Just Starting Out?

Building an Analogue Synth?

I would guess that as you are reading this then the answer is yes or possibly maybe depending on the level of difficult or whether it is cost effective.

I built my first analogue synth as a teenager back in 1980 in my bedroom from a series of construction articles in an electronics magazine, the synth was called the Digisound80. Regretfully I had to sell it a few years later as I needed the cash, if only I still had it now! I remember making the front panels by hand (over 50 modules) and using press on transfers (letraset) for the legends. All PCBs were hand soldered and I even made my own custom modules including an analogue sequencer. Despite being so ‘hand made’ it looked very good as long as you didn’t get too close up because applying transfers to form the scale around the knobs did get rather tedious and accuracy did suffer. More importantly it did sound fantastic and was rarely off it but I was not and still not a musician but that did not stop me from making wonderful sounds often inspired by the great Tangerine Dream who I still go to see in concert when I can. So all of these years later, I find myself building a modular synth again but now commercially for soundtronics.co.uk, so has anything changed in the last 30 odd years?

What has changed in the last 30 years?

Whilst the Digisound and many other synths were based around a series of specialised chips from companies like CurtisElectro Music Specialities (CEM) and SolidState Micro Technology for Music (SSM), the MFOS is broadly based around discrete components and basic building block chips such as Op-Amps. Sadly, the excellent SSM and CEM chips are no longer produced and can attract high prices for those seeking replacements for their existing equipment. Using discrete components does mean that a design can survive longer as it is frequently possible to find substitutes when a semiconductor manufacturer stops producing a product initially used in a design. You will find alternative components offered in the parts list for MFOS modules although some harder to find components may still be preferred.This means that modules are likely to have a higher component count which means more soldering and possibly a more involved calibration procedure but product life is certainly extended by eliminating the need for specialised chips.

Fabricating the front panel can make all the difference to your final build, there are a number of companies that will cut, punch, drill, coat and print your panels even for a 1 off (check out Front Panel Express).These may not be cheap but the results are by all accounts very high quality.

Calibrating the modules, especially the oscillators can be quite demanding but test gear is more affordable today than it was 30 years ago and you can even use your PC via its sound card for some setting up.

The internet has also made a huge difference with the opportunity to source components worldwide to seeking advice from like minded people through forums such as electro-music.com.

Buying an assembled module or kit?

The aim at Soundtronics is to produce a good quality product at a competitive price. To achieve this, we will have resources available that you may not have at home to increase productivity and keep costs down. We have an assembly jig where we can hold say 16 VCO PCBs all at once, insert components by hand in stages of increasing height. At each stage, we spin the jig over and solder away with a foam backed lid stopping the components from falling out. Then there is forming and cropping all of those resistors, again we have a tool that can form and crop 10,000 resistors per hour prior to insertion in the PCB. Our time costs money but you can still solder up your own boards with a basic fine tipped soldering iron and some basic hand tools and potentially get equally as good results as us.

There is no disguising that building a modular synth is labour intensive, especially the panel wiring and setting up. The front panel itself can be made from raw aluminium sheet, drill, spray and apply your own transfers. You can equally pay for a custom made panel but at Soundtronics have taken a different approach and will be producing front panels in-house. We have a CNC milling machine to form all of the panel cut-outs and we have purchased a laser cutter / engraver that can handle sheet sizes up to 900 x 600mm for the engraving. We will use matt black anodised 3mm thick Aluminium sheet for which we have found a source that gives a good quality image after laser engraving which is near white.

Setting up the modules is rather important, getting the tracking right for the oscillators as an example to stay in tune as the control voltage changes. Without test gear, you could attempt to tune by ear (well I couldn’t) but even some basic test gear will aid in the task. At Soundtronics we have the necessary test gear including 5 and 6 digit multimeters, storage and conventional oscilloscopes, frequency meters, signal generators etc. Even then we are finding we need something else to make life both easier and better such as a voltage calibrator for setting the 1V octave changes.

Finally, do you have the skills and experience to build the modules, can you recognise components, know which way around they go, and if it doesn’t work first time, be able to fault find? On the MFOS site, Ray Wilson has made recommendations as to what experience you should have in order to build each module.

Our aim at Soundtronics is to cater for all from supplying that one component you simply cannot find anywhere else to a fully assembled suite of modules in a bespoke cabinet.

At the time of writing this article, we are still finalising the front panel engraving, making up calibrators for transistor matching / octave calibrating and optimising the choice of components for the heart of the analogue synth – the VCO. More on these very soon but what ever decision you take on the build, we at Soundtronics may well make the task not quite so onerous.

Good luck and hope to hear from you soon.

Paul Cooper

Soundtronics

7 Jan 2014