The unofficial Naim tuner

Malcolm,
I live fairly near you and have been getting a lot of RF recently, for my it is my phono stage, it started about 3 weeks ago and seems very sporadic.
I don't realy know what to do about it though.
David

It would be better if your favourite equipment were less sensitive to interference.

Paul

How can this be done?

malcolm

We had a similar issue last year. The mast in question was to be used by Railtrack and the mobile companies.

We objected, had public meetings and talks with the council and the phone companies - the applicaion was turned down!

We objected on health grounds (I know what the Stewart Report says - its the bigest arse covering excercise I've had the misfortune to read - an 'independent' report commissioned by a government who stood to gain £20bn from 3G licences, indepedent yeah right!) not RFI but it seems to be a growing problem.

but in my case it was broadcast radio, presumeably from an existing transmitter. Could it be a new fault in the Snaxo? Does it have supression (capacitor?) which could have failed. Seems to work other wise, but the radio was loud enough to make attempts at playing music pointless.

malcolm

Was it really FM? AM seems more likely. Was the signal coming from both woofer and tweeter?

I wonder whether a dry joint in an interconnect would be sufficient to cause this? Perhaps moving the wires about a bit would be instructive. Take care...

Paul

Alan, if you get "breakthrough" via this erection(!) you have the right to have the RADIO Authority investigate any problems associated with radio interference.
as a licenced radio amateur i have had this experience;but I was the object of the investigation!.the engineers' inspected all my eqpt and transmissions and lo and behold BT telephones were at fault.....telephones are not licensed to receive radio broadcasts.
Dennis
(GM0PHG)

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Originally posted by Alan Ball:
A notification of a planned erection arrived through my door the other day for a 29m high secure radio transmitter right opposite my house.

Apparently this is for Railtrack and on railway property so no planning permission was required and we have no right to complain etc.. bastards !

If this bloody thing causes me any grief with RFI then they might find it mysteriously getting knocked over by a stolen JCB one night.

RFI is getting to be a real problem for us music lovers and it will only get worse. It sounds like there might be a market for an audiophile hi-fi stand/faraday cage.

-A-

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quote:

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How can this be done?

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In a number of ways.

The first problem is a simple one of filtering and screening - Naim systems are sensitive to RF for several reasons, they are not ideally screened and have very wide internal (and sometimes external) bandwidths.

MC phono stages are the classic problem - lots of gain, and very little filtering.

The problem then is that Naim purport that adding the necessary filtering reduces sound quality, so there is a trade-off to be made, and your dealer should be able to help here, Naim apparently offer several levels of RF 'kits' to increase immunity.

The other solutions are not an option to you unfortunately - the other big problem with RF comes from the use of bipolar junction transistors - these, particularly when used in low-noise circuits, preclude the use of linearity improvements that can help reduce RF sensitivity.

FET's are MUCH better in this regard, and are far more RF immune.

First options for you are to look at earthing, moving cables, cleaning contacts (a dirty joint can act as a rectifying junction, de-modulating the RF it picks up) and general housekeeping.

The speaker cables are a possible route in too - a small capacitor can be added at the 'speaker end to help - but seek advice from Naim as to safe values / types.

In your case it sounds as if the SNAXO or PSU is the problem, check cleanlines and cable dressing around here - move cables for min. pickup is a perfectly valid solution.

Failing that you have to find other equipment you like the sound of

Andy.

Postscript.

It should be noted that in most cases, despite the frustration and affront this brings to the equipment owner, RF problems are almost always faults in the equipment, and rarely in the transmitters.

There are exceptions, but fundamentally if your kit acts as a radio, when it should be a preamp etc., it's not working properly and it has a fault.

Unfortunately fixing that fault may affect sound in other ways - welcome to the real world of audio design...

It's only going to get worse though - wireless LAN's, phones, mains signalling

Andy.

Malcolm,
Just as a thought, I replaced the interconnect between my phono stage and my pre with a more shielded cable and low and behold the interference disappeared.
Andy negative super regs, you know they make snse :-)
David

I am quite used to the phono boards in my 52 making the chirpy noise from picking up my daughter's mobile phone in the next room. What really surprised me this time was the clarity of the signal and the fact that it was independent of the pre-amp. I am a connector fanatic, so little likelyhood of a dirty external connector, but the Snaxo was s/h so anything I should check out inside the box?
I know, I know, send it back to Salisbury, but really if we did that every time a bit of Naim kit made a funny noise, we would never be able to listen to any music.

malcolm

Malcolm,

I'm not familiar with the XO, but are there any plug-in connections inside the box?

Try just moving cables, it can be surprisingly effective. Sometimes closer, rather than spaced apart is better. Is the Hicap serviced or reasonably new - PSU's are a common place for RF to get inside - maybe a swap, if you have another, is an option.

Andy.

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Originally posted by Andrew L. Weekes:

The speaker cables are a possible route in too - a small capacitor can be added _at the 'speaker end_ to help - but seek advice from Naim as to safe values / types.

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Andy,

I've queried this before..

cheers, Martin

quote:

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Date: 17-Jun-99 19:10
Author: Martin Payne
Subject: Capacitors


(A friend with a non-naim system) has found that placing a small capacitor (1 nf Polystyrene) across the speaker terminals eliminates RF pickup from the speaker cables.

I want to try this, but obviously I'm well aware that Naim amps don't like a capacitative load. Is 1 nf a safe amount to place across the speaker terminals? (I'm using 8m runs of NAC A5 from NAP135's into active Isobariks).

Thanks, Martin

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Date: 18-Jun-99 04:15
Author: julian vereker
Subject: 1nF


Very likely ok, - on 8M this is more than doubling the cap, - but since the 1nF is at the speaker end, the amp has several microH in series with it, and so there should be no safety issue.

julian

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E-mail:- MartinPayne at Dial.Pipex.com

The problem went away as quickly and completely as it presented. I didn't change a thing. Radio is a truly mysterious force.

malcolm