AM (amplitude modulation) in Zebra?

[Sendy]

I know we have ring modulators, but I'm a fan of AM and was wondering if it was possible in Zeb. I have tried putzing around balancing a ringmodulator signal with it's carrier and modulator waves, but couldn't get the characteristic AM type waveforms. (Typically I like to comb waves with higher octave square waves, creating gaps of silence in the wave, which you can then modulate - this is only possible with AM AFAIK).

This maybe my lack of expertise, but if not, it would be awesome if the Ring module could have a knob that let you blend between AM and RM, or just a switch between the two.

[mcnoone]

This sound was done using 2 fm operators, using different fm modes.
1 of them is am.
http://www.box.net/shared/6x2ud64vcc
It's part of a bank, I'm working on.
Instead of describing it, just pm me, and I'll send you a link to it, so you can see what was done.

[Urs]

AM is equivalent to SignalA x (1 + SignalB), which is A + A x B

Thus if you mix a dry A into RingMod(A x B) using two Grid lanes, you get Signal A amplitudemodulated by Signal B.

Cheers,

Urs

[bmrzycki]

That should definitely be a tip for the manual. Urs, am I doing this right?

[mcnoone]

Here I thought it was something that could be done using the am modes of the fmo's.
Boy was I wrong.
These might help...
http://www.fas.org/man/dod-101/navy/docs/es310/AM.htm
http://www.tpub.com/neets/book12/48k.htm
http://en.wikipedia.org/wiki/Amplitude_modulation

[Howard]

That should definitely be a tip for the manual.

Added
BTW: The balance between Lanes 1 and 2 looks the same as what I ended up with (checked with Smexoscope) for full cancellation.

[bmrzycki]

That should definitely be a tip for the manual.

Added
BTW: The balance between Lanes 1 and 2 looks the same as what I ended up with (checked with Smexoscope) for full cancellation.

I did it by ear with 2 sawtooth waves (no detuning). I tried to find a sweet spot that made a similar sound to the AM slider on Reason's Thor, the only other synth I have that does AM. I was a bit surprised I had to boost the RM signal so much to get a similar feel. Even so, it's a great little trick!

[Sendy]

AM is equivalent to SignalA x (1 + SignalB), which is A + A x B

Thus if you mix a dry A into RingMod(A x B) using two Grid lanes, you get Signal A amplitudemodulated by Signal B.

Cheers,

Urs

Wouldn't it be awesome to be able to play the word "amplitudemodulated" in Scrabble... *dreams* ... Not possible in one swoop, but if "amplitude" was already on the board...

Anyway, thanks for the clarification. I could have sworn I tried that. I had both oscs and the RM module on their own lanes, and was messing with the mutes and levels. I'll give it another shot.

Mcnoone - thanks for your offer. I'll give you a shout if I get no luck.

And yes, AM is awesome in my opinion, much nicer than RM (unless you want to make Dalek voices!). You can really mess around with a waveform with it.

[Sendy]

Ok, problem solved. Here is/was my sticking point, for anyone interested:

I was using a PWM pulse as the modulator. If you set the levels up to give perfect cancellation for a 50% duty square wave, everything would be fine, until the duty changed, at which point things would go askew and you'd lose cancellation, ruining the AM effect.

This is, as far as I can tell, because Zebra's PWM, no matter how you make it (Symmetry, wavetable, phase tab), moves it's DC orientation up and down to take into account the relative power of the positive and negative portion of the waveform. This is in contrast to, say, TAL Noisemaker, whose pulse waveform never veers from the same two levels, regardless of duty cycle.

Therefore, when you want to amplitudemodulate a wave (i.e. sawtooth) with a PWM pulse (which is a really cool effect), you have to modulate the carrier lane's volume in proportion to the PWM modulation in the mod matrix, to exactly counteract the offset. This is easy enough to do by ear/sight. When you have the balance right you'll be rewarded with a sawtooth (or whatever) with a variable duty cycle.

From there you can do loads of cool things, such as effecting either the carrier or the modulator with sync sweeps, filters, sample reduction, changing octaves, etc. Some really gnarly, biting digital sounds to be had here

[bmrzycki]

Therefore, when you want to amplitudemodulate a wave (i.e. sawtooth) with a PWM pulse (which is a really cool effect), you have to modulate the carrier lane's volume in proportion to the PWM modulation in the mod matrix, to exactly counteract the offset. This is easy enough to do by ear/sight. When you have the balance right you'll be rewarded with a sawtooth (or whatever) with a variable duty cycle.

I'd be very interested to see/hear one of these presets. It definitely sounds unique.

[Sendy]

Therefore, when you want to amplitudemodulate a wave (i.e. sawtooth) with a PWM pulse (which is a really cool effect), you have to modulate the carrier lane's volume in proportion to the PWM modulation in the mod matrix, to exactly counteract the offset. This is easy enough to do by ear/sight. When you have the balance right you'll be rewarded with a sawtooth (or whatever) with a variable duty cycle.

I'd be very interested to see/hear one of these presets. It definitely sounds unique.

I haven't any finished presets in Zeb using this technique. I am making a soundbank for TAL Noisemaker, though, and have a whole bunch of sounds using this technique. If you like I can send those to you. If not, I'll put a few Zeb examples up when I get a moment.

[bmrzycki]

I haven't any finished presets in Zeb using this technique. I am making a soundbank for TAL Noisemaker, though, and have a whole bunch of sounds using this technique. If you like I can send those to you. If not, I'll put a few Zeb examples up when I get a moment.

I don't have Noisemaker. No rush on the Z2 presets, when you get a chance I'd be interested. Good luck on that bank!

[pdxindy]

Therefore, when you want to amplitudemodulate a wave (i.e. sawtooth) with a PWM pulse (which is a really cool effect), you have to modulate the carrier lane's volume in proportion to the PWM modulation in the mod matrix, to exactly counteract the offset. This is easy enough to do by ear/sight. When you have the balance right you'll be rewarded with a sawtooth (or whatever) with a variable duty cycle.

I'd be very interested to see/hear one of these presets. It definitely sounds unique.

+1

[Sendy]

Therefore, when you want to amplitudemodulate a wave (i.e. sawtooth) with a PWM pulse (which is a really cool effect), you have to modulate the carrier lane's volume in proportion to the PWM modulation in the mod matrix, to exactly counteract the offset. This is easy enough to do by ear/sight. When you have the balance right you'll be rewarded with a sawtooth (or whatever) with a variable duty cycle.

I'd be very interested to see/hear one of these presets. It definitely sounds unique.

+1

Well, some of my wavetables do exactly the same thing as what AM'ing a PWM pulse with another waveform does, so I'd recommend you check those out. However, there are benefits to using synthesis as opposed to wavetables. Firstly, there's more flexibility and modularity, and secondly, the resolution setting can be set at a minimum, since you're using static waves.

I'll post a few examples soon, as well as some other preset-sketches I've made, and my updated wavetable collection!