Yes. A REAL working data entry knob!
Go watch the vids of it in action!
http://www.youtube.com/user/SynthetechAfter figuring out what to tap into on the Korg's circuits and designing a decent way to decode an encoder's switching patterns (grey code) to drive / trigger the Korg's UP/DOWN buttons... I finally built a working circuit / mod!
Alot more time/effort was put into this than I ever imagined it would take, but it looks like after I tweak on it a little more I'll be able to protoboard it up permanently inside my Korg.
I'll be using an encoder that has a push down momentary switch so I can swap between Patch#, Parameter Group 1, Parameter Group 2.. then back to Patch # again.
I found out this encoder setup will not only change a parameter, but it will also allow you to go up or down when the screen is displaying the patch # (change patch#'s up or down).
Something odd did happen here and there while developing this mod... I believe it can erroneously trigger the Firmware Flash memory to CLEAR / erase out if the Korg's Ground signal manages to be passed on to Diode4 or 5 while booting the Korg on (or sometimes maybe if a +V signal goes into the Korgs ground signal???).
This was of course frightening the first time it happened, but all I needed to do was reload Firmware. The Boot/Patch memories were not affected.. so when I reloaded Firmware, it still had all my custom sounds in the Patch/Banks(whew!) and thankfully the Boot Rom was unaffected.
Sounds reckless that it happened, but I kept trying and this was the only bad reaction I would get from the Korg... it happened several times though :/
Mike, I dont know if there is a sequence of holding down a certain button while powering up that clears the Firmware.. but that's apparently what is happening... it will say on the screen CLOSE.. or even the word CLEAR.
Once I've seen one of those come across at boot, I have no firmware and it'll keep saying Error4 and Error6.. and of course if you check the firmware version, it'll say "0.0".
But it's an easy fix.. I only had to reload it back in (6 times now).. ugh.
I found that it was best to power on my breadboard in synch with the Korg.. I also suspect one of my encoders gets stuck in a "sweetspot" where the trigger circuit is sending a constant UP/DOWN signal to the KORG CPU when its booting.
When I used a encoder with dentents to let me know its in the ALL OFF position, I do fine. But if I used the encoder without detents, I suspect it was stuck so a constant ON signal was going thru while powering up.
Mike, if you know what might be doing this and a way to avoid it (place a diode in somewhere???).. I sure could use a suggestion.
Needless to say, its in early development right now.. plus I need to order more parts! Other encoders, other values of resistors and capacitors, a decent little protoboard to put it on and some kind of nice knob to complete it all.
It's looking like a higher end encoder like the "Bourn" encoders at Mouser with a 30ppr/30 detents value is the way to go. I tried cheapo Alps encoders and they were more prone to signal bounce than the Bourns.. but of course you pay 2x more for the Bourns.
And of course it'll be one with a push down momentary switch so I can trigger the Prog/Patch button.
A cool thing that can happen, as you'll see in the vids, is that if I slowly turn between detents and then stop between the detents.. it'll latch ON. IE: if you were going up and hit the latch spot, it will act like you are holding down the UP button continuously.. same thing for going DOWN. This is a jogwheel effect and may be useful at times for large values like 0-99. A 30ppr encoder will have to be turned 3 full turns to go from 0-90.
Thankfully most parameters are smaller numbers to adjust and can be changed within one full turn.
I don't have a schematic made up yet.. I'll post one when I get the kinks worked out.
To summarize the mod parts used in the vids:
24ppr/24 detent grey code encoder.
2 0.1uF electrolytic capacitors
2 1K Ohm resistors
1 7414 Hex Schmidt Trigger (inverting)
1 7474 Dual "D" Flip Flop
1 4066 Quad Bilateral Switch
that's it... plug them into a breadboard, wire them up, hook it into the Korg and magic happens. I did try using a Bourns 30ppr/0 detents encoder, but it gave me grief at power up. But when it did work, it worked very well.
-Blaine