Inlet filter for valve use?

P

penance

Arrogant Cock
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I know the use of IEC inlet filters is not so good for some equipment.
I have an IEC inlet with built in filter (choke and cap type) is there any problem using this with a valve amp?
 
Many over at WAD don't like them and use this

IEC_mains_filter.gif

This little circuit can be easily added to the back of the IEC inlet inside your amplifier. It will help to suppress mains interference and mains spikes. Many thanks to Richard for the idea.

'X' class capacitors are the only legal type of capacitor you can place across the L & N wires. 'Y' Class can be used from L & N to E but they can introduce noise.

The parts you will need are:

2 x RS "X class" mains suppression caps .047uF (RS210-487) or .068uF (RS210-493) soldered between L & N and N & E

1 x VDR (Voltage Dependant Resistor) 250V spike suppressor (Maplin HW13, RS 238-621) for 230v mains or RS 238-592 for 130v mains soldered between L & N

In addition you will need some small bore insulating tube to slide over the legs of the components, this will help to prevent short circuits.

WARNING: Mains voltages can kill. The reader is responsible for his/her own safety if there is any doubt the reader should seek professional advise or not undertake any work of this nature! WAD and the contributors to the FAQ of this BB will not be held responsible for any personnel injury or equipment damage.

Before you start make sure the equipment is unplugged from the mains! Use the diagram below as a guide only and solder the components onto the rear of the IEC mains inlet socket.
Click to expand...
 
With these type of filters, they are so cheap that it is usually recommended to put them on everything except the hifi. Kill the noise at source rather than try and filter it, and maybe have detrimental effects, on the hifi.
 
Hello Lee
What is your view on using ferrites at the plug end of everything connected to the mains except the hi-fi equipment?
Idea is to stop the RFI/EMI entering the mains in the first place.

Thanks
 
Ferrites will only do so much. A filter like the one Lee suggests will start to operate at much lower frequency and so by the time you get up into the MHz range the level of attenuation is rather higher. Of course, nothing stops you using ferrites as well, for a little extra effect.
 

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