[sdiy] help finding roland filter schematics?

[rob]

Hi
>From my research into Roland filters, I would suggest:

Roland developed the OTA based filter as seen in the early Jupiter 4, and
Roland 100M, and others.
Initially using the CA3080, then locally sourced BA662 (near equivalent =
BA6110). There isn't much difference.
They developed the IR3109 chip to reduce costs, its 4x OTA's on a chip with
the expo and it appeared in the Jupiter 4 later model.
These was also used in the Jupiter 8 and 6.
Further reductions in space and cost led to the D80017A with a VCA included.
Then the IR3R05, which is highly likely to be the same design... 

What DOES make a difference is the OTA capacitors and the resonance design.
The use of SMD capacitors probably makes the sound dry compared with high
quality polystyrene caps.
The resonance design is more crafted in the early designs as it does NOT
have to fit into SMD minimium packaging nor accommodate external voltage
control for patch memories (and an extra OTA). See how Tony Okaley has
studied this factor and created some great designs. 
This is why we like the older synths...

Well this isn't all theory. I have designed and now building these filters:

Roland 100M filter using BA6110, with HPF
Roland Jupiter 8 filter, using an IR3109 (with HPF)
Roland Juno 106 filter, using D800017A clone
Roland JX8P filter using the IR3R05
Roland SH-5 Filter....diode ladder LPF and Op Amp BPF

Have a read of Tony Oakley's COTA filter for some excellent insight and a
great filter!
http://www.oakleysound.co.uk/cota.htm

Or the filter page at my web site:
http://www.emulatorarchive.com/Filters/filters.html

Regards
Rob
www.emulatorarchive.com



hey there

in my quest to better understand OTA filters, i have been trying to find
some of the old roland OTA filter schematics in readable scans.

i found this CHART which lists which of the roland filters use regular
OTA's.

http://fa.utfs.org/diy/roland_filters/index.html


so i am looking for readable SCHEMATICS of the SH1, SH2, SH7, and maybe sh09

also...these are probrably good ones to look at in general for vco and lfo
ideas,etc.

a few questions...does anyone know how much a BA662 compares to a ca3080?

also...in the later ROLAND OTA CHIPS are these basically just 4 otas on a
chip? or is there something fancier going on? are these available as
schematics anywhere?

Thanks SO MUCH!!






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