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Arp Odyssey Ring Modulator
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Arp Odyssey Ring Modulator
Hi, I built the Arp Odyssey Ring Modulator for Eurorack, but it seems not to be behaving. When I looked at the Schematic, a few things came to light...

Firstly, the call for a 4011N, I cannot find a 4011 with the suffix N anywhere.
I tried a MC14011BCP, a CD4011UBE, and neither worked, so I looked at the Arp Odyssey service manual and that calls for a 4011AE, I tried this and still no luck. Maybe there is a 4011N in some far reach of the universe, but sadly, I cannot find one anywhere.

I also checked the audio socket pinouts as that was mentioned, but my Lumberg sockets match the pinout precisely.

Then I noticed...

"+15V" in the schematic! Now, +15V is not available anywhere in a Eurorack system, yet the power header is clearly designed for a Eurorack system... Could this be the problem? I know some +15V circuits can be adapted to run with a +12V PSU with a few resistor changes, but which component changes would allow me to use this +15V circuit with a +12V PSU?
+12 or +15V doesn't matter. Are you aware that this circuit only digests pos. input voltages, but eurorack modules are allowed to output +-10V ? ;-) Neg. input voltage probably kills the 4011 due to missing input protection.
Are there any musical reasons to build such a crappy circuit, instead one of the many other ringmod circuits ?
EDIT: with "crappy" I don't want to blame ARP: the PDF says the original circuit was made for ringmodding 2 ARP VCOs. I bet they have the fitting voltage levels. But for common euro rack usage it's crap without AC coupling and level shifting the inputs to V+/2
This circuit is intended to be hardwired to the Odysseys VCOs square output, which is 0-15V. In order to get it to work typical (bipolar) VCOs, you'll have to dress up your signals before going into the 4011.

A simple comparator followed by a diode for each input will do. It'll also work with shapes other than square. Have a look at the schematic on this site and copy the front end:

It doesn't sound much like a ringmodulator or balanced mulitplier at all, by the way. It has it's own sound, which can be fun.
CD4011UBE should definitely work. I have those in my real Arp odyssey. Ring works great.

Not entirely relevent: I had heard that using real, vintage RCA 4011 chips on the VCOs would help with high frequency "bleed". I did not find this to be the case. The new 4011s seem the same to my ear.
It might help if you could go into more detail on what’s not working. Is it completely silent? Passing audio but not sounding particularly like a ring mod? Magic smoke going everywhere?

Was there anything in particular that led you to suspect the 4011 IC, or just that you couldn’t find one with the right suffix?
I dunno...

A 4011 CMOS chip will not tolerate negative (or bipolar) input or rail voltages as typical with modular synths. So one would either protect the chip from this upstream, or process input signals to add required offsets. Either of these will restrict functionality as the circuit was designed to deal with only with Odyssey VCO, and these only have unipolar (0 to +10V) outputs.

If you are not too invested with this by now, you might make an adjustment to the ARP 2600 ring mod, which won't be smoked by bipolar VCOs and is rather nice (or nasty if you prefer). The 2600 RM can double as a VCA.

While the OddyRM might be crappy in a patchable context, its not crappy in an Odyssey. I will volunteer that it is hampered because the Odyssey does not have sine shapers on the VCOs. Ring Mod is the most fun with sine waves. [if it did, there would be a different ring mod, because ARP's sine shapers result in bipolar outputs]
Ok, it seems to be working now after using positive only waveforms as suggested. If I'd realised this was the case, I would never have built one. Sounds great in my Odyssey though.

elektrouwe wrote:
Are there any musical reasons to build such a crappy circuit, instead one of the many other ringmod circuits ?

Asthetics, I wanted a DIY ring mod that was available with a black panel for my modular, this was the only one I could find... I'm building an all black system, my last system was all silver, my portable system is whatever goes...

Anyway, it's coming back out and going in my ever growing "crappy modules" pile, until I can find a decent one available with a black panel.
I’ve built a similar one using 4093 gates configured as an XOR.

You can condition the incoming waves with NPNs, and then follow the XOR with an op amp differential amp to shift the signal to bipolar. It actually works quite well and has a unique sound. I can post the circuit so you can see the IO handling if you like.
Not sure if this is helpful or not. I think it sounds pretty nice though.

Here's an alternative that I also like:

And then of course if you want a super clean multiplication there's always the AD633. I think the CMOS and diode ones sound a bit more unique though.
Would you mind to also post a few samples? thumbs up
degeneratedsines wrote:
Would you mind to also post a few samples? thumbs up

This one uses the CMOS one.
I like it a lot! it sounds very complex but that might be because you used an already complex sound source.
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