Phone calls

Question

Electronics

Hello.
I have this external USB audio card.

I wonder if there are any ways to get rid of interference from a mobile phone? Where exactly are these interferences? I tried to drive the phone near the map, and via the USB cable, and via the headphone cable - it was not possible to localize.

Are there any shielded USB cables? I read somewhere on the net about wrapping the card itself with foil or a ferrite ring on wires, but I did not find specific instructions. Please advise something other than buying a new card.

Answer 1

Try this: http://forum.ixbt.com/topic.cgi?id=12:46426

Answer 2

I have pickups on the speakers, I solved the problem like this: I got into the habit of leaving the phone on the shelf :)
Shl. I think it is not logical to disassemble monolithic working columns. ferrite rings and foil did not help ...

Answer 3

What kind of leads are coming? If these pickups are audible, then they may be where the analog signal goes. You should not even try to shield the USB cable - the problem is not in it.

Answer 4

I have such a suspicion that the pickup goes through a common ground loop between devices - roughly speaking, your cord connects the grounds of two devices and the same ground is connected through a common network. Only breaking this circuit will help - a low-current signal MUST NOT be transmitted over a common ground - this is the use of galvanic isolation or differential pairs.
It would not be superfluous to look with an oscilloscope at the output voltage of the sound card relative to itself, as well as relative to the ground of the amplifier and at the same time - the voltage directly on the USB connector of the card itself. You need to look for the presence of "interference" in all these places. After all, another option is possible that the mobile phone transmits interference through wires into the USB-card, where it penetrates through capacitive connections into especially sensitive places of the analog path, then nothing can be done about it.
But still, I think that the pickup occurs through a common ground loop.