# Beginner: Just want two tones and the sum of them

Hello!

I’am a teacher for physics. I want to show signals of two tones and superposition of them. To get not too confused I would like to use two scopes, one for the two tones not superposed and the other scope for the superposition.

I would be really happy for getting some help!

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@ Ahornberg: Thank you so much for your quick and very helpful reaction! This is exactly what wanted have!

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I see there still a further question for me: Is it possible to control the phase position of a sinus signal? I would like to simulate interference depending on phase. (Maybe I should open a new thread for this topic)

Maybe XFX Wave by Blamsoft could help here:

In the upper display of this module you see the scope.

In the lower display you can drag the volume of harmonic frequencies upwards and the phase of each harmonic downwards. See also the manual page 5 https://blamsoft.com/wp-content/uploads/2018/02/XFXWaveUserManual.pdf

This will reset both VCOs to start at the same point, and the delays can be used to shift the phases

Thanx again! Maybe it’s an useful tool for that but for me the description doesn’t sound like solving my problem. Maybe it’s not clear what I want to do. In the pictures you can see the green and red signal. The superposition is painted in blue. As we can see the amplitude of the blue depends on the difference of phases between the green and the red signal. That’s what I want to control: the difference of the phases.

Oh yeah! This looks great! Thanx! I got version VCV Rack c1.1.6 - where can I find Time and Triggers MKII?

If you want to show the effect pf phase differences as per that diagram and aren’t opposed to using an LFO, the Bogaudio 4FO offers control over the phases of the output signals:

Got It thanx again!

Wow! I’m flashed by VCV! That’s awesome! I’m doing my physics curses for 11 years now. This is the future and looks pretty cool and is really comfortable to handle! Thanx very much!

Just to add to my more knowledgeable colleagues Bogaudio XCO lets you set the phase of it’s outputs:

I’m not a physics person so that may not be useful to you.

This got a problem with superposed signal…

How we can see is the superposed amplitude zero because the phasedifference 180 Degree. But!!! the mixer puts out a sound anyway! It doesn’t care about the phasedifference

I tried it with yours devices - with the 4 FO und CountModula Mixer, coundn’t find the CountModula Oscilloscope. With that combination situation is just a little bit better : when phasedifference is 180 degree, output volume of the mixer is zero - that’s fine! But in every other case there is no difference between 20 degree oder 0 degree of phasedifference in the volume. Seems to me like a mixer kills the phase information and sums up an average volume of each signal. … Is there anybody who knows how to “teach” the mixer to treat the signals “right”?

Not at my PC at the moment, so I can’t check the patch. But there are different modules designed for summing and other operations (already in the core vcv modules). In addition try to set the VCO to digital, I don’t know if that has an effect on the sine wave, but on the other waves the analog setting is for a slight variation of the pure waveform. And another tip: Connect the square wave output of one vco to the “ext”-input of the scope and set the trig to ext. (right row) that way the display of the waveforms is synced.

Dear Markus, thanks for your advices. Switching on digital seems to bring no differences. Also synced to square wave makes no difference. But maybe I didn’t follow your instruction completely the right way.

There’s nothing wrong with the mixer (I mean for any mixer). Check out my video and you will see that there’s a difference in the volume when the phases differ 20 degrees or 0 degrees (watch the VU-Meter).

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Thanks for your video! Mmmhm, I can see: there is a big difference between 180 degree und not 180 degree. But when we left the “next-to-180-degree-area” there is no difference anymore in my opinion. Maybe we have to think about the logarithmic dB-Scale and/or the subjective-human feeling for volume - I don’t have enough expertise in that topic. So far I still believe there is something wrong. Maybe that has something do with latency. I noticed when I increase the sample rate - on the one hand I get a terrible sound, on the other hand I get more influence of the phasedifference to the volume.

I FORGOT TO MENTION: I mean there is no difference in the SOUND of your video far from the “next-to-180-degree-area”. The curves behave very well!

For example from 0:33 to 0:50 my audiosystem puts out same volume, whereas the amplitude triples!

The human ear perceives volume in a logarithmic way, that’s why the dB-Scale is a logarithmic scale.

There’s also no difference soundwise because the result of summing up this 2 sine waves is again a sine wave with the same frequency. If you use 2 sine waves with frequencies that are an integer multiply apart to each other, let’s say 200 Hz and 400 Hz, then mofifying the phase of one of these sine waves results in very subtle changes in the sound perceived by the human ear.

The human ear mostly distinct different sounds by different overtones. You have to do a frequency analysis of a sound to get it’s characteristic.

My ears percieve a rising volume from 0:33 to 0:50. Maybe your audio system doesn’t work as ecpected?