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Oscillator buzz on 2 voices of Mopho X4

Oscillator buzz on 2 voices of Mopho X4
« on: August 13, 2017, 06:11:29 PM »
Hello everyone. Recently, while running through patches that I hardly use, I noticed a low buzz on voices 1 & 2 (I'm thinking sub osc) of my Mopho X4. I've sent DSI an email today to see what they thought, and if needed, I will send my unit in for repair. But, I'd thought I'd post the issue here in case anyone else has seen this issue, or sees it in the future.

You can hear an example of the issue in the audio recording at

This example is using the factory preset, 'Classic Synth'.

For troubleshooting, I've uploaded the latest Main and Voice firmware, currently at Main 1.1.6 and Voice 1.12, but this did not resolve the issue. Then, per the manual, I attempted to run the Filter Calibration. Filter Calibration would start but get stuck on "* Calibrating V1 Filter *". I left the Mopho X4 sitting for over a day on this before powering the unit off (the only thing I could do as all of the buttons were no longer functional), then retrying. I came to find out that if I changed the patch to something other than 'Classic Synth', the Filter Calibration ran and would complete in approx 2 minutes. Unfortunately, this did not resolve the buzz issue on 'Classic Synth".

Opening the filter did nothing to reduce or eliminate the buzz.

I do not hear the buzz issue on any of the test patches, or an init sound.

I've re-uploaded the factory presets, with no change. Also, I've reset the Global Settings to default, with no change.

I will await word from DSI Tech Support and will post an update. However, if anyone has any comments, feel free to share.


« Last Edit: August 13, 2017, 06:16:18 PM by bpasternak »

Re: Oscillator buzz on 2 voices of Mopho X4
« Reply #1 on: January 22, 2018, 10:57:18 AM »
Hmm. It's hard to tell what aspect of the sound you're describing as buzz, but the main difference I hear between your lower notes and higher notes is a product of the fine tuning of your oscillators. Try setting slop to 0, turn on oscillator reset for both oscillators (I don't have my mopho in front of me but I think that's what they call it), and fine tuning both oscillators to 0. If you no longer hear the buzz, then what you're asking about is not an issue but just the way waveforms work. If you are still hearing the buzz, then I'm not sure what you're referring to.

Re: Oscillator buzz on 2 voices of Mopho X4
« Reply #2 on: January 22, 2018, 10:58:00 AM »
Or I guess more simply, you could just turn the oscillator mix all the way to one side or the other and see if that makes your issue go away.


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Re: Oscillator buzz on 2 voices of Mopho X4
« Reply #3 on: January 22, 2018, 04:18:13 PM »
I hear what you're hearing, I think. On some (not all) of the high Fs, it's a lower-frequency component.

I think this is a consequence of oscillator beating, and is probably normal. For experimental approaches, wbajzek is probably  on the right track; try fine-tuning the oscillators in the patch. It might not go away when mix to hard left or right, simply because there's some oscillator bleed on the X4.
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