VOGONS


First post, by Benedikt

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There appears to be a parallel port dongle for almost every remotely popular synthesizer chip nowadays, but I have not seen anything based on the AY-3-8910 series, yet.
Is there nothing we can do about that?

Surely we could build a hypothetical AY-LPT just like an OPL2LPT, OPL3LPT, TNDLPT, CMSLPT, SID LPT or whatnot and put everything in a 3D-printed case, but as a wise person once put it: "Good engineering is cheap engineering."
So how exactly can we make the thing cheaper?

It occurred to me that if you solder the PCB to the DB25 connector in a slightly unorthodox way, a socketed 24-pin DIP chip like the AY-3-8913 can be squeezed into an ordinary adapter case.
This is the mockup I threw together for illustration purposes:

aylpt_mockup.jpg
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aylpt_mockup.jpg
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Simple AY-LPT mockup
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There would have to be one wire for GND, but everything else on the second row of the DB25 connector is not really needed.

The device would need power (preferably regulated 5V via USB), an audio output jack (preferably stereo) and maybe a volume wheel.
The front panel could be either printed cardboard (cheap) or maybe a thin PCB (premium).
Internally, there would have to be at least an SMD crystal oscillator and a couple of SMD resistors.

These are the configurations I can think of:

  1. Unbuffered line-level output
  2. Buffered line-level output
  3. Amplified output with volume control

What are your thoughts?

Reply 1 of 4, by Jo22

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Hi! This sounds fun! ^^

The rare Covox Sound Master had got an AY-3-8930 tone generator,
so even for the sake of completeness alone,
it would make sense to have got an AY dongle, too.

Covox Sound Master Reverse Engineering / Replica

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Reply 2 of 4, by Benedikt

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I'm aware of the Covox Sound Master, but I think I'll settle on a CPC-style circuit, instead. The CPCs were quite a bit more common.

cpc664_stereo_output.png
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Stereo output of the CPC664 (from Amstrad's schematic)
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In that case, the AY-chip runs at 1 MHz and a network of resistors combines the three output channels to a stereo signal.
The stereo output on the AY-LPT dongle could then either use that directly or add an emitter follower and/or single-transistor amplifier with or without volume wheel.

Reply 3 of 4, by LordMortiferus

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I found several schematics for an AY-LPT device used for example in ZX Spectrum emulation. Maybe this is of intrest for you:

LPT-AY by Vitaly Mayatskih & Alexander Kulik
LPT-YM by Romanich
AY-LPT by Jarek Adamski for ZX Spectrum and Timex Computer
Infos by tronix286
Infos by krssh

USB-AY by tronix286 and on vcfed