Regarding the LMR400 cable, I went over the connectors with a magnet and the whole thing is magnetic, its basically steel and probably acting like an antennae for EMI.
As per decentlevi's experiment, I placed 3m copper tape over the connectors and this made a huge improvement in the sound quality.
Highly recommend trying this.
As per decentlevi's experiment, I placed 3m copper tape over the connectors and this made a huge improvement in the sound quality.
Highly recommend trying this.