MOSPhaser volume drop

[Footkerchief]

Hi, I just picked up a used MOSPhaser. Everything seems to be working fine, except that the output gain is way lower than the input gain. Is this normal for the module, or does mine have a problem?

[Synthbuilder]

Is this normal for the module, or does mine have a problem?

The output should be a little quieter than the unprocessed input signal. This is to allow for the peaks you get when you turn the emphasis control up full. How much quieter is it? And which version of the MOSphaser do you have? 5U or Eurorack?

[Footkerchief]

The output should be a little quieter than the unprocessed input signal. This is to allow for the peaks you get when you turn the emphasis control up full. How much quieter is it? And which version of the MOSphaser do you have? 5U or Eurorack?

Thanks for the info -- this is the Eurorack version. When I add the module to the chain, with Emphasis fully clockwise, I get about a 6 dB drop. The drop is even bigger when I turn Emphasis CCW (though I assume this additional drop is normal and caused by the filter design).

[Synthbuilder]

I get about a 6 dB drop.

This is probably working as it should. It has to reduce the input signal because at certain settings and with a 5V peak to peak input signal it will produce very strong harmonics that can exceed the +/-10V maximum output voltage and so will clip. Phasers can produce pronounced peaks and troughs in the frequency response. So at some input frequencies it will sound quiet, while at others it will be very loud.

You'll hear the effect if you use something like a 220Hz square wave straight out of an oscillator and sweep the frequency control.

A square wave, sawtooth wave, and white noise will also not sound as quiet through the phaser as a triangle wave or sine wave. This is because inputs with a broader spectrum are more likely to have at least some frequencies unaffected by the phaser's deep notches.

[Footkerchief]

I get about a 6 dB drop.

This is probably working as it should. It has to reduce the input signal because at certain settings and with a 5V peak to peak input signal it will produce very strong harmonics that can exceed the +/-10V maximum output voltage and so will clip. Phasers can produce pronounced peaks and troughs in the frequency response. So at some input frequencies it will sound quiet, while at others it will be very loud.

You'll hear the effect if you use something like a 220Hz square wave straight out of an oscillator and sweep the frequency control.

A square wave, sawtooth wave, and white noise will also not sound as quiet through the phaser as a triangle wave or sine wave. This is because inputs with a broader spectrum are more likely to have at least some frequencies unaffected by the phaser's deep notches.

All good to know, thank you!