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I am experiencing the following peculiar noise signal when recording from my Behringer Xenyx Control 2 over USB.

There is frequency at around 2293 hz as show: Frequency spectrum with peak at 2293hz

And over time, it produces the following plot: Frequency plot over approx. 5 seconds

What on earth is doing this?

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  • $\begingroup$ It has occurred to me I need to specify: - iMac 27" - All powered via a UPS $\endgroup$ – Peter J. Nicholls Jan 27 at 3:32
  • $\begingroup$ Try using a ferrite core around the USB cable. I'm not sure it'll help, but it might. $\endgroup$ – MBaz Jan 27 at 3:56
  • $\begingroup$ Yes got ferrite cores on all essential USB. I’m wondering if it’s the device itself. It’s such a peculiar pattern. Although next phase, extra shielded USB? $\endgroup$ – Peter J. Nicholls Jan 27 at 11:45
  • $\begingroup$ Ferrite cores and shielding the USB cable are unlikely to help. This is not a USB problem (per se). $\endgroup$ – Hilmar Jan 27 at 15:19
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It's NOT USB problem. If you there was anything wrong with the digital connection, you would get drop outs or nothing at all. The error detection/correction on the USB bus is binary: either you got all the bits or you didn't.

This is clearly analog noise, probably from switching power supply. It happens most likely in the analog front end of the mixer. Once it's digitized, it can't pick up this type of noise anymore.

You can try a different USB recording device or throw a USB hub in the path to isolate the iMAC power from the Xenyx power see if it helps. It's also entirely possible that the Xenyx will do this no matter what: Behringer has a reputation for great value, but also for sloppy design and poor quality control. The Xenyx is a blatant ripoff of the Mackie Onyx (as the name implies).

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I can think of at least three suggestions for this :

There is a phenomenon that can happen in audio systems if you plug it to a power source without proper groundind , you get an annoying hum similar to this.

Since this looks like a sine interference I would look for a source that would cause such an interference e.g. CPU fan which works at about that range

Third I would think if this is cauesed from a feedback loop, turn the gain up in your input if it rises it's probably not the usb.

Edit: I am suggesting things that are not directly caused by the usb since:

A) usb uses digital communication and that means the noise creates a sine wave noise in the data, unlikely to be consistent.

B) usb uses error detecting on it's communication in two levels on every packet and on the sequence sent (using acks) which means a noise on the usb signal would cause it to fail.

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  • $\begingroup$ I’m wondering if it’s the device itself. It’s such a peculiar pattern. Although next phase, extra shielded USB? $\endgroup$ – Peter J. Nicholls Jan 27 at 11:45
  • $\begingroup$ I don't think this has anything to do with the usb (from the reasons I listed above) I do think that this probably something with the device either through actual sound input to the system ( such as a PC fan or feedback loop ) or some ground loop going on if your two devices are powered by different sources though I think the former is probably the case since it is in expected frequency range for it. $\endgroup$ – shaiel cohen Jan 27 at 14:47

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