Remote control motorize volume board use a two gang volume pot 4 channel single end input  selected by relay, on board regulate supply so only need a 9 or 12V ac power transformer (not included)
Can also control the input by a rotary encoder
100K Alps motorized pot
board size: L 120mm X W 55mm

Kits include:

one pcs of mian pcb, one relay board, IR receiver, one rotary encoder and one remote handset