SV: a 2600 2600

Ben Stuyts ben at stuyts.nl
Fri Mar 24 09:42:28 CET 2000


Theo wrote:

> I reverse engenieerd my ACN cardige, (the first mod was done about
> half an hour after first use) have to look them up but if it is anny
> use to you i can mail the schematics.

Hi,

That brings back old memories.... You mean the ACN SoundTrack cartridge? I  
made that thing somewhere around 1987. That is really nice to hear somebody's  
still using them.

> The sampling rate is conrtolled by interupt, eats a lot of cpu time.
> Data is written to the romport by a dummy read. A1 to A7 set the address
> the data is written to, A8 to A15 hold the data.

It was made to be compatible with another sampler cartridge at that time...  
Uhm, forgot the name. Some English product I think. That was important, because  
a lot of software would work with it that way. That's why we choose the weird  
'write by reading' trick. If I remember correctly, by setting up your registers  
careful you could reach sampling/playback speeds of up to 55 kHz that way.

> The AA filter is fixed at 10KHz with a 6dB slope.

It sounded a bit harsh, didn't it? B-) Wasn't it 12 dB by the way? Can't  
remember exactly. I do remember it had to be cheap. The English cartridge had a  
lower frequency cut-off, but sounded too mellow at higher sampling rates.

Somewhere last summer I finally moved all the project's documentation into  
storage somewhere, and I dumped all my old ST stuff.

Please tell me about your mods?

Kind regards,
Ben



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