[sdiy] New DIY synth has born

[Rainer Buchty]

>This can lead to some (nice) distortion at the SID filter stage - and
>we all love such non-emulatable analog effects, no? :)

It's interesting, that so far noone figured out how the combination
waveforms (e.g. saw+tri) *really* are constructed.  Especially, since
they are also slightly different between 6581 and 8580.  So the
emulators take an approach which sounds quite close but on bit level
they is still not correct.

>Fortunately changes become active immediately.

Ah, so that was only a limitation of good old SoundMonitor.

>I'm not sure if it's worth the effort to use an 8bit CPU for controling
>so much SIDs and OPL3s at once. Such a synth doesn't only live from a
>static initialization of the sound registers, the fun begines once
>multiple parameters are modulated by different sources (LFOs, EGs,
>"wavetable sequencers") and this requires a lot of horsepower

There was a nice synthesis engine in the German 64'er Magazine, the
Modulator (introduced 4/85, IIRC, with full source in 10/85). That thing
offered 8 really awesome LFOs, a software ADSR-type EG (with switchable
polarity) and a patch matrix, so that it was not only possible to route
LFOs and EG to SID resources but also modulate the LFOs frequency *and*
pulse width (if square wave was selected for an LFO).

And it still fit into the IRQ routine (50Hz interrupt) so that it
virtually ran in the background and didn't interfere with the BASIC
interpreter.

Based on that software, you'd probably need at least one 6502 per
hardware voice.

Rainer