I did a brief functionality check before listing the item. I connected the output from my DAP to the 1, 2, 3, and 4 phone jacks and checked the input with headphones. (Phono and mic inputs were not checked.) There is considerable crackling in each fader and knob. This crackling sometimes causes only one channel to work or no sound to be produced. In such cases, the sound could be restored by wiggling the faders and knobs. The effects seem to be functioning properly. (I have not checked the master output or USB, but they were working when I checked them a few years ago.) The main unit has many scratches and stains. The insulation near the base of the power adapter is torn. This listing includes only the main unit and the adapter. I have not checked every detail, and the condition is not good, so I am listing it as junk. Please understand this before purchasing.