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Quad VCOs and phase cancellation - dreams of a Mono/Poly
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Quad VCOs and phase cancellation - dreams of a Mono/Poly
nashsnazzy
I was one of the folks that plunked down the coin for the iOS app of the Korg Mono/Poly. I must admit, I love the app, but I also miss my real Mono/Poly.

I'd like to have four VCOs buzzing away in my eurorrack. When I've tried this in the past I would loose volume when I added the 2nd and 3rd VCO in with the mixer. Do I need VCOs with soft sync to accomplish this?

Then there is the issue of x-mod. Is there an easy guide on how to patch the Mono/Poly style cross modulation in eurorack? I've seen other guides on how to cross modulate but I'm not sure if these are the style the Mono/Poly utilizes.

Any help is appreciated.
Cheers
Rex Coil 7
nashsnazzy wrote:
I was one of the folks that plunked down the coin for the iOS app of the Korg Mono/Poly. I must admit, I love the app, but I also miss my real Mono/Poly.

I'd like to have four VCOs buzzing away in my eurorrack. When I've tried this in the past I would loose volume when I added the 2nd and 3rd VCO in with the mixer. Do I need VCOs with soft sync to accomplish this?

Then there is the issue of x-mod. Is there an easy guide on how to patch the Mono/Poly style cross modulation in eurorack? I've seen other guides on how to cross modulate but I'm not sure if these are the style the Mono/Poly utilizes.

Any help is appreciated.
Cheers
Former Mono/Poly owner here. LOVED the danged thing, so much so that I've gone the extra mile to recreate some of it's glory in my own modular (a 4 VCO 5U system that's specifically designed to be a performance synth while retaining full-on modular capability).

While mine isn't a Euro machine (it's a Dot Com) I can say that I don't experience volume loss when all 4 VCOs are at full song in unison.

To reduce phase cancellation some, mix all four VCOs at slightly different volume levels. That really helps with keeping them from killing each others' output levels. Also, if you're using pulse waves with PWM, use PWM depth sparingly, and try to adjust each VCO's center-width a bit differently in each VCO (said another way, don't set all four VCO's initial pulse width at the same percentage, set them a little bit differently from each other).

It might help other folks with responding to you if you offer a bit more info, such as VCO brand/models, and mixer brand/model. There may be little issues with various VCO brands, or mixer brands/models.

X-Mod: I used the hell out that feature with my old Mono/Poly, it really made the synth fatten up a lot, and made it produce digital-type sounds ("Danger Zone" riff was nearly indistinguishable from the DX-7 that was used in that song). I don't know how many VCOs are involved when the "X-Mod" button is selected (that is to say, even if all 4 VCOs are in Unison mode, when the X-Mod button is hit I don't know how many of the VCOs are cross modulating .. it may have been only two at a time).

It may also be that in X-Mod mode (perhaps) VCO 1 is FM'd with the Modulation Generator oscillator, instead of cross modulating the VCO with another VCO. I simply cannot recall.

"Cross Modulation" can mean a lot of things, especially when that phrase is used as a sortof branding thing by a manufacturer. It may mean it very literally, or it may mean something less literal. If I had to guess (which I am) I'm going to say it simply is using two VCOs to frequency modulate one another. VCO1 is modulating VCO2 .... and VCO2 is modulating VCO1. If patchcords were involved, they'd be set up in an "X" fashion, one going from VCO1's output in to VCO2's FM input ... at the same time VCO2's output is fed in to VCO1's FM input ... like an "X" (hence "X-Mod").

In any case, all VCOs involved must be modulated by a VCO(s) that track 1v/oct (so the master and the slave are both tracking 1v/oct). That's how I set up my modular when I do cross modulation.

So ok .... that's all I got! smile

(Pic of my system, it's in a state of flux at the time the pic was taken, it looks a bit different now, but the 4 VCO architecture remains intact. Note the 4 VCOs in the upper row of the right hand cabinet, they are the only modules with yellow knobs ... the VCO mixer is dead center of the oscillators. I'm in the middle of a nearly full-on normalizing project with it at present .. nearly every patch cable seen in that picture will be replaced by hard wired connections .... those hard wired connections may be defeated through the use of normally closed switching jacks and patch cables).





(image of internal patching, the "normalizing rail" I installed is featured in this image)








Yes, I know my synth is a dirty little piggy .... I'm also addressing the dust issue inside of it, as well as making a full back panel to keep the dust out.

Hopefully others may offer some solutions to the "X-Mod" mystery ...

smile
moremagic
X-Mod on the Mono/Poly is VCO-1 to the other 3, or VCO 1 to VCO 2 and VCO 3 to VCO 4, depending on whether you have the switch set to single or double

In fx mode, you can select Sync (hard sync which follows the same direction as X-Mod), Sync & X-Mod, or X-mod, and also set the modulation depth from MG1 (which goes audio rate) to all VCOs.
nashsnazzy
Rex - Thanks for the info and for sharing!

Moremagic - So it sounds like X-mod is really just FM, is this correct?
Dave Peck
nashsnazzy wrote:


I'd like to have four VCOs buzzing away in my eurorrack. When I've tried this in the past I would loose volume when I added the 2nd and 3rd VCO in with the mixer.



I think there must be some information missing here. Simply mixing four slightly detuned VCOs together in a mixer module does not result in a drop in signal level.
Rex Coil 7
moremagic wrote:
X-Mod on the Mono/Poly is VCO-1 to the other 3, or VCO 1 to VCO 2 and VCO 3 to VCO 4, depending on whether you have the switch set to single or double

In fx mode, you can select Sync (hard sync which follows the same direction as X-Mod), Sync & X-Mod, or X-mod, and also set the modulation depth from MG1 (which goes audio rate) to all VCOs.
How is it that you know this? I'm not trying to be rude, I just want to know how you came about obtaining the information regarding how Korg set up the Mono/Poly.

I ask this because I've inquired about the Mono/Poly's features in the past. There were so many conflicting answers, it became clear that a number of responders were mistaken. I mean when one person says "blue" and another says "green", they obviously cannot both be correct.

So it would really help the technical credibility if you could say how/where you came about the information.

Again, not calling you out, just saying that it would really support your assertions if you cited your source.

Thank you!
moremagic
Rex Coil 7 wrote:
moremagic wrote:
X-Mod on the Mono/Poly is VCO-1 to the other 3, or VCO 1 to VCO 2 and VCO 3 to VCO 4, depending on whether you have the switch set to single or double

In fx mode, you can select Sync (hard sync which follows the same direction as X-Mod), Sync & X-Mod, or X-mod, and also set the modulation depth from MG1 (which goes audio rate) to all VCOs.
How is it that you know this? I'm not trying to be rude, I just want to know how you came about obtaining the information regarding how Korg set up the Mono/Poly.

I ask this because I've inquired about the Mono/Poly's features in the past. There were so many conflicting answers, it became clear that a number of responders were mistaken. I mean when one person says "blue" and another says "green", they obviously cannot both be correct.

So it would really help the technical credibility if you could say how/where you came about the information.

Again, not calling you out, just saying that it would really support your assertions if you cited your source.

Thank you!
uh, i play mine a lot so i know what it does i guess sad banana

theres been a number of threads where folks asked what a mono/poly does and ive always given the same answers cuz mines always done the same thing

as far as X-Mod vs FM . . . well i think Korg just weren't that great with the vocab back in the day. this was only a couple years after they stopped calling their filters 'Travelers' and used the letters VCF
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