Eliminating mains hum

[ukbassboy]

So our band practices beside a transmission antenna - we get full on air traffic control transmissions to pilots that are as clear as day coming through our gear! 

[TimR]

It'll be mains bourne. Something was running in the building that night that's not normally running. 

 

As others have said possibly a fridge. I'd go hunting around if it happens again. Maybe someone bought a drinks fridge in for an event. 

[BillyBass]

Electrician here.

 

Be aware, people, those plug in socket testers have their limits, they are not an alternative to a proper test by an electrician.  I use them to indicate whether a socket is on or off and for testing polarity (whether the conductors are wired the right way around).  In the UK, the potential difference between the line and neutral and line and earth is supposed to be 230v +10%-6%.  If there is a poor earth and there is some earth leakage, and say the potential difference between line and earth is e.g. 120 volts, those socket testers won't pick that up.

 

They are useful as indicators of issues, just don't rely on them.