So you think that when you connect your expensive £2000 amplifier onto the mains supply that you will have a source of infinite electrons that are perfectly clean and with a nice 50Hz sinusoidal waveform… Wrong ! (Well, here in the UK and Europe at least)
The European standard for which governs domestic power supply is EN50160:2000 and this basically allows utility companies to get away with murder concerning the quality of domestic power supplied to homes. Europe has standardised on 230V since 2003, but this actually means 230V ± 10% for 95% of the time. I have measured the mains supply voltage in my home and it never drops below 247V ! That doesn’t make things easy for the power supply in your expensive audio/visual equipment.
What are the issues with the mains power ? There are several key factors :
1) Voltage fluctuations such as power dip and transient over-voltage conditions.
2) Harmonic noise cause by higher frequency components of the fundamental supply frequency. It’s more than just 50Hz in there !
3) Non harmonic noise cause by things like your fridge switching on and off, or your neighbours garden pond pump.
4) Feed impedance. So you think you’ve got an infinite supply of electrons (or holes, if you prefer) – think again. Impedance at different points in the circuit conspire to throttle your beautiful amplifier from getting all it wants.
5) Leakage of return currents via other paths than Neutral connection.
And there are many more…
Solutions to these problems can cost thousands. Mains filtering or even mains regeneration are common (and expensive solutions !), but a big improvement can be made by having a low impedance connection to your mains supply. This is achieved by using low resistance mains cable and good quality connections.
Another area which offers big improvements is the use of screened mains cable. The mains cable dangling out of any piece of electrical equipment can be considered as an aerial which both transmits and receives electro-magnetic radiation. The shield on a screened cable provides an excellent path to receive high frequency noise and enter into the enclosure of your kit. Fitting this cable with RF (radio frequency) absorption filters can prevent some of this without increasing the overall impedance of the connection by too much.
So, in summary here are a number of steps that should be considered when trying to improve the mains supply of quality audio/visual equipment :
1) Use a good quality mains lead with large diameter conductors.
2) Use a screened mains cable with RF filtering.
3) Make sure that the connectors on the mains cable (i.e mains plugs) are high quality with good surface finish.
4) Keep the mains lead short as possible 1m or 1.5m.
5) If possible use a dedicated mains spur.
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