RF interference through my phono stage.


I've noticed I can hear faint radio signals through my amp when the phono input is selected. I do not have a tuner at the moment so I know it's not coming from my system. What can I do to eliminate or minimize this problem?

I'm willing to get a line filter/conditioner if it would help, but only if it's reasonably priced.
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That's not uncommon. See the following thread, in which the problem was ultimately resolved by connecting a braided rf ground strap between preamp chassis and power conditioner ground, and between power amp chassis and power conditioner ground. Since your system does not have a power conditioner, a comparable connection would be to ac safety ground (e.g., a screw on a power strip or wall outlet). Many other things were tried and suggested as well, some of which may work for you, including different connections of the rf braid.

http://forum.audiogon.com/cgi-bin/fr.pl?htech&1230309974

I doubt that adding a line filter/conditioner will help, though, because the signals are most likely being picked up through the air, not through the power line.

Regards,
-- Al
You might try Cardas Caps on your unused inputs:

http://www.diycable.com/main/product_info.php?products_id=230
This is a common problem on many phono stages. The signal is most likely coming through the air as Almarg stated. One simple and effective solution is to attach a ferrite core to the ground wire between the turntable and the phono preamp stage. You can get these at Radio Shack (or through Audioquest, ect). If you can find it TDK made a RF noise blocker ferrite core that works well. If you find one experiment with the number of turns that you wrap the ground wire through the ferrite core. Note: RF and EMI noise is mostly unnoticed by Audiophiles until the noise is removed from the circuit, then they realize that it is one of reasons that they were unhappy this the sound of their phono setups.
This is a common problem on many phono stages. The signal is most likely coming through the air as Almarg stated. One simple and effective solution is to attach a ferrite core to the ground wire between the turntable and the phono preamp stage. You can get these at Radio Shack (or through Audioquest, ect). If you can find it TDK made a RF noise blocker ferrite core that works well. If you find one experiment with the number of turns that you wrap the ground wire through the ferrite core. Note: RF and EMI noise is mostly unnoticed by Audiophiles until the noise is removed from the circuit, then they realize that it is one of reasons that they were unhappy this the sound of their phono setups.
Etbaby, I've been looking into what you are saying and I'm not sure what I need. Do I need to get one of these clip on ferrite cores for the power cord as well as the ground wire/rca plugs? Should I wrap the ground wire around one of these things as close as I can get it while still reaching the preamp?

Thanks for the help.
Chris_383,

If the RFI is something that has started lately and seems to have gotten worse the problem could be simply a corroded signal ground connection on an ic or even a signal ground pin connection on the cartridge. Try unplugging and plugging in the ics in the phono input jacks a few times and see if that helps. If the TT has phono jacks check them as well. Also check the connections on the cartridge
Hi Chris,

Go to Wikipedia and look up ferrite cores. The graphics shown in the writeup show how the ferrite core is used.

1. Do you need a core on the power cord? Probably not. The key is to add one core at a time and note the effect on the sound. That is, is the RF or EMI is eliminated.

2. Start with the turntable ground wire. Insert the wire between the core now reattach the wire between turntable and the phono section.

3. If this eliminates the noise then you don't have to do anything else. If this does not eliminate the noise. Try attaching a ferrite core to the left and right connectors of the tonearm interconnect. Does this eliminate the noise? If not, try a ferrite core on the power cord. of the phono preamplifier or the turntable motor.

4. Continue this process until the noise is eliminated.

Hope this helps

Etbaby