u-he

hakey · Post by **hakey** » Mon Feb 12, 2018 6:54 pm

Can anyone think of a clever way to rectify a signal, eg, the output of an oscillator, in ACE?

Failing that, a stupid way would do.

Howard · Post by **Howard** » Tue Feb 13, 2018 8:38 am

Stupid way here… at least it *seems* to be almost full-wave rectification.
BTW I arrived at this solution after 10 minutes trial-and-error. I haven't worked out how/why it works yet.

Screen Shot 2018-02-13 at 09.32.36 .png

hakey · Post by **hakey** » Tue Feb 13, 2018 1:58 pm

Thanks, Howard.

Will give it a go.

hakey · Post by **hakey** » Tue Feb 13, 2018 2:49 pm

Thanks for the suggestion, but I can't get it to work here.

Looking in the scope, the signal starts above the origin but quickly wanders back (the +5V DC gets filtered by a HPF?).

Maybe I'm missing something... what values are the multiplier knobs set to?

dlarseninclusive · Post by **dlarseninclusive** » Wed Feb 14, 2018 4:10 am

I was tinkering with this, (Good looking out Howard... you are of course the man) so far for me the +5v, does rectify the signal, but also drops it a number of octaves. (Might be 5, have not measured) But too low to hear.

Howard · Post by **Howard** » Wed Feb 14, 2018 5:21 am

You guys are doing something wrong. The multiplier is of course either +1 or -1, you can see that the multiplex (sic) knobs are close to 50% (tune them by ear) and there is no "octave drop" whatsoever. Try harder!

hakey · Post by **hakey** » Wed Feb 14, 2018 9:17 am

My attempt at copying Howard's patch and the result.

Various combinations of multiplex knob values tried, to no avail.

What am I missing?

ACE_rect1.png

ACE_rect2.png

Edit: viewed close up, the resulting waveform looks like a cycloid. Rectifying a triangle wave should produce a unipolar triangle double the frequency of the original?

Satch1 · Post by **Satch1** » Wed Feb 14, 2018 1:36 pm

You don’t need the +5V. Just connect the signal to a left input and the mod input, and set the amount to max. This works really well with a sine wave but with other waves it adds harmonics, so the signal is an octave up but a bit different than just pitching the original wave up an octave. That’s what I’ve found anyway.

hakey · Post by **hakey** » Wed Feb 14, 2018 1:44 pm

I don't get a rectified signal with that method, Satch. The signal is still bipolar.

Satch1 · Post by **Satch1** » Wed Feb 14, 2018 1:59 pm

Yes you are right. I thought it was shifting the polarity, but it was just squeezing the waves peaks and troughs together. I tried it with Howard’s approach again with an LFO modulating the filter and that seems to do the trick... unipolar with twice the rate.

hakey · Post by **hakey** » Wed Feb 14, 2018 7:22 pm

Sorry, Satch, I don't follow you. Does the signal run from the multiplex into the filter?

Howard · Post by **Howard** » Wed Feb 14, 2018 9:15 pm

hakey wrote:I don't get a rectified signal with that method, Satch. The signal is still bipolar.

Sure it's bipolar - there's a DC blocker on the output (and elsewhere IIRC). However, your triangle wave should definitely have double the frequency now.

Before and after rectification.jpg

Howard · Post by **Howard** » Wed Feb 14, 2018 9:19 pm

Here's the example patch for those screenshots:

Rectify.h2p.zip

VCA1 carries the original signal so you can compare.

Satch1 · Post by **Satch1** » Wed Feb 14, 2018 9:39 pm

hakey wrote:Sorry, Satch, I don't follow you. Does the signal run from the multiplex into the filter?

Yes, to modulate the cutoff. The LFO was sent to the multiplex the way Howard demonstrated first. Just a little test to hear clearly what is happening.

hakey · Post by **hakey** » Wed Feb 14, 2018 10:18 pm

FWIW, was trying to find a unipolar sawtooth to use as an envelope for pseudo sequencing with the mapper. Looks like that isn't possible.

Thanks for the suggestions.

u-he

KVR Audio

ACE - rectify a signal?