For this listing, I performed a brief operational check. I connected the output from my own DAP to the phone jacks 1, 2, 3, and 4, and confirmed the input with headphones. (Phono input and microphone input were not checked.) There is significant crackling on each fader and knob. Due to this crackling, sometimes only one channel works or sound cuts out. In such cases, moving the faders and knobs vigorously made the sound audible again. The effects seem to be functioning correctly for each function. USB input/output and master output were OK. The main unit has many scratches and dirt. There is a tear in the insulation near the base of the power adapter. Only the main unit and adapter are included in this listing. I have not checked the details, and due to the poor condition, I am listing it as junk. Please understand this before purchasing.