2-layer board methodology in audio design

[Piotr]

@vintage

There is so much conflicting information around,

To add to your confusion here you can find in my opinion the best articles I have ever read about PCB design:

Decoupling capacitor via placement

I didn’t read that book but I suppose you can replace it with: I think it is enough for most pcb designers.

Decoupling capacitor via placement

About 2004 I found an interesting serie of EMC articles by Keith Armstrong (for many years I didn’t know if Keith is a woman or men name). Later they became no accessible, but when I tried to find them few years ago I found them once more: http://www.compliance-club.com/pdf/DesignTechniquesPart1.pdf http://www.compliance-club.com/pdf/DesignTechniquesPart2.pdf http://www.compliance-club.com/pdf/DesignTechniquesPart3.pdf http://www.compliance-club.com/pdf/DesignTechniquesPart4.pdf http://www…

I want to remind you once more - when this PCB was designed the designer assumed 0 cellphones working in the immediate vicinity of the device.

@vintage

The design is a duplication of a 1981 design where a single layer board was used. I’ve replicated the component layout and attempted to maintain the same copper trace routes per the original 1981 layout.

I don’t understand what you are saying.
If the original was single layer and you tried to maintain the same copper trace routes you should have single layer PCB while you have two layer.