I have read some articles extolling the virtues of USB DACS (such as those from Wavelength Audio), and wondered how such DACs compare with a "conventional" DAC used in conjunction with a Squeezebox. Any feedback is welcomed. Larry
The USB port on the Squeezebox is NOT an output.
In order to use it with a USB DAC you will have to modify the software on the Squeezebox. There are software mods out there, but they require some expertise with Linux to install and configure.
At that point it will depend on the DAC or converter you use.
USB is generally worse in terms of jitter than Coax, but an asynch converter or DAC with an asynch USb input should be immune to that jitter, and so might sound better in the end.
I have to disagree with part of that response.
I have a Logitech Touch and it is simple to install the USB output app, which can be done directly on the touchscreen (absolutely no Linux expertise needed). I have no idea about any other squeezebox devices.
My Squeezebox Touch works great with USB out to the Meridian Explorer, all the way up to 24/192. My setup is not in my main listening system though. I have a portable squeezebox server in my car, running on a Raspberry Pi + USB hard drive, connected to the logitech touch via a short ethernet cable, then USB out of the Touch to the Meridian Explorer, line out to the AUX in of my car stereo. This setup blows away both the stock Kenwood DAC and the DAC in an iphone. Best sound I've ever had in the car.
As for usb vs. spdif, it really depends on too many factors for me to make a general conclusion