noisy crossover


I have finally built an active filter to fit in with my Naim system.The problem I am having is an earth loop or rf problem {hissing and foreign radio with a splash of the washing machine motor}.I have tried different ways of wiring it up.

audio in and power(snaps)on 5 pin din and audio out on 4 pin din x2 out two each p amp MASSIVE HISS.

audio in 5 pin din and 2x 4 pin din with audio out and power from each amp TINY HISS with the other noise as mentioned.

I have put caps across the audio in and out to 0v BETTER.

Anyone know what to do

The Naxo crossover already has an rf filter at the input (R4/R5/C2) so if you are picking up radio stations it must be later in the circuit.

First off, do you have the crossover in an earthed metal enclosure or is it just open for testing? If the latter, try it in a suitable case.

If this does not cure the problem, you could try an additional rf filter in front of the second stage (Q5). Replace R13 with two 4k7 resistors in series. From the mid-point of these resistors, connect a 470pF capacitor to ground.


Fixed it. I had put an active filter in place of the passive noise filter on the +ve infeed and it is Bollocks so I went back to the one specified and it is great. The radio stations were picked up by 1nf caps that I fitted across the input and outputs to prevent noise HA!

I am now writing the whole thing up and listening to the system.Amasingly I have(and other listeners)noticed that I do not need to reduce the hf ,it is not bright.

If you have any details you think I may need to include in my report please say so.

All credit will be given to all helpers and neil for reverse engineering the naxo.I have studied and reproduced the board with high grade components and an input buffer for each pass band not split atfer input buffer.