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

[ASSI]

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.  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).



Achim.
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