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Background Noise Issue, DSI Mopho Desktop Synthesizers
Old 23rd October 2012
Gear interested

Thread Starter
Background Noise Issue, DSI Mopho

Hi everyone, I've been coming to this site for a long time now, and I've finally decided to post something.

Anyway, I have a puzzling issue with my DSI Mopho. Even when I have the lpf cutoff set to 0, I hear a faint, unfiltered tone in the background. This tone is always present regardless of the filter settings, although it is covered up when the cutoff is at a high setting. I have not inadvertently left another synth active somewhere.

It's like there is no way for 100% of the sound to be filtered, and every patch seems to have this issue. I have had the mopho for a while but never noticed this issue until now. It's hard to say whether this is a new issue or if I've just noticed it now as it's only really noticeable at a quite high volume. Any idea what it could be? Thanks.

I made a short track to illustrate the problem (WARNING: careful with the volume on this):
Mopho issue by PierreHazan on SoundCloud - Create, record and share your sounds for free
Old 23rd October 2012
Lives for gear
Have you checked to see if the VCA is open slightly in the menu? You said it's on other patches so that's probably not it. Have you tried turning each of the oscillator waves off completely by selecting the shape to off? Does it happen with both oscillators? Also, have you tried the calibration routine?
Old 23rd October 2012
Gear interested

Thread Starter
Hi, thanks for the quick response. VCA is not open and it happens with both oscillators. Unfortunately running the calibration routine didn't do anything either. I have read that all Mophos and Prophet 08s have slight oscillator bleeding issues, so perhaps this is another common issue. If anyone reading has a Mopho and can confirm whether or not they have this issue, I'd appreciate it.

Here's an image of my current settings:

Last edited by Pierre Hazan; 23rd October 2012 at 10:36 PM.. Reason: Adding an image for clarity
Old 23rd October 2012
Lives for gear
I have the mopho keyboard and tetra and no, I don't have this problem. Maybe try contacting DSI support or check out
Old 23rd October 2012
Gear interested

Thread Starter
Thanks, I'll contact them.
Old 24th October 2012
Gear interested

Thread Starter
I got a quick reply from DSI. I also sent them the recording I made:

"What you're hearing is a combination of the oscillators bleeding through the filter as well as the noise floor of the synthesizer. The oscillator's bleeding through the filter is expected, nothing is physically wrong with your synth.

Due to the analog nature of our synthesizers, the signal to noise ratio on our instruments is about 80db. If you're used to using digital instruments (plugins) with zero noise floor, the noise floor of our instruments can come as a surprise. If you are finding the noise to be problematic when recording, you might use a noise gate to gate the noise away."

So it seems I have nothing to worry about.
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