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Hum, digital noise


So, still no luck with the noise issues. I think I try everything possible, every combination of power supplies and cases, running the ER-301 in one case and the Output in another one, etc.
No luck. Still noise when I scroll through the screen, switch to admin/scope, at boot, etc.


Would you like to return it to me for analysis?

Also, did you say that you had no noise with a Monorocket case?


I might borrow one from a friend and see if the same thing happens.
Also, after testing, it happens also with my monorocket case. It’s noisy in all cases with all power supplies and with all output modules.


I’m referring to these posts from last year. Was there a change in your setup since then?


Honestly I have no idea if something changed or if I was drunk. I changed some of the modules for sure. What I can say is that it happens on the Monorocket case as well.


Did anything to do with how your case’s power supply is grounded change over time? Change surge protectors, wall outlet/plug, move to a new house, split equipment across different power strips, etc.


Has anyone had any noise issues with 4MS power or the Pods? I’m having noise issues on a small system I built (301 + Hermod) with a Synthrotek Case Power Mini Yellow, so I’m thinking of switching to a 4MS row power or Pod60


I think nothing has changed since June 2017.


Could you elaborate? Waiting on my 301 and would hate to burn it on first plug in!


This has been removed on new models.



Ah, great thanks! Feeling much safer now!


I apologize for reviving this old thread but I’m experiencing a type of digital noise bleed on audio outputs 1,2,3,4 of my used ER301.

Below is a recording of the bootup sequence, menu navigation to Admin mode finishing with a Measure speed in Card Console.
The audio has been recorded straight into a Fireface 800 with a prior gain “calibration” using a sine OSC at 1KHz hiting -6db on the inputs to avoid cliping.

Original version with bootup sequence (peak amplitude -67db in Adobe Audition)

Normalised, digital noise bleed (!VERY LOUD!)
Normalised, digital noise bleed (!VERY LOUD!)

I’ve tried 3 different eurorack cases (two Doeper PSU3s and one Intellijel 7U Performance Case) with different power cables and patch cables, exhibiting the same problem.
For now, the unit is installed in the Intellijel case. Only the Audio I/O 1U and Headphones 1U modules are connected for further troubleshooting and experimenting.

I did a thorough visual inspection of the unit and discovered no leaks/tears, capacitor bulges or shorts on the traces. I’ve also checked the output jacks, no issue as I can see.
Here are my measurements with the multimeter:

DGND to 3.3V = 3.28V
DGND to 5V = 4.92V
DGND to A5V = 4.94
LEDG to LEDV = 4.92V
GND to 10V = 9.88V
GND to -10V = 9.91V
GND to OLED_EN = 3.28V
Jack sleeve OUT1 (ER301) to jack sleeve INPUT1 (Headphones 1U) = 0.005V

The impedance inside the modular from ground connection on the bus board to DGND = 00.1 - 00.2Ohm (200 setting on the multimeter)

After doing a bit of trial and error experiments I’ve noticed a significant drop in noise (around 13db less from the original recording) IF I do a straight connection with a wire between DGND and the ground connection on the bus board. This makes the ER301 very usable and almost noise free.

My knowledge of electronics is quite limited so I suppose there is a ground connection problem somewhere on the board? Or maybe a fault somewhere on the Olimex SOM?
Hope this helps you @odevices and please point stuff I could check.


What happens if you instead of connecting to a ground connection on the Intellijel bus board, you connect to the GND test point next to the ribbon connector on the ER-301? (i.e. ER-301 DGND to ER-301 GND)


Thanks a lot for doing this.
I have the exact same noises.

And I also made an experiment two weeks ago : i brought my ER 301 to a friend’s place, who also has a ER 301. So I could compare the two units, and also try to compare with my place (different electricity network, but also the case. He’s got a 4MS Row 40, which I also used at home).
Result was : both units produce the same noises. But it seemed to be much quieter than at my place.

Also, I just finished another case, this time with a Doepfer PSU3. Same issue (at least at my house).


I tried this now and the noise doesn’t drop, it stays at the same level as if no cable is connected.


Now what happens if you short the ER-301 GND (i.e. test point near the power header on the back of the ER-301) with the bus board GND?


Connection from ER301 GND to busboard GND cuts the noise significantly. I’ve also tested a connection from the Jack sleeve to busboard GND, it does reduce noise as well…


Perhaps you can guess the next step, but now I would short the GND pins of the header (used by the ER-301) on the bus board to the GND location on the bus board that you have used in the last 3 tests.


Just did this now and the noise reduces pretty much, if I would solder it and make a permanent connection it would go even lower I believe.


So now we can make a preliminary hypothesis: The bus board was not designed to source 300mA of current from that particular header (not all headers are going to be equal!). To test the hypothesis, move the ER-301 to the header that is closest to the GND location that you have been using on the bus board.