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

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?

How is this setup ? Use the big Knob on top: ( also use triangle and square waves)

two_tones_2 edit.vcv (7.3 KB)

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You beat me to it! Yes, I think there are several osc with multiple outputs and phase controls. But this is the most well known, for sure.

Where is this Oscilloscope from? I don’t see it anywhere in the VCV Library.

It’s got the count modula logo on it.

Yeah, it didn’t show up in a search for me, either. Search could be better…

Indeed it does.

Yet scrolling through all 3 pages of VCV Library (Count Modula) reveals nothing about it, and the Count Modula user manual v1.14.0 shows two screenshots of it on page 40 illustrating behaviour other modules, but has no documentation for the OSCILLOSCOPE module itself.

Is it still in development or something? It looks great.

 Here’s a big piece of the puzzle - Count Modula Binary Sequencer - #3 by CountModula

Fair enough.

Some related stuff.

Assuming not all readers are into physics, but do like some simple and hopefully usefull experiments…

If a mixer does the summing/mixing of 2 (or more) sines cycling at the same frequency, then the phase difference between the signals/sines will just affect the overall amplitude.

But…as soon as we have more then one frequency in the spectrum, phase shifting and summing/mixing will affect the spectrum (relative amplitude of the frequencies in the spectrum). Roughly causing comb filter effects.

E.g. try phase shifting 2 saws, triangles or pulses/squares (e.g. try using Bogaudio XCO, an oscilloscope and a frequency analyzer).

Also when traveling from a sound source and reaching your ears, phase differences become relevant. The (minute) phase difference is then used to determine the direction of the sound source.

Since sound might need to travel a tiny bit longer to reach the other/furthest ear, the signal will be a bit further in its phase/cycle. Compare: Haas effect.

This is also why reverb algorithms include allpass filter to mess up the phase of the spectrum, suggesting differences in distance and direction for spatial effect.

And why summing nice and wide stereo signals back to mono might completely mess up the whole spectrum/sound.

Your brain is an amazing stereo spectrum analyzer.

It used to drive me crazy responding to alarms in Radio Master Control when I’d be trying to determine which device was emitting the piezo tone. The interference between multipath reflections would make you think it was over here, then move your head a few inches and it sounded like it was from … way over there…?

I have a private collection of modules (well several collections actually) that are either partially developed or are finished but not destined for release. The oscilloscope is in the former category. It is partially developed and only just functional. When it is finished and I’m happy with it, I will release it but it is not a high priority for me at the moment.

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My Answer at 4:16 pm 5th of May: I’m sorry, I’m a newby and not allowed to reply anymore before the next past 20 hours. The error was in the realtek audio settings on my pc!!! There is an option - in german it’s “Signalverbesserungen aktivieren” means something like “activate signal enhancement”. This tool kills what I wanted to see/hear! Sorry to everyone for the confusion! There was and is everything alright with the mixers, I can hear this after deactivating the option. Damn windows/realtek option… I spent 5 hours to detect this …and big thanx to Ahornberg again for convincing and bringing me to the source of the problem.

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Hello dag, thanx for your idea. I tested the Bogaudio XCO, I like its design and handling. But I don’t understand what’s the aim/use of it. I can influence the phase but it’s changing without doing something. Means phasedifference isn’t constant although I’m not switching.

Wasn’t the suggestion to use a different Bogaudio osc? There are quite a few of them, and they don’t all have the same features.

The Submarine Phased oscillators might help: They will happily generate tuned waves of the same shape, with independent phase control for each of the 4 waves

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And, btw, Submarine has several oscilloscopes that are super useful. If you need a “storage scope” or if you want to precisely measure some timing difference they are great.

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Haha. Yeah. I recognize that…trouble finding some annoying high pitched sound source.

Slightly off topic, but nonetheless related…

There might be some physics (and biology) behind that…

We are generally good at hearing in the mid range (e.g. where speech lives). Not so good at higher or lower frequencies. Less need for that apparently. Not just for spacial location, but also for hearing them at all (see Equal-loudness contour).

For spatial location: The higher the frequency, the shorter its cycletime/wavelength. At some point the wavelength wil be shorter then the distance between your ears. So comparing phase will no longer work (we run into sort of an aliasing issue, not picking up the same cycle with the other ears anymore, but a different/next one). At the lower side of the spectrum, the phase difference will eventually become too small to detect.

Wikipedia on Sound Localization

For frequencies above 1600 Hz the dimensions of the head are greater than the length of the sound waves. An unambiguous determination of the input direction based on interaural phase alone is not possible at these frequencies.

Going down the spectrum…we run into other issues…

For frequencies below 800 Hz, the dimensions of the head (ear distance 21.5 cm, corresponding to an interaural time delay of 625 µs) are smaller than the half of the sound waves. So the auditory system can determine phase delays between both ears without confusion. Interaural level differences are very low in this frequency range, especially below about 200 Hz, so a precise evaluation of the input direction is nearly impossible on the basis of level differences alone. As the frequency drops below 80 Hz it becomes difficult or impossible to use either time difference or level difference to determine a sound’s lateral source, because the phase difference between the ears becomes too small for a directional evaluation.

It doesn’t help that higher frequencies / shorter wavelengths completely phase in/out way faster then lower/longer. So when not only travelling directly from a source to ear, but also getting mixed/polluted with delayed copies, bouncing of surrounding surfaces, things get even more complicated real quick.

Miraculously, the brain has various other tricks to solve for many these issues. See Wikipedia article.

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This thread has evolved since my post in ways that I’m not qualified to discuss. I’ve only used the XCO when i need to match the phase from 2 different oscillators that i’m rapidly switching between.

Did you get all the information you needed to use VCV Rack in your experiments?

To just show/hear 2 sines phase in/out you can also use any oscillator (even ones without phase control). Just send output1 and output2 to an oscilloscope e.g. VCV Rack stock Scope). On that scope you can see both oscillator waveshapes plotted. Also send the output of each oscillator to a mixer, and the output of the mixer to another Scope. Here you can see the sum/mix of both waveshapes. Also send the output of that mixer to the audio output, so you can hear the mixed signal.

Now just detune one of the oscillators a bit. The first Scope will now show both oscillator shapes cyclically going in and out of phase. The second scope will show the sum of these signals. For a Sine wave this means the amplitude will cycle from max to silence to max etc. Since the same output is also going to the audio output you will hear a sine cycling from max volume to silence conform the amplitude on the second Scope.

A bit of a technical thing: you can synchronise the Scope(s) by using the output of an oscillator as an external clock (EXT under TRIG in the VCV stock Scope). This will give you a stable plot.

You can thus mix any oscillator output (any waveshape) and see/hear what will happen. You could add Frequency Analyzers for the oscillator(s) and the mixed signal to see the spectral content of both signals and their sum/mix. E.g. for a richer signal then a sine (e.g. 2 x Saw or Saw + Square or any combo/mix) you can see/hear the ‘phasing’ (comb filter) effect wherever the spectrum of both waves overlaps.

If you plan to use Bogaudio XCO, then I would suggest to connect from the “main” MIX outputs. Thus you can experiment with other waveshapes (or mixed shapes) too. You can use the individual MIX levels to control/modulate their individual output levels in the ‘main’ MIX (and if so desired, PHS for their individual phase).

Another technical thing: you may have noticed that both oscillators may have a stable phase. But not necessarily the same phase. If you want to use the PHS and want both oscillators to start at the same phase, you can connect the output of oscillator1 to the sync input of oscillator2. This will effectively restart the cycle of osc2 whenever osc1 restarts its cycle, forcing the same phase. The PHS will still change the phase though.

When synced, don’t detune them, since this will result in chopping (not finishing) osc2’s cycle/waveshape whenever osc1 restarts its cycle, changing its waveshape and spectrum and thus create the screeching ‘oscilator sync’ effect (due to the sharp ‘cut off’ edge) . But that’s another world.

Modulating Phase at audio rates will result in Phase Modulation (‘FM’), creating sidebands. But that’s another world to discover.