Korg Poly800/EX800 Users

Just a quick buzz, i just finished modin' the Poly-800 to switch between a
12db/24db filter modes.

The 12db is really wicked, brighter fuzzier and it overdrives quite nicely. There
really is a huge difference between he two filter modes, so it's a worth while
mod to keep in mind. It's pretty straightfoward thanks to the pinouts provided
in the archives by Marjan.

Wonder why they left this feature off the the poly800, did they not realize how
smooth that phat filter sounds in 12db mode? Silly korg....

plutoniq9

On 14/7/02 12:57 AM, "plutoniq9" <Plutonique9@...> wrote:

Just a quick buzz, i just finished modin' the Poly-800 to switch between a
12db/24db filter modes.

The 12db is really wicked, brighter fuzzier and it overdrives quite nicely. There
really is a huge difference between he two filter modes, so it's a worth while
mod to keep in mind. It's pretty straightfoward thanks to the pinouts provided
in the archives by Marjan.

Wonder why they left this feature off the the poly800, did they not realize how
smooth that phat filter sounds in 12db mode? Silly korg....

plutoniq9

where can i get this mod for the Poly800mk1?

}:-S

Hi Plutoniq9!

I should have studied electronics if I knew that I would like to
modify synths, but I didn't.

Can you help with some more details how to switch 12/24db?

It sounds so cool what you're saying about the effect, so any K800
should have that switch...

Thanks in advance,
keep on tuning that thing,

Olaf

--- In korgpolyex@y..., "plutoniq9" <Plutonique9@h...> wrote:
> Just a quick buzz, i just finished modin' the Poly-800 to switch
between a
> 12db/24db filter modes.
>
> The 12db is really wicked, brighter fuzzier and it overdrives quite
nicely. There
> really is a huge difference between he two filter modes, so it's a
worth while
> mod to keep in mind. It's pretty straightfoward thanks to the
pinouts provided
> in the archives by Marjan.
>
> Wonder why they left this feature off the the poly800, did they not
realize how
> smooth that phat filter sounds in 12db mode? Silly korg....
>
> plutoniq9

Try something even better then just a mere switch: add a knob.
I was expecting that a panpot between 12db and 24db would allow wierd
values like 18db, but instead a bit of phase cancellation kicks in
and the sound becomes muffled, almost. Add a bit of flanger and it
sounds softer and warmer then a night's sleep on a feather pillow.
If your making music that needs harsh noises, you can still turn the
knob hard to either direction and hear 'pure' 12 or 24db, without
the muffling.

If anyone is intrested, I can post a sound byte...

On Tue, Jul 30, 2002 at 12:41:56AM -0000, plutoniq9 wrote:

> It seems that the most flexible way of Modifying the 12db/24db filter
> capabilities would be to add direct output jacks for each of the two filter modes
> + one audio input jack into the chorus unit. This, I think, would be the most
> non-limiting mod you could do.

I'll agree, non-limiting, but you'd need an external mixer to complete the
effect I discribed. Nothing at all wrong with that If you want your Poly to
be a near-modular, but I'm trying to keep gear to a minimum. I have a
tendancy to play live on occasion.

>
> Another worthwhile mod (while on the subject), would be to add an On/Off
> switch to turn the Noise Gate into bypass mode. I've found that the Noise Gate
> (Which is FET "F1" on the KLM-598 board), can indroduce a slight click when
> it switches + it seemed to be that it cut off the tails of the "Release envelopes".
> To add the bypass switch, use a SPST toggle switch to open/close a
> connection between Transistor "DTA1" emitter & collector pin (One will be the
> middle pin of the transistor the other will connect to Resistor "R19".

Did that a while ago, except I forgot the switch. No click for me, hah.

>
> Also, If you've added the VCF Audio Input mod I posted, here's a cool trick.
> While monitoring from the headphone output, patch one of the Poly-800's
> Line Outs back into the VCF audio Input. What this does is setup a Voltage
> Controlled feedback loop, IE. Envelope 3 will control the feedback level.
> So Imagine you set up Envelope 3 with a long Attack + Long Release
> Envelope, when you hit a note, both resonance + Chorus feedback will fade in
> with the Attack, release the note and it fades out... Pretty nice patch, you have
> to tweak the onboard resonance + the master volume knob to get useable
> results, but once you found it, it's a beautiful sound.

Is there any noticable difference between the left and right line outs?
Positive and negative feedback sound different when the chorus is used
as a flanger, there might be something with this as well.

>
> Peace
>
> P9
>

Check your schematic again. It's mixed into the right output in the opposite
phase. This is so that as the delay changes over time, one side gets duller
and the other gets brighter... standard feature of any stereo chorus unit.

It's done with a rather odd looking mess of opamps in the top-right hand
corner of the chorus board's schematic. It looks like it's only going to
one side, plot out what signals are going where and whether postitive or
negative phase and you'll see.

On Wed, Jul 31, 2002 at 01:05:30AM -0000, plutoniq9 wrote:
> Well, funny enough, I didn't think to use the Right output, but looking at the
> schematics I see that the chorus is only routed to the Left output.
> I'll check out patching the right output to the VCF input. Hopefully it works as
> voltage controlled resonance.
>
> Seeya
>
> P9

It seems that the most flexible way of Modifying the 12db/24db filter
capabilities would be to add direct output jacks for each of the two filter modes
+ one audio input jack into the chorus unit. This, I think, would be the most
non-limiting mod you could do.

Another worthwhile mod (while on the subject), would be to add an On/Off
switch to turn the Noise Gate into bypass mode. I've found that the Noise Gate
(Which is FET "F1" on the KLM-598 board), can indroduce a slight click when
it switches + it seemed to be that it cut off the tails of the "Release envelopes".
To add the bypass switch, use a SPST toggle switch to open/close a
connection between Transistor "DTA1" emitter & collector pin (One will be the
middle pin of the transistor the other will connect to Resistor "R19".

Also, If you've added the VCF Audio Input mod I posted, here's a cool trick.
While monitoring from the headphone output, patch one of the Poly-800's
Line Outs back into the VCF audio Input. What this does is setup a Voltage
Controlled feedback loop, IE. Envelope 3 will control the feedback level.
So Imagine you set up Envelope 3 with a long Attack + Long Release
Envelope, when you hit a note, both resonance + Chorus feedback will fade in
with the Attack, release the note and it fades out... Pretty nice patch, you have
to tweak the onboard resonance + the master volume knob to get useable
results, but once you found it, it's a beautiful sound.

Peace

P9

--- In korgpolyex@y..., trip@b... wrote:
> Try something even better then just a mere switch: add a knob.
> I was expecting that a panpot between 12db and 24db would allow wierd
> values like 18db, but instead a bit of phase cancellation kicks in
> and the sound becomes muffled, almost. Add a bit of flanger and it
> sounds softer and warmer then a night's sleep on a feather pillow.
> If your making music that needs harsh noises, you can still turn the
> knob hard to either direction and hear 'pure' 12 or 24db, without
> the muffling.
>
> If anyone is intrested, I can post a sound byte...

Well, funny enough, I didn't think to use the Right output, but looking at the
schematics I see that the chorus is only routed to the Left output.
I'll check out patching the right output to the VCF input. Hopefully it works as
voltage controlled resonance.

Seeya

P9

> Is there any noticable difference between the left and right line outs?
> Positive and negative feedback sound different when the chorus is used
> as a flanger, there might be something with this as well.
>
> >
> > Peace
> >
> > P9
> >

This is how I implemented the mod on my Poly. I hope this helps...

The filter chip is marked "Korg njm2069". In my Poly it's mounted in a socket,
making it very easy to notice. Solder wire leads to pins 5 and 6 (these are
the filter outputs.)

Connect these wires to the opposite terminals of a SPDT switch. Cut C103 from
the poly mainboard and solder it's negative terminal to the common point of
the switch, then solder a wire from it's positive terminal to it's positive
pin position on the board.

Make sure it works, then find a way to mount your switch in the case.
An interesting expirement is to mount a 100k pot in place of the switch,
one can get some really nice soft pads near the middle, gets really quiet
though.

On Tue, May 13, 2003 at 08:15:53PM -0000, evans_simard wrote:
> Hello.
> do you mind to provide me the details about the modification..
>

--

"Americans and freedom it happened. (APPLAUSE) We will not resent
world, and to America. Their prayers. It will come to stop it,
eliminate of thank your count."
-- Bush + Travesty Generator

Hello.
do you mind to provide me the details about the modification..

--- In korgpolyex@yahoogroups.com, moose <moose@p...> wrote:
> On 14/7/02 12:57 AM, "plutoniq9" <Plutonique9@h...> wrote:
>
> > Just a quick buzz, i just finished modin' the Poly-800 to
switch between a
> > 12db/24db filter modes.
> >
> > The 12db is really wicked, brighter fuzzier and it overdrives
quite nicely.
> > There
> > really is a huge difference between he two filter modes, so it's
a worth while
> > mod to keep in mind. It's pretty straightfoward thanks to the
pinouts provided
> > in the archives by Marjan.
> >
> > Wonder why they left this feature off the the poly800, did they
not realize
> > how
> > smooth that phat filter sounds in 12db mode? Silly korg....
> >
> > plutoniq9
> >
> >
> where can i get this mod for the Poly800mk1?
>
> }:-S