282 picking up RF (as in actual radio station)

Posted by: feeling_zen on 28 November 2015

Oh dear. Did a full rebuild of the system yesterday. And now I can hear a local radio station from a couple meters away from the speakers. Not good.

By process of elimination I disonnected all source inputs on the 282 and powered off everything else so that the only things powered up are the NAPSC, SCDR, and 250.2. A radio station is picked up on all inputs selected and is not affected by volume control so that tells me it is introduced after that stage or possibly as the bias current which could point to the SCDR. But if I mute the preamp entirely the problem goes away so I don't think it is picked up in the 250.

It is driving me nuts.
Posted on: 28 November 2015 by feeling_zen
Just for elimination I removed the Hatpin XLR and put the stock lead back in. No improvement in the problem.
Posted on: 28 November 2015 by feeling_zen
It gets weirder.

Another system for the AV setup which normally has a fair bit of nominal hiss from the speakers now has absolutely no background hiss at all (not a whisper with my ear up against them). Yet this system was not rebuilt and in fact the Naim setup is on its own dedicated spur from the mains rung while the AV setup is on a rung that isn't even earthed. But rebuilding the Naim was the trigger for the awful RF on the 282 and the new improved noise reduction on the AV setup.

I have never experienced RF this bad before.
Posted on: 28 November 2015 by Simon-in-Suffolk

Does the radio station get louder in the evening? Is there an increased hiss and hum noticeable now you can hear the radio station? 

I would check the mains earth, but assuming a new radio station has not set up very nearby. I would disconnect and reconnect all connections.. and if still an issue contact your dealer, it could be a decoupling capacitor has gone open circuit.

Simon

Posted on: 29 November 2015 by feeling_zen
cheers Simon. I was hoping you might respond to this.

Yes it is most definitely louder at night. Though I don't think the background hiss has changed noticeably.

Off to pick up some ferrite chokes now and redo the wiring again. The whole building's wiring is only 2 years old and I had the dedicated spur installed at the same time so the earthing should be okay.
Posted on: 29 November 2015 by Simon-in-Suffolk

Hi, by all means try the chokes, but I doubt this is going to help with how you describe this.. IE the interference occurs when nothing is connected, but goes when you hit the 282 mute..

can you recognise the radio station? Is it a nearby FM one, or a distant AM one..

When you move the 282 to a different room, or plug into a different spur, is there a difference?

if not it really sounds like a connection has gone high impedance, (check all 282 plugs and connectors are correctly seated) or a decoupling cap has gone pop.

Simon

 

 

Posted on: 29 November 2015 by feeling_zen
Will experiment for a few days. The chokes were on the off chance the RF was coming in via the Snaic leads to the SCDR. But I've found they are not stocked in the regular places so will need to order online - in bulk! At least they are dirt cheap.

I can drop a spare HCDR in to really eliminate that but my money is the 282 itself.

Will do as you suggest for the others too. Not being a radio listener in general I can't pinpount the station other than a Japanese language classical station. If I listen long enough  I'm sure they will say.
Posted on: 29 November 2015 by feeling_zen

Just updating as I test because I find this problem interesting and frustrating in equal amounts.

Just swapped the SCDR for the HCDR and guess what? The problem is there but is very different.

 

  • SCDR: Problem is quite pronounced from some distance away and both channels.
  • HCDR: Volume of the radio station being picked up is reduced and only via the left channel (yes I put the link back in on the 282).But I can still make out more than half of what they are saying.

 

In both cases, the background hiss, which is quite pronounced, is unchanged. Still have some more tests to go before I raise this issue with my dealer.

Posted on: 29 November 2015 by feeling_zen

For the electrical engineers out there...

 

I tried the PS on a different mains spur. Very interesting. The problem was immediate MUCH worse. I could listen to the news reported on the radio being picked up from the sofa quite clearly on both channels. And this was with the HCDR which on the dedicated spur was the quietest and in fact non detectable on the right channel.

 

Now on a different spur it is merely more pronounced on the left but clearly audible on both. In doing this, the wiring that could have anything to do with this problem has naturally been redone several times with different haphazard dressing to no effect.

 

But this proves one thing. Dedicated spurs are not a waste of money.

Posted on: 29 November 2015 by sheffieldgraham

When you substituted the HCDR for the SCDR did you try both SNAIC's in turn?

Just trying to eliminate the cabling.

Posted on: 29 November 2015 by feeling_zen
Originally Posted by sheffieldgraham:

When you substituted the HCDR for the SCDR did you try both SNAIC's in turn?

Just trying to eliminate the cabling.

Nope. But I will do now.

Posted on: 29 November 2015 by feeling_zen

Become more of a one-sided blog than a thread.

 

Anyway, 3 developments:

 

  • I initially stated that the problem goes away when the 282 is muted. When retesting everything again, I found this to not be true. The background hiss is cut off but the radio station can be heard unchanged (clearer for the lack of hiss). I suspect when I tested before, I hit mute just as there was a natural pause in programming.
  • Using the HCDR I used a different SNAIC lead, to test that suggestion. No effect.
  • I no longer think the issue is worse at night. It was fairly easy to hear this morning.

 

I've involved my dealer but since we are on opposite sides of the planet, that is going to be a slow exchange. I will keep posting here just in case the final resolution helps someone else identify a similar issue in the future.

Posted on: 29 November 2015 by Ron Toolsie

IME RF breakthrough in Naim systems is not so much a problem with the preamp as it is without the power amp. Indeed in the old days, Naim used to do some tweaks to their power amps that made them less prone to this malady, at the expense of some sound quality. 

 

If it is the power amp that is picking up RF, then you need to find what is acting as the main antenna. The usual culprit is the speaker cables, but can be interconnects (although these typically are shielded, unlike speaker cables). 

 

So if you recently rebuilt your system, it is likely that you may have moved the speaker cables just enough to tune them into some local broadcast. 

 

I also have had this RF breakthrough with a Prefix (which was not uncommon), and found out the orientation of the ground wire from the LP12 was its antenna. 

 

So, if changing wires does not work, then try changing their orientation. 

Posted on: 29 November 2015 by feeling_zen
Originally Posted by Ron Toolsie:

IME RF breakthrough in Naim systems is not so much a problem with the preamp as it is without the power amp. Indeed in the old days, Naim used to do some tweaks to their power amps that made them less prone to this malady, at the expense of some sound quality. 

 

If it is the power amp that is picking up RF, then you need to find what is acting as the main antenna. The usual culprit is the speaker cables, but can be interconnects (although these typically are shielded, unlike speaker cables). 

 

So if you recently rebuilt your system, it is likely that you may have moved the speaker cables just enough to tune them into some local broadcast. 

 

I also have had this RF breakthrough with a Prefix (which was not uncommon), and found out the orientation of the ground wire from the LP12 was its antenna. 

 

So, if changing wires does not work, then try changing their orientation. 

Yup this was actually one of my first thoughts because I did change the speaker cable dressing from coiled (before I had the problem) to the Naim recommended way of gently folding it horizontally on the floor snake fashion (there are pictures of this somewhere on the forum with A5).

 

So to test this, I disconnected the 250 from the PSU and left it powered on with the assumption that if the 250 and speaker cables are the cause, then I should still hear the problem. But alas, both hiss and radio vanished so I guess that is not the cause.

 

Given that the results are different between HC and SC and also mains spur, I am suspecting that the mains earth itself is the antenna.

Posted on: 29 November 2015 by Quads

I have the 282 now and have some RF noise (right channel mainly) but only when playing phono through the Stage Line K. This comes in starting at around 9 or 10 on the volume dial. All other sources are fine. Interestingly, the 202 which I still own, does not exhibit any such problem. Possibly, the 282 is more sensitive in this regard?

Posted on: 29 November 2015 by Simon-in-Suffolk

Just our interest Mr Zen.. what sort of earth arrangement do you have in your house (assuming you know) .. Is it true ground earth or a shared PME arrangement?

its a shame your dealer is on the other side of the planet... that is going to be tricky.

I still suspect a failed cap in the 282.. or a high impedance connection on one of the ground connections on the sockets.. However in this circumstance this is when I would borrow an alternate 282 to see if the issue still happens.. that sounds challenging for you perhaps in your situation? I guess an alternative is to see if the issue occurs at a friends house, perhaps some distance from yours?

Simon

Posted on: 30 November 2015 by feeling_zen

@Simon,

 

No idea. My assumption (which I hate making) is PME since (a) It is a building with 500 other flats and (b) earthing generally only plays a safety role in Japan. Generally there are only 2 plug sockets with earth in a standard home; the spot for the washing machine and the spot for the fridge and both are via a bare wire stripped off the mains plug and thumb screwed to an earth bolt next to the plug socket. In my case I paid to have full 3 pin plug sockets installed throughout and a dedicated spur for the Naim and confirmed it was wired to spec within my unit but beyond there is anyone's guess. It tells you something about the attitude to earthing here. Either way, I am not sure there is a way to test for this though if I knew what to look for (I don't) the building management would have to let me into the service room of the basement.

 

Friends that I can test with are sufficiently far away and out in the sticks where not sure if it would be a meaningful test. They are bound to have very different background RF noise and even if there is a problem with the 282, I would expect their distance from Tokyo and position in a valley to mask the issue. I am sure the two 58 storey towers of steel and tinted glass that have recently sprung up next door don't help anything.

 

If my dealer or Naim tell me what to look for I can check components with a multimeter for anything open circuit. I have a feeling my dealer will use this as the opportunity to get it fixed, sell it and get me onto the 252 they reckon I should have had from day one

 

 

Posted on: 30 November 2015 by feeling_zen

Got some homework from my dealer:

 

  1. Do not assume that disconnecting the XLR from the 250 and hearing no interference eliminates the 250 or the speaker cable arrangement. RF needs a full circuit so all that test did was break the circuit, without aiding in pinpointing the culprit. Dealer suspects bad earthing but that it is being picked up in the 250 still.
  2. Ferrite chokes are still a last resort and not a solution to a problem like this. Ignore them until the source of the RF is understood.
  3. Throw the breaker, remove the housing on the wall socket and check the earth connectivity and again at the breaker end. If this is dodgy or loose then all other tests are a waste of time. If you can get the building inspectors to check earth all the way to the basement on the pretext of a safety concern, by all means go for it.
  4. Take a multimeter and check the continuity of all the snake lead pins, the XLR, and the earth on the power tap under different flexings to see that continuity is not broken.
  5. Undo one change at a time. Since I redressed the speaker cables and PowerLines, even though I did so according to Naim's recommendation, go back to coiling and test. If eliminated, do the same with the PowerLines.

 

Report findings back to dealer next week.

 

Posted on: 30 November 2015 by Ron Toolsie

My bet is STILL it is the speaker wires acting as dipole antennas in their uncoiled states. But checking (with an abundance of caution) the tightness of the ground wire connections on the wall socket and within the breaker box is also a good idea. Even a few tenths of an ohm added resistance due to loose wires can be audible. 

 

There are some high performance speaker wires that are shielded, and possibly more immune to pulling in RF. Including, I believe Naim's own SL speaker wires. 

 

Also, I have heard of some people who have gotten rid of RF breakthough due to signal interconnects and Snaics by wrapping them in aluminum foil to provide additional shielding. 

Posted on: 30 November 2015 by feeling_zen

@Ron,

 

I will definitely be testing this by reverting the cables to previous arrangement.

 

Did find one problem that made my blood boil. I paid good money for dedicated spurs and I have found out that the electrician did not want to order a larger breaker box with more spurs on it so actually what he did was make the dedicated spurs (I had one installed in each room) common with the lighting spur for each room. Let's see how it goes. It is past the 1 year grace period allowed in the contract to raise problems after construction but on the other hand, the problem is not with the quality of what they did but the fact it is not as contracted in the first place.

Posted on: 01 December 2015 by sheffieldgraham

If you have an agreed specification and he failed to meet it, doesn't that constitute a breach of contract. More than a warranty issue.

Posted on: 05 December 2015 by feeling_zen

Problem resolved and root cause found. To come to the point, Ron Toolsie, you were correct. The speaker cable arrangement was the problem.

My primary mistake in testing this the first time round is not understanding that the RF picked up needs a circuit to manifest. So leaving the 250 on but unplugging the XLR and suddenly getting no RF noise was the wrong thing to do and led me to the wrong conclusion (the 282).

Anyway, I checked the integrity of the grounding on the plug socket which was fine and at the breaker box which was so so. Not much I could not about the latter. Proprietary TEPCO unit where all the (unmarked) earth wires are stripped and pushed into a bank of earth punch panels very similar to a giant AT&T phone patch panel. They can only go in once as it is a disposable design where you have to break the seal on the entire bank to remove one and then fit a new earth panel and punch them all in again. So I had to assume this was okay.

Checked continuity of all the PowerLines, SNAICs and XLR cables. Perfect.

Redress only one cable at a time and check for differences.

Although my dealer also suspected the speaker cables, he told me to start with the power leads and work from there towards the speakers since everything hinges on the quality of the earth connections. As a result, the speaker leads were the last thing I changed and the only thing that impacted the problem. I guess they did not like being snaked sideways as per Naim's recommendation. Coiling might be the lesser of two evils here.

And as mentioned I also found out that my dedicated spur is not dedicated at all. The Naim has to share the mains with 3 LED lights, the phone, and a rice cooker - non of which use an earthing pin anyway. The resolution of this oversight would involve removing an entire wall of built-in shelves, tearing up the floor in the living room (including the underfloor heating), and all the marble tiling in hallway leading to the cupboard with the breaker box. I have to concede it is not worth it and like everyone on the planet that has ever had to deal with tradies, I have been shafted and need to let it go. You'd think using the same construction company that built Tokyo Tower would avoid this BS but I guess not.

Anyway, I was without the main system for 7 days because of this and am ecstatic to be back in listening mode.

Posted on: 05 December 2015 by Simon-in-Suffolk

Glad, you got it sorted.. Not entirely convinced of the explanation as it still sounds like some sort of earth issue interacting with the speaker cables in your example..remember signal earth is through the preamp with Naim.. anyway keep an eye / ear on it if and when you get new sources.. BTW coiling speaker cables is a no-no as you are creating common mode inductance that could interfere with the amp /speaker coupling.

Annoying about the spur, not least the LED lights on it... but as you say let it go.. You can always use some filtering later on if needed.

Now enjoy your tunes 

Posted on: 05 December 2015 by feeling_zen

Thanks Simon,

That is a real possibility. I'm open to any ideas on how to actually test the earthing. So far all I could do was test cable continuity of all pins and look at the earthing in the breaker box and give it the once over. If anyone has a practical way of verifying this of zero or moderate cost I am all ears.

Posted on: 05 December 2015 by Harry

I paid an electrician to install a dedicated spur, He could not understand what good it would do but he took the money and did it. Three double unswitched sockets on 10mm cable.

It was years later that I discovered by accident, as you do, that one double socket goes back to the fuse box and the other two come off the lounge ring main.

The electrician is long gone and untraceable. We borrowed a MusicWorks Megablock, wondering if it would make much difference. It did. Which was in its own way comforting because this is the reason we wanted a dedicated spur.

Screwed by trade.

Posted on: 05 December 2015 by feeling_zen

Tradies. Only people that haven't been shafted by a tradie are those who have never had work done. As a friend in the business once confirmed to me, even he, as a tradie, cannot not be shafted by another tradie.

Back on topic, good ways of testing the earth pending, there are other issues at play here. My room does not let me dress the speaker cables in a very sensible way. Big no nos  other than coiling include:

  • Dealing with the slack near the amp end or speaker end. It should be snaked somewhere in the middle. Unfortunately there is nowhere to hide between my rack and speakers so the cable was snaked under the rack directly under the 250. Either that on open floor in front of a raised doorway.
  • Running the speaker cables parallel with mains cables. Unfortunately the only available socket with earth is directly between the speakers below the TV. The Naim resides off to one side so there is no avoiding the fact that the speaker cables, mains extension cord, and a LAN cable all have to run together for about 3.5m. Stupid thing is there are plug sockets unused directly behind the rack but they do not have earth because of some BS Japanese building code that prevented me from having more than a certain number of earthed sockets installed.

I am wondering whether running the speaker cables through thin 1cm pipe lagging will provide enough insulation from the mains and network cables. It's hurdles like this that make me feel like it may not be worth upgrading anything until we build a new home and solutions to these problems can be built-in.