Hello
a few months ago the previous designer/engineer of the Ifi Idefender told me that this device applys arround 100 ohms between the usb input and usb output port, and i wanted to DIY something without complicated circuitry
actually now that i think about it im not sure if a dac would work with just the 100 ohms ground, its probably better to always use a external power supply and connect the pc ground trough the resistor (if you completely disconnect pc ground your dac usually doesnt get detected, so some gnd connection is nessecary)
i currently building a small pcb/usb dongle for this purpose
the current layout looks like this:
Has someone some ideas or sees errors with this?
Current Features:
a few months ago the previous designer/engineer of the Ifi Idefender told me that this device applys arround 100 ohms between the usb input and usb output port, and i wanted to DIY something without complicated circuitry
actually now that i think about it im not sure if a dac would work with just the 100 ohms ground, its probably better to always use a external power supply and connect the pc ground trough the resistor (if you completely disconnect pc ground your dac usually doesnt get detected, so some gnd connection is nessecary)
i currently building a small pcb/usb dongle for this purpose
the current layout looks like this:
Has someone some ideas or sees errors with this?
Current Features:
- EMI/EDV filter IC on each usb port
- variable resistance to the pc gnd (not connected, 100 ohm, 1k, 500, 333, 250, 200 (and some theoretical combinations under 100 ohm) (it might be a good idea to make a passtrough switch so A/B testing is possible)
- 4x panasonic fc 470 uF capacitor bank to improve power, which can be "disabled" for A/B purposes
- external power supply barrel connector
- usb power from the pc can be disabled or enabled, depending if you use a external power supply or wanna make sure that the power is not connected