[Amps] EMI Filtering

[Steve Flood]

I don't see them used in amp supplies - at least in the various commercial or 'handbook' designs I've come across - but are they considered a good idea or quite needless?

Followup - when I rewire my shack next month for 230v, I am bringing in a 10awg, 4 wire cable (black-black-white-bare) from the service panel to a NEMA 14-30 wall socket.  (My power supply will have a 120 circuit in it as well, so I followed the advice of a previous AMPS topic.)  The 230v EMI filters I looked at (Qualtek) only have two connectors on the 'load' side.  What happens to the neutral lead? Does it just 'go past' the EMI filter?

Tnx, 
Steve KK7UV