Korg DSS-1 filter mod?

corroded.circuits · August 14, 2009, 03:04:58 AM

I've been entertaining the idea of picking one of these up to get my pads and drones fix. From what I hear the DSS shares the same filter as the DW-8000, and possibly the Poly-800?

I've seen one place (ClassA Electronics) that offers the cutoff/res mod for the DW but, have yet to see any info regarding a DIY mod. Has anybody tried this? Is it as simple as the sh-101 filter overdrive/cleaning mod? Just a matter of removing a resistor and soldering in a pot in it's place?

Info, opinions and feedback are appreciated.

Cheers

Circuitbenders · August 14, 2009, 01:04:42 PM

The DSS-1 uses the same filter chip as the poly800, its called the NJM2069.
Theres a load of info here:
http://www.sounddoctorin.com/synthtec/korg/njm2069.htm

If you're lucky there will be some callibration trimmer pots on the board that can just be removed and replaced with pots on the front panel. If not it looks like you'll be need to stick a control voltage into pin 13 or 14 somehow.

corroded.circuits · August 18, 2009, 10:00:53 PM

cheers for the info

YashN · October 30, 2011, 04:40:12 AM

Most probably you'll have to find a way of controlling all filters simultaneously with a small circuit and a pot.

I doubt you'll find answers here.

Quote from: corroded.circuits on August 14, 2009, 03:04:58 AM
I've been entertaining the idea of picking one of these up to get my pads and drones fix. From what I hear the DSS shares the same filter as the DW-8000, and possibly the Poly-800?

I've seen one place (ClassA Electronics) that offers the cutoff/res mod for the DW but, have yet to see any info regarding a DIY mod. Has anybody tried this? Is it as simple as the sh-101 filter overdrive/cleaning mod? Just a matter of removing a resistor and soldering in a pot in it's place?

Info, opinions and feedback are appreciated.

Cheers

YashN · November 16, 2011, 04:56:28 AM

I found a way to tap into the global cutoff and resonance of all filters simultaneously on a DW-8000 which is very similar.

Much fun.

Haven't gone round to actually performing the whole mod, but the tests are conclusive for now.

Circuitbenders · November 16, 2011, 11:55:18 AM

In theory i guess it'd be fairly easy to add a pot to anything with digital control over an analogue system simply by tapping into wherever the digital control becomes analogue.

I've used this to good effect on a Korg Poly61M where its a pretty simple job to find where the digital section creates the control voltages for the VCA and VCF etc, and to install pots to control the levels of these voltages before they get to the analogue section.

YashN · November 16, 2011, 10:41:51 PM

Yes, I guess the Poly61 is similar too and it's a question of getting those global traces rather than modding each of the filters separately. I saw a heavily modded DW-8000 on MatrixSynth recently, and I believe the person did it the wrong way, i.e. mods for each filter separately≥ This becomes a control nightmare, of course.

Getting that 12dB/24dB switch working on the other hand is a different story. I thought it would be an easy thing to do with an eight pole double throw switch, but little did I know then that these are extremely rare pieces indeed. I guess I'll have to find another way with analog switches and relays.

Circuitbenders · November 16, 2011, 10:50:21 PM

when i first started fiddling with my poly61M i was intending to use 4053 analogue switches to switch in and out entire sections of knobs at a time, or else you're kind of defeating the object of having a programmable synth. Ideally i'd be able to pull up a preset or saved sound and then switch in and out the 4 knobs for the ADSR if i fancied some realtime tweaking or not. Luckily it turned out that i'd only ever need a maximum of 4 switches at a time, and 4PDT switches are pretty easy to find.

YashN · November 27, 2011, 11:29:14 PM

A physical switch -> two 4-pole analog switches for the 8 lines.

Does that work?

Circuitbenders · November 28, 2011, 01:43:01 AM

you mean one toggle switch controlling 8 double throw CMOS switches?
I don't see why it wouldn't work. lots of guitar pedal makers use 4053's for switching don't they? I think you can only get 3PDT switches as CMOS so you'd need 3 IC's. i could be wrong though

YashN · November 28, 2011, 10:57:49 PM

No, I thought there were 4-Pole CMOS switches so I would have needed 2 of them, but 3 x 3-pole is fine too. I just need to switch the 8 lines with the least number of components and soldering.

YashN · December 16, 2013, 02:09:55 PM

Quote from: YashN on November 16, 2011, 04:56:28 AM
I found a way to tap into the global cutoff and resonance of all filters simultaneously on a DW-8000 which is very similar.

Much fun.

Haven't gone round to actually performing the whole mod, but the tests are conclusive for now.

Actually, although Res has a global point, Cutoff doesn't: I was tapping into one of the resistors for Voice 1, so only Cutoff for the filter in that voice was being controlled. Not sure if it can be done but I have seen someone mention using the Temperature Compensation circuit to feed it a global CV.

This links to Pin 14 if I'm not mistaken - the VCF Lin Input.

Would that work?