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Approximating Prophet-5's poly-mod on Prophet '08?

dswo

Approximating Prophet-5's poly-mod on Prophet '08?
« on: December 31, 2015, 09:08:22 AM »
To date, I've kept my instruments and my computer separate. (For some reason, an iPad doesn't seem to count as a computer.) But Arturia offered me such a good price on its V Collection Series 4, that I couldn't really say no. This morning I was flipping through the Prophet-V pad presets, trying to understand what makes them work, and wondering how I could approximate the original Prophet-5's poly-mod feature on the Prophet '08. Specifically, I'm interested in the pulse-width mod. Maybe it's just narrow experience on my part, but the poly-mod version of PWM seems different from the LFO version, and I can't figure out why.
« Last Edit: December 31, 2015, 05:11:24 PM by dswo »
David Wilson-Okamura
English professor

eXode

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Re: Approximating Prophet-5's poly-mod on Prophet '08?
« Reply #1 on: January 06, 2016, 03:36:53 AM »
Specifically, I'm interested in the pulse-width mod. Maybe it's just narrow experience on my part, but the poly-mod version of PWM seems different from the LFO version, and I can't figure out why.

On the Prophet 5 the LFO was global (i.e. one LFO that controls all voices simultaneously). When using OSC2 in LO mode on the Prophet 5 via the Poly Mod it acts per voice. This is also why modulation sounds different between the LFO and the Poly Mod.

All the LFO's on the Prophet 08 are per voice so that part of the Poly Mod PWM is approximated already, you can't get the standard LFO behaviour though as there's no way to make the P'08 LFOs global as far as I know. You can't do cross modulation at higher audio rates on the Prophet 08 (as the LFO's max out at C4, iirc), and you can't modulate one oscillator with the other on the P'08 either.

I hope this answers your question! :)
« Last Edit: January 06, 2016, 11:02:49 PM by eXode »

dswo

Re: Approximating Prophet-5's poly-mod on Prophet '08?
« Reply #2 on: January 06, 2016, 04:30:03 PM »
Thank you, eXode.
David Wilson-Okamura
English professor

Re: Approximating Prophet-5's poly-mod on Prophet '08?
« Reply #3 on: August 01, 2016, 02:24:20 AM »
Hey Guys,

Actually, assuming I understand what you mean by 'Global', what eXode says is not correct (sorry eXode ;)).  If you enable the 'Key Sync' button for each of the LFOs you want to be global, then those LFOs will stay in sync with each other across all voices.

Re: Approximating Prophet-5's poly-mod on Prophet '08?
« Reply #4 on: August 01, 2016, 07:50:37 AM »
...Presuming that, in polyphonic mode, the individual notes of your chords are all struck at the exact same time.  Otherwise, the LFOs will not be perfectly synchronized.
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Re: Approximating Prophet-5's poly-mod on Prophet '08?
« Reply #5 on: August 01, 2016, 08:20:18 AM »
I thought it was the other way around. If the LFO is NOT key sync'ed, it will be synchronized across all voices. I'll give it a try next time I have a chance.

Re: Approximating Prophet-5's poly-mod on Prophet '08?
« Reply #6 on: August 01, 2016, 10:21:00 AM »
From the Manual:

"Key Sync When this switch is enabled (lit) the LFO is re-started each time a new note is played. Key Sync is set independently on each LFO."

I always use Key Sync with LFO-generated filter sweeps in polyphonic mode to keep all the notes sweeping at the same time.  Otherwise, it's chaos.
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Re: Approximating Prophet-5's poly-mod on Prophet '08?
« Reply #7 on: September 01, 2016, 07:55:04 AM »
From the Manual:

"Key Sync When this switch is enabled (lit) the LFO is re-started each time a new note is played. Key Sync is set independently on each LFO."

I always use Key Sync with LFO-generated filter sweeps in polyphonic mode to keep all the notes sweeping at the same time.  Otherwise, it's chaos.

I finally had a chance to play around with this last night. I added a LFO to modulate the cutoff frequency and found ... that the modulation for all of the voices were in sync with each other, no matter when I played them. Strange. That's not the behavior I had seen earlier. Thinking that somehow I might be modulating a global parameter (clearly I wasn't but just in case) I turned key sync on and played notes at different times. The LFOs definitely got out of sync as expected.

Here's the interesting part. When I turned key sync off, the LFOs remained out of sync! This was the Aha! moment. The LFOs are always running (the LEDs are pretty clear that way) and retain their phase when the key sync is off. Since they are digital, their phase is exact. Thus LFOs that are in sync will always remain in sync as long as their frequency is not being modulated somehow.

In my case I had to get a bunch of LFOs that I forced to be out of sync to be back in sync again. Easy. Just turn key sync back on and play an eight-note chord. Then turn key sync off. At that point the LFOs were all back in sync again.

tl;dr -- if you're trying to approximate the Prophet 5's global LFO, you need to get your LFOs in sync by turning key sync on, playing an eight note chord, and turning key sync off again.