Hey. I’ve read all the posts I can find on the UCA but can’t seem to find exact problem.
I have Pioneer DJM450 connected to Audio Technica decks playing vinyl which has been working fine when connected to a Sonos 5.
I now want to stream/record on my Macbook Pro (Retina, early 2015) running newly installed Big Sur.
I have bought a Behringer UCA202
DJM is connected to UCAusing RCA cables from Master 2 on the DJM450.
UCA202 connected to Mac via USB…
Changed sound input & output on Mac to USB codec. Playing a record on the decks, the volume shows input on Mac sound preferences.
Open Audacity and hit record; again, volume levels are fluctuating up, but can’t hear anything (Mac volume set to max)
I also can’t hear anything when plugging headphones into the UCA.
Also connected Sonos 5 back to the UCA via output (RCA) - no sound is coming out of this when I set it to line in
And when trying to use Pioneer software & Rekordbox, the mixer doesn’t show as connected.
Any help massively appreciated.
According to the manual for the DJM450, the Master1 and Master2 output should have parallel ouputs, so if you haven’t already, hook up some powered speakers to Master1 to verify you are getting output here.
According to the manual for the UCA202, you need to set the monitor switch to the ON position and adjust the volume control to hear the input in the headphones. As long as you are getting power to the Behringer box, and you are getting output from Master1, you should be able to monitor Master2 through the UCA202 with the headphones. To me, this doesn’t seem to be a Mac or Audacity issue.
I hope this helps. 
Note: as you check the forum, you will find a number of posters having issues with their mac/Pioneer/DJM450/Rekordbox configurations. Check also at https://forums.pioneerdj.com/
Thanks so much. I’m not quite sure why you suggest I test master 1 (unfortunately I don’t have the right kind of cables). Master 2 was working fine with a Sonos previously though.
The tip about the switch on the UCA was spot on: sound now coming through headphones plugged into them.
The Mac also now recognizes Audacity as using the mic, but still no sound coming through the Mac.