Analog FM Synthesis?

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HideawayStudio
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Analog FM Synthesis?

Post by HideawayStudio » Fri Aug 20, 2010 12:26 am

I've been playing with discrete analog FM synthesis recently and really love the smoothness analog has to offer over digital in a domain obviously to later be totally eclipsed by Yamaha's DX series. My experiments have effectively been with modular equipment and so I'm wondering which vintage analog synths, if any, were capable of generating half decent FM timbres - eg. bells. The more I've experimented, the more I feel this is relatively unexplored territory for analogs (much like my opinion on the under-utilisation of formant filters/resonators in analog synthesis).

A Quick Demo of Some of My Analog FM Experimentation In Action:
http://www.sendspace.com/file/kz183k
Last edited by HideawayStudio on Fri Aug 20, 2010 12:43 am, edited 2 times in total.

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Re: Which Vintage Analogs Offer Usable FM Synthesis?

Post by ninja6485 » Fri Aug 20, 2010 12:42 am

how about the arp odyssey?
This looks like a psychotropic reaction. No wonder it's so popular...

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Re: Which Vintage Analogs Offer Usable FM Synthesis?

Post by HideawayStudio » Fri Aug 20, 2010 12:51 am

ninja6485 wrote:how about the arp odyssey?
Yes true... any decent demos of specifically FM timbres?

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Re: Analog FM Synthesis?

Post by Electroluver » Fri Aug 20, 2010 2:02 am

I think the Korg Monopoly uses some FM synthesis.

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Re: Analog FM Synthesis?

Post by Automatic Gainsay » Fri Aug 20, 2010 4:11 am

FM synthesis is not the same as "frequency modulation." To achieve actual FM synthesis (as opposed to mere frequency modulation), you have to be able to modulate an oscillator with an full-range oscillator, not just an LFO.
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Re: Analog FM Synthesis?

Post by smoothcriminal » Fri Aug 20, 2010 5:00 am

Is modulating the filter frequency with the oscillator or whatever the Akai AX60 does considered "FM?"

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Re: Analog FM Synthesis?

Post by pflosi » Fri Aug 20, 2010 6:49 am

Automatic Gainsay wrote:FM synthesis is not the same as "frequency modulation." To achieve actual FM synthesis (as opposed to mere frequency modulation), you have to be able to modulate an oscillator with an full-range oscillator, not just an LFO.
it's also handy to have sine waves…

Aside from that, there are plenty of synths that can do it. The A6 can create some nice FM timbres, though not vintage ;)

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Re: Analog FM Synthesis?

Post by V301H » Fri Aug 20, 2010 7:53 am

The Oberheim Matrix 12/Xpander is capable of two operator VCO FM which can be layered with other FM programmed voices for more complex sounds.

The Oberheim Matrix 6 and descendants are also capable of some simple FM synthesis with their stable DCO's.

The Roland Jupiter 6 gets some of the best bell-type sounds of any VCO analog I've heard using Cross Modulation or Oscillator Sync.

As mentioned the ARP Odyssey is exceptionally good at Ring Modulator bell/gong/chime-type sounds. Presumably the ARP 2600 is at least equally as capable.
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Re: Analog FM Synthesis?

Post by meatballfulton » Sat Aug 21, 2010 12:39 am

The weakness of "analog FM" is VCO instability, as the oscillators drift it's impossible to precisely control the sideband frequenciess. That's why most of the time it's limited to metallic and dissonant sounds.

Then you need lots of oscillators (a DX7 uses up to 6 per voice, 96 total) as well as a way to modulate the osc pitches and levels. That's why modulars are best suited for FM timbres.
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Re: Analog FM Synthesis?

Post by Virgule » Sat Aug 21, 2010 1:57 am

:)
Last edited by Virgule on Mon Oct 11, 2010 8:40 am, edited 1 time in total.

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Re: Analog FM Synthesis?

Post by HideawayStudio » Sat Aug 21, 2010 4:12 pm

Virgule wrote:Don't know if this is a fair comparison but interesting nonetheless.

"In analog polysynths, DCOs can be stable enough to maintain the precise frequency ratios required for FM synthesis. However, FM is only truly versatile when you have access to a large number of oscillators, VCAs and contour generators. Just consider the size of the modular synth that you would need to emulate a DX7: 96 oscillators, 96 VCAs and 96 multi-stage EGs for the oscillator levels, plus pitch envelope generators and their associated VCAs, innumerable mixers and heaven knows what else. The total system would incorporate hundreds of modules and weigh many tons."

From Synth Secrets, Part 12: An Introduction to Frequency Modulation, written by Gordon Reid (serialized in Sound On Sound).
Impressive but it's making assumption that the user requires polyphony and/or needs to synthesize the sound in real time :D My short demo at the top of this thread would require a monstrous modular setup if it were played live. That said, doesn't it just make the DX-7 seem even more of a marvel of hybrid electronic design! :shock:

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Re: Analog FM Synthesis?

Post by matia » Sat Aug 21, 2010 5:14 pm

i've taken DX7 algorithms and recreated them on a Serge and SMS rig. It sounded incredible but required SO many multiples, VCA's, and envelopes it was pretty ridiculous (in a really cool way). without a rig that big (9 panels of serge and a massive sms) i don't think i would be able to do it.

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Re: Analog FM Synthesis?

Post by hfinn » Sat Aug 21, 2010 5:54 pm

Roland Jupiter 8, Prophet 5, and matrix-12/Xpander come to mind...

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Re: Analog FM Synthesis?

Post by russell.mcclellan » Sat Aug 21, 2010 10:30 pm

A lot of people say that the unstable tuning is a main reason it's hard to do pure FM synthesis on analogs. While this is definitely a factor, it's hardly the largest impediment.

A big part of the DX7 sound (and in traditional computer based FM) is the notion of "negative frequencies", meaning that when you go past zero you get frequencies with the phase reversed. This turns out to be sorta hard to do in analog. Also, the bright, clean sound of FM sometimes relies on using sine waves as the base wave. It's not as easy to make voltage controlled sines as it is to make other wave forms.

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Re: Analog FM Synthesis?

Post by impaler42 » Sat Aug 21, 2010 10:37 pm

The Doepfer Dark Energy has FM synthesis capabilities, but whats really interesting about it is that they offer linear and exponential FM. I really enjoy messing around with the exponential FM knob. It can create some pretty metallic and disonant sounds.
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