im thinking of making a common mode filter board and putting it in my amplifier. will the filter have to be shielded even within the metal chassis of the amplifier? and what use will be if in the future i decide to build an ac filter box much like the popular do-felix? i guess my second question is if there is any point in hooking up 2 commons mode filter in series with the ac cord between them
A mains filter is normally fitted either before it enters an audio amplifier or directly at the mains input as part of a mains input socket.
If you look at various amplifier wiring runs either the mains transformer is very near the mains input or the mains wiring is tightly run against the opposite side of any AF amplification or far away from sensitive audio sockets
If you look at various amplifier wiring runs either the mains transformer is very near the mains input or the mains wiring is tightly run against the opposite side of any AF amplification or far away from sensitive audio sockets
If the CM filter uses a toroidal choke, then its leakage flux lines are unlikely to travel very far from it, and a separate box may not be necessary. A separate metal box is often used to prevent any radiated EMI (electric field) out of/into the filter.
As to whether two CM filters could be used, the answer is definitely a yes, but then the second filter wouldn't have much work to do. Further, CM chokes can also make things expensive.
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ahh they ARE toroidal which explains why you see them exposed the way they are in some name brand equipments.
my other question still stands tho- will the benefits still stack up if you wire them in series (one in the amp, one in a separate box)? i see how it might be a good idea to target them for different frequencies with the one in the amp using smaller choke for higher freq filtering
my other question still stands tho- will the benefits still stack up if you wire them in series (one in the amp, one in a separate box)? i see how it might be a good idea to target them for different frequencies with the one in the amp using smaller choke for higher freq filtering
Hello,
If you use a incoming power filter unit that has the plug receptacle and filter in one unit (usually shielded), sometimes has a fuse as well, then that should be quite adequate. Unless you have an unusual amount of RF being generated either inside the box or from a nearby radio station transmitter, not likely to get any benefit from using two. Law of diminishing returns. IMHO.
If you use a incoming power filter unit that has the plug receptacle and filter in one unit (usually shielded), sometimes has a fuse as well, then that should be quite adequate. Unless you have an unusual amount of RF being generated either inside the box or from a nearby radio station transmitter, not likely to get any benefit from using two. Law of diminishing returns. IMHO.