How to eliminate RFI in turntable setup?

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I am picking up RF interference in my turntable setup, which is located on the 34d floor of our home. I have a MC cartridge connected to a headamp that is connected to a separate phono preamp. With everyting connected, I can detect a radio station even at normal listening levels. When the phono cable is disconnected from the headamp, it's all quiet. I can't seem to solve it with grounding schemes - have tried all the ones I can think of. I seem to recall that RF can be eliminated with a small capacitor across the inputs. Is this correct? What size? Would this change the loading of the cartridge and hence its performance?

Perhaps I am overlooking something?

Suggestions are greatly appreciated. Thank you.
 
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Excellent, thank you. Where do the ferrite beads go? Just inside the phono section? I know there are many sizes of these. I have some very tiny ones that fit on 24ga. wire. Or are you indicating the large ones that go on a power cord?

Try a 10nF COG/NPO ceramic capacitor, with very short leads.
It won't affect the MC response at all.

Sometimes it works better between the RCA shell and the chassis,
instead of across the input. The leads must still be very short.
Ferrite beads are another possibility.
 
The LC filter is certainly a good candidate, I have used it myself many times with success, and for much harsher perturbations (high pressure Xe lamps starters), but to correctly select your inductor, you need to know the approximate RFI frequency: beads will work mostly for FM, but FM rarely causes audio detection.

The conversion mechanism is mostly envelope detection, which "works" best with AM signals.

Normal AM broadcasting takes place between ~100kHz and 2MHz, and the effect of most beads at these frequencies is going to be marginal.

An inductor, in the 200µH to 2mH range, possibly damped by an additional series resistor should work better.

If you use a very large inductor, you will certainly eliminate the interference, but you also risk damaging the audio highs.
It depends mostly on the impedances of your system.

Here is an explanatory diagram:
 

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Where do the ferrite beads go? Just inside the phono section? I know there are many
sizes of these. I have some very tiny ones that fit on 24ga. wire.

Yes, the small type. What kind of station is causing the interference?

First, I would try a 10nF COG/NPO ceramic between the input RCA socket
ground shell and the chassis, for each input. Its leads must be short.
If it doesn't help, just leave it in place anyway. It won't do any harm.
 
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I can't tell what station is causing the interference so I don't know if it's AM or FM. I am able to detect voices and some static. This is only a problem on the 3rd floor of my house - not the main level.

Thanks for all the great suggestions.
 
I have tons of RF/EMI in my house. Electrical grid and atmosphere too! And other BIG problems.

I have a lot of Schaffner FN 9244B RF/EMI filters and Würth 150 kHz ferrites.

When the phono cable is disconnected from the headamp, it's all quiet.
Try with a good RF/EMI ferrite like these from Würth. One or two rounds (cable). It is trial and error. If the attenuation is too much there is a loss of dynamics in the music.

Schaffner FN 9244B:

[IMG, only link] http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-specs.png

[IMG, only link] http://maty.galeon.com/WP-imagenes/...affner-FN_9244-typical-filter-attenuation.png

[IMG, only link] http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-cicuit.png

B: medical


Würth 150 kHz http://www.farnell.com/datasheets/1919956.pdf

and https://www.digikey.com/product-det...ity-products/LFB095051-000/240-2277-ND/703465
 
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