[sdiy] Roland SH-3A "chorus"

[>>>marjan<<<]

> I spent a nice afternoon today with a friend who brought
> his SH-3A. I was surprised how good this sounds, for
> a single-VCO synth.
> 

It's a strange beast with some odd fearutres. I think it's
inspired by early Korgs, esp the divide down trick so you
can mix saw/squares from several octaves. Envelope was simplified
copy of System700 IIRC, all descrete VCO, Ladder filter,
few lfos. One fixed envelope, advanced S&H, 3080 VCA.

> The " 8'-Chorus " function plays an important role in this.
> Sounds a bit like PWM, but not what I exaclty would expect from
> PWM. How is this done ? Are the schemos online somewhere ?
> 

It is PWM, as I mentioned it shares this fearutre too, as seen
in early Korgs, which also called it chorus. Too bad, it's only
on 8', but it could be easily modified to do all of them.
It's plain ol' coparator driven by dedicated LFO.

> The filter is a Moog-ladder as far as I could tell, btw.
> Thought I read somewhere they'd changed it from the
> -3 to the -3A. But this -3A definitely had a Transistor ladder.
> 

It's moog ladder, later they change it to diode ladder as
moog sued them, or something. It was at AH long time ago.
You can find the schematics at the musicmachines at hyperreal.

cheers,

-- 



marjan


me    : Marjan Urekar
e-mail: urekar.m at eunet.yu
s-diy : http://surf.to/marjansystems
music : http://go.to/forcemajeure