My TF suffers from distorted sound when the volume is above about 50%. It is a pioneer 4x50Watt unit, constant power 4x22 watt.
I tested the radio itself on the bench, and there it works fine, but it needs 14 volts for full power, at 12 volts distortion already is visible on the scope at an output level of 12 watt.
That is also in the manual in the tech specs. So Pioneer sells a radio of 4x50watt, but looking in the specs, at the standard 12 volt level it only produces 4x12 watt, that is a huge difference and for 4x22 watts it needs 14,4 volt.
I know that my battery has a voltage of about 13 volt, with running engine. And probably in the interior at the back of the radio it will be less due to resistance in the wires.
To overcome this, I want to have dedicated radio wiring from the battery directly to the radio : + and -. So I have ordered a few meters of 6mm2 red+black wiring and fuse, next week I am planning to feed the wiring from the battery through an unused bulkhead rubber grommet, and from the inside the wires can be picked up behind the glove box, and from there to the radio.
Hopefully that will to the job, otherwise I must look how the get the battery voltage to the normal 14,4 volt, or get a radio with better specs, or install an amplifier that really works at 12 volt.
New pair of wires is for now the easy option.