I have two computers connected through this device:
to two sets of commercial audio speakers, designed for connection to the computers. (3.5 mm plugs typical to consumer computer sound)
Obviously the idea is to be able to switch the speakers to one source or the other for certain applications but be able to switch them both to one source for other applications.
One of the computers connected through the Crossplay is a MacBook Pro. The other is a largeish "SuperMicro" PC. The signal from the server contains a high-pitched noise in the upper audio frequencies. I haven't put the signal to a counter or a scope but it sounds like it's in the upper audio bands, between 18kHz and 20 kHz if my ear is at all good.
The "Crossplay" itself is powered by what I imagine is the cheapest possible USB-level power supply. Connecting the power supply to different sources, predictably, didn't change the noise on the line. Neither did using different unshielded cables, though the same cables which "had noise" didn't have the noise when connected directly to the MacBook Pro.
Therefore, the noise appears after testing to come from the sound card on the computer. However, since the noise isn't apparent when the speakers are connected directly, they must be getting amplified through the Crossplay.
My EE days are long past. The questions are:
What is the electrical source of the noise? My guess is that since the PC's inner spaces are electrically noisy, the source is the ground plane of the PC. Further, that the very inexpensive and ungrounded circuitry in the Crossplay is part of what amplifies the noisy signal. (My other guess is that the Mac's circuitry is simply better designed, hence, no noise from that source; the Crossplay is still amplifying it but 0x0=0...)
And, how would you filter it? Find a way to ground the Crossplay? Something else?
I'd prefer to just find a way to shield a cable or clamp on some kind of high-pass filter, but I'm handy with a soldering iron and Radio-Shack parts if that's what it takes.