How to eliminate FM RF coming thru turntable?

Al & Spencer thanks for your input.

Al -- my cartridge is a Grado MM. Would you please exlaborate what sort of capacitors to use. I'm not too electronically literate.

Spencer -- I did hook up to a solid state phono stage. Did get RF, but was able to manipulate the turntable ground and this eliminated the RF.

Here's something more puzzling. When I re-plugged my turntable into the Rogue 99 tube phono stage, I noticed that the RF disappeared when I touched the pre amp. At first it was my arm on the pre amp with my fingers touching either the turntable ground wire or the turntable leads. I thought great, if only I can find a spare arm to leave on top of the pre amp. The heat would probably make it stink up my living room though. Then I realized if I simply touched the pre amp, the RF disappeared. I tried a separate ground to the pre amp, but this did not prove successful: the RF was back. Yet, when I laid a hand or fingers on the pre amp, the RF disappeared.

If you guys have any more suggestions, I'm game. I feel now, there has to be a simple solution, I just don't know what it is.

Can you tell me exactly what model Grado it is, so I can look up its recommended range of load capacitance. Although many of the Grado's are fairly insensitive to load capacitance, which may be helpful. Also, how long is your phono cable (which adds significant capacitance)? I'll then try to pick out a suitable capacitor.

Your body has capacitance, and that is why touching the preamp affects the RF. When you say you connected it to a separate ground, if you just used a plain wire to do that, the wire's inductance may have made it ineffective at rf frequencies. What you should probably try is a braided ground strap instead, which makes for a much more effective connection at rf frequencies. Or as a temporary experimental arrangement, if possible, try making the ground connection with the shield of a coax cable.

I should have a little time tomorrow to research these parts further.

Regards,
-- Al

Al -- my Grado cartridge is the Reference -- out put 4.0 -- length of the cables are approx. 24" -- they came with the Techno arm for the Michell Gyro Se -- again, I really appreciate your thoughts and suggestions regarding this --

Brian

I have a 4mv Reference Sonata, which simply says "insensitive to load capacitance," and I suspect the Reference is similar in that respect. Also, your phono cable is very short. Both of these factors suggest that you can feel free to add any reasonable amount of capacitance, perhaps up to a few hundred picofarads (pf), without affecting the sound at all.

But it may not be necessary to do that, if a good ground strap would have a similar effect to what you found when you touched the phono preamp. It looks like the best way of getting that, without having to purchase a large quantity from an industrial distributor, is via e-Bay. You can search there under "ground braid." Here is one good example:

http://cgi.ebay.com/20-Tinned-Copper-Braid-3-4-Flat-Wire-85A-Max-Ground_W0QQitemZ370134600553QQihZ024QQcategoryZ26213QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

If that doesn't do the trick, and you want to try adding capacitance, it looks like no one makes anymore the kind of kit I referred to, that I had many years ago, containing a set of capacitors installed on rca plugs. So you'd have to make your own.

Here is one example of a y-cable that you would need; there are many others, as you no doubt realize:

http://www.bhphotovideo.com/c/product/488449-REG/Phoenix_Gold_ARX_569_Silver_500_Series_RCA.html

The most convenient and inexpensive way of getting the rca plugs and capacitors would be, if you can stomach doing so, from Radio Shack. Their part number RSU 11537479 is a set of four gold-plated rca plugs. Part numbers 272-123 (100pf), 272-124 (220pf), and 272-125 (470pf) would be reasonable capacitor choices. Start with the 100pf, and if that doesn't do it go up from there.

You can also find suitable capacitors, with similar values, here:

http://www.tubesandmore.com/

Or if you want to wade through a vast selection of potentially higher quality parts, from an industrial distributor, go to http://www.digikey.com

You would have to be prepared to solder the capacitors to the rca plugs, of course.

But it might be simplest to start by trying the ground strap approach (using it either in place of or in parallel with the ground wires you've tried -- it shouldn't matter which), which could very conceivably solve the problem.

Regards,
-- Al

Thanks Al, will get on to your suggestions and see what happens -- might take a few days -- again, thanks for the input --