Model 15/921B syncing

System 55 • System 35 • Model 15
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dschwabe
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Joined: Wed Jan 18, 2017 12:49 pm

Model 15/921B syncing

Post by dschwabe » Wed Jan 18, 2017 3:56 pm

I only recently got to try out oscillator syncing on my Model 15, trying to achieve the same screaming overtones that I am used to from my Voyager and pretty much any other synth offering sync. But to my surprise, the 921Bs don't react at all as expected. When I simply patch the SAW-out of OSC1 into the sync-in of OSC-2 and toggle between soft, hard and off positions of the sync switch I can hear the effect of getting both in perfect sync (when listening to a mix of both). But when I modulate the pitch of OSC-2 (e.g. a simple decay slope from the envelope) I would expect it to try to stay in tune with OSC1 but producing the typical overtones. But nothing like that happens in my case. I pretty much mainly hear the pitch modulation. Even just turning the fine-tune knob on the slave should give me some of that type of overtones, but doesn't.
I also followed hints from other threads to put the saw-out through the mixer first or even VCA to amplify the signal, but no difference. I also do keep the range of the master osc one or two octaves lower. I also tried switching the roles of two 921Bs, but the same issue persists (which tells me that there is likely nothing technically wrong with my modules).
Could someone clarify this for me? Am I doing something fundamentally wrong?
I don't have a long experience with Moog modular modules so probably don't know about certain quirks and idiosyncrasies.
Thanks!

EricK
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Joined: Fri Apr 09, 2004 2:09 pm

Re: Model 15/921B syncing

Post by EricK » Thu Jan 19, 2017 12:56 pm

You won't get that kind of sync from a Moog 921b.

Someone posted this video awhile bac

https://www.youtube.com/watch?v=ub2vQ7Ypls8


Here is an excerpt from an email from a friend of mine who talked about this issue with the production manager at Moog.
As it turns out, the 921 design was NOT the synch you and I want and know. It’s not what Seb offers on his 921b, nor is it what is on the Voyager or my Liberation or whatever dusty Moog you might have there. It’s a Phase Locked Loop synch which is way different from Hard synch and will only ‘lock’ when it is near certain harmonics (up to the 5th or something like that). So you can get some very minute degrees of that warbling sound in and around a few positions on the tuning dial but otherwise the locking breaks and you get beating/detuned effect which is NOT war we are after.
I think you can mess around with your 921's clamping point to do what you are trying to do but I forget at the moment how to patch it up.
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dschwabe
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Joined: Wed Jan 18, 2017 12:49 pm

Re: Model 15/921B syncing

Post by dschwabe » Thu Jan 19, 2017 3:06 pm

Thanks Eric.

Yeah, I found that video via a post on MuffWiggler after I had posted here. Exactly what I found myself doing and wondering.

Haven't had time yet to involve the 921 module (with its clamping for phase and waveform options) into the patch but will certainly try.

I find it strange that Moog even decided to offer a soft/none/hard "sync" switch on the 921B with the effects being so subtle.

I wonder how the Model 15 iPad app implemented the oscillator sync. I bet they went with the more well known behavior...

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