Noisy class-D amp with boost converter

[elektrinis]

Was looking for a single board stereo amplifier for my car, but slightly more powerful than you could get from 12V. Ended up finding this one (see 1st attachment).

It's based on class-D chip TPA3116 (which is quite good and works well). And it has dual 5-amp boost converter XL6019.

The problem I am having is this thing is quite noise on high frequency audio range.
I understand the routing is pretty poor, as analog audio traces go right under the boost inverter... However are there any ways to mitigate this?


Bonus question. The inverter is made of two identical inverters running in parallel. There is two of everything drawn below.
Each inverter has two more diodes than it would typically need. First there is a beefy diode in series to 12V input. What is this for? To keep the amp running when I crank the engine? Anything else?
And then there is an extra diode in series to output of the inverter, before the capacitors. (see 2nd attachment)

Does it have something to do with two inverters in parallel? There seems to be no capacitance before this diode.

[trobbins]

Your noise may be be related to ground loops for input signal and power - sketch out your arrangement and identify where the power is being sourced from, and look for a ground loop.

Have you confirmed the speakers are floating, with no ground connections?

The input diode is a form or reverse polarity protection, to reduce warranty returns based on 'it doesn't work'.

[elektrinis]

The noise is there when nothing is connected, only speaker. The noise is strongest when potentiometer is set at 50% and it lowers when set to 100% or 0%.
For the input diode, I guess I can simply short it to get rid of some heat.
The output diode, however, has a strange configuration, with capacitors behind it.

[mikerj]

I suspect the output diodes are to prevent the regulators control loops fighting each other since their output voltages won't be exactly equal. I am surprised there is no cap prior to the output diode though, I'd have though that would potential cause problems with regulation.  It's all a pretty nasty bodge IMO.

[trobbins]

The noise is there when nothing is connected, only speaker. The noise is strongest when potentiometer is set at 50% and it lowers when set to 100% or 0%.

You have got power connected ?
Have you shorted the signal input socket?
How long is your speaker wiring, and is it a pair (ie. twisted, or joined)?
You have got 2 speakers connected?