Maybe I am missing something here, but when I plug in my CD player, MP3 player, computer, etc into a channel or or even ST1 or ST2 on my QU 16 and my Qu 24 the sound is unbalanced. I don’t hear vocal, or melody, etc. Just the background recorded track. I have tried playing with different ways of connecting it, either through XLR or 1/4 inch and still the same. Even if I play with EQs which seems odd as I should just play it flat and I should hear how it recorded track should be.
Sounds like you are feeding a stereo miniature TRS jack into a balanced TRS or XLR. The effect of this will be to only give you the difference between the L and R stereo signals. So anything that appears in the middle of the stereo image, such as vocals, will all but disappear.
It would be the same with any other mixer where you were feeding an unbalanced stereo signal into a balanced mono input. What you need is a cable which takes the unbalanced stereo TRS to two unbalanced TS plugs, or XLRs that you can then plug into two input channels. If you have previously used a mixer which has a stereo unbalanced input then of course it would previously have worked, but they are unusual to say the least on serious mixers.
Something like this might do the trick
Or this
I’m not recommending these particular products, just showing examples of the sort of lead you need.
…then the other mixers do not have symmetrical inputs on 1/4 inputs.
ST3 is a regular stereo input on TRS connector, ST1/ST2 need two cables for stereo, all you need is a proper split cable from mini TRS into two mono 1/4 connetors. This should be common to all mixers or other gear, the Qu behaves absolute correctly.
[Edit, as been too late] …as Mike wrote
