Blast from the past – The Stylophone Schematic

by Stephen Hobley on September 30, 2010

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Years ago (and we’re talking more than a few) my parents finally gave in and bought me the closest thing you could get to a real synthesizer – The Stylophone. Mine was the white one – there was a slightly more advanced model that was black with faux wood trim. The sound was monophonic, and had a warm, “buzzy” quality to it. It was played with a stylus (hence the name) on an etched metal keyboard.

A few years ago they released a “retro” version of the Stylophone, but I’m sorry to say that the tonal quality of the updated version is not the same as the original – almost all the circuit diagrams I can find feature a 555 timer as the source of the square wave oscillations – but if I recall correctly (after opening up my Stylophone  many times in 1977)  I don’t remember ever seeing an integrated circuit at all.

So this got me to thinking that the original Stylophone was not built on a 555 timer at all, but maybe something like a transistor pair oscillator (flip flop).

I recently uncovered this schematic, that seems to be authentic and does not feature the 555 timer. Additionally if you check out the picture of Brian Davis on this page you can see him holding up the etch mask – I don’t see anything that looks like a socket for a DIP-8 chip. (Schematic came from Sean Kerrigan’s page here)

I’ve been meaning to rebuild a traditional Stylophone for years, over the next few months I’ll have to see about getting it done.

And then there was this:

The Stylophone 350 (“Super Stylophone”) this one was duophonic, and had a bunch of different sounds, *and* the world’s first D-Beam controller – a photocell that could be covered with the hand to modulate the sound further. Very cool.

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{ 5 comments… read them below or add one }

Download MP3 June 24, 2011 at 4:27 am

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Chris Dancer August 22, 2011 at 2:29 pm

I’m sure your stylophone schematic is genuine. I remember looking inside mine and only seeing a few transistors and a lot of resistors.
It’s a beautifully minimal design. The audio oscillator is based on T1, a programmable unijunction transistor. A phase shift oscilator built around T2 provides the vibrato, and T3 is the power amp!
The distinctive buzz comes from the narrowness of the pulse wave and the highly non-linear amplifier.

Rick Dexel May 14, 2014 at 11:51 am

I have an original 350s that I bought in 1977. I want to use it again in live performances, without relying on the batteries. Have tried 3 different 18V power supplies. Left stylus plays unwanted modulation with power supply , but plays properly in battery mode. Does anyone have any ideas ? Where can I get a schematic ?

Rick D.

Stephen Hobley May 14, 2014 at 11:54 am

My first thought would be that the power supply is introducing unwanted modulation into the signal path. Is there any way you can scope the output of the supply? If it ripples you could try filter capacitors.

Also, power supplies rarely give out exactly the right voltage, depending on the load of the circuit you could be getting anything up to 24v.

Steve GS July 22, 2017 at 6:24 am

In answer to Rick’s query – the current consumption from the battery is very low – about 13mA max, and less than 5mA when quiescent – ie. with stylus off the keyboard and vibrato off. So why compromise its portability and risk introducing hum problems? Better just to use a decent battery.

Stephen – your circuit bears no resemblance to mine. I think yours, with a unijunction oscillator and resistor networks must be a later model. I’ve traced out the circuit in one I bought on eBay a few months ago – see http://www.stevegs.com/music/stylophone/

And yes – the modern Chinese copies from Amazon don’t sound as good…

Regards,
Steve G-S

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