Wednesday, March 15, 2017

Rare R.A. Penfold DIY Analogue Synthesizer


via this auction

Only two others have been featured on the site before. You can find some demos here. Note this is based on the Electronic Synthesiser Construction book by R.A. Penfold which you can still find used on Amazon, albeit for over $250.

Considering this is a DIY synth based on a book, I don't know exactly how rare it can be considered. I guess it depends on how accessible the parts would be to make your own. The following is the description from the listing:

"This is very possibly one of the rarest synths on the planet - I know of only one other in existence and it is a rack-mount version. There is a youtube video of that synth showing that it has a very capable sound. A quick Google should find it.

The Penfold synth is based on the circuits described in the rare (and expensive - over £200 on Amazon!) out-of-print book 'Electronic Synthesiser Construction' by R. A. Penfold and published by Babani Books in 1986

The book has circuits and construction info for all parts needed for an analogue synth - VCO, LFO, Noise Generator, Filter, Envelope, VCA, Keyboard controller, Power supply etc.

This unit has been constructed with the following sections, all are on separate circuit boards mounted inside the rear panel, with all front panel controls wired directly to the circuits -

Keyboard + Controller (sample and hold)
CV in
VCO 1
VCO 2
White Noise Generator
LFO 1
LFO 2
VCF
VCF Mixer
Mixer
ADSR
VCA
PSU
Audio Power Amp & Speaker

Quite a lot of functions in a compact format. The construction appears to be semi-modular with around a dozen patching jacks on the front panel, very reminiscent of the MS-20. The case of this synth is made from wood, quite solid construction, approx 1cm thick all round. The front control panel and rear connection panel are aluminium sheet. All the front panel controls are securely mounted to the panel and all feel very solid. All pots and switches feel good too - the pots are tight and smooth and all the switches have positive action. You will notice that there are no control legends on the panel, possibly a design decision by the (unknown) builder, or maybe they just never got around to it. but all the control functions (or circuit designations) are marked on the inside of the panel for reference. There is no base cover on this unit, I'm not sure if it ever had one, but it should be very easy to fabricate one if required.

The power supply requires 240v and has a standard iec connector and fuse on the back panel. The internal speaker is also mounted inside the rear panel with a metal grille.

The synth is complete and has worked in the past, but there are some known problems - the keyboard is not working (one missing ic, one broken key, possibly other faults) and has been partly disconnected internally and one of the smaller pcb's has come loose inside. The condition of all other parts is unknown as the unit has not been powered up in a long time and I don't want to risk anything. However it all looks to be in good condition inside (though a bit dirty and dusty) with nicely laid out PCB's and nearly all the wiring seems to be intact. I get the feeling that it probably won't take too much work to get this up and running again.

A full copy of the original book is included (in bound A4 format) with all circuits described. There are no hard to find components, it is all standard stuff (no curtis ic's etc)

This will obviously appeal to the serious synth collector or someone with a particular fondness for this breed of DIY synth. This is an extremely rare piece and I doubt you will see another like this for sale anytime soon."

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