Noob question: Oscillator vs. Operator

Discussions about anything analog, digital, MIDI, synth technology, techniques, theories and more.
Post Reply
Envergure
Newbie
Newbie
Posts: 12
Joined: Wed Oct 01, 2008 12:39 am

Noob question: Oscillator vs. Operator

Post by Envergure » Wed Oct 01, 2008 12:51 am

What's the difference between an "oscillator" in subtractive synthesis and an "operator" in FM?

User avatar
Synthaholic
Expert Member
Expert Member
Posts: 1206
Joined: Tue Aug 21, 2007 5:43 pm
Gear: Motif XS6, TX802, D-550, A6
Location: NH

Re: Noob question: Oscillator vs. Operator

Post by Synthaholic » Wed Oct 01, 2008 1:25 am

An oscillator creates a waveform, which then (in a typical subtractive synth) goes into a filter, then an amplifier, and eventually to the audio outputs. On most synths, each voice consists of either 1 or 2 oscillators (or 3 in some cases like the Minimoog) feeding through a mixer into a single filter and VCA per voice.

An operator on an FM synth is (a digital representation of) an oscillator, envelope generator and amplifier (controlled by the envelope generator). The operator acts either as a carrier (makes a sound) or a modulator (which modulates another operator). The EG/amplifier for each operator is independent of each other (operators don't share a "VCA" like on a subtractive synth). FM synths generally have 6 operators (DX7 and its cousins), or 4 (DX11/9/21/100) per voice.

To go a step further, let me define a "partial" as used in the Roland D-50. A partial is the D-50's version of an operator, consisting of either a VA-style oscillator+lowpass filter, or a PCM wave generator, along with the digital amplifier (digital version of a VCA) and associated envelopes. Two partials are combined to make a tone (either in parallel, or one ring modulating the other), and a patch can consist of 1 or 2 tones (so, up to 4 partials). So, unlike a typical analog synth, the D-50's partials don't share filters, EGs or amplifiers.
Two VCO: thanks to the push rods, one can choose several forms of waves at the same time!
(from a Babelfish translation of a Jupiter-6 site)

Yamaha: Motif XS6, TX802 Roland: D-550 Alesis: A6 Andromeda

nuromantix
Junior Member
Junior Member
Posts: 104
Joined: Fri Jan 04, 2008 5:03 pm

Re: Noob question: Oscillator vs. Operator

Post by nuromantix » Wed Oct 01, 2008 3:00 am

Whilst the previous post is correct, a simple answer would be: they are the same thing - "Operator" is simply what Yamaha decided to call the oscillators in its 80s FM synths.

User avatar
xpander
Synth Explorer
Synth Explorer
Posts: 1541
Joined: Sat Jun 02, 2007 7:15 am
Gear: UltraProteus, Xpander, 200e, Minimoogs, Radias, Prophet VS, PolyEvolver, Arp 2600
Location: los gatos, california
Contact:

Re: Noob question: Oscillator vs. Operator

Post by xpander » Wed Oct 01, 2008 5:18 am

first, in FM as used by Yamaha (which is really phase modulation) it actually isn't using oscillators- scanned wavetables if i remember. second, Yamaha is describing these "oscillators" as used in the context of a greater mathematical function therefore operator is a correct mathematical label.

the real reason is mainly the first- FM synths hit when digital was big & new & especially not analog- so emphasizing that it didn't use oscillators (although "virtually" equivalent) was a selling point- it was different & new & digital.

RedElectricMoon
Newbie
Newbie
Posts: 13
Joined: Mon May 14, 2007 4:18 pm

Re: Noob question: Oscillator vs. Operator

Post by RedElectricMoon » Wed Oct 01, 2008 9:34 am

Whilst the previous post is correct, a simple answer would be: they are the same thing - "Operator" is simply what Yamaha decided to call the oscillators in its 80s FM synths.
It's not. Operator is a lot more than oscillator as Synthaholic said. A single operator is like the whole synth in itself from oscillator, through eg to amplifier.

By the way, some ppl say they prefer 4 operator synths to 6 operators because:
a) 4 ops are easier to program
b) they sound different
c) they have other waveforms than sines too.

*a) the principle is the same in 6 and 4 op synths, 4 op synths usually offer less choice of values for different parametres (less capable microprocessors) resultng in narrower sound palette.

*b) 6 ops can be programmed to sound the same as 4 ops - you can leave the remaining two operators inactive.

*c) If you do 4 ops sounds on a 6 ops synth, you have 2 ops free. With two ops you can create the remaining waveforms (saw, pulse, square, triangle) that arent available directly. You can use them in stacks as an audio source or a modulator. So it is not true that a DX7 cannot, for example, modulate a sine wave by a saw wave.

User avatar
Jack Spider
Retired Moderator
Retired Moderator
Posts: 902
Joined: Thu Nov 03, 2005 7:42 pm
Gear: -
Bit One
Boss DR-220
Boss DR-660
DSI Mono Evolver Keyboard
Korg LP-10
Roland XP-50
Yamaha QX21
Location: Old Blighty

Re: Noob question: Oscillator vs. Operator

Post by Jack Spider » Wed Oct 01, 2008 10:36 am

William's video explains things well:

http://insidesynthesis.blogspot.com/200 ... art-1.html
I didn't get where I am today by posting on internet forums.
http://www.myspace.com/thegreenalsatian
http://www.soundclick.com/greenalsatian

User avatar
CS_TBL
Synth Explorer
Synth Explorer
Posts: 1677
Joined: Wed Jul 12, 2006 3:47 pm
Gear: All "In-The-Box"
Mainly FM8
Location: NL
Contact:

Re: Noob question: Oscillator vs. Operator

Post by CS_TBL » Wed Oct 01, 2008 10:55 am

The bottom line is that FM is cool, regardless of whether you want oscs or ops!

FM is like a violin: a b***h to learn, a joy to play.
"You know I love you, CS, but this is bullshit." (Automatic Gainsay)
s: VSL/FM8/EWQL/LASS h: DX7/FS1r/VL70/SY77/SN2r/JD800/JD990/XV88/Emu6400/Poly61/Amek35:12:2/genelec1030 r: Violin/AltoSax/TinWhistle c: i7-4770/RAM32GB/SSD
FM8 vids

Envergure
Newbie
Newbie
Posts: 12
Joined: Wed Oct 01, 2008 12:39 am

Re: Noob question: Oscillator vs. Operator

Post by Envergure » Thu Oct 02, 2008 12:17 am

xpander wrote:first, in FM as used by Yamaha (which is really phase modulation) it actually isn't using oscillators- scanned wavetables if i remember. second, Yamaha is describing these "oscillators" as used in the context of a greater mathematical function therefore operator is a correct mathematical label.
Thanks! That makes sense to me.
CS_TBL wrote:FM is like a violin: a b***h to learn, a joy to play.
lol nice one!

Gregor Samsa
Junior Member
Junior Member
Posts: 107
Joined: Wed Mar 19, 2008 6:12 am
Gear: Too much (not enough).
Location: Chicago
Contact:

Re: Noob question: Oscillator vs. Operator

Post by Gregor Samsa » Thu Oct 02, 2008 1:02 am

The difference between an oscillator and an operator for me was about half a bottle of aspirin. I got rid of my dx- never could get a decent grip on it.
Image

User avatar
urbanscallywag
Newbie
Newbie
Posts: 39
Joined: Mon Apr 14, 2008 7:03 am

Re: Noob question: Oscillator vs. Operator

Post by urbanscallywag » Thu Oct 02, 2008 1:31 am

xpander wrote:it actually isn't using oscillators- scanned wavetables if i remember.
Why isn't a phase accumulator and a lookup table considered an oscillator?

Post Reply