Hi
i have couple of A64 boards. I use them with microphones and usb WiFi adapters (Ralink)
i have following problems. If i connect USB WiFi adapter with external antenna (not the small dongle with built in antenna), i get extensive digital noise on microphone input. I don't get this noise when USB WiFi adapters with built ion antennas, i don't get this problem. I even tried to use short USB extension to move the adapter a bit further from the board, but the noise is still present.
For power i tried bot battery and external 5V adapter.
The microphone is standard electret capsule connected via shielded cable and 3.5mm jack.
Anybody ever encountered similar problem?
There is some logic behind this happening, what you can easily try is use extension USB cable so that the USB-WIFI adapter is not plugged next to the board and away from the MIC. Using extension cable will help you determine where the distortion comes from empirically.