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

[Dan Gendreau]

> 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.

Have a look at the TR707 and TR909 schematics (HH, CC, RC sections) for an
example of this technique.

-Dan G.