[sdiy] E-Drum antics, EPROM data dumping

[Metrophage]

I decided to take a break from my MG-1 modifications (and heaps of
repairs...) to check out these modules. The E-mu E-Drum was a version
of the Clavia Drum Plate, 8-bit percussion ROM-pler with a few
articulation and tone controls, the top is a piezo drum trigger pad. I
bought three of these, supposedly broken, off of a guy for $20. One
version 1.1 and two version 1.2.

Only thing which really needed repair were the crap Piher plastic pots.
Bad news putting plastic pots on anything meant to be played with a
stick! Also, to keep the drum pad on, the units were wrapped in many
turns of 15-year old packing tape. I peeled off the tape and scrubbed
the cases with alcohol to reveal the beautiful baked-enamel finish,
scrubbed the PCBs, and replaced the broken plastic pots with 1/8"
sealed pots. 

These things feel quite nice! The pad feel is quite something: the
steel chassis is cut out, and epoxied over it is an aluminum plate
covered with rubber, with a piezo disk epoxied under it. The kewl
articulation feature is that it is very velocity sensitive. Sounds to
me like the pitch increases with velocity, though this might just be
because the higher frequencies are more audible with increased
amplitude.

Between my three units, I have only two ROM cartridges: "Electronic
Snare 1&2" and "Gong". The cartridges are basically a 256k ROM on a
PCB. Since I was just kicking myself for not getting VCDO parts in a
recent purchase, I am going to tinker with these units to hold me over.
I assume the main difference is that an ordinary waveform VCDO for
general-purpose synthesis is induced to repeat its data over and over
in relation to a clock VCO, whereas the longer drum samples are just
read out once upon recieving a pulse.

I just got a "Willem" EPROM reader/burner PCB recently, so I figure I
should use it to try to rip the data off of the ROMs. By studying the
ripped data I hope to understand how the audio data is formatted on
there. But even if I can extract the data off of the ROM... I'd expect
it'd look like hex or binary gibberish to me. I really wonder how I am
going to recognize audio data by sifting through the contents! Time to
get my windoze machine out of the mothballs and onto the bench!

CJ


		
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