ETI 4600 (Maplin 4600) Redesign to use modern chips.

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Mark
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ETI 4600 (Maplin 4600) Redesign to use modern chips.

Post by Mark » Sat Dec 22, 2018 6:35 pm

I am a professional electronics engineer with considerable experience of the ETI - Maplin 4600 synthesiser. Back in 1974 a friend, with little electronics experience, endeavoured to build this 'beast of a synthesiser' and he soon ran into difficulties. I was called in to assist with the project resulting in my becoming very well acquainted with it. We eventually resolved all the problems and got it going well.

In those days I worked for Plessey at the prestigious Alan Clark Research Centre in the Northamptonshire countryside developing all manner of new technologies some 10 to 20 years ahead of their time. So the very first ETI 4600 VCO I managed to get going was fired up in Plessey's 'Bipolar Process 3' electronics lab.

Now, getting on for half a century later these rare, but very underrated synth's are still around in various conditions. Being almost retired, I decided to revisit this project in my own electronics lab and re create some of the modules. This is not straightforward because many of the components and especially key microchips are now obsolete. So I decided to redesign areas of the original circuitry to enable me to use modern devices.

So far I have redesigned elements of the VCO's and have a core circuit up and running without the need for the now obsolete 4416AE chip. The various waveform shaping circuits still have to be built but should present no problems. I have also redesigned elements of the White/Pink Noise Generator and Controller module and have a fully functional completed module. I will probably tackle the VCA modules next. I can see there will be clear problems with both patch board and the keyboard but I also believe modern solutions can be found.

Perhaps surprisingly I am not a musician and can't even play a keyboard, so the keyboard may not be a vital component for my trip down memory lane. To be honest I'm not sure how far I will take this project. At one end it may end up as an elaborate and rather curious sound effects generator and at the other end I may go on to re build the entire thing with 21st century modifications. Much may depend on the extent to which I can convince my wife of the virtues of such an expensive and time consuming project. Interestingly, I have even considered adding totally new modules to the original to give even greater versatility to this outstanding design. There are many possibilities and to an analogue electronics engineer some fascinating new concepts exist.

Whatever the future may hold for this project, it is awesome to hear elements of this vintage synth springing back to life almost half a century later. I wonder when the last 'new build' of one of these modules was heard for the very first time.

stickman393
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Re: ETI 4600 (Maplin 4600) Redesign to use modern chips.

Post by stickman393 » Sat Dec 22, 2018 8:09 pm

Hi Mark, Welcome!
I know just enough about electronics and synthesizers to recognize what a challenging project this must be, but also, how much fun!
Definitely a labour of love.

I've never heard of the ETI Maplin 4600 synthesizer.
https://encyclotronic.com/synthesizers/ ... 600-r1429/

I'm reading up on it now.

Mark
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Re: ETI 4600 (Maplin 4600) Redesign to use modern chips.

Post by Mark » Sat Dec 22, 2018 10:55 pm

Thank you and yes it's fascinating. It was a design published by Electronics Today International (ETI) in the UK and by Silicon Chip magazine in Australia In 1973/4 as I recall. Components were supplied by the now defunct Maplin in the UK and probably Jaycar in Australia. So it was constructed by amateur enthusiasts giving rise to 'various' build quality. Nevertheless, a properly functioning unit would rival the big boys. It is a powerful and very versatile design that many who are fortunate enough to own one still love today. But it was a big project especially for its day and a challenge even for an experienced constructor.

You can find demonstrations on You Tube, here is an example. This is part one of four:



If you'd like to know more you can find the original construction article here:

Part 1: file:///Volumes/OLD%20LAB%20PC/Old%20Lab%20PC/My%20Documents%20-(A)-2/My%20Pictures/Electronics/Synth%204600/MaplinETI4600%20-%201%20of%202.pdf

Part 2: file:///Volumes/OLD%20LAB%20PC/Old%20Lab%20PC/My%20Documents%20-(A)-2/My%20Pictures/Electronics/Synth%204600/MaplinETI4600%20-%202%20of%202.pdf

Hope you enjoy reading about it.

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