@GarethW the filter in the Infinity socket may be faulty. Can you try removing the faceplate which will expose the test and try connecting the hub and phone directly to that using a filter? I know the diagram of the socket below is not the same as yours but the location of the test socket should be the same.
Just to add to what @NeilO has said, it could be that your internal wiring is incorrect.
This links to a diagram showing how your wiring should be connected.
With the bottom section removed, all extension sockets shold be dead, with no dial tone on them, and any other device that is plugged into an extension, should also stop working.
If if that is the case, then you should not need a microfilter on the extension, as that would already be filtered.
@NeilO No, the noise is still there when plugged into the test socket; although I only have one filter to use to check.
@Keith_Beddoe Yes, the extension socket stops working.
@GarethW There is one test that would need to be done to totally eliminate the NTE as a possible cause, and that would be to totally remove it, and try the "real" test socket that is situated behind it. It is held in place by the two screws, one at each side. This test socket is the demarcation point between the Openreach external network, and the customer equipment.
The test socket that you used, is in fact routed via the NTE internal connections, and relies on a push fit connector at the rear, which plugs into the "real" test socket situated on the fixed backplate.
Its not unknown for this connector to make a poor connection, or create a high resistance joint due to oxidisation, so its work checking.
@Keith_Beddoe Oh, I had it in the back one to begin with. With just the front plate removed: there is noise with the phone in test socket, and the Hub in the top socket; but if I plug the Hub and phone into a filter and then the test socket I can’t connect to the internet (red light and flashing red B.)
If you cannot get any Internet connection at the "real" test socket, with both parts of the NTE removed, then that would suggest that that socket is not in fact the master one, and somehow the line is coming into the NTE via a different route.
The picture that @NeilO posted, represents what you would see, with both parts of the NTE removed, as the NTE simply fits over the existing original faceplate.
The fact that you get nothing at that point, would seem to indicate a wiring issue somewhere.
On the back of that original face plate, which is normally screwed to the wall, would be two terminals marked A and B.
This is where the incoming line to your house should terminate, as there are testing and lightning protection components there.
If there are no wires there, then something is wrong.
@Keith_Beddoesorry for any confusion. I hadn’t realised that the front panel came off as well when I undid the screws the whole thing came away.
The situation is: there is internet connection from the ‘real’ test socket when connected via a filter -although there is still noise on the line.