It's the buzz buzz buzz in the drum of the ear, or, making my amplifier a tinfoil hat to stop GSM noises from my phone.

September 23, 2009 6:22 AM

It's the buzz buzz buzz in the drum of the ear, or, making my amplifier a tinfoil hat to stop GSM noises from my phone.

Like many others, I have GSM buzz in my speakers. But, I frequently don't have the option of setting my phone to silent while I'm working, because I'm working on the phone. That leaves the options as a) not getting to listen to music while working, or b) letting hideous noises that come out of my speakers every hour at a much higher volume than the music make me aggro. So, I've done some research (and read the old and inconclusive GSM noise questions here in AskMe) and I've concluded that it's most likely my amplifier lacking shielding. I'm going to put ferrite chokes on my speaker and audio cables just in case, but the main plan of attack is to put a faraday cage around the amp since it's out of sight. What is a good way to construct the cage with the following specs:

1) blocks interference really well,
2) isn't terribly expensive,
3) will last/can be moved (i.e. alternatives to tinfoil),
4) has some possibility of heat dispersal so it doesn't kill the amp.
5) no negative electrical safety implications (I can't imagine what these could be but I thought I'd throw it in there in case there is anything I'm overlooking in this department).

Thank you!

posted by Halle to technology (8 answers total)

You might not need to go to these extremes. It's been suggested that you can place your phone on an electrostatic bag from a hard drive to eliminate the buzz.
posted by sjuhawk31 at 6:51 AM on September 23, 2009

You can make a simple, nice faraday cage using only foil tape and a cardboard box. Just find (or make) a box that's the size of your amp. Cover it in foil tape.

As for cooling, you can cut holes in the box if you need. Foil tape is easily cut so you can do it with a knife. But I would put the box on a wooden block and use a hollow punch to make sweet, sweet circular vent holes in a honeycomb pattern. That would be badass.

The smaller the holes, the higher frequencies they will block.
posted by fake at 7:03 AM on September 23, 2009

If your amp is already in a metal case, nothing you add to its outside is going to improve its Faraday shield qualities much. I'd expect you to get much better results by choking all its "antenna" connections. If ferrite beads on audio input, speaker and mains leads improve things a little but don't fix them completely, try toroidal ferrite cores with a few turns of lead wound through the holes.
posted by flabdablet at 7:17 AM on September 23, 2009

You might not need to go to these extremes. It's been suggested that you can place your phone on an electrostatic bag from a hard drive to eliminate the buzz.

I saw this, but shielding the phone is out of the question since I need the signal strength to reach the phone and I have to be able to interact with the phone all day. Actually, I'm slightly surprised this is a good solution for anyone since signal strength is usually fairly important to people.

If your amp is already in a metal case, nothing you add to its outside is going to improve its Faraday shield qualities much.

Are you sure this is the case? I've read multiple discussions of ferrite beads that ended up with participants saying the beads didn't work for them, at which point an audio engineer comes in and explains that the fundamental issue is that the amps aren't well-shielded, so all the ferrite beads in the world won't put a stop to a signal that is coming out of the speaker outputs of the amp. It seems to me that if an electrostatic bag around the phone will stop the buzzing, won't the equivalent around the insufficiently-shielded amp have the same result?
posted by Halle at 7:56 AM on September 23, 2009

I don't know why you think setting the phone to silent will make any difference, but try the ferrite beads out. They should be your first plan of attack.

If the amp is out of sight, it's probably far enough away from the phone to not be picking up noise. Can you move the phone yet further away?
posted by turkeyphant at 8:50 AM on September 23, 2009

Snarkily put, but yup, it wouldn't make any difference. I think I read a discussion in which someone was recommending it and I didn't filter it out as silly since it isn't an option for me in any case.

The amp is out of sight but 3 feet away from the phone. Neither the phone nor the speakers can move but the amp probably could, although it would be pretty annoying (especially if it didn't help much) since the speaker cable is cut to the current length. I'm not sure creating a much longer run of speaker cable really gets me ahead here, though.
posted by Halle at 9:08 AM on September 23, 2009

I built a headphone amplifier for work. Alas, I shared an office with two others which meant 3 GSM phones, making the amp quite unusable. I had to build version 2 with an internal faraday cage.
posted by phliar at 12:58 PM on September 23, 2009

Very nice phliar! Do you think it would work having the cage on the outside of the metal case rather than inside?
posted by Halle at 1:19 PM on September 23, 2009