[sdiy] Data formats in Eprom based drum machines and Romplers

[Paul Maddox]

Dan,

> > are there any other formats I should be familiar with ?
>
> Not really another format, but if you may want to be aware of a variation
on
> the "linear encoding" ROM format.
> Another trick that was used to increase dynamic range back in the day in
> some drum machines (most notably the Roland TR909, TR707, TR727, and the
> Boss DRP-* pads) employed a hardware envelope to the DAC output. The data
in
> the ROM was audio-compressed and the hardware envelope (either an RC
> envelope or derived from the rom address using an exponential DAC)
restores
> the original dynamic range. The ROM data will sound very harsh if you do
not
> account for this output EG in some way.


Also be carefull of the Address lines..
The tr909 is a good example.. to make PCB layout they switched some address
lines,
so if you read data starting from address 0000 you will get noise out of it,
and not a hihat :-)

Paul
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