huge respect for these guys for their achievements, products and thinking. Check this out. 

Euro to Buchla CV Interface Module

I was commissioned by a client to design and build an interface module that allowed his Euro synth to modulate his Buchla synth and vice-versa.

Format Jumbler?

Euro uses 3.5mm mini jack sockets and Buchla uses 4mm banana sockets (which are colour coded). However this design is not just a 'format jumbler' because aside from the connector differences the signal ranges are different.  Buchla uses CV signals in the range of 0V to +10V and Euro uses nominally ±5V (well actually anywhere between -11ish Volts to +11ish Volts).  My client wanted 4 channels of Euro to Buchla and 1 channel of Buchla to Euro. 

Design Spec

The design spec I settled on was ±5V in (Euro) gives 0V to +10V out (Buchla) on channels 1 to 4 and 0V to +10V in (Buchla) gives ±5V out (Euro) on channel 5. As you can see the inputs and outputs both have 10V swings and so a gain of 1 is required but with a 5V offset (-5V one way and +5V the other). The input impedance of 100k and output impedance of 1k was used as it's fairly standard.  I used clamping diodes on the Buchla outputs so that an input more negative than -5V didn't cause a negative output to the Buchla. Because there might not be a common ground reference between the two synths a GND socket was also added to the design. Note that Buchla colour coding uses black for CV outputs and ground connections, blue for CV inputs.

Implementation

As the job was for just one module I used one of my standard 8HP front panels (order code 8HPP) and a new DIY prototyping PCB (order code DIY3) to build the design onto. 

The 8HPP front panel has 10 3mm pilot holes which had to be opened out to fit the 4mm and 3.5mm sockets plus a new hole for the GND socket. I settled on the position for the GND socket equidistant between the four lowest connectors really just for best spacing; I looked at putting it below the lowest two connectors but decided (incorrectly) that there would be not enough space to get fingers in and also avoid the mounting rail.

8HPJ (left) and 8HPP (right) Front Panels

The DIY3 is a bigger version of the DIY2 prototyping board and allows more complex circuitry to be realised due to the larger breadboarding area, power rail support for op-amps and A-100 Bus support (it is effectively a hybrid between DIY1 and DIY2 boards). The idea behind DIY3 was to be able to do more with jack-socket only designs such as buffered mults and attenuators, amplifiers, logic and gate/trigger circuits etc.

DIY3 Prototyping Board

The First Module

Here is the first module which I'm pleased with. It showcases the DIY prototyping board's capability nicely. The client was happy too.

The Second Module

On the back of the first order another client expressed an interest in the same functionality but preferred the GND socket to go below the lower two connectors. There was enough room to clear the mounting rail but pushes it closer to the channel 5 connectors than is ideal but still looks ok.

Further Modules?

I have another two expressions of interest for these modules especially if they were production rather than prototype versions. One suggestion was for front panel graphics to be added using the same font/style as Buchla which I like the idea of. Another thought is that not just CV translation is useful, gate/trigger translation would be useful too (as they are not compatible between the two 'standards'). I could also provide these as very basic kits (all the bits you need, a circuit diagram and a layout pattern). If I can get a few more interested parties to make it viable I would consider a small production run with purpose designed PCBs and a screen printed front panel. So if there is any interest out there please make your thoughts known to me.

Trunk-line Module

I was commissioned by a client to make some Trunk-line Modules. These are similar to the Analogue Systems RS-250 module but offer rear facing jack sockets instead of unterminated jacks that you have to solder wires to and is ideal if soldering is not your thing.

8HP 10-channel Trunk-line Module front jacks

8HP 10-channel Trunk-line Module rear jacks

The point of a Trunk-line module is to provide front panel access to either outboard equipment such as mixers, sound cards, MIDI/CV units etc., or to provide connection across a very large synth (using two modules) so you don't have to use very long patch cables on the front panel. Most of us don't have big enough synths to warrant this so these really are for large synths that are more like installations.

The photos show an 8HP 10-channel module; I have made a few of these modules to order and because of the small quantities involved there are no screen-printed markings (due to the setup costs). I'd like to know if anyone else would be interested in a Trunk-line module and, if there were large enough numbers, I'd do a small production run with screen printed markings, so please let me know; I could also do a 4HP 5-channel version and versions with solderable sockets too.

CV Tools US Distributor Announcement

I am very pleased to announce that Analogue Haven will be distributing CV Tools Modules (not kits) in the United States. I am aiming to get a sizable stock to AH by mid-July. (Sorry 2 months late but they are there now: Edit)

Any enquiries for kits or specials (e.g. plain front panel, faster/slower slew rate, less/more gain etc., please e-mail me.

First review comments and user's video for the CV Tools Module

Over half of the first batch of CV Tools have been sold, many in kit form. Here is some feedback from a few kit builders and module users:-

"Finished the CV Tools module. It works as advertised ;) No warts!

I must compliment you on your kit. The packing and organisation of components are as good as I've ever seen. Documentation is on the money for newbies ... All in all, I'm extremely satisfied ..." Steven H (VICMOD)

"An excellent simple tool. Great for cascading polyrhythms. Really easy to use and very surprising differences depending on where you tap the signal." Stephen R (VICMOD)

"...I was really impressed with the documentation and the way everything (in the kit) was bagged/labelled...CV Tools seems like a real Swiss Army Knife. I can already think of countless ways I'll be using it with my Oberheim SEM ... and humble modular." Alex M

"Tinkerbell lives!  Tonight I patched a triangle wave LFO into channel 3 of CV Tools and took the slew output into a quantizer (A156) set up to run minor arpeggios.  I can control the range of the arpeggiaic ascend/descend and even build in rhythm just using pots 3 & 4 - then out to two VCO's tuned apart. Out through a digital delay and reverb in ProTools and  . . . instant magic - fairy dust!  What fun . . " George B

Also check out this thread on Muff's entitled Some thoughts on the Synovatron CV Tools
 

Just to keep things balanced some people have expressed a lack of enthusiasm for the front panel, some about the font and some about the fact that the graphics is on a matt laminated laser printed vinyl overlay. The beauty of the overlay is that multiple colours, shades and fading effects can be easily implemented, the down-side (for me) is they are expensive and difficult to fit accurately. 

The solution is that the second batch of CV Tools will have a standard screen printed front panel (something like TipTop Audio quality). I will be offering either a very low cost swappout or a low-cost retro-purchase to existing users who would prefer a more conventional graphic - I prefer happy customers over a few extra £. Hopefully you'll come back for more!

Here is the current overlay panel next to the artwork that will be taken to the screen printers (where there is grey it will be the brushed anodised aluminium showing through so it will look a bit better). Any comments, likes and dislikes gratefully received - I will give the artwork to the screen printer in just over a week's time.

First Eurorack DIY Prototyping kits and cables are now shipping

The first orders have been received and are now being shipped. 

Synovatron Electronic Music is underway!!

Eurorack synth prototyping products now available

Please check out the product and support pages on this blog. 

Kits and cables are also available through eBay; just search "Modular synth prototyping kit" or click here

Update on New Eurorack modular synth prototyping kits - Circuit boards have arrived

The new DIY prototyping circuit boards have arrived. They look good and the quality is very good.

The pots, pot brackets, headers, caps and jacks all fit which which is a huge relief.  To give you an idea of what they'll look like assembled checkout the preliminary piccies below of both types of board with some components assembled ready for prototyping to start. Note I have added some LEDS to one of the DIY2 boards too.

Time now to sort out the packaging, data pack, options and pricing - about another week before they become available.

Update on front panel artworks

Just thought I'd give a little more detail on front panel artworks as there is already some interest.

The picture below of my module currently in development shows the CAD drawing for a 12HP front panel in the top left. The adjacent front panel overlays show an evolution from a very simple, flat looking artwork to more 'sexy' metallic looking and coloured alternatives with some apparent depth.

 
Edit 08/07/11: The following graphics, based on ink-jet/laser printable vinyl overlays, was attempted on the first off batch of CV Tools modules but has been withdrawn in favour of a standard screen printed panel for two reasons. The first was that it was not liked that much by customers; people saw it as a cheap label. The second was that it was expensive and difficult to apply accurately. I will still use the overlays for prototypes.Please read the following but note it has all been superceded by events.

My task is to make this a service that is affordable by streamlining how I go about setting out the pot scaling, legends, functional grouping (separating lines or boxes). A good place to start from is if you use Schaeffer Front Panel Designer to get the panel made then I can use the DXF file generated to align the graphics to the holes; obviously with as much description from you as possible about what you actually want to see.

The one-off 2mm anodised panel from Schaeffer cost me 27 Euros (about 23GBP, $35US but it is beautifully machined!!); I anticipate the cost of an artworked plastic overlay would need to be less for that size panel to make it attractive, including my design effort (that's why I need to streamline the process - the slicker I get the more viable it'll be!).

The hardest part is lining up the overlay accurately on the panel as the overlay is self-adhesive. I'm getting quite adept at this now as I have prototyped several overlay types. You do get several chances and I may include a spare.

I am still developing the technology as it needs to have great graphics, be cheap to make whilst still having good wear and scratch resistance properties.  This balance is not easy and I will still need to explore better processes and techniques so initially this will be for smaller prototypes with some caviats on how much abuse it can handle. The artwork is great quality though and the durability is reasonable but could be better. The price will reflect this fact. Having said all that I'm going to use it in my system as it stands as I don't tend to abuse my hardware.

Any suggestions and comments would be most welcome.

New Eurorack modular synth prototyping kits preview

Hello fellow synth fans,

In the next few weeks I will be producing a range of Eurorack standard modular synth prototyping kits for synth constructors and enthusiasts; these kits will comprise Doepfer compatible printed circuit boards (PCBs) and components. 

These  will enable you to make neat prototype or one-off projects that accomodate bracketed pots, PCB mounted jacks, switches and LEDS so that they can be easily mounted to a module front panel.

The idea is that you build your designs on the breadboards supplied and get the front panel manufactured separately, either by yourself, or by a company such as Schaeffer http://www.schaeffer-ag.de/en (I can provide some template files that you can use directly or can modify as you require. I will also look at providing some standard panels e.g. five pots and five jacks but this is still being costed; more on this in the coming weeks).

I will also be able to provide you with a relatively low cost high quality front panel overlay to give your module a professional appearance; this service will also be explained in more depth in the coming weeks.

This is an overlay I made for a product in development
(this is the next product - a versatile voltage processor)

There will be 3 kits available:


Kit 1: This comprises 2 single-sided prototyping matrix-type breadboards and cable as follows:-

• DIY1. This PCB is primarily for mounting control pots and prototyping most of the circuitry on a breadboarding area.  It is provided with 5 control pots and mounting brackets; the pot values supplied are 50k linear (type B) but you can request 10k, 100k linears (type B) or 1M log (type A); 2 100nF decoupling capacitors and a 16-pin header are supplied fitted to the board; the pots and brackets are supplied loose. Not all pots need to be fitted and there is provision for PCB mounting of LEDS. The PCB has +12V, -12V and 0V busses.

• DIY2. This PCB is primarily for mounting jack sockets but switches (Taiway series 200 sub-min toggle switches) and LEDS can also be fitted.  It has a smaller breadboarding area than DIY 1. It is provided with 5  3.5mm jack sockets but some can be left out to fit switches or LEDs.

• Doepfer compatible ribbon cable.

• Data sheet.

Kit 2: This comprises just the DIY 1 breadboard and five pots and brackets.


Kit 3: This comprises just the DIY 2 breadboard and five jack sockets.

A range of components such as pots, brackets, knobs, jacks and cables will also be available.

This is just a preview and I will put up more details, costs and photos in the coming weeks.