NJM2069 VCF chip information

     The following preformatted information was provided by some people in the synth diy group and is a wealth of information about this hard to find info on chip! Larry Hendry sadly passed away shortly after this and his contributions of this nature are greatly missed. -Bob Weigel

Good information Paul.  I can add a little to this.  Korg also used this
chip in their first sampler - the DSS-1.  The entire voice board in this
hybrid is analog except for the A/D + S&H for CPU control of the VCA/VCF and
digital delays.  BTW, in the Korg DSS-1, they did use both the 12 db and 24
db outputs and used an external analog switch to select which of these went
to the VAC input.

Here is information I can add to what Paul has already given:

Pins 1 and 2 are indeed CV level controls for two input signals (pins 20 and
21).  However, they control the signal prior to the VCF like an input mixer
to the VCF.  I believe they do give a log response to a linear control.  In
the DSS-1, voltages at this pin are 0v = 0% volume, 3.83 volts = 50% volume,
and 7.65 volts = 100% volume.  I have not checked the actual signal level.
But, to my ears, I am getting the correct response using a linear control
voltage. Those are the voltages produced by the CPU + D/A + sample and hold.

Pin 9 VCA LIN is actually used for total VCA level in the DSS-1.  The noise
source is external and is applied to pin 19 (VCF signal IN).  I do not see
any internal control of this level in the VCF section.  If it is there, I am
missing it.  If I am reading the schematic correctly, in the DSS-1 the noise
source level is controlled externally prior to being applied to pin 19.

Pin 12 Vee is also -5 volts in the DSS-1
Pin 22 Vcc is actually +12 volts in the DSS-1

Pin 13 VCF cutoff LIN CV is not used as a control point in the DSS-1.  It
appears to me to be a trim-able temperature compensation circuit.  So,
apparently the 2069 needs that for accuracy of the VCF freq.

Pin 14 VCF cutoff LOG is used for all VCF control in the DSS-1.  But, all
voltages are generated by the CPU + D/A + S&H.  So, the cutoff control and
(apparently) linear envelopes are added together in the CPU and sent to this
pin via D/A + S&H

I think Paul has a type-o below since his pin out list does indicate that
pin 6 is the -24db filter output.  It appears he meant to say pin 14 (VCA
log) is tied to ground.

So, in summary everything I have learned about this chip so far suggests
that you have 3 signal inputs at pins 19, 20 and 21.  Pins 20 and 21 mixed
under external CV control. Those are summed with pin 19 (no internal level
control) and all 3 are direct inputs to the VCF.

VCF signal outputs are pins 5 (12db) and 6 (24bd) which in my case are
connected via external analog switch to the VCA input at pin 7.

PIN 8 on my schematic is listed as "CB" (something I do not yet understand)
It is connected with a cap and diode over to pin 9 which is the linear VCA
control.  The VCA control is for all signals as all sources were already
mixed prior to the VCF.  It is interesting to see pin 8 listed as the LOG
CV. I'm glad to have that new information (new to me anyhow).

Pin 10 is the VCA audio output, but I show pin 11 as the audio ground.  In
any case, it is tied to ground.

I have been playing around with this chip for a while and I am still in the
learning process.  Why?  Because the DSS-1 is one of my beloved machines and
I have a spare one I can hack on.

I hope this additional information was useful.  I hope to have more later,
including a project where I plan to make use of this great little chip.
But, right now my day gig is trying to kill me, so I am behind on all things
synth related.

Larry Hendry

-----Original Message-----
From: owner-synth-diy@dropmix.xs4all.nl
[mailto:owner-synth-diy@dropmix.xs4all.nl]On Behalf Of Paul Maddox
Sent: Wednesday, May 11, 2005 3:33 AM
To: SynthDIY
Subject: Re: [sdiy] NJM-2069 (Another Korg IC)


>> 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
you can see the 12dB output just isn't connected (what a waste!).

Here's what other info I have -
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.


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
the mix as 'real' vca control is performed digitally inside osc chip driven
soft envelopes.

hope that helps.