Calibrating output signal amplitudes

Hey module builders!

Suppose you build a VCO that has 3 output waveforms. Do you calibrate the amplitude of these to make sure they are the same volume or do most people don’t care about this?

And when you do, do you simply add a trimpot between the output and ground for this (given that you use an opamp before that)? A higher trimpot value raises the output impedance but lowers module power consumption. I’m thinking a 10k pot sounds like a good balance between the two.
Maybe I’m worrying about these things too much, but I’d like to learn from people who have made more modules and can perhaps tell me what to look out for. Or perhaps nobody bothers calibrating anything at all?

Thanks in advance!

If I don’t say stupidity, all the waveforms come from the Square, and the more they are “rounded / cut” the more they lose in dynamics.
It is therefore normal to have a Sine more low than a Triangle and this one than a Square.
Most people just leave it that way I think.
Otherwise it would be better to increase the low values, rather than lower the dynamics of Square.
I adjust them after in my mixer :slightly_smiling_face:


Agreed. I just adjust levels with a super simple mixer first stage.

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It’s a little different than that, some oscillators have a triangle core and others have a ramp core, from which other waveforms are derived, but that doesn’t make them smaller necessarily.

But it is true the amplitudes out of a 3340 are different for the different waveforms.

It is also true the perceived loudness depends on the wave shape as well as the amplitude. A sine wave sounds quieter than a square wave of the same height.

Rather than cutting volumes with trimpots on the outputs, a better approach is to add amplifiers on the outputs. That leaves you with larger amplitudes and lower impedance outputs. The Kassutronics VCO3340 for instance does that.

The MFOS VCO creates the triangle wave from the ramp in such a way as to keep the same ±5
V amplitude, the sine shaper has an amplifier as an integral part of it with a trimmer to set ±5 V, and the pulse wave is created as ±12 V and attenuated down to ±5 V.


Thanks for the replies. So having a consistent loudness/amplitude is not considered that important then.

t is also true the perceived loudness depends on the wave shape as well as the amplitude. A sine wave sounds quieter than a square wave of the same height.

That is a good point indeed!

One reason I am asking is because I’m doing PWM using an opamp comparator which gives me a pulse going from 12V to -12V. I figured that it might be good to attenuate this because I “think” it is good to have some headroom. Herhaps bringing it down to 10V/-10V or 8/-8V would be a good idea?

It is still good (read, convenient) if all outs of one VCO have the same amplitude (or loudness, up to you), so you can switch from one waveform to another without having to adjust levels on the “following” modules.

Yeah +/-12V is pretty hot…
Look here :

Audio signals are typically +/-5V, max +/-10V

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Thank you! That makes a lot of sense :slight_smile:

Absolutely do divide that down. ±5 V is commonly used for synth audio signals. Here’s the pulse wave section from the MFOS VCO: