[sdiy] patching polys(ESQ), newbie question, electronic kits

[Rainer Buchty]

>I was reading through sketchy information suggesting that the waveforms
>pass through a DCA before the VCF and finally VCA, and started looking
>more closely at the schematics - thinking that perhaps A) a shoddy DCA
>may contribute to the undesirable qualities of the waveofmrs or B) this
>DCA could somehow be pushed up a little in voltage to get hotter
>signals to the filter.

See http://www.buchty.net/ensoniq/ for schematics of the ESQ1 and also
the datasheet for the soundchip.

You could try messing with the VOLFDBK (12) and WVREF (14) pins. I doubt
that the DCA contributes much to the "undesireable" qualities, because
it's just a basic multiplying DAC setup.

The oscillator itself is a rather crude design; it's just a plain phase
accumulator without any interpolation, so with longer samples and an
"off" playback frequency it will start to whine.

>Turns out the CEMs are fed by a voice selector/(de?)mux IC.

Yes. With the ESQ1, the DOC soundchip outputs 24 oscillators (8 voices)
in a time-sliced manner which are routed to the appropriate 3379 for
analog postprocessing according to the current pattern of the channel
address bits.

If you want to go true lo-fi you could also try knocking out the lower
address bits. (Paul M. sez: "De-res!" :)

Rainer