Lowering System RFI


The first, and in many ways, the most important part of our battle plan against RFI is a good ‘shunt’ mains filter. The word shunt means that the filter elements are not in line with the power being fed to your hi-fi – and this approach avoids the pitfalls of reduced current feed to power amps. In practical terms it means we can make a very simple plug-and-play product that you simply plug into an unused socket.

But hey, shunt filter circuits are just like any other circuit – they suffer badly from microphony. So guess what, we build the circuit on its own little acoustic labyrinth.

Vertex AQ Systematic Approach – Lowering System RFI
kill the noise with multiple Jayas – click to enlarge

The electronic circuit in the shunt filter basically allows any high frequency noise which might be on the live, or neutral, to be ‘shunted’ onto the earth line and drained away from your system. Take a look at some of the photos of the Jaya mains filter to get an idea what these things look like. And now we need to look at our systematic view once again to get an idea of what these components will do.

What we are showing here is the effect of installing 3 shunt filters into the system – because we can cover a few extra important points that way. First you should note that you can never completely remove RF noise. The ever present barrage of radio signals, particularly things like mobile phone nets and wifi, will be picked-up all around your wiring and if you try to reduce it at one point, it is still very much present just a few feet further down the wire. And of course the other big noise generator is the hi-fi itself.

So if we imagine we have put the first filter in the middle socket of the distribution rail, it would lower the RF there from 4 to 3 say, and from 4 to 3 in the electronics too – and you will hear a good improvement. But if you work back from the system, with 1 or 2 more filters, you get a cascade effect, and on the diagram we show how with 3 filters the noise at the electronics is reduced down to 1, very low. Now bear in mind that this example will vary in actual application from case to case – but the principle of noise over distance and cascade filtering is an important one, and one which has often been the key to lifting an otherwise disappointing system up to greatness.