I am trying to wire up an audio amplifier circuit using the Kemo M031N 3.5W amplifier:
I have connected the wires from the amplifier to a terminal block. With a suitable 10V power supply and a 2W 8Ohm speaker but no input signal (ie nohing connected to the input wires at all), there is no or very low noise (which is a good start). I have connected one of the input wires to the PSU ground, which is also connected to the speaker.
The problem I have is that whatever I attach as an input signal (even when there is no actual signal), I get a lot of noise from the speaker. The noise is a mixture of bursty static noise (every 2-3 seconds) and a louder fast clicking. This noise appears at a low level even if I just touch the input wire at the terminal block with a screwdriver.
I have tried using a 10V regulated (home brew) PSU, the 5V from a Raspberry Pi and a PP9 battery. All have the same noise effect, to varying degrees (the battery was best but the noise still audible).
If I connect good quality (unscreened) speaker cable to the inputs on the terminal block, the noise is slightly louder. When I touch the other ends of the speaker cable together, the noise is very loud.
I have tried adding a 10k and a 2k2 resistor across the inputs with no change. I have also tried a 330uF capacitor across the supply at the terminal block.
Does anyone have any ideas on what I could try next?