[sdiy] What is a korg 2069AD?

[>>>marjan<<<]

Hi there,

> 
> Pin    function
> 1      Ground ?
>        Schematic says that it is a specific ground
>        but I can't read what it says.
> 


IN GND, it's gnd for vcf input from ext source


> 2      Level 1 (cv input ?)


CV for level of input 1 in VC Mixer - you determine
input amount with CV.

> 
> 3      Level 2 (cv input ?)

CV for level of input 2

> 
> 4      Resonance control input
> 5      Not connected on either synth

12db/oct output

> 6      24db VCF output
>        connects to pin seven on the DW, but organized
>        differently on the poly800

As I said, Poly800 doesn't use built in VCA as main
VCA, rather as attenuator for noise volume.
DW prob uses it as it's supposed, main VCA

> 
> 7      VCA in
>        I'm pretty sure this is the signal input
>        for the VCA, but then, what is
>        sig1 and sig 2 (see below)


this is direct input to VCA

> 
> 8      VCA log control input
>        goes to ground on the DW, but the poly800
>        appears to label this the VCA log input.

AS it says log CV input for VCA part. Makes different
volume (VCA) response than lin input. Not used in p800.

> 
> 9      VCA lin control input


VCA lin CV input.


> 10     VCA out
>        I think this is the VCA output, that's what
>        it's labeled. On the DW it goes into an opamp
>        buffer and then out to a voice specific point.
>        On the Poly800 it goes to pin 19 which is VCF
>        input something or other, but on the DW, pin
>        10 connects through a resistor to a point
>        common to all voices.  So pin 19 is NOT the VCF
>        input. (see pin 19 below)

main VCA output. DW uses it as it should be, but p800
it's attenuator for noise so it's being mixed into
vcf. Poly800 has separate "VCA" for each osc and vcf,
but those are made thru software envelopes not analog
cct. You can look at it as third input to 2069's VC 
mixer, as those are just two OTAs mixed.

> 
> 11     VEE,GND (this, I believe is the power ground)

main GND it is


> 12     VSS, - supply voltage, probably -12 to -15

- supply, not sure for the voltage range

> 13     VCF lin control input

lin CV in, for manual cutoff control (here you hack
manual pot on p800)

> 14     VCF log control input

log cv in, for control CVs

> 15     VCF caps connect these pins to ground
> 16     |
> 17     |
> 18     |

these are the caps for 4 OTAs that determine main
filter range (each filter is RC element, R being
simulated by OTA, it's VC current source and that
cap is C element from the filter).

>        I have no details on the specifics. In both
>        synths these pins go to ground through a
>        .001 mf poly cap.

prob it's preffered value in datasheet 

> 
> 19     Ahh, the mystery pin. On the DW it connects
>        through a resistor to a common control point.
>        On the p800 I think it connects to pin 10,
>        however, the p800 schematic is quite hard to
>        read so this may not be right.

No mystery, it's main audio VCF in

> 
> 20     Sig2 input

audio input of signal 1 for VC mixer

> 21     Sig1 input


audio input of signal 2 for VC mixer


> 22     VCC, + supply voltage, +12 to +15

+ supply

> 
> Ok,Here's what I think, if you know better, please
> correct me.
> 
> The audio inputs to the filter should be supplied to
> pins 21 and 20. The gain of each input is controlled
> by a cv input on pins 2 and 3 respectivily. Resonance
> CV input should be supplied to pin 4, cuttoff CV
> should be applied to pins 13 and 14 for lin and log
> control respectively.  The output of the VCF is taken
> from pin 6 and, like on the DW, can be fed right into
> pin 7, the VCA input. Note, on the DW it goes through
> a np electolytic cap of 10mfd.  The VCA is controlled
> via pins 9 and 8 for lin and log control respectively.
> The output of the VCA is taken from pin 10 and fed
> into whatever opamp buffer you wish.
> 
> Pins 1 and 11 go to ground, pins 12 and 22 go to
> negative and positive power respectively.  Pins 15
> through 18 connect to ground through .001 mfd poly
> caps. I presume the values can be varied.

Maybe smaller values, but, again, 1n is prob most
optimal value

> 
> Pin 1 is a minor mystery, what does it ground?
> 

vcf input gnd

> The major mystery are pins 5 and 19.  I think both
> relate to the VCF, pin 19 should control something,
> what I don't know.  Perhaps pin 5 is a 12db output? I
> have no idea, I'm just guessing.
> 
> Any help would be apprecieated.  At least if there
> isn't any more info, this much will be in the
> archives.
> 

see previous notes


Anyway, you have little audio processing chip in there:
VC mixer (with input and CV for each input, output)
VCF (audio, lin CV, log CV inputs, 4 cap pins, 12 and 24 db/oct
     separate outputs, resonance CV input)
VCA (audio, lin CV, log CV inputs, output)
power (+/-/GND/signal GND)

It's a small modular, you can connect it to your wish (if you use
it outside of the synth, naturally).

I wonder in Korg repairshops have some spares? It'd be nice
VC processing module (add preamp, bufferes, distortion, waveshaper
and PSU and it'd be a killer).
 
-- 



marjan


me    : Marjan Urekar
e-mail: urekar.m at eunet.yu
s-diy : http://surf.to/marjansystems
music : http://go.to/forcemajeure