Korg35 Experts

[foRUMS 4 punkdISCO]

Thanks Tony - from what you say, it is definitely out of my ability..  Some
of the presets have quite a bit of resonance anyway so its not a biggy..

Btw, I just wrote up what I did and sent to AH:

To AH:
======
The Korg Sigma has 12 Korg35 filters (early MS20) but for some reason the
joystick and Filter CV Input only controls the 8 filters in the Synth
section and not the 4 filters in the "Instrument" section

The mod is very simple:
1)	Find the Joy Stick CV bus on board KLM-167C and connect this to
board KLM-168C:
a.	Electric Bass Korg35 IC pin 2 with 47k inline resistor
b.	Tuba Korg35 IC pin 2 with 47k inline resistor
c.	Horn Korg35 IC pin 2 with 44k inline resistor
d.	Trumpet Korg35 IC pin 2 with 31k inline resistor

The inline resistors are required to give optimum range of control otherwise
you might not have any audio until the Joy Stick is at, say, 50% etc.  The
existing front panel "fc" knobs for the above 4 instruments still give you
extra control so you do get some additional range control.

I wired in 4 way toggle switch so I can go back to factory.  It is pretty
handy having CV and Joy Stick just controlling the Synth filters, leaving
the Instrument filters as per their preset setup.  However, Im sure some
people might decide to just leave out the switch and have the extra control
permanent. 

Pictures:
https://flic.kr/p/ocCQAk
https://flic.kr/p/os5vMS
https://flic.kr/p/ou5M1G
https://flic.kr/p/otUp3A

I won't have time over the next few weeks to do any audio demo's but it
sounds frickin ace especially when you hook up some Envelopes or LFOs to the
Filter CV input giving you a proper 2 oscillator synth that can generate 19
waveforms all at once, running through 12 Korg35 filters!

I actually now prefer the Instrument section as the Joy Stick only controls
the LPF.  On the Synth section, the X-Y Joy Stick controls both LPF and HPF
and I always feel like there is no position that fully and independently
closes the LPF.  With the Joy Stick at 9oClock, this should be the LPF fully
closed so nice and bassy however, at 9oClock the HPF is also at 50% so you
actually just get a BPF at about 50%

With the Instrument voices (with this mod), with the Joy Stick at 9oClock,
you just get a lovely LPF almost fully closed (nice and bassy)

btw, I got a lot of pointers from this excellent page by Richard Atkinson
(thanks Richard, if you are read this..)

http://rga24.blogspot.co.uk/2010/04/korg-sigma.html

Schematic:
http://www.synfo.nl/servicemanuals/Korg/KP-30_SERVICE_MANUAL.pdf

hugs,

Paul
London
www.punkdisco.co.uk