RF interference 300 DR

It's coming through the speaker leads. Try to arrange them differently. 

Re-connect the 272 and take a look at your speaker leads. As HH says, try re-arranging.  Also the solder connections on the plugs.  What cable are you using, and what length?  Running the amp close to instability by using the wrong speaker cable can cause RF pickup.

I am using Naim NAC A5.  They are 5 mts long.  I had tried rearranging them without success.

OK thanks.  Are you running left and right channels of the NACA5 close together or apart?  Try running them close together.

my speakers are about 8 feet apart if that what you meant.    

Richard means try getting the two wires close together if you can. You can't easily move the speakers, but try it with the amplifier somewhere else and see what happens. Just put it on the floor and move it about. 

ok, many thanks.  I will do it when I get home tonight.  I will keep you posted.

BPou,

Are both units plugged into the same circuit? Was there any remodeling or rewiring done in the house? You checked ground, have you checked phase on each socket your gear is plugged into with a GFCI circuit tester?

I recall reading about dedicated circuits (in the US) and there is a situation whereby when gear is mistakenly connected to both phases the circuit wiring can act as an RF antenna. I don't claim to know the details, just that it can happen.

Hi Joerand, yes, both units are connected to the same circuit.  I use a Tripplite Isobar and all is connected there.  This bar has RF filtering for the AC line.   I have not checked polarity.  

I moved things last night with not success.  I changed the speakers cables to eliminate the possibility of a problem with the solder in the original cable, no change.   Frustrating!

The cable company is coming on Saturday to check the cables and connections.  They detected that there is noise entering their system from my apartment.

Let see...

Be interested to hear this outcome.. intrigued by the comments that the cable company believe there is noise/interference coming from your apartment.....

Radio Breakthrough, which is what you describe, as opposed to RF interference which is usually something else, often occurs when some part of your setup is acting as a tuned circuit resonant to some extent to a radio carrier within an area of relatively high radio field strength and through distortion is effectively demodulating the radio carrier.. so disrupting the tuned circuit by changing dimensions and layout of cable runs can disrupt the tuned circuit and you hear no more radio.... 

Radio Breakthrough is interesting... as you are actually hearing the products of intermodulation and rectification distortion from radio frequency energy coupling into your electronics... now where RF carrier is modulated such as with a radio station you can hear and detect it.. however the same can happen with other RF sources such as from computer, powerline adapters, SMPS, bad electronic lighting, poor solar panel inverters etc but the distortion artefacts produced might not be as  easily recognisable and should have a lesser field strength.. but they will be adding a degree of distortion to your audio replay.

So if possible prevention is better than cure.. and identifying the source of the interference should be priority... and if you can do nothing about it, then focus on disrupting your system coupling with it (changing wiring, layout, check grounding etc)

Simon

Out of interest, can you determine what the radio station breakthrough is - local station, foreign station ?

I am curious too.  

I believe it is a local station since the transmission is in English.

I used to get RF interference on my old Rega turntable, it was always Radio Russia & in English.  My fix was a ferrite on the phono leads 

BPou posted:

I am curious too.  

I believe it is a local station since the transmission is in English.

 

Is it 24x7? Also can you listen around the fixed times like 12noon 6pm - as you should get a radio ident.

With radio breakthrough interference it is not uncommon for coupling to come via the mains - depending on house wiring, alignment and local field strengths - and so ferrite clamps / ferrite rings around the mains wiring can also magically make the breakthrough disappear.

S

Bpou, good advice from Simon above.  Just to be ware of the obvious, do you have any transmitters close by?  Be aware that in some countries it seems that high rise buildings rent out their roof space for transmission equipment.  Also, buildings that use a steel frame can also form a kind of reverse faraday cage effect where RF can be amplified to alarming effect.  I discovered this first hand when setting up for the Montreal hifi show some years back. The room we had was split into a larger part and then a smaller ante-room.  The problem was that the CD555 we had for demo refused to work in  the large room but worked perfectly well in the ante-room. There was a lot of head scratching on that one, and a number of long calls back and forth with the factory. It culminated in Doug and I walking around the room each carrying one half of the CD555 and the PS connected to a long extension lead.  As we walked around I would try to operate the player.  No dice.  Only when I stepped across the threshold either out through the door or through to the ante-room did the player suddenly whirr into life.  After consultation with R&D, the conclusion was that RF levels were so concentrated in that room it was interfering with the control system.  We ended up running the CD555 in the ante-room with no problems.  Oh, and we drew lots for who was going to man the main room... 

Many thanks for your suggestions and inputs.  This is driving my crazy!

They breakthrough is happening 24/7 though it is stronger at night, probably around 6:00 or 7:00 PM.  I invested a lot of time yesterday trying to isolate the problem.  Physically disconnecting the pre to the amp does not eliminate the problem, which make me think that interference is not coming through the pre.  I tried re-arranging the layout of the speakers cables and there was some improvement in one channel but no eliminated.  This makes me think that it is coming through there.  But it never disappear though it attenuates in one of the speakers.  This lead me to check the cables between the AMP and the PSU (it is a 300 DR).  I noticed that moving then in certain directions produce some changes too.  Thus, the problem may be there.  is that possible?  

My previous amplifier (AVM) was completely silence.  Physically nothing has changed in my apartment since then.

The cables between the 272 and 300 are unscreened cables (they are basically 3 core mains cable) so moving these will have an effect but normally this should not be a problem... 

So...

Do you get the interference with headphones ?

If yes -

1 - Start with 272 only (disconnect 300) - any interference ?  If no :- 

2 - Reconnect 300 (no speakers connected) - any interference ? - If no :-

3 - Reconnect speaker cables. 

What else is connected to your 272 and how is it connected.  Does this happen on all sources ?

It may perhaps be possible that it's getting in via the Burndies on the NAP300...

As an adjunct to my post above, I do recall some years back that I came across a similar problem to the one we had in Montreal, albeit this was in a customer's house.  Anyway, I seem to recall that re-dressing the pair of Burndy leads on the CD555 (I can't now recall whether it was dressing them together or apart) greatly improved the situation.  This was all done "remotely", trying to advise by e-mail, so not easy. However, it's worth noting that I did eventually discover that the customer lived in the shadow of a very high powered transmitter.  The power of transmitters outside of the UK can be very much higher than is normally found here and it appears it was high enough to cause the problem.

Hi James, no interference with headphones.   Crystal clear.  I interpret this that the 272 is sending a clear signal to the 300.

As mentioned before, physically disconnecting the 272 and 300, the interference is still there.  Thus, I believe it is between the amp and speakers.  1) the burndy cables that connect the amp to the psu; and/or, 2) the speakers cables.

Connected to the 272:  1) ethernet cable to router internet/NAS; 2) CD player via optical cable; 3) computer connected via audiophilleo spdif.   

it happens on all sources.

Thanks

Ok - thanks for that. Just wanted to know what was connected. Speaker cables seem highly likely but it would be good if you could confirm Richards question regarding any nearby transmitters. What does your dealer say as they may be able to offer a solution if they know the local area has problems with high RF levels ?

Just one more thought - i take it the Signal ground switch on the 272 is set to chassis ?

BPOU - just looking back through the forum, i recognise your system from the system pics thread. You seem to have a 272 with XPS and the 300 + PS in a stand under the TV - you also mention you have the AV system connected via analog connections to the 272. Have you always had interference or has it recently started. If so what has changed ?

James

Hi James, you are correct, that is my configuration.  Nothing has changed, probably the interference has been there since last October when I moved to Naim.   My system sounds very good indeed.

Two weeks ago I decided to put my ear on top of the twitter and discovered that there is a very low volume/level  interference going through.  It is very low, you have to put to ear against the twitter to hear it.  Since we are always looking for the best possible sound quality, I guess that though my system sounds good, there is an extra level of performance that I am missing.  My migration from AVM/Marantz to Naim was precisely seeking for the best.     

Hi BPOU - ah ok. Sounds like it's at a very low level if you have to put your ear against the tweeter to hear it. Worth checking the earth switch on the 272 is in the right position and also if you do have the AV receiver connected to your 272 via its analogue connections (as you mentioned in your system pics post)  then try removing those too and see if the noise goes. 

James

ok. The cable company came over on Saturday, they found not faulty equipment (Tivo box and cable modem/router) at home.  The technician said it was a filtering devise at the distribution panel and changed it.  

Now, for the radio breakthrough.  I changed the layout of the speakers cables and put ferrite beads on the AC line and burndies.  It reduced the radio significantly though still there.  Now it is more a noise without much modulation.  Now you cannot understand the people talking but can hear a small noise of voices if you put your ear against the twitter.   I am gld to say that there is improvement in the sound quality.  

I found that the National Public Radio antenna is around 2 miles from my apartment and I live in the top floor of a highrise, in fact the tallest in the area.  Probably the footprint of the antenna is too high in my location.  I may need to move...!

My speakers cables are 15' long.  I wonder if shortening them to 11' ( I understand that this is the minimum length recommended by Naim) would reduce the noise even further.  

Thanks again for all the great inputs.

BPou posted:

My speakers cables are 15' long.  I wonder if shortening them to 11' ( I understand that this is the minimum length recommended by Naim) would reduce the noise even further.  

I would be reluctant to shorten your cables - 3.5m (just over 11') is Naim's recommended minimum length for NACA5. There is a suggestion that the optimum length is 5m or more, so you may lose a little performance here, with no guarantee that it will solve your other problem.