[sdiy] Additive/Subtractive synthesis?

[Theo]

Maybe you should look around the sites of pp on this list a bit.
Bookmarking  http://www.musicsynthesizer.com/ could be a good start.
Seems to me you are making things more complex than needed,
and at the same time _much_ more limited than what circuitry with the same
complexity could do.

BTW are you in Belgium?
I ask cause they have "something" with "final projects" over there.

Cheers,
Theo


----- Original Message -----
From: Ishaan Dalal <izx at xizx.net>
To: Neil Johnson <nej22 at hermes.cam.ac.uk>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, April 21, 2003 4:55 PM
Subject: Re: [sdiy] Additive/Subtractive synthesis?


>
> > > This seems the simplest on paper, since changing the Q/center freq of
a
> > > state-variable filter on the fly looks like a giant pain.
> >
> > Not if using OTAs.
>
> Actually, I was thinking of using the UAF42, and one of the application
> notes describes a way to digitally tune Q/ctr_freq, but uses 2 DACs.
> Ultimately, however, it is analog voltage controlled, so I might be able
to
> fix 'em somehow. My circuit can (in theory) actually produce 3 octaves,
with
> a one note per octave polyphony limitation (i.e., you can only play C in
one
> of the 3 octaves at once). The way this is done is using a CMOS counter
with
> divide by 2, 4, 8 outputs, all three going to a 4:1 mux. Depending on the
> position of the key, the mux connects the relevant output to the VCA/F,
> effectively increasing the range to 3 octaves. Haven't worked out how to
> simultaneously tune the LP (or BP) filter.
>
> > > On the other hand, subtractive would certainly be more compact,
allowing
> > > me to dispense with the individual oscillator for each note.
>
> What I was thinking was, say, a master saw source at 220 Hz, going to the
> VCF of each key, which BP'd the appropriate Fourier multiple, probably
> amplifying it too, and each key sending this to the output mixer.
>
> > But SSM2164's are cool... I happen to know a guy who sells them in small
> > quantities :-)
>
> Actually, Analog Devices has SSM2164s in active production, at least the
> DIP/SOIC versions. They also have a 4-quadrant quad analog multiplier
> (MLT04), which I believe would serve just as well....what do you say?
>
> > Additive synthesis is where each note is constructed from two or more
> > simple (in)harmonic components (e.g. sinewaves) from separate
oscillators.
> > A recent example being the Kawai K5000 synthesizer (or its older cousin,
> > the K5), which constructs each note from upto 128 digitally-generated
> > sinewaves.
>
> If only I could use (and knew how to program :-) a DSP!
>
> > Subtractive synthesis is where you start with a harmonically rich
waveform
> > (e.g. sawtooth) and filter out (subtract) some harmonic components to
> > modify the sound.
>
> Actually this is supposed to be a "Digital Logic Design" project, but I've
> managed to keep the instructor placated with stuff like PCM sampling
> (drums/cymbals and a 30-second sequencer). Wouldn't want to make it "too
> analog", at least I can claim the one oscillator/note as a "digital tone
> generator" :-)
>
> > Anyway, terminology aside, it sounds like you have a fun project ahead.
> > If I were you, I'd go for a simple one-oscillator-per-pnote synth to
keep
> > the circuitry simple, and so you don't need to bother with keyboard
> > scanning or MIDI processing.
>
> Precisely, a "piano" clone with a rudimentary ADSR and a somewhat variable
> VCF is more than enough work for something due in two weeks time! :-)
>
> Cheers, and thanks for the advice,
> Ishaan
>