Re: SFX sound expander

From: Richard Atkinson (
Date: 1998-12-18 23:02:33

Hi Randy... my thoughts on the sound expander:

> The SFX Sound Expander was made by Commodore UK.  It's based around a
> Yamaha OPL2 FM sound generator.  It was basically a SoundBlaster for
> the C64/128.  There were also some companion products, such as the SFX
> Sound Sampler (piece o' junk) and a full-size 64 key keyboard.  There
> was a SEVERE lack of software to support this product.  It certainly
> was released in the UK and was probably only rare on this side of the
> Atlantic.  I had Jim Brain include it in his canonical list of CBM
> products where you can also find the CBM model numbers.  I doubt that
> CBM could get FCC approval for the device for sale in the US, as it
> seems to kick out vigorous RF at NTSC color burst frequency.  It
> probably screws up most of the tv sets in the neighborhood (certainly
> every set in my house) when I turn it on.

There is indeed an NTSC colour crystal in the case and since there's
absolutely no shielding whatsoever, I wouldn't be surprised if this thing
fails FCC regulations. However, there was nothing to stop Commodore
putting one on, with the 3 spring-loaded contacts that touch the grounded
shield in the '64 (like the REUs).

As to the chip itself, well I don't think it's an OPL2 or OPL3 as these
were 2 operator FM synth chips (used in Adlib and Soundblaster). The unit
I have sounds very much like 4 operator FM, such as the chip inside the
Megadrive or Sega System16 coin-ops. It's capable of 8 note polyphony or 6
with some *really* cheesy drum noises, but you're better off using SID for
percussive sounds. Yamaha keyboards such as the DX9 or DX27 used 4
operator FM with 8 algorithms; perhaps there is documentation to be found

More as and when I find it; I'm trying to disassemble the bundled software
using an Action Replay, but it's hard-going since I don't have the AR's

Merry Christmas,


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