Fwd: Re: [sdiy] What is a korg 2069AD?

[TooManySynths]

Hi All,

My 2069 Filter seems to be, well, um filtering so I
thought I'd pass along what I've found out in case
anyone else cares.  I'm forwarding this to AH, if it's
old news, well it ought to be in the archives. Several
people have asked but I have yet to see any response.

> > As I recall, the filter chip in the DW-8K is the
> > same as the filter chip in 
> > the Poly 800 (could be wrong).  If it is, it's a
> > very nice little thing, 
> > capable of self-oscillating and so on.
> 
> That is correct. I discovered the poly800 schemos on
> the web and thought to check to see if it uses the
> same chip. I presume at most the poly800, dw6000 and
> dw8000 would use this chip. I can't imagine anything
> else korg was doing at the time that would use that
> particular chip.  In fact, I believe the next major
> korg synth post dw8000 was the M1.  
> 
> 
> So, a little reverse engineering of the DW circuit
> board combined with the POLY800 schematics has given
> me some information.  Do any of you know any more
> than
> about this chip. Any question marks you could help
> me
> eliminate would be appreciated.
> 
> Pin    function
> 1      Ground ?
>        Schematic says that it is a specific ground
>        but I can't read what it says.
> 
> 2      Level 1 (cv input ?)
>        This pin goes to a common bus on the DW
>        so it is a control input that would affect
>        all voices in a polysynth
> 
> 3      Level 2 (cv input ?)
>        This goes to a pot and to a voice specific
>        control point on the DW.
> 
> 4      Resonance control input
> 5      Not connected on either synth

Update: It is an output of some sort. It sounds like
something less than 24db filter, but then again, what
do I know.  I'm sticking with my guess that it is a
12db/ocatve out. I don't have the skills to really
test this. Well, I have an idea how, but I don't have
the paitence, if you know, please fill us in.  If you
want to build a filter with this chip, you might want
both outputs available.

> 6      24db VCF output
>        connects to pin seven on the DW, but
>        organized
>        differently on the poly800
> 
> 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)
> 
> 8      VCA log control input
>        goes to ground on the DW, but the poly800 
>        appears to label this the VCA log input.
>        Although I know better, it follows as it is 
>        next to the VCA lin input, and the VCF
>        control
>        inputs are aligned the same way.
> 
> 9      VCA lin control 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)

Ok, I'm not sure what the DW is doing. BUT, pin 19
seems to be the output from the two channel mixer AND
the input to the VCF.  Makes sense really, but I don't
know what the DW is doing via it's common, albeit,
resistor isolated, connection.
> 
> 11     VEE,GND (this, I believe is the power ground)
> 12     VSS, - supply voltage, probably -12 to -15
> 13     VCF lin control input
> 14     VCF log control input
> 15     VCF caps connect these pins to ground
> 16     |
> 17     |
> 18     |
>        I have no details on the specifics. In both
>        synths these pins go to ground through a
>        .001 mf poly cap.
> 
> 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.

See above, pin 19 is the VCF input.

> 
> 20     Sig2 input
> 21     Sig1 input
> 22     VCC, + supply voltage, +12 to +15
> 
> 
> 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.  

This is all true, for a simper circuit, just feed the
input into pin 19 and skip the two channel mixer.

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

About the only remaining pin mystery, since my filter
is making sick nasty sounds this very minute, I don't
really care, it's just gonna be grounded on my filter.
 
> 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.

I'd still like to know for sure on pin 5.

> Any help would be appreciated.  At least if there
> isn't any more info, this much will be in the
> archives.
> 
> Thanks
> Daryl

Hope this helps someone else in the future.  If korg
has the data sheet readily available, just call me
dumb, it was a lot of fun anyways.

Later
Daryl



__________________________________________________
Do You Yahoo!?
Get email alerts & NEW webcam video instant messaging with Yahoo! Messenger
http://im.yahoo.com