MI Kinks outputs inverted

Eurorack
#1

I was patching with kinks and looking at the output on an oscilloscope. Both the half and full rectifiers are inverted - the negative half remains and the positive half is cut off. Has anyone else seen this with kinks or another module?

The min and max are working fine, as is the S&H section.

I did try a half-rectified wave from another synth to make sure it wasn’t the (software) scope that was faulty and that one appeared the right way up.

I’ve checked the power cable and that seems to be OK.

Any ideas on what to try next?

#2

I have never heard of this problem before!

Theory 1: all diodes (except one!), on your Kinks module have been cabled backwards. This has not been detected by the automated optical inspection, and again, this has escaped the factory test procedure.

Theory 2: your scope inverts the phase, and your other synth inverts the phase of its output. You mention a “software” scope. Which model/brand is it? You mention a “synth” – which one is it? It is not uncommon for non-modular devices, designed to operate on audio signals only, to not care about the phase of the output signal. Audio interfaces might sometimes do that too.

Do you have access to an actual scope to verify that? Or to a signal generator of trusted phase?

#3

Thanks for the response.

On further inspection it’s either the scope or my audio interface that is inverting the signal.

I did some patching comparing disting mode A4 (which is a half-wave rectifier) with kinks and it also appeared upside down. I also tried sending a unipolar audio rate LFO from MATHS channel 4 into kinks. If MATHS output was positive it passed through but not when it was negative. So it’s working correctly.

To answer the questions from theory 2: I’m using the VST oscilloscope from SocaLabs, hosted in reaper.
The synth was Pittsburgh Microvolt 3900. I was using the harmonic sine wave which is meant to be a sine into a half-wave rectifier. Strange that this wasn’t inverted.

#4

Then it’s theory 2: your audio interface inverts the phase of its inputs (it has no audible effect on audio anyway), and your synth doesn’t care about the polarity/phase of its waveforms (again, no audible effect). I have also sold several thousand units of a synth that didn’t try to get the phase of its output correct, and not only once did anyone complain about it!

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