Fun Stuff - P2000
Sequential Circuits Prophet 2000
Introduction
I bought my P2000 for $150, thinking it should be useful for as a controller
for my analog modular (via MIDI) and to learn the basics of sampling. I was
intrigued that a 12 bit sampler with arpeggiator and analog filters would sell
for so little. I reasoned that I could always sell the unit if I got tired of
it..... I got ahold of the schematics and turned the unit on. At first I thought
it didn't work right because of the weird factory patches on power up - I didn't
get any sample disks with it! But I think it works correctly. Here are some
things I learned about the P2K since buying it....
The Floppy Drive
The main problem and probable reason for the synth's low value is that the P2K's
floppy is not pc compatible. The disks are not compatible, and the format on the
disk itself is unreadible in a pc. The controller chip on the P2K is an old
Western Digital IC (WD1770) that was used on some Commodore machines and others.
For all I know, the track format could be in a spiral pattern rather than
concentric! You can use the DOS version of Samplevision for sample storage
and transfer them to/from the synth via MIDI.
1V/Oct. Controller??
I noted that the filter chips are voltage controlled. I played with using this
voltage to control my modular synth. A cheap 8 voice polyphonic CV controller...
It did seem like it may work but there was something in the design that would
glitch the cv. It would be necessary to add circuitry to buffer the voltage and
prevent the glitch from occuring.
Filter CV Trimming
I noted that the filters at high resonance have noticable differences in
frequency response for a given assigned note. It may be useful to add trimmers
to get them all "tweaked".
VCA Panning
The CEM3379 filter/VCA chips on each voice have panning VCA's that are not
used in the design. I must admit that the standard output structure of the
unit - where a voice is periodically alternated between left and right channels -
drives me nuts. This was the main reason I thought my unit was defective. Might
be interesting to use the resonance or filter freq. cv to pan each voice's
output to really make it confusing... Hate to see those VCA's just sitting
there.... Maybe add an optional ring modulation "feature"?
Alas..
A few months ago I traded off my P2K for a Frontal Lobe unit I had hoped to use
with a recently obtained Wavestation AD. I could never remember how to program
the P2K and, while I liked the sound of the unit, I didn't have a bunch of sample
disks made up so it didn't get used much. Alas, the Frontal Lobe unit did not work
with my Wavestation AD and I trashed its firmware when I replaced a voltage regulator
inside it - all the code was stored on NVRAM! So if you know anyone who can fix it
I'd love to get in contact with them!
email me:
barry.l.klein@wdc.com
created 5-5-99
back home