Hi, i tried to understand the link with voltage amount with the volume or anything,
What do you use ‘bipolar’ function for to manipulate sound? obv it is going +_5 and unipolar is going only + or _ 10. when i am using lfo. what if i reduce the voltage to ±1? what it is linked with ? volume?
I can see unipolar got low frequency, and i dunno why it has it ?
I’m almost there to get it but i think i am missing the important one fact.
Thank you in advance.
Hi @musicismylife ! I’m not completely sure I understand your question, so please tell me if this isn’t helpful.
Audio signals are typically expected to be bipolar and centered around 0V. Otherwise they have what’s called “DC offset,” which is usually undesirable for something intended to be listened to. (By the way, the DC offset almost certainly explains the big low-frequency bump that seems to show up in EQMaster, which is designed for audio [=non-offset, bipolar] signals.)
The reason that many LFO modules have a unipolar/bipolar switch is that their primary use is to modify another module, and it’s a sound design choice whether you want that modification to go in both directions or only in one direction.
If you want to get a feel for this, I’d recommend reproducing the following modules (I’m using LFO instead of WT LFO because it plays more nicely with the scope, but the concept is the same):
The LFO is modulating the pitch of the VCO (note that this only works if the FM knob is turned up on the VCO–I’d use a small value, like 10%). With the right scope and frequency settings, you can see as well as hear this; with the LFO at 2Hz and the VCO at 60Hz, and the scope zoomed, you can see (as in the picture) that the audio peaks are closer together (higher frequency) when the LFO goes up and farther apart (lower frequency) when the LFO goes down). The VCA on the left reduces the amplitude of the LFO; the VCA on the right reduces the amplitude of the VCO. Both go to the scope, and the VCO goes to audio (make sure you have your headphone/speaker levels down for this patch).
Now, notice what happens when you (#1) change the offset setting of the LFO; (#2) lower the amplitude of the LFO; (#3) lower the amplitude of the VCO. (#1) changes the LFO from raising and lowering the pitch (bipolar) to only raising the pitch (unipolar). (#2) reduces the effect that the LFO has on the VCO’s frequency (same as turning down the FM knob on the VCO, except that you can control it with CV–try patching another LFO into the input of the left VCA and see what happens. Only (#3) actually changes the amplitude of the audio.
The way you phrase the question is confusing, but if I understand you correctly, one of your questions is about the role of unipolar versus bipolar signals for modulation. The answer is that you can use both, and the LFO police won’t come and arrest you, but one is better suited for some things and the other is better suited for other things. Examples:
The common “vibrato” effect, which is a slow modulation of the frequency of an oscillator, is best done with a bipolar LFO. The reason is that it sounds best, because the frequency deviation is equally distributed on either side of the actual VCO frequency. If you use a unipolar LFO instead it can easily sound out of tune.
The common “tremolo” effect, which is a slow modulation of the amplitude of an oscillator, is usually done with a unipolar LFO. The reason is that you usually want the amplitude to start at zero or higher and then peak at a bit higher than that, rather than have it completely pause its sound output at times.
My rule of thumb for using unipolar og bipolar signals for modulation is roughly this:
When you have a situation where the level of a parameter is dialed in to sound “just right”, but you want to modulate it a bit, it’s often best to use a bipolar modulator.
When you have a situation where a parameter “shouldn’t go lower than this” and you want to modulate it a bit, you dial it in to that lowest point, and then use a unipolar modulator. The same goes for the “shouldn’t go higher than this” scenario, where you instead dial in the highest point and then use an inverted unipolar modulator.
So it’s often a question of what is the easiest or most natural way to accomplish what you want, but often you can use either bipolar or unipolar, you simply learn it by doing it.
You are introducing DC offset when you do this. The electrical system that makes audio happen wants to swing around 0 volts, especially when at rest it stays at 0 volts. Otherwise, when your bottom signal is at rest it is about 5 volts above 0 volts. So amplifiers are constantly pushing out positive voltage when at “rest” and loudspeakers are pushed off of center and probably distorting. If this continues unabated it will destroy said amp and speaker eventually as they never rest and always output distorted signal and lots of noise especially in the low end. Try to avoid it in audio. Some mixers like MixMaster having setting to remove DC offset it detects in its signals, but it’s best to not offset audio signals.
this helped me to understand, thanks for the explanation.
Thanks for all detailed explanation that I wanted to know.
