[sdiy] NJM-2069 (Another Korg IC)

[Paul Maddox]

Larry,

> Pin 9 VCA LIN is actually used for total VCA level in the DSS-1.

ahhh, nice trick.

> 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.

Its the same on the DW8000, noise is controlled 'globally' rather than per 
voice.

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

now that's interesting.

> 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.

its used in the DW8000, each of these has its own trimmer, which goes to a 
common line, supplied from heaven only knows where.

> 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

yep, same on the DW8000.

> 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.

oops, well spotted.

> 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.

yep.

> 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.

nice, which analogue switch did they use? 4066? or something a little 
better?

> 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).

Thats the one that goes to ground on the DW8000, not pin 6 :-)

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

on the DW8000, it just goes to ground, its not specific about 
audio/digital/mother earth.

> 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 like it because its a neat, small way of adding a complete vcf/vca/mix 
section to a synth engine.
One other point of note, the chip is 0.4" wide, wider than the standard 0.3, 
and not as wide as a 28/40pin 0.6"

> 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.

keep us (and me) informed!

> But, right now my day gig is trying to kill me, so I am behind on all 
> things
> synth related.

hope things ease up soon.

Paul.


> Larry Hendry
>
>
> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at 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)
>
>
> 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 -
> ----------------------------------------------------------------------------
> --
> 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.
> ----------------------------------------------------------------------------
> --
>
>
> hope that helps.
> Paul
>
>
>
>
>