Just a little problem i got myself a Meridian Explorer 2 DAC which works ok it’s just when used with a TP-LINK TL-WN823N WiFi Dongle the Pi won’t boot, if i change to a TP-Link TL-WN821N the Pi will boot and work for a while but then lock-up
Both dongles work fine with the Pi it’s just when you add the USB DAC into the mix there’s a problem just wondered if it could be down to using a iPad charger and it’s not supplying enough juice ?
It is an RPi 2 B is it? Not an RPi B+?
It could for sure be a power supply issue. The RPi has only one (OTG) USB bus which cannot supply enough current to support multiple (power hungry) USB devices. You could try a powered USB hub. Or something like this http://ifi-audio.com/portfolio-view/micro-iusbpower/, but that is relatively expensive 
Another issue could be that both devices (your DAC and Wifi dongle) use to much resources from the USB bus. Try to play different resolution audio files (16/44,1, 24/96 to 24/192 or 32/384) to see if/how issues increase. Maybe play the audio files directly from the RPi (store them on your SD card) and switch off/remove the Wifi dongle. See what changes.
It’s a raspberry Pi 2 did have a look at the iUSBPower but christ there expensive 
Hi !
Don’t know if it could help with rpi2, but for me it allow to use a usb disc that was not oo due to lack of power, just try it : https://projects.drogon.net/testing-setting-the-usb-current-limiter-on-the-raspberry-pi-b/ and let us know.
Hi…
You can change the RPI USB current limit. Have you already done this?
Enable 1.2A Current Limiter on Raspberry Pi Model B+ or Pi 2 Model B
This only works with Model B+ or Pi 2 Model B
Add the following lines to your /boot/config.txt
max_usb_current=1
safe_mode_gpio=4
Get a Good USB 5V 2A Power Adapter
Get a Good Micro USB Cable
Think i’ve got my problem sorted now as i bought a 5V 2A Ultra HQ USB Power Supply from ModMyPi and been using for the last hour and both wifi dongles and the DAC are all working fine now 