[tuatoru]

In fact there is a way or two.

The extra resistance (2 to 10 milliohms probably) of the wire between the two boards, together with the smoothing capacitors on the downstream board, acts as a low pass RC filter.

Also the capacitors on the PS board may be low-inductance types, and filter HF noise more effectively than the caps on the amplifier module.

Having the diode bridge further away from the amp module's inputs means the antenna action of the rectifier's leads is less effective: the RF power of over-the-air rectification transients at the inputs is reduced by the square of the distance.

The layout of the amp as shown is good, except that I'd shorten and cable-tie wires to help prevent hum loops.