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Adding patch points+knobs to Korg's Arp Odyssy?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Adding patch points+knobs to Korg's Arp Odyssy?
WonderAliceLand
The original Arp Odyssey had the ability to be modified, allowing you to add 3.5mm patch points and knobs by drilling and soldering. I heard that Korg's Module Arp Odyssey (the version I have) is authentic to the analogue circuitry of the original and was wondering if it was to the point where you can still add patch points and knobs.

Would love more control as well as possibly being able to interface more directly with my eurorack.

Thanks in advance!
fuzzbass
It comes down to how Korg laid out the PCB. The Odyssey circuits are mostly just taken from various versions of the 2600, so semi-modularization is possible. On the schematic, you can create a section output by just teeing a line off the trace that connects to subsequent circuits. For inserts, you will need to interrupt input paths and place switched jacks in-line. On a 2600, most of the panel jacks are inserts to the inputs of the many CV and Audio mixers on the beast. The Ody has a bunch of such mixers too, albeit with fewer inputs. Look at the panel switches for section outputs and possible insert points.

I have not opened up my KARPODYSSEY, but the construction is undoubtedly SMD, and is probably small/dense/single board.
Jaytee
AFAIK, Korg used identical schematics as the original, to the point that they reproduced the frequency range design error in the 4072/4075 filter. So any mods that apply to the original will probably apply to the Korg version as well.

But as Fuzzbass surmised, it’s all SMT in there. Not the easiest to work with or trace. But if you’ve got a decent soldering iron and a steady hand, should, in theory, be possible to do what you’re asking. Kinda surprised we haven’t seen anyone try it yet tbh.
wackelpeter
Jaytee wrote:
Kinda surprised we haven’t seen anyone try it yet tbh.


warranty period isn't over yet… wink
Jaytee
wackelpeter wrote:
Jaytee wrote:
Kinda surprised we haven’t seen anyone try it yet tbh.


warranty period isn't over yet… wink


Warranty’s only a year, right? There are definitely some out-of-warranty Odysseys out there. That said, I suppose I can understand that fewer people will be interested in hacking on their $800 Odysseys than a $50 Monotron. hihi
wackelpeter
Jaytee wrote:
wackelpeter wrote:
Jaytee wrote:
Kinda surprised we haven’t seen anyone try it yet tbh.


warranty period isn't over yet… wink


Warranty’s only a year, right? There are definitely some out-of-warranty Odysseys out there. That said, I suppose I can understand that fewer people will be interested in hacking on their $800 Odysseys than a $50 Monotron. hihi


hmm… not 100% sure but i think it's 2 years at least here in Germany...

But yes, you're Right i had laid Hands on my monotron faster then he could blink with an eye… i assume he's still working… but haven'T touched for years…
WonderAliceLand
fuzzbass wrote:
interrupt input paths and place switched jacks in-line


Is this soldering or drilling and soldering? My wife is worried about drilling into the board, as the odyssey is our most expensive single piece of equipment by a good margin.
Jaytee
WonderAliceLand wrote:
fuzzbass wrote:
interrupt input paths and place switched jacks in-line


Is this soldering or drilling and soldering? My wife is worried about drilling into the board, as the odyssey is our most expensive single piece of equipment by a good margin.


You won’t need to drill into the PCB, but you will likely need to cut some traces on the PCB to allow new inputs. Cut traces can typically be repaired, but...if the thought of making permanent alterations to the odyssey makes you uneasy, it may be best not to embark in the first place.

Drilling the case/panel is probably inevitable too, unless you’re thinking of some kind of breakout box?
WonderAliceLand
Jaytee wrote:


You won’t need to drill into the PCB...if the thought of making permanent alterations to the odyssey makes you uneasy, it may be best not to embark in the first place.

Drilling the case/panel is probably inevitable too, unless you’re thinking of some kind of breakout box?


My Odyssey already has the freerun LFO on it, so I know the warranty has been void. Thinking about taking the faceplate off, strip the paint off, and paint it like a scene from Alice in Wonderland, probably a combination of the tea party, the hookah smoking caterpillar, and the Red Queen's Courtroom. Also I plan to drill a few holes in the top and will probably do that after I strip the paint. I would like a nice interface and a new look.
Jaytee
In *that* case... post some pictures when you’re done! This sounds like a super rad project!

For the cut traces, you’ll already be soldering to either side of the cut trace to install the normalled jack, either by finding a convenient pad further down the trace or by carrrrefully scraping back some solder mask to expose the copper trace, so if you end up wanting to repair the trace, just replace the jack wiring with a jumper. I might practice on some scrap PCBs first.
WonderAliceLand
Jaytee wrote:
I might practice on some scrap PCBs first.


I have quite a few extra, so I'll give it a try. Depending on how that goes I'll either open it up or not... I'm good with hardware but I haven't even soldered together my first 3340 VCO (still waiting for parts), so putting that solder to the arp is really worrying me.

My big problem is I don't know where to find a layout of which paths are what, so I don't know where to look for (or scratch off) a spot.

Really inspired by these pics:
Jaytee
WonderAliceLand wrote:
Jaytee wrote:
I might practice on some scrap PCBs first.


I have quite a few extra, so I'll give it a try. Depending on how that goes I'll either open it up or not... I'm good with hardware but I haven't even soldered together my first 3340 VCO (still waiting for parts), so putting that solder to the arp is really worrying me.

My big problem is I don't know where to find a layout of which paths are what, so I don't know where to look for (or scratch off) a spot.

Really inspired by these pics:


So what I would do is download the Odyssey service manual (the original ARP one; the Korg one is probably not available), and maybe the 2600 service manual as well. Spend some time with them to get an idea of where useful inputs and outputs might be, on a theoretical level. Print them out even, and make some notes. After that, it would be time to crack open the Korg and start poking around. It won’t be an easy task to correlate the SMT parts to the schematic, but with enough double-checking with a multimeter, you should be able to get there eventually.

And yeah, in the meantime, practice practice practice. Up above I was meaning practice scraping away traces to reveal a copper layer you can solder to, but soldering practice too. Through hole is easier to mod because there are all kinds of component legs and big pads to solder to; SMT is more difficult because there’s just not much extra space to add wiring that wasn’t originally intended. But it’s not impossible!
artilect99
Can you elaborate on the free-run LFO mod, if you know how it was done? I know how it was done on the original because there is documentation everywhere, but the difference in physical layout between the original THT and the SMD Karp is the problem... maybe you could post a pic of the board where the modification was done? That would be amazing....

As far as modularizing the Karp, this is something I've been wanting to do for a long time too. There's tons of documentation on it for the original, so the problem seems to come down to translating from the original layout to the new SMD board layout.

General wisdom seems to be that lots of signals are brought out to the panel already in the form of switches, so adding outputs is easy (theoretically, though I can't find anybody who's done it. hyper )

Adding normalled inputs is a little harder bc it involves cutting traces and using switching jacks, but in theory no big deal -- it's just about translating between the schematics and the SMD layout.

Let's say someone was going to do this -- what jacks would be most important?

The S/H mixer goes everywhere on the Ody so if you added input jacks to that, you could inject external signals into just about anything.

I'd also want DC coupled noise outs, direct osc outs, envelope outs, VCA in, maybe a 1v/oct in for osc2 if thats possible... if I could decide on what ins/outs to do I would be one step closer to seriously f**king up my arp... MY ASS IS BLEEDING
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