I have a Sony Sony DSX-A110u which is a car stereo having 4*55W Speaker out and a Sub-woofer out. The subwoofer-out port it a female RCA jack. which looks like this
I am using the sub-woofer out jack to feed in a another stereo-subwoofer amplifier which takes in 3 wires Left, Right & Ground as a input
As you can see the car's stereo subwoofer output both channel separatel via RCA jack so naturally, To give input to my other amplifier, I joined the ground pin of RCA cables to make it 3-pin stereo format.
Now the problem is, As soon as I join the ground wire of the both RCA out, The volume output of other subwoofer amp gets really low and makes a Tick-Tick noise once every second, Like some digital signal has been passed with the audio signal. Its more noticeable in higher volumes.
The tick-tick noise continues even when nothing is playing on the stereo.
The amplifier works fine in MONO mode otherwise! (Using just 1 RCA jack)