Cross Mod, Audio Mod, Ring Mod?

Discussions about anything analog, digital, MIDI, synth technology, techniques, theories and more.
Post Reply
User avatar
Distorted_Frequency
Newbie
Newbie
Posts: 58
Joined: Tue Oct 05, 2010 2:31 am
Real name: Rob
Gear: DSI Prophet 08, Univox MiniKorg K2, Roland Juno 106, TR-909. RIP Custom Guitars, Rocktron Prophesy Pre, VHT 2:90:2, Rocktron Midi Mate.
Band: ToxicDose

Cross Mod, Audio Mod, Ring Mod?

Post by Distorted_Frequency » Tue Oct 08, 2013 7:01 pm

Are cross mod and audio mod the same thing? If they are, is that the same as freq mod? Also are they different from ring mod?

I read SoS Synth Secrets, Part 13 and technically understand what is happening, but can't find enough applicable information to discern the 4 types of modulation.

All I know for sure is ring mod makes DEVO sounds haha

Thanks,

Rob
Image
FAST, LOUD, RUDE!!!

commodorejohn
Synth Explorer
Synth Explorer
Posts: 1574
Joined: Mon Aug 12, 2013 2:39 am
Real name: John
Gear: Roland JX-10/SH-09/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/X5DR, Ensoniq SQ-80, Oberheim SEM
Location: Sacramento, CA
Contact:

Re: Cross Mod, Audio Mod, Ring Mod?

Post by commodorejohn » Tue Oct 08, 2013 7:25 pm

I'm not entirely certain. I've read plenty of commentary that says "cross mod" = FM, but a lot of times in the manuals for the synths which feature it it's claimed that both oscillators affect each other's timbre (?) But on my JX-10, at least, it responds like FM and only affects the timbre of one oscillator, so it's possible the manuals are just full of it. (My Matrix-6 manual makes a similar claim about one of its sync settings, but I've spoken to a guy who's looked at the internals, and it doesn't sound like there's any kind of FM at all!)

In any case, frequency modulation isn't the same thing as ring modulation (which is just another name for amplitude modulation.) They do have similar effects on the sound, but AM (as I understand it - mostly from Synth Secrets) only produces one pair of sidebands for each pair of frequencies in the two input signals, while FM produces a whole series for each pair.
Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73

User avatar
meatballfulton
Moderator
Moderator
Posts: 5837
Joined: Wed Apr 13, 2005 9:29 pm
Gear: Logic Pro X

Re: Cross Mod, Audio Mod, Ring Mod?

Post by meatballfulton » Tue Oct 08, 2013 8:34 pm

On some analog synths the term cross mod means exponential FM (frequency modulation), one VCO is the carrier, the other the modulator. This may be termed audio mod, X-mod or just FM on some synths.

Audio mod on Dave Smith synths in particular is exponential FM of filter cutoff by one of the DCOs.

Ring modulation is similar to AM (amplitude modulation) except the output contains only the sideband frequencies, the carrier and modulator frequencies are absent.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

User avatar
nathanscribe
VSE Review Contributor
VSE Review Contributor
Posts: 2889
Joined: Fri Aug 11, 2006 1:03 pm
Location: The right side of the Pennines
Contact:

Re: Cross Mod, Audio Mod, Ring Mod?

Post by nathanscribe » Tue Oct 08, 2013 9:39 pm

What he said.

Also, whereas Cross Mod is usually a term applied to synths with oscillators tied to the same basic control source (regular analogue polys, for example, where the pitch is mostly going to be audio frequency and pitched to a scale governed by the keyboard before adding modulation), FM can be more broadly applied to systems where oscillators can be more happily independently controlled (sub or sper-audio frequencies, non-scaled, and not necessarily primarily driven by the keyboard or basic pitch control source).

Clearly I'm generalising, but I've mostly seen the term X-mod or Cross Mod used on fairly standard synth architectures, FM on freer systems.

max badwan
Active Member
Active Member
Posts: 298
Joined: Tue Aug 06, 2013 1:34 am
Real name: Max
Gear: T1, XV 5080, ES1, Zaquencer
Location: Sydney, Australia

Re: Cross Mod, Audio Mod, Ring Mod?

Post by max badwan » Wed Oct 09, 2013 1:01 am

For what it's worth, Cross Mod on the JX 8/10 is (1) hard sync (DCO 2 locked to DCO 1), (2) cross-mod (DCO 1 and DCO 2 mod each other), similar to ring mod, and (3) 2 op FM (DCO 1 carrier, DCO 2 modulator).

max badwan
Active Member
Active Member
Posts: 298
Joined: Tue Aug 06, 2013 1:34 am
Real name: Max
Gear: T1, XV 5080, ES1, Zaquencer
Location: Sydney, Australia

Re: Cross Mod, Audio Mod, Ring Mod?

Post by max badwan » Wed Oct 09, 2013 1:03 am

Audio mod on Dave Smith synths in particular is exponential FM of filter cutoff by one of the DCOs.

So the same as Poly Mod on the SCI Prophets?

commodorejohn
Synth Explorer
Synth Explorer
Posts: 1574
Joined: Mon Aug 12, 2013 2:39 am
Real name: John
Gear: Roland JX-10/SH-09/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/X5DR, Ensoniq SQ-80, Oberheim SEM
Location: Sacramento, CA
Contact:

Re: Cross Mod, Audio Mod, Ring Mod?

Post by commodorejohn » Wed Oct 09, 2013 1:20 am

max badwan wrote:For what it's worth, Cross Mod on the JX 8/10 is (1) hard sync (DCO 2 locked to DCO 1), (2) cross-mod (DCO 1 and DCO 2 mod each other), similar to ring mod, and (3) 2 op FM (DCO 1 carrier, DCO 2 modulator).
Really? The way the manual makes it sound, setting 2 is a combination of hard sync (1) and cross-mod (3).

Hmm. Now I've got a synth capable of ring modulation for comparison, I'm gonna have to run some experiments on this...
max badwan wrote:Audio mod on Dave Smith synths in particular is exponential FM of filter cutoff by one of the DCOs.

So the same as Poly Mod on the SCI Prophets?
The Matrix-6 has this capability as well (I think the Matrix-12 does too.)
Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73

User avatar
meatballfulton
Moderator
Moderator
Posts: 5837
Joined: Wed Apr 13, 2005 9:29 pm
Gear: Logic Pro X

Re: Cross Mod, Audio Mod, Ring Mod?

Post by meatballfulton » Wed Oct 09, 2013 3:18 am

max badwan wrote:So the same as Poly Mod on the SCI Prophets?
No, different.

Never owned an SCI but Wikipedia sez:

The "Poly-Mod" feature routed the output of the filter envelope generator and the second oscillator in each voice through two mixer knobs, which could then be connected to the pulse width and pitch controls on the first oscillator, to the filter cutoff frequency control, or all three at the same time.

In other words a super-simple mod matrix with 2 mixable sources and three selectable destinations, all getting the same modulation mix. This allows audio rate filter FM (filter modulated by osc 2) and audio rate osc FM (osc 1 modulated by osc 2).

On DSI synths Audio Mod is fixed to filter cutoff only (i.e. filter FM). The DSI mod matrix goes way beyond what PolyMod with four mod routings between dozens of sources and dozens of destinations each with it's own depth parameter, but the two analog DCOs are not available as mod sources so audio rate osc FM is not possible.

DSI Evolvers have two more 100% digital oscillators and allow FM and/or ring modulation of each other. Being low resolution digital this easily leads to aliasing, turning all four options on at once quickly yields super ugly metallic noises.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

Post Reply