L5730
Addicted to Fun and Learning
- Thread Starter
- #81
If your PC uses an earth grounded (3 prong) power brick, try a doubly insulated 2 prong power brick. Breaks earth ground while meeting regulatory safety requirements.
I tried a 5v disconnected usb cable and two different usb optical isolators (both based on the analog devices chip) without success before this solved my usb issues (noise and bit hits)
The PC PSU has a 3-pin IEC connector which must be grounded, no question about this (with exception of star grounding, but I ain't going there).
It's a desktop tower with a 750w ATX PSU.
All laptops and Raspberry Pi each have a 2-pin (plastic earth) to AC/DC transformer for their power, and so have no connection to ground, and therefor no loop. However, connecting the DAC analogue output to the same computer that is connected via USB does produce some noise.
The D10 digital and analogue grounds are common and this helps to cause a ground loop across the device. However, if the device connected via USB and the device(s) connected to analogue out do not share the same ground, there is no problem. If one is mains earthed and the other not (eg. amplifier and laptop) there is no problem.
I am thinking of grabbing an ADuM4160 based isolator form ebay for £8, de-soldering the DC-DC transformer (because they are crap noisy ones and ~200mA is useless). Then I could add a micro USB B port for external (not mains earthed) PSU power.