Just bought the UA-4FX and was trying to get it working in advance mode
on a fedora 11 box. I had the same problem getting hiss noise like
nose given by a fm radio tuned to off station while playing a sound
even though the kernel recognizes the UA-4FX as usb sound device.
I was finally able to get it working. What I did was I updated the
pulseaudio to 0.9.15-14 which is the latest verion. On the fedora 11,
it can be done by yum update.
While trouble shooting, I found out that the pulseaudio installed in
the fedra 11 was unable to transfer sounds to the UA-4FX in format
24bit/44k, 48k or 96 since it had the bugs unable to handle 24bit
format. As the result of the bug, the pulseaudio transfers sound in
standard format 16bit/44k even though advance mode of UA-4FX requires
24bit/44k, 48k or 96. Miss matching sound format caused noise.
Also the alsa wiki page suggests the patch for UA-4FX but it was
already integrated to the kernel 2.26.8. As fedora 11 has the kernel
2.26.9 installed, I did not need to patch the kernel.