Advice on RFI with a new integrated amp


I need some assistance on my Exposure 2010S. The only input I am using is the cd player, but with volume turned all the way down, I am picking up radio signals. If I turn the dial to the moving coil phono setting, even though nothing is attached to it, I can hear radio pretty loudly.

The corner of the house where our stereo is in under the outside wires, and it sits right next to the terminal for our Verizon Fios -- not the most ideal location, but it
is the only option.

Using the CD pots on the amplifier, you can only hear the radio pretty faintly, when the volume pot is turned all the way down. If I am playing cds, you can't hear anything, but since when I switch to the phono/aux1 setting, as I mentioned, I am picking up radio signals, and
the volume is louder. From what I read (and hear), it appears that the phono pot (perhaps in cahoots with the moving coil phono stage) is acting as a antenna, and picking up signals, which are cross-talking
across the other inputs on the amp.

How would you recommend addressing this? I am currently considering
shorting terminators on the phono, and other output pots and found some terminators online (audiophilia article).

At first I thought it might be my changing the speaker cables, from very thick cables to the slimmer DMNs, but that would not explain why the RFI is louder at the phono input than any of the others.

Whatcha think? Does this make sense?

The other option would be RCA caps.

Thanks,

Marty
martyw

I am currently considering
shorting terminators on the phono, and other output pots and found some terminators online (audiophilia article).
Do not install shorting plugs on the outputs. Ok on the inputs....

At first I thought it might be my changing the speaker cables, from very thick cables to the slimmer DMNs, but that would not explain why the RFI is louder at the phono input than any of the others.
Does the radio station get louder if you increase the volume?

How long are the speaker cables?
If you still have the old speaker cables reconnect them and then listen for the radio station.
Thanks Jea,

On point one, sorry -- I meant inputs.

On point two, yes, the volume increases if I turn up the volume, but again, it is most prevalent on the phono setting. On the other settings, it is there, but very much in the background.

On point three, the old cables are gone -- they were spades, and not compatible with the new amp, so I sold them.
Thanks again -- Marty
I agree that shorting plugs on all of the unused inputs (especially of course the phono input, but I'd suggest the others as well) should be step 1.

I doubt that the speaker cables have anything to do with it, in part because the very low output impedance of the amplifier would tend to "short out" any rfi/emi picked up there. And also because it would seem unlikely that anything picked up there would make it back to a circuit point near the input of the preamp section, where it could be amplified.

I'd suggest one other experiment that I'm curious about. Do you get the same radio signal pickup when NOTHING is connected to the inputs of the 2010S (meaning with the cdp disconnected)? (Obviously, turn power off while you are disconnecting the cable).

Regards,
-- Al
Hi Al,

Thanks for the tips. I ordered the shorting plugs, and they should arrive later this week.

I do get radio when there is nothing connected to the inputs. I played around with putting a ferrite bead (from an old USB plug) by the phono input, but it made no difference.

When I am using the other pots, you can only hear the radio, when your ear is very close to the speaker, but it is pretty annoying nonetheless....

Thanks,

Marty
Hi all,

So the shorting caps didn't address the RFI, even when in the phono stage. Would the next step be swapping out the moving coil stage and putting back in the other piece (I am not sure what its is called -- I think internal jumper? If so, who can do that?

Thanks -- Marty
Hi Marty,

Are they truly shorting plugs, which look like an rca plug and connect the center pin to the outer ground sleeve? Or are they just caps, which simply cover the opening on the jack (which I would expect would not be an effective fix)?

Assuming they are shorting plugs, yes removing the moving coil stage would seem like a logical thing to try. Presumably it comprises a small removable circuit board dedicated to that function, since it is an option with that particular amplifier.

You might ask the manufacturer or dealer how to identify it when the top cover is removed, in which case you could probably remove it yourself (while taking precautions to prevent the possibility of damage being caused by static electricity -- let us know if you'd like further advice in that regard).

Good luck!
-- Al
Another thought, while I had the shorting plugs in -- I have nothing connected to the "outer ground sleeve" Is that the little metal piece on the back bottom of the amp that says ground?

Thanks -- Marty
No, by "outer ground sleeve" I simply meant the cylindrical outer part of the rca phono jacks themselves, which the shorting plugs would connect to the center pins of the jacks.

-- Al
So the shorting caps didn't address the RFI, even when in the phono stage. Would the next step be swapping out the moving coil stage and putting back in the other piece (I am not sure what its is called -- I think internal jumper? If so, who can do that?
11-21-09: Martyw

The only input I am using is the cd player, but with volume turned all the way down, I am picking up radio signals. If I turn the dial to the moving coil phono setting, even though nothing is attached to it, I can hear radio pretty loudly.
11-17-09
Not sure if the question was asked and answered. What happens if the CDP ics are disconnected from the Exposure 2010S? With the selector switch set to the CD source is the radio station louder?
Hi Jea48. The radio station is the same. I also swapped out the moving coil phono, and it is still coming through. I'm giving up on this one -- posted it on Audiogon last night for what I paid for it.

Any ideas for well shielded pieces? I am currently looking at Odyssey, either their cyclops integrated, or the khartago power amp paired with the Vincent SA-31. Any thoughts if that would work? Odyssey gear seems pretty well-shielded.

Thanks -- Marty
Marty,

You might try some clamp-on ferrite beads on the power cord of the amp and on the speaker cables.
You never answered how long the speaker cables are....

RFI Tips And Tricks
Quote from Link:
AUDIO AMPLIFIERS
It's quite likely that the audio amplifier is performing RF detection. You need to place ferrites on the speaker cables as close to the audio output (right at the PC board if possible) with as many windings as possible. If it is audio detection, it won't matter at all how many ferrites you install on the power cord or cable TV or antenna cable although this will cut down on the amount of
RF getting into the TV via those conductors. Direct pick-up onto speaker wires causes most problems. Don't go into the television if it is not your own.

Jim
Sorry -- they are 6 feet DMN cables
Jim, I really doubt that the writeup you referenced is applicable in this case. It is dealing with the situation where a ham radio transmitter, which typically may be outputting several hundred or even 1000 watts of rf energy, is interfering with a neighbor's tv set perhaps 100 feet away.

In that situation, yes, it seems conceivable that speaker cables in or connected to the tv set could pick up some of that energy, from where it would blast its way into the audio or video circuits of the tv and be rectified, and perhaps amplified as well.

With Marty's integrated amp, on the other hand, the speaker cables are likely to be picking up rf measured in microvolts, or millivolts at most, corresponding to nanowatts. That pickup will be loaded down to much less than even that low level, by the amplifier's output impedance (likely a tiny fraction of an ohm), and also by the speaker, which is not capable of reproducing low level rf signals unless they are both rectified and amplified.

The power cord and wiring would seem to me to be an unlikely entry point as well, due to the capacitive filtering, etc., that is in the amplifier between the ac input and the signal path.

Best regards,
-- Al
Hi Al,

You are probably right but if Marty has some ferrite beads it won't cost him anything to try them on the speaker cables and or the power cord. Maybe the radio tower transmitting antenna is close to where Marty lives..... Or maybe it is a hi-power radio station.

The amp received a good review from Stereophile and I can't imagine the proper shielding was not incorporated into the design and build of the unit.

Is it possible the amp could sound good and still have a cold solder joint somewhere along a signal ground path?
Jim
Is it possible the amp could sound good and still have a cold solder joint somewhere along a signal ground path?
Yes, that certainly is conceivable, Jim, although of course it would be very difficult to troubleshoot.

Marty, I realize that this is all probably moot, because you are proceeding to look for a replacement amplifier, but I see in the thread that you started today that you actually did mention nearby radio transmitters. It would be interesting to know how far away they are, whether they are am or fm, how many watts they are (perhaps that is indicated on their website), and if when you hear them through your system you hear actual music and/or voices, or just static-like interference.

Regards,
-- Al
Hi Al and Jim,

Not sure how far away they are, maybe 1 mile? The signal is FM. Besides the amp, the only thing that changed is the speaker cable (from wireworld biwire to DMN single run). Interconnects and speaker cables are the same.

Figured the easiest thing at this point is to quit while I am ahead, sell it, and find an amp I can demo at home first.

Thanks,
Marty
Hmm ... It's hard to envision how an FM signal could be detected/decoded by your integrated amplifier into something resembling intelligible voice or music, assuming that is indeed happening. AM would be a different story, and more easily explainable.

A home demo of the next amp certainly seems like a good way to proceed. Good luck!

-- Al
HI Al,

Couldn't the rca inputs act as an antenna? Or could it be the speaker wire?
Hi Marty,

Yes, those things could certainly pick up low level rf energy. But as I explained above it seems very unlikely that pickup on the speaker wires could result in audible sound. And the rca inputs presumably wouldn't have been able to pick up anything significant when you had the shorting plugs on them.

And as I said, it is very difficult to imagine how an fm signal could be decoded into intelligible audio by anything that is not specifically designed for that purpose. Perhaps it is really being caused by a more distant am station.

Regards,
-- Al
Not all ferrites are the same.

Marty if you try ferrites on your speaker cables and or power cord make sure you install them as close as possible at the entry point of the amp.
Marty,
Is this your speaker cable?
http://www.dnm.co.uk/cables.html
http://www.stereotimes.com/cable022205.shtml
yes it is.
Marty,

Might be a waste of your time but I would go to HD or Best Buy and buy some cheap twisted pair speaker cable and see if it solves your problem. Flat ribbon speaker cable is prone to RFI,... works as a good antenna.

Another thing to check out is the radio station. Do you know for sure which one it is. If so give them a call and ask to speak to their engineer. Ask him if they are broadcasting also in AM. Also explain your problem to him. He may be able to help. At the very least he will give you the broadcast transmitting frequency.
I have some zipwire from best buy, but it is unterminated. The exposure only works with bananas. Is there any way to test it with the unterminated wire?

thanks -- Marty
Marty,

If the DNM speaker cable is acting as an antenna , in your situation, parallel wire (Zip cord) will more than likely do the same thing. Read page 11

You will need to use twisted pair cable. You might check Radio Shack for some cheap cable and banana plugs for testing. If it solves your problem then you can buy something better.
Jim
Thanks -- to be honest, I am ready to sell it and move on. Not to mention, I really miss the warmth of my old tube amp, so I am going to try and find something that gets me closer to that.
Solved it!!!!!!!!!! It was the solid core cables!!!! I tried some stranded radio shack cable and cheap banana plugs and no more radio coming into the amp. PHEW!! Of course, still going to sell it -- I miss my tubes, but glad to know I am not crazy!

Thank you all for your help!
Glad to hear it, Marty. But I'm truly surprised, given all the reasons I cited as to why it was unlikely to be due to speaker cable pickup. So somehow what was being picked up in those cables was making its way back to the front end of the integrated amp, where it could be affected by the volume control and source selection, amplified, and detected/rectified somehow (I still doubt that it was an fm signal, for which no detection mechanism is present).

Jim, I owe you a beer!

Regards,
-- Al
Thanks Al and Jim -- It was a bit of a wild goose chase, but glad to have figured it out in the end. I probably should I have tried swapping speaker cables in the first place, but I didn't have any to try so I looked for other possible causes -- oh well. At the end of the day, it is just not the right amp for our situation. There are only two Exposures listed for sale here (including mine), so I don't imagine it taking too long to sell.

Thanks again for all of your help -- Marty
Well gentlemen,

Looks like the devil is still hanging around. I am trying out a new amp and new speaker cables (nait 5i and naca) and am still getting some RFI (can only hear it when 6 inches or so from the speaker). Is this normal? Could it be from the power cords? All my cables are bunched together behind our media cabinet as well...

Thanks -- Marty
Hi Marty,

Can you describe the sound of the "rfi." If it is just high frequency hiss, audible only within 6 inches of the speaker, it certainly may be normal and would not be uncommon. It could be low level noise intrinsically generated in the power amplifier, preamplifier, or (if it is volume control sensitive) in the source component. Or it could be due to pickup in interconnects, from power cords or from sources of rfi elsewhere within the house or external to it.

Best regards,
-- Al
Hi Al,

Exactly -- high frequency hiss, but with a beat. Since it clearly is not the amp or the interconnects, I will try swapping out the stock power cords.

Thanks again for all of your help!!