I'm using a fairly high quality power supply. I bought a ground loop isolator and connected it between the trigger output and my modular. It effectively eliminated the high-pitch noise. I would need one for every trigger board connection I'm using which is a pain. I could hook it up to the main output, but the cheap version of these devices mangle the bottom frequencies. Maybe the trigger board jacks need some coupling capacitors to mitigate this issue?
This issue is quite annoying, indeed... NF filters on the audio outputs didn't work at all for mine.
One workaround solution i have been using is with the help of the rosie module, by make noise. Sending the LXR out to the stereo returns of rosie leads to no noise. This make LXR's internal sounds and triggering usable at the same time. ...finally
a solution inside the LXR would be much better though, so, hoping for a simple solution too.
I noticed that there was some serious ground-loop issues with my unit. Turns out it was the USB cable, so I fixed that. However there are still some rather odd digital sounds when parameters are changed. I'm starting to have a feeling that it might be the OLED that's actually creating the noise as the screen updates. Is this possible?
I experimented a bit this afternoon to get rid of the interference I get when using the trigger IO and the audio at the same time and I think I have a solution. The digital ground-loop noise starts when the ground of the triggers and the ground of the audio are joined. Since, probably due to some internal resistance, these are not at the same level and the trigger one is more or less directly connected to the AVR CPU, this loop carries the noise. Ground-loops 101 teaches us to cut these loops and I tried in 2 ways and both work:
1. Use an isolator transformer in the audio path. This makes sure there is no direct electrical connections between both end, effectively cutting the ground loop. Works fine but is a bit cumbersome to always have to connect an extra device. It also affects audio (at least if you use a cheaper one, like I did with a phone-line transformer).
2. Cut the grounds of the trigger IO's. I first tried with a trigger cable that has no ground connection (by simply cutting it in the connector). This obviously will not work if only the trigger is connected, since there would be no ground return path, but when also the audio is connected to the same device (a modular system in my case), there is a ground path for the trigger signals over the audio ground and everything works fine too! Without extra isolator transformer. Since I always have audio connected on the LXR, I decided to cut the grounds on all trigger jacks on the trigger IO board.
There is something odd going on between the grounds for sure. I have a quick fix though, jumper the ground on the trigger board to one of the GND connections on the audio output (not the switched side). For some reason, only that spot works, anywhere else on the board does not. Reduces it to almost nothing
I've had the same issue. Turned out to be my MIDI cable connected out from the LXR in to my MOTU Firewire audio interface MIDI IN. Does not happen when I plug the cable into the MIDI in on the LXR. Removing it removed the sound.
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The strange thing is the other PSU doesn't cause problems with other gear, it's just the LXR that doesn't like it.
NF filters on the audio outputs didn't work at all for mine.
One workaround solution i have been using is with the help of the rosie module, by make noise.
Sending the LXR out to the stereo returns of rosie leads to no noise.
This make LXR's internal sounds and triggering usable at the same time.
...finally
a solution inside the LXR would be much better though, so, hoping for a simple solution too.
1. Use an isolator transformer in the audio path. This makes sure there is no direct electrical connections between both end, effectively cutting the ground loop. Works fine but is a bit cumbersome to always have to connect an extra device. It also affects audio (at least if you use a cheaper one, like I did with a phone-line transformer).
2. Cut the grounds of the trigger IO's. I first tried with a trigger cable that has no ground connection (by simply cutting it in the connector). This obviously will not work if only the trigger is connected, since there would be no ground return path, but when also the audio is connected to the same device (a modular system in my case), there is a ground path for the trigger signals over the audio ground and everything works fine too! Without extra isolator transformer. Since I always have audio connected on the LXR, I decided to cut the grounds on all trigger jacks on the trigger IO board.
Hope this helps somebody else too ;-)
BTW. if you want to know everything and more about ground loops, read this: http://web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf