MUTOOLS

Nonno · Post by **Nonno** » Mon Feb 02, 2015 2:55 pm

Hi, I'm trying to make an AM patch in Mulab, but I can't figure out how to get unipolar signal. I read something about audio Audio pos/neg Splitter and Audio Inverter, but in this way I get 2 positive semiperiod (or 2 negative), both from 0 to max amplitude. In other word, I need something to add an offset and halve the amplitude to get an unipolar signal.
Thanks for help,
Gabriele

mutools · Post by **mutools** » Mon Feb 02, 2015 8:46 pm

You can use the ring modulator for doing AM. The second audio input will amplitude modulate the first audio input. Does this answer your question?

Nonno · Post by **Nonno** » Tue Feb 03, 2015 5:28 am

Yes, I know I have to use RM module. But, to make AM the second signal must be unipolar signal, whereas in RM the second signal is bipolar signal as the first is. This is why I'm looking for a method to make unipolar signal from a bipolar one.
Many thanks for you suggestions.

mutools · Post by **mutools** » Tue Feb 03, 2015 9:17 am

Why do you want the second signal to be unipolar? It's no prob that it's bipolar, when it goes negative it will still amplify the first signal but with inversed polarity, and that's ok, no?

camsr · Post by **camsr** » Tue Feb 03, 2015 2:15 pm

No, that's not the same thing. Ring modulation also makes negative sideband frequencys, in addition to AM's positive. He needs a module to rectify the signal, which is just the absolute value of the signal.

mutools · Post by **mutools** » Tue Feb 03, 2015 2:27 pm

If you need the absolute value of an audio signal, hook up a Pos/Neg Splitter and connect an Audio Inverter to the Neg output, then the pos output + inverted neg output combined give pos for pos and pos for neg = absolute. Hope i explain well.

mutools · Post by **mutools** » Tue Feb 03, 2015 2:41 pm

Ok i reread the OP and understand what you mean. You need out=(in+1)/2. (supposed audio is using the -1 .. +1 range) Doing the /2 is possible using an amplifier but the +1 is not yet possible cause there currently is no module yet to offset the audio. Added to the wishlist.

Nonno · Post by **Nonno** » Tue Feb 03, 2015 6:29 pm

Yes, thanks to camsr for the help. What I need is the possibility to add a DC offset to a wave, so that will oscill between 0 and 1. Amplitude modulation is like a tremolo but the frequency of the modulator lies in the audible range. Maybe is there a way to get amplitude modulation from a tremolo patch?
Many thanks,
Gabriele

mutools · Post by **mutools** » Tue Feb 03, 2015 7:20 pm

There indeed is a Tremolo preset in the library, have a look at it. But that's using an LFO and it sounds like you want to do it on audiorate, right?

mutools · Post by **mutools** » Tue Feb 03, 2015 9:06 pm

Ok, the next version has an Audio Unipolarizer module. Thanks camsr for the interesting info.

AndreasD · Post by **AndreasD** » Wed Feb 04, 2015 3:27 am

Jo,
not just make it unipolar, but to add DC offset can be quite helpful.
The OSC module in M4 were able to provide that, but a DC remover was added in M5.

mutools · Post by **mutools** » Wed Feb 04, 2015 8:53 am

The Unipolarizer is already in there (=in the forthcoming M6.3.3). So you want an extra "Add Offset" module? In what case can it be useful to add/sub offset to audio?

AndreasD · Post by **AndreasD** » Wed Feb 04, 2015 2:49 pm

Correct.
This could be the Constant Modulator for audio.
There are various uses, from harmonic distortion, create square waves and PWM the really analog way, and many others, as I usually use new modules extensively just to learn how to use them.
But, no pressure, just a suggestion...
And I didn't know that the unipolarizer is there already

mutools · Post by **mutools** » Wed Feb 04, 2015 5:15 pm

AndreasD wrote:from harmonic distortion

How so?

create square waves and PWM the really analog way

How do you mean? You can do all kinds of PWM using the MFO. And if you want to let it sound more analog you could start from a more analog (square) wave. No?

Just trying to understand the need for an audio offset module.

AndreasD · Post by **AndreasD** » Fri Feb 06, 2015 3:28 pm

There was the request for an Offset (aka DC voltage) for the audio channel (red connections).
With the new Unipolarizer that can be created. Jo, no further work is needed from your side.

Audio DC.jpg

What it does: The Unipolarizer adds an offset to the incoming audio. If you subtract the audio from the output of the Unipolarizer (done by the Audio Inverter), the offset is the remaining signal. With the blue Amplifier you can adjust the offset level. The red amplifier is to give the original audio the same level as the unipolarized audio, which is -6dB.

In the picture I used a test generator as input, but feel free to use any audio source you have around. The audio itself is eliminated entirely!!
So if you use this inside a Polysynth, use any oscillator or audio source you have.

EDIT: Safety warning: Do not let this signal go to your speakers/headphones. DC voltage will damage them. Always use a High Pass before you leave the digital world. Mulab is a clean application with no such HP installed by default

MUTOOLS

KVR Audio

Amplitude Modulation