Can Wirless Access Point cause humming?
Posted by: luckyguliver on 30 April 2011
I put this post up in Hi Fi forum but nobody replied so far and I get more an more frustrated because my S/H Nap 150x is sitting in the box.When I wired it up to SB3,Sneaky Ds and then to CD player I've noticed that there is humming sound (or rather the sound which you can hear when you make phone call and you were put through with fax machine but not that loud) coming out of my speakers. When I switch off the amp this sound becomes louder for a moment just before the amp switches off completely. ...When I was playing with power cables I switched off by chance a Wireless Access Point which I use to connect Sneaky Ds to NAS/router/internet in another room. At once the noise was greatly reduced but not completely therefore I switched off another WAP which is in main room (router/NAS/computer). I was pleasantly shocked when I realised that this ennoying sound disapeared.You can easly guess that this noise returned as I switched on WAP. What do you reckon what is going on? Can WAP interfer with power amp causing a ground loop? Did anybody experienced such a problem? How can I fix it?
Posted on: 01 May 2011 by Simon-in-Suffolk
Hi, yes a WAP could cause issues that any RF transmitting device could cause if located very closely to sensitive electronics that are not shielded/correctly balanced/terminated etc.If you find your system is also susceptible to GSM mobile noise it does sound like some intermodulation interference (kind of like the opposite of harmonic distortion) from the RF fields coupling into your system.
However you might want to change the orientation on the WAP, or adjust it's antenna I see if the noise goes. Is the WAP a consumer one or industrial one?. Industrial ones can often put a stronger signal out, and it is usually possible to reduce the output power accordingly.
Another thing to try, assuming you have checked you haven't any floating earths or grounds, is putting ferrite chokes around your interconnects, mains and speaker leads (ie every lead in and out of your amp). That will tend to attenuate any coupled RF energy. This is what the RSGB usually recommends for sensitive audio systems susceptible to RF interference.
Posted on: 01 May 2011 by james n
Are you using a pre amp or just feeding the various sources you mention straight into the 150 ?
James
Posted on: 01 May 2011 by luckyguliver
All devices went straight into the 150..
Posted on: 02 May 2011 by DavidDever
There is no ground reference in the system (between mains and signal).
Posted on: 02 May 2011 by Adam Meredith
Originally Posted by luckyguliver:
I audited briefly Naim gear in the nearest Naim shop and I thought I'll give a go, why not? I brought second hand Nap home yesterday ....
This system has a lot of non-Naim variables and these will make diagnosis from a distance difficult.
You first best bet would be to talk to the "nearest Naim shop" and ask if they can help get the NAP 150 they sold you to work correctly within your system.
Unless you didn't buy from them.
Using a Naim power amplifier without a Naim preamplifier can work but leaves the amplifier open to problems the preamplifier might control.
Your 'humming sound' seems not to be 'hum' but something else.
If it were like the sound (which you may not have heard) produced when a mobile telephone is too close to an amplification system then it sounds like your lead is too long and/or the shield is not operating correctly due to the lack of a ground reference - as DD suggests above.
Posted on: 02 May 2011 by luckyguliver
Thanks everybody for replys 
Indeed this sound is like fax machine on the phone or something and it's pretty loud on the top of that. I wonder if WAP is working properly. I bought this item off ebay (like nap 150) as a refurbished. Maybe I get another one and give a go...I might also vist the nearest Naim shop to seek for a advice...
Posted on: 02 May 2011 by luckyguliver
Originally Posted by Simon-in-Suffolk:
However you might want to change the orientation on the WAP, or adjust it's antenna I see if the noise goes. Is the WAP a consumer one or industrial one?. Industrial ones can often put a stronger signal out, and it is usually possible to reduce the output power accordingly.
By the way, I am using D Link DHP 302 which is designed for personal use . How I can change orientation on the WAP? There's no antenna attached
Posted on: 02 May 2011 by luckyguliver
With regards to Richard Dane's questio:
It seems the WAPs are pushing out some heavy RFI and this is upsetting the NAP150x. Question is how it's getting in there; through the ether, via speaker cables, interconnects, or through some other device connected to the system.
I think it's getting there through either power cable or speaker cable because I cen hear this sound (peeeerrriiipeeerrpeeeee when I have power amp connected to speakers only.
Posted on: 02 May 2011 by Simon-in-Suffolk
Hi, ok the antenna is probably built into the printed circuit board. Therefore the best way is to move the WAP physically around.
However I would recommend those ferrite chokes (the clamp on ones can work well).
Simon
