I know it's the wrong forum - I should write to Roland.
I played something on the device yesterday, because I recorded a guitar.  And now I hear a tiresome buzz at about 400 Hz at the output from my Roland Octa Capture. I restartet the computer, I turned the interface on and off, I turned the buttons, but the 400 Hz buzz is constantly aloud and annoying. There are no cables in the inputs.
It is also no preference wheter SONAR is running or not.
Even if the output-volumen is set to 0 there is a small buzz, if I make the volumen louder, the buzz gets also louder.
Can someone help?
 
 

You are not operating your device in a large aircraft by any chance? 400 Hz is a common frequency of aircraft power. 

No - I'm 15 miles from the nearest airport.
My guitar tuner says 450 Hz.

If the interface is sampling at 44.1 kHz...I'm gonna guess that your buffer size is around 96 samples (427 Hz).  If so, I'll further guess that the interface is repeating whatever is in one buffer over and over again.
 
I get this from time to time with my M-Audio 1418 interface when some (not all) Voxengo plugs are in the project.
 
I get around it by changing the buffer size in the ASIO settings.  Sometimes I just change it from what it was to what it wasn't and back again.  Most times that works too.

Buffersize is at 1024. The buzz does not change when I set to 512, 384 ... 96.
The buzz does also not change when set to 44, 48, 96 or 192 kHz.
I also turned the interface and the computer multiple times off and on.
I work with a great buffersize, because I mainly digitaze tapes and vinyl and therefore a graet buffersize is better.
Perhaps the device is broken after more than 3 years?

What happens when you disconnect the USB cable? In other words test it as a stand alone audio device.

You probably already have done these but just in case have you tried to reset the unit?

https://www.rolandus.com/...owledge_base/201975929

Do you have the latest firmware and drivers?

http://www.rolandus.com/s...y_product/octa-capture

THambrecht
Buffersize is at 1024. The buzz does not change when I set to 512, 384 ... 96.
The buzz does also not change when set to 44, 48, 96 or 192 kHz.
I also turned the interface and the computer multiple times off and on.
I work with a great buffersize, because I mainly digitaze tapes and vinyl and therefore a graet buffersize is better.
Perhaps the device is broken after more than 3 years?

Well...it does mean that you're not seeing the same problem that I had.  According to my theory, your buzz should have been 43 Hz at 1024 samples and would change with the buffer size.

Thank you all.
The "reset" helped. The buzz is still there, but now it is below the hearing threshold. The buzz does not change if I change buffer or frequency. But now I only hear it when I turn up very very loud.
I also hear a fine buzz from two other computers with the Roland Quad Capture - exact 1 octave deeper.
Possibly this is a basic problem with all Roland interfaces. I didn't hear such a buzz from computers with a Focusrite Scarlett 2i2.
Main thing is, that the buzz is NOT on the recording. It's only very quiet on the output.
 
 

Just a guess, but my guess would be a leaky filter capacitor in the interface's switching power supply. The symptom would be a constant buzz/hum even with all inputs turned down.