Another RF Interference Question

Oh, coiling up the din cable between my Dac V1 and amp and moving it to just the right spot helps, but I guess with an SU you wouldn't have the din cable issue...

tufts0207 posted:

Of note, I just spoke with someone at BJC and apparently my location in Seattle, I am in very close proximity to some strong radio towers that I'm getting blasted by. Anyone have a suggestion on shielding from RF signal for the whole SU? Is this possible? 

I feel your pain. I was in a similar situation for several years, when I lived about a mile south of the three radio masts at the top of Capitol Hill. I could see them from the kitchen window. After much experimentation - ferrite chokes made very little difference – I got rid of most of it by pinching the slack of the A5 speaker cable into a hairpin shape and then, starting with the “point”, coiling it into a spiral. This was probably harmful to SQ, but the intereference was so bad that it was a worthwhile tradeoff. The exact placement of these coils was significant, and every so often, I’d have to move them an inch or two this way or that.

Another huge difference was made when I ditched the phono boards in my then-102 and got a Linn Linto. The home dem was one of the very few jaw dropping audio experiences I’ve had in my 28 years of Linn/Naim ownership. Prior to that, I had never heard music on vinyl emerging from a near-quiet background, and I was astonished. After that, RF breakthrough was reduced to a minor and intermittent annoyance.

Fast forward a few years, and we moved a few miles south, to the Columbia City neighbourhood, and the RF problem went away on its own. The charm of the Linto had faded a bit by then, and I changed to a SuperLine, with no regrets, and (still) not a trace of extraneous noise coming through.

Good luck with the quest. It’s a very dispiriting problem to have to deal with.

CABLE Position  may cause it .reduce length of mains cable could work

Ok - I had a look, there are a few NPR radio transmitters in the Seattle area - and I assume you referring to the AM transmitters. The transmitters listed I could see were all Class A or Class B - which means they are transmitting between 10 and 50kW

Therefore the electrical field strength from your closest transmitter 3/4 of a mile a way could be upto around 0.45V/m to 1 V/m in your house - through orientation and house construction and nearby buildings will most likely diminish this.

But in short with that sort of field strength any thing with a tendency to act as a tuned circuit with the frequencies being transmitted will most likely induce radio breakthrough .. so I really would try NACA5 and different lengths of it - that way you know you have an optimum reactive speaker cable load on the Naim amp... although with such a high field strength it may be a change in orientation of the speaker cable is still required to couple less to the transmitter field strength.

BTW those creating coils - I am not sure that is the good idea unless all other options have failed. To my way of thinking a coil is going to 'excite' the tuned circuit - but will change its resonance point so a particular station is perhaps less likely to break through for a given speaker/amp/cabletype/cable length ... but I guess if you are plagued by this then anything that gives relief is worth a try..

Simon

Some VERY good advice here. My feeling would be to hold off on 'solutions' b, c, d, e as being (probably) good ways to waste money without any relevant benefit.

I've experienced problems like this with customers in Dublin and Chicago. Often, given how long ago I worked in retail, the most extreme source was the cartridge, tonearm cable and phono stage but the speaker cables were usually the next - and most mysterious.

Best advice would be to speak to a local Naim dealer (preferably of long standing) and hope to benefit from their experience. The test I would have recommended IS the use of headphones without the speaker cable attached.

Your result points to the speaker cable interaction as being, at least, the major source of interference. As these are acting as a tuned circuit (or aerial) length, orientation and the presence of straight sections will contribute to how 'well' (or 'badly' from your point of view) radio is picked up. I suppose it might even be possible to adjust these parameters to selectively tune your favourite local station but it is likely that the strongest will tend to dominate - and you didn't buy the SuperUniti as a glorified, and bad, tuner/amplifier.

Bringing the speaker cables out into the room and arranging them casually into disorganised paths from amplifier to speakers may give you variations in interference. While not much help in the long term, variations in intensity might indicate that changes in cable length could be beneficial. It may also be possible that changing the orientation of the system to a wall at right angles would also have some effect - although this, too, may not be possible/desirable.

As suggested - speak with a local Naim retailer. If no full solution can be found, at least some amelioration may be possible. You might ask for the loan of a few, sensibly different, lengths of speaker cable to see if you can effect a change. Better than buying and getting no result.

The best of luck. this problem can be most intractable.

Has anyone in US who's posted on experiencing the same problem tried a screened speaker cable ???     It might be worth trying a cheap test with a few bucks of shielded power cable,   leave the shield unconnected at both ends & hook up the speaker in the normal way & see if that helps.