[sdiy] NJM-2069 internals. Was: Re: SSM2040

[bayne d'artagnan]

On Nov 6, 2007 12:40 PM, ASSI <Stromeko at compuserve.de> wrote:
> On Montag 05 November 2007, bayne d'artagnan wrote:
> > I agree. I've never been able ot find a solid opinion on what's
> > inside the filter. Many have said that it sounds like a cloned 2044.
>
> The 2044 is a ladder filter, while the KORG/NJM2069 is most certainly a
> quad OTA VCF, seeing that all the caps go to ground in the Poly800
> schematics.

Yes, see about three messages up. :)

> It also packs a dual input mixer, a direct input to the
> VCF, resonance and both expo and linear cutoff control plus a dedicated
> VCA, again with expo and linear control.  The VCA is before the filter
> in the Poly800 and apparently just used to feed in the noise. There's
> probably an unused 12dB/oct output on pin 5 that's not in the Poly800
> schematics (the DSS-1 has a 12db/oct mode on the filter and this is the
> only pin unused).

That's right. Pin 5 is the 12db output. If I wasn't being clear, the
basic layout of the chip and pinout are all on line as well as
descriptions of control voltage levels etc. What I was interested in
finding out is what can we say about the OTAs? What would korg have
put on the chip? What processes might have been used? Does New Japan
Radio make chips on contract like Rohm did with the BA662?  Do they
have anything else in their line past or present that would give any
insight like the BA6110?