What do you mean by ‘different fliter’ – are you talking about microfilters or something else?
If you take the faceplate off the master socket and plug directly into the internal socket instead (known as the ‘test socket’) and your connection improves, you have an internal wiring issue.
The other thing the adslnation does is isolate the ringer wire. There’s a third wire in most domestic installations which used to be necessary back when phones had mechanical bells in them. These days it acts as a dirty great big aeriel channeling noise into the DSL singal.
BT do a thing called an iPlate which disconnects the ringer wire but it’s pointless as a) you can get an adslnation plate for the same money which is better and b) you can manually disconnect the ringer yourself.
So, whilst you’ve got the master panel off, look for a third orange wire connected to pin 3. If it is, pull it out of the connector. The only thing you need are the two blue wires (pins 2 and 5 IIRC).