[sdiy] NJM-2069 (Another Korg IC)

[Paul Maddox]

Johannes,

> Btw, I remember there was some page about the NJM-2069 (Poly-800 and
> others). I think it had a pin-out, and some mentioning that you could
> get either 12 dB/oct or 24. I can't find anything anywhere! Has Korg
> shared any information on this chip?

The best schemctaic example is the DW8000 schematic, thats on the web 
somewhere,
you can see the 12dB output just isn't connected (what a waste!).

Here's what other info I have -
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I'm tempted to think that the pins labled "Level 1 & Level 2" (Pins 2
& 3) are the Log CV's for Osc1 & Osc2 VCA's respectivley.

I imagine "Pin9" (VCA LIN), is the Linear CV for the Noise Source,
maybe the Level + EG3 CV's are summed together into this Pin.

Pin 6 (VCA Log),is tied to ground. This at least, is the Log CV for
either the OSc1/Osc2 or Noise. So, thats one down at least.

------------------------------------------------------------------------------
KORG NJM2069

Pin# Function

1 Audio In GND (GND)
2 Mixer Signal 1 Level CV In
3 Mixer Signal 2 Level CV In
4 VCF Resonance CV In
5 VCF 12dB/oct Audio Out
6 VCF 24dB/oct Audio Out
7 VCA Signal In
8 VCA Level CV Log In
9 VCA Level CV Lin In
10 VCA Signal Out
11 Vss (GND)
12 -Vee (-5v)
13 VCF Cutoff CV Lin In
14 VCF Cutoff CV Log In
15 VCF cap C4
16 VCF cap C3
17 VCF cap C2
18 VCF cap C1
19 VCF Ext Audio In
20 Mixer Signal 2 In
21 Mixer Signal 1 In
22 +Vcc (+5v)

Chip has separate
*VCA with in,out and lin&log CV ins,
*VC Mixer with two audio inputs, two CV ins for each input level control,
it's output is hardwired to vcf audio in (no ext pin here),
separate gnd for input signal
*VCF with separate ext audio input (in addition to hardwired input from
vc mixer), output, lin&log cv ins, four pins for integrating capacitors,
vc resonance with pin for res cv

This is almost half of synt-chip type just like old CEM chips, but
sounds much fatter IMHO. Short look at pins 5/6 reveals easy mod for poly800 
to get
2/4 pole filter... Poly800 misuses it's vca for adding 3rd vc audio channel 
to
the mix as 'real' vca control is performed digitally inside osc chip driven 
by
soft envelopes.
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hope that helps.
Paul