Good day

I recently bought Marshall AS50D Acustic amp in South Africa.

When I plug cable to the amps, it makes tick tick tick sound every second. Nothing plug at other side of cable. Then When I plug it to guitar. It still make tick tick sound at the background. When I make guitar pick volume to full. This noisy disappear.

I tried to change cable to noiseless cable, change power cable. Still same..

My volume setting at the amp are always at 12.

Switch on off other function doesnt make any different. (Reverb, chorus)

 Please help!!