Why don't any synths do amplitude modulation anymore?

[Music Engineer]

Amplitude modulation is often called ring modulation.

is it? if so, then it is wrong. amplitude modulation modulates the amplitude like this:

Code: Select all

ampModOut = (1 + amount*modulatorOut) * carrierOut;

where modulatorOut is a signal between -1 and +1 and amount is between 0 and 1. if carrier and modulator are sine-waves, then the output signal contains the carrier frequency as well as the sum and difference frequency between carrier and modulator.

ringmod on the other hand is a simple multiplication of two signals:

Code: Select all

ringModOut = signal1 * signal2;

this signal contains only the sum and difference frequencies

[arke]

You're using Reason? Set the LFO2 on the Subtractor to Maximum Keyboard track, then the amount has to be set to a certain border value but I'm not sure which, I think its all the way down. Then just adjust the amount - voila, amplitude modulation.

[Meffy]

IM USING REASON HERE.

Saying so at the outset would've saved a good deal of wheel-spinning. It's a long way from "Why don't any synths do AM?" to "How can I do this specific kind of AM in Reason?"

If just hitting the "Tab" key and experimenting with CV cables and such doesn't get you going, I recommend heading over to the Reason forums, logging into the Props User Forum (where some genuine experts hang out), and asking there. Explain exactly what you want to do in your first post so people don't answer questions you aren't asking, and choose an informative, factual subject line. "How can I do this kind of AM in Reason?" would be a good choice.

[camsr]

arke, tried that but its not what Im after. Notice how you can select waveforms for the LFO, well instead of the built in waveforms I want to use the waveform of the oscillators. Cant do it in reason. The most I can do is use the Malstroms built in waveforms for its modulator, but not my own. Ill try them out and see if any are suitable.

[Meffy]

Ask EditEd4TV on the PUF. His ideas are always interesting and usually musically useful. A splendid chap.

[arke]

arke, tried that but its not what Im after. Notice how you can select waveforms for the LFO, well instead of the built in waveforms I want to use the waveform of the oscillators. Cant do it in reason. The most I can do is use the Malstroms built in waveforms for its modulator, but not my own. Ill try them out and see if any are suitable.

I'm sure theres a way, we just haven't thought of it yet

I don't have Reason installed so I can't try it, otherwise I'd already have a solution

[Borogove]

Amplitude modulation is often called ring modulation.

is it? if so, then it is wrong. amplitude modulation modulates the amplitude like this...

That would be the part where I said "technically that's not correct."

Note that your AM formula:

Code: Select all

ampModOut = (1 + amount*modulatorOut) * carrierOut;

Can be rewritten as

Code: Select all

ampModOut = (1 * carrierOut) + (amount * modulatorOut * carrierOut);

So consider a synth with a mixer stage where you can add the unmodulated carrier to the ring-modulated product (modulatorOut * carrierOut) in varying amounts -- you can smoothly blend between pure ring mod and your amp mod formula in the mixer.

That's why I don't think it's worth making much distinction between them.

[fac]

because amplitude modulation (other than the usual amp env) sounds crap

That was a joke comment, right?

[Rellik]

Note that your AM formula:

Code: Select all

ampModOut = (1 + amount*modulatorOut) * carrierOut;

Can be rewritten as

Code: Select all

ampModOut = (1 * carrierOut) + (amount * modulatorOut * carrierOut);

Woah...

Thanks for point that out - that was a big "audio math = audio reality" rush for me

[mojogigolo]

get vaz modular. end of story. (Amp mod and ring mod are essentially the same? craziness.)

[aciddose]

depth 0.0 ... 1.0
out = a * (b * depth + (1.0 - depth))

extremely simple. full am would be depth = 0.5 while full ring would be depth = 1.0

between is a smooth fade, with xhip try enabling ringmod and adjust the osc.b amplitude in the mixer.

works with normal waveforms, and pcm.

http://xhip.cjb.net/temp/adxhip_fix_3.dll

http://xhip.cjb.net/temp/am_ringmod.mp3

plain sine on both oscs, adjust osc.b from -48db to 0db and wiggle, via cc lfo->osb.b amp, funk.

[Music Engineer]

So consider a synth with a mixer stage where you can add the unmodulated carrier to the ring-modulated product (modulatorOut * carrierOut) in varying amounts -- you can smoothly blend between pure ring mod and your amp mod formula in the mixer.

That's why I don't think it's worth making much distinction between them.

yes, i see. this is also consistent with the fact, that RM contains sum and difference frequencies only, carrier aontains the carrier only (obviously) and AM contains carrier and sum and difference frequencies

[Borogove]

So consider a synth with a mixer stage where you can add the unmodulated carrier to the ring-modulated product (modulatorOut * carrierOut) in varying amounts -- you can smoothly blend between pure ring mod and your amp mod formula in the mixer.

That's why I don't think it's worth making much distinction between them.

yes, i see. this is also consistent with the fact, that RM contains sum and difference frequencies only, carrier aontains the carrier only (obviously) and AM contains carrier and sum and difference frequencies

Right. Now, in the case of RM'd pure sine waves tuned to the same or nearly the same note, that means that the carrier fundamental isn't present in the output spectrum, which is very noticeably different from the AM case, but if the carrier *or* the modulator has significant second harmonics, the carrier fundamental will reappear as a difference frequency. Obviously, in more complex cases where one or the other has an irregular spectrum or the frrequencies aren't simply related, it's harder to guess whether the carrier fundamental will appear.

[fac]

Just to add a few more ideas: if you have a synth that has two oscillators with ring mod, you can usually control the amount of each osc and ring mod in the mixer. Pure ringmod would be obtain by turning the oscillator levels all the way down, while standard AM would be when the three elements (osc1, osc2, RM) are at the same level.

Some synths that allow this configuration are PlastiCZ, VAZ Plus 2 (sort of), Waldorf Microwave 2/XT, and many others.

Also, some synths allow for AM but not RM (ie.- Wusikstation). In this case, all you have to do is mix the AM output with the inverted AM inputs, so the frequency components corresponding to the inputs will cancel out and only the sum and differences will remain.

[Meffy]

(Amp mod and ring mod are essentially the same? craziness.)

Do the maths. :-)