Friday, 3 August 2018

New Modules and Kits from Synovatron

The current range of eurorack modules available from Synovatron is shown below; please email synovatron@btinternet.com for full price/payment details, combined shipping discounts etc.:

CVGT1 - 8HP Euro to Buchla CV-gate-trigger-pulse translator
Ready-built module - £138.00 GBP + delivery + VAT (if applicable) - in stock

VXP1 - 14HP Voyager Output Expander
Ready-built module - £180.00 GBP + delivery + VAT (if applicable) - in stock

VXP1-OS - 14HP Old School Voyager Output Expander
Ready-built module - £180.00 GBP + delivery + VAT (if applicable) - in stock

Jacks - 4HP 3.5mm minijack to 1/4" jack format jumber
Ready-built module - £40.00 GBP + delivery + VAT (if applicable) - in stock
DIY kit - £33.00 GBP + delivery + VAT (if applicable) - in stock

Euro Bananas - 6HP 3.5mm minijack to 4mm banana socket format jumbler
Ready-built module - £45.00 GBP + delivery + VAT (if applicable) - in stock
DIY kit - £38.00 GBP + delivery + VAT (if applicable) - in stock

Trunks & Mults - 6HP 8-channel trunk lines and two 4-way multiples
Ready-built module - £55.00 GBP + delivery + VAT (if applicable) - in stock
DIY kit - £45.00 GBP + delivery + VAT (if applicable) - in stock

More info on Jacks, Euro Bananas and Trunks & Mults modules and kits on this page.  


Euro Bananas, a pair of Trunks & Mults, Jacks, CVGT1 and VXP1


Sunday, 10 April 2016

VXP1 Voyager Output Expander for Eurorack

(BLOG UPDATED 3rd August 2018)

News


VXP1 and VXP1-OS are now available off-the-shelf directly from Synovatron for £180.00 GBP (excluding delivery and VAT) so if you are interested ping an email to synovatron@btinternet.com for price/payment details. 

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 now in production:

 

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



Saturday, 13 June 2015

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. All modules are actually available - it's just the support info that's lagging behind but should be done very soon.

Pricing for the cvgtElements range is as follows:-

The pulsers (GTPulse, PulseGT) are 21.60GBP each, the scalers (CV1.2, CV.83) are 24.00GBP each and the chicBus is 9.60GBP. Prices include VAT but if you are outside the UK or EU then the VAT free prices are 18GBP, 20GBP and 8GBP respectively. Shipping is extra. 

Please enquire at synovatron@btinternet.com

Friday, 22 May 2015

Synovatron Documents Downloads

EDIT 31May 2015:

For those who have tried to download from links printed on kits, fliers and data sheets etc without success: I apologise but the original file hosting site has shut down without warning in recent weeks. All Synovatron docs have now been rehosted onto Google Docs where they can be viewed or downloaded. The new links are shown on the Support tab above where all downloadable documents will be maintained from now on - if you experience any problems with file downloads please email me at synovatron@btinternet.com. Keep an eye out for new and updated documents. Any additions or significant updates will be announced on the blog as they occur.

The documents added to Google Docs are:-

CV Tools User Manual 
CVGT1 User Manual 
cvgtMM User Manual 
GTPulse Data Pack 
ASM2DB Adaptor Fitting Instructions & uZeus Tech Note 
DM2ASB Adaptor Fitting Instructions 
5ASM2DB Adaptor/Expander Bare Board Data Sheet and Fitting Instructions

Saturday, 17 January 2015

ASM2DB Tech Note for use with uZeus ribbon cable bus

Here is a guide if you are using the uZeus ribbon cable backplane.

(apologies I didn't have a real uZeus backplane to hand but hopefully you get the idea)

Saturday, 8 November 2014

Custom Half-width Buchla Modules

I was asked to design and build a pair of custom half-width Buchla modules for some clients. They each had two half-width slots spare in their custom built cases and wanted to fill the spaces with Euro to Buchla CV and gate translator modules.


The brief was simple (and the same for both clients): 5 channels of 1V/oct to 1.2V/oct CV translation and 5 channels of gate boosting to Buchla levels; the Buchla stepped pulse was not required, just big pulses (10V or more).

This was a great opportunity to use the Synovatron Proto range of prototyping boards which accomodate 5 channels and offer stackability if more circuitry is required than will fit on one board; see below.

The Proto range of boards
As the Proto boards are designed primarily for Euro there was space on the 4U Buchla front panels to add some extras in the form of a passive attenuator. Here are the front panel designs that we agreed on:-

CV and Gate modules
To keep costs down it was decided not to have panel marking as the functions are obvious.

The CV module design used a straightforward precision amplifier with gain of 1.2000 (yes that accurate), 1M Ohm input and 0 Ohm output impedances. The gate module used comparators and output and LED drivers. The outputs each have diodes in series allowing them to be wire-ORed by just connecting outputs together (common to Buchla, wish it was used on Euro).

The CV module electronics fitted nicely on a ProtoJax board with plenty of space as you can see:-


For the gate module I decided to put the input comparators and sockets on the ProtoJax board and output buffers and LEDs on the ProtoXp board and stack them together (it  probably could all have been put on one board but it was simpler to make use of the space). The stacked ProtoJax and ProtoXp boards can be seen here:-



The gate board was powered from an MTA connector and the CV board took its power from the gate module (hence the 10-pin ribbon headers for a linking ribbon cable); this was at the client's request as they only had one spare connector (these are very low current modules and daisy chaining them didn't cause any crosstalk issues). 

The finished panels looked pretty good; they were made by Schaeffer using Front Panel Designer http://www.schaeffer-ag.de/en/front_panel_designer/the_idea/.

  
If you are interested in the Proto range of PCBs or in having a custom module built then please contact me at synovatron@btinternet.com


Saturday, 27 September 2014

Synth Repairs


Analogue Systems RS-40 Noise, Sample and Hold, Osc


This came in as 'defective'. After a while it became obvious the noise output was not working. This was traced to an open-circuit LEVEL contol pot (10k lin) which was replaced. Still it didn't work as a sample and hold - i.e. I was expecting to see a stepped output from S\H OUT. Not having used the RS-40 before it took me a while to realise that the noise and clock signals are not normalled to the Sample and Hold circuit like the front panel markings suggest; the lines linking NOISE OUT to EXT SRC IN and INT CK OUT to EXT CK IN suggest to me these are linked in some way but no. 
RS-40
After looking at the jacks it was clear that these are not normalled (I'm not sure if this is the case with all RS-40s but this one looked clean and unmodified so I'm assuming it was factory standard). I used external patch leads and to link the noise and clock outs and ins and hey presto it worked. The first thing that I saw on the scope was at each sample point the sampled signal is present for what I guess is the duration of the sample pulse (about 0.2ms). When using the RS-40 to modulate a VCO I could not tell that the noise spikes were a problem, in fact it is probably above hearing range (at least mine). 
 
Noise spikes

However I didn't much like it and I didn't much like not having the noise and clock not normalled to the S/H circuit. I spoke to the owner and he agreed to have a couple of simple mods applied.

The noise and clock signals are present on the jack board close to where they would have to go for normalled connections. The switched contacts were connected to ground on both EXT SRC IN and EXT CK IN jacks by solder bridges. I removed the solder bridges and fitted links as can be seen here. This worked a treat allowing it to work without patching but still allowing external signals to be patched in if need be.

Solder removed from red arrows and links applied at yellow arrows
The noise spikes 'problem' although not audible was fixed by placing a 10nF cap across the S/H output amplifier's feedback resistor (27k) making it a low-pass filter with a cutoff of 590Hz. This got rid of the spikes without adding noticeable slew.

10nF capacitor

Spike free steps