General > General Technical Chat

Audio HUM fixed

(1/2) > >>

Zfrenchy:
Not sure it is at the right forum, but ...

I had a very bad ground loop hum on my audio system, after I tried a lot of things, I finished by totally eliminated the hum with this circuit.



JUST TO BE SAFE, can a EE tell me if this will put my AC circuit or my equipment in danger ?

bob91343:
Looks reasonable but the font is so small I can't read it.

Vovk_Z:
Yes, looks fine. But if somebody (not EE) asks this question then I can't be sure. :)

richnormand:
You show two-prong AC plugs. On my old audio system with several components pre-dating the three prong usage I used to locate a good copper pipe and run a ground wire to it or use a three prong plug with a known real ground pin to test the setup. Use a DMM on AC between the ground and each device chassis. Do not have anything else plugged to it or between them. If there is a sizable reading reverse the (two prong) AC plug to minimize the reading. Do this for each unit. Once they are all OK I would run a ground between all of them to the real ground and the hum would disappear.

You can get cheap testers at the hardware store to see if the neutral and hot are reversed and if the safety ground is OK at the wall. Several old houses I lived in had only two prong sockets and found many were reversed (hot/neutral) with respect to a proper ground. There was a period where a two prong plug had a wider blade on one side to have proper polarisation but they were pretty useless in that scenario as they would fit both way in the old style socket.

From the equipment you mentioned I would assume the two-prog plugs are indeed polarised (wider blade on one side) and should be OK.
On the subwoofer is there a ground lug or some screws directly on the chassis available instead of using a clip on the RCA? Would be OK if the RCA outer shield is at chassis ground but not if it is isolated/floating to prevent ground loops...

Brumby:
Single point earthing of each piece of equipment is a good first step and isolating signal paths (as shown) is the simplest and most effective solution - as long as the transformer performance is up to spec. to give you suitable audio quality.

Looks good.   :-+

Navigation

[0] Message Index

[#] Next page