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Topic: Audio interference from phone when powered through headphone amp (Read 7401 times) previous topic - next topic
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Audio interference from phone when powered through headphone amp

Hi there,

Based on advice I gratefully received from members of this forum on headphone amplifiers and what would suit my needs best, I bought the Topping NX1 headphone amplifier seen here: http://www.amazon.co.uk/NX1-Portable-Headp...e/dp/B00IE2AKD8

While I'm very happy with the performance of this device in terms of amplifying the signal from my HTC One X+ (it sounds great!), I now frequently have to contend with those annoying beeping sounds that speakers sometimes emit when a mobile phone rings nearby. Weirdly, this even occures when my phoned is set to aeroplane mode. I was wondering whether anybody has any tips on how I might eliminate or at least mitigate this effect. It usually happens at least once, quite loudly, and for a several seconds, during each song I listen to, which does significantly diminish my overall listening experience. Here's hoping one of you guys might have a solution!

Cheers

Audio interference from phone when powered through headphone amp

Reply #1 –
You mean the amp alone generates noise when exposed to RF energy?  I guess buy a different amp?  Sounds like it doesn't have good RF rejection on the inputs.

Audio interference from phone when powered through headphone amp

Reply #2 –
Does this problem only occur when the phone is clicked into a docking station [or just a cord is attached] as I suspect?

Audio interference from phone when powered through headphone amp

Reply #3 –
Quote from: mzil on
Does this problem only occur when the phone is clicked into a docking station [or just a cord is attached] as I suspect?


I don't have a docking station, just a 10cm 3.5 to 3.5 cable. It never happens if I plug my headphones into my phone directly if that's what you're asking

Audio interference from phone when powered through headphone amp

Reply #4 –
Quote from: saratoga on
You mean the amp alone generates noise when exposed to RF energy?  I guess buy a different amp?  Sounds like it doesn't have good RF rejection on the inputs.


I guess that's what I mean. Basically, I get those typical beeping kind of sounds we've all heard from speakers when a nearby mobile phone starts or is about to ring, and I only get this when my headphones are plugged into the amp rather than the phone directly. I hope the only solution isn't to buy a new amp!

Audio interference from phone when powered through headphone amp

Reply #5 –
I guess you could open up the amp and try to figure out whats wrong with its design.  Given that its a cheap amp, I'd probably just buy one that was more noise resistant.  Have you looked at the Fiio stuff?  Its cheap, fairly good quality, and I've never heard of them having RFI issues.

Audio interference from phone when powered through headphone amp

Reply #6 –
-Use a longer cord so the RFI signal is weaker because it is farther away. [assuming the problem isn't traveling down the wire]

-Sometimes simply rotating one of the two pieces of electronics 90 degrees from how you had it also can reduce interference.

Audio interference from phone when powered through headphone amp

Reply #7 –
you have to check if the noise comes from the signal that get's into the amp or if it's RFI related. just turn everything ON as you would to listen to music and unplug the LOD cable from the amp to see if you still get noises.  those are 2 completely different problems.

if it's "only" that your phone in airplane mode doesn't really stop emitting something (3G wifi ...) then you might find a solution by just disabling everything independently(airplane mode appeared to work when it wants on several of my gears where I still wasted battery as if wifi was still ON. and turning wifi OFF separately did the trick, so who knows?).


anyway I spent a real long time trying to clear this with an old RSA amp and my advice just like the others suggested(if you really need an amp) is to get another amp after you have inquired that it isn't too sensitive to EMI.
I don't think any amp is fully shielded, but the magnitude of the noises can really be night and day depending on the model.

Audio interference from phone when powered through headphone amp

Reply #8 –
Haven't heard interference from my smartphone which is usually about 30 cm away from my NX1 (and not plugged into it), or I would have reported it.

The equivalent headphone amp from FiiO would be the E11K, but I don't think it's available yet. It's also got an all curved design, which means it won't lie flat and sit still on anything. I have no clue why they did that, but I really dislike it.

Then there's the E12, but it's bigger and significantly more expensive (over 4 times more expensive than what I paid for the NX1).

Audio interference from phone when powered through headphone amp

Reply #9 –
Quote from: castleofargh on
you have to check if the noise comes from the signal that get's into the amp or if it's RFI related. just turn everything ON as you would to listen to music and unplug the LOD cable from the amp to see if you still get noises.


Thanks a lot for this tip. I've tried what you suggested and I still get interference even after I disconnect my phone from the amp, so it must be RFI causing the problem. I also manually turned off my wifi adapter rather than relying on aeroplane mode and this seems to have alleviated the problem notably. I still get the interference occasionally but it occurs less frequently, more quietly, and for shorter periods than it did before. I'm confident that manually disabling the wifi and getting a longer cable so that I can place the amp and phone futher apart should near enough, if not entirely, eliminate the problem. So, once again, thanks for the advice. It's been a big help and has saved me the cost of purchasing a new amp

Audio interference from phone when powered through headphone amp

Reply #10 –
One way to test for RFI is to stick the offending product in  a Faraday cage to block it's radiation [again assuming it isn't raveling down the wire, at least partly.]

It is sort of crude but you can use your microwave oven as the Faraday cage.  Problem is you probably can't close the door fully because of the wire and they are actually tuned to block the specific frequencies microwave ovens make, not all RF, but still I notice my bars of reception plummet when I put my phone in my oven, shut it for the signal strength bars to refresh and then opening it quickly to see what they have fallen to.