[jules650]

I received my Heed Canamp last week and it picks up a local FM station when it is switched on in my room, particularly when the volume is at zero. It does get quieter but is stil audible when the volume of the amp is turned up. It doesn't make much of a difference whether I connect the RCA cables.

I noticed that it doesn't have this problem at my sister's flat so it's probably caused by the crappy wiring in my room. The building I live in is quite old. Is there anything I can do to solve this problem? (I've tried connecting to different power sockets in my room, with/without multi-socket adaptors and with different sources, none of which have worked)

 

[Gonz]

Probably something like this Tripp-lite power strip w/filters would solve the problem. You can spend much more for line conditioning, if so inclined.

 

[jules650]

Bump!

I still need help on this. I bought a Belkin surge protector that's supposed to have a 65dB RFI/EMI noise attenuation. For a few days I thought that it solved my problems but then it was back as strong as ever. The noise comes and goes and varies from barely audible to being a major annoyance.

It's really getting on my nerves that I can't enjoy this headphone setup that I've bought. Any other suggestions? (I'm only living in this crappy place for another 6 months, so I'm not planning on spending too much money to solve this problem)

 

[Paragon]

For power line conditioning, I won't get anything other than an Isobar. Worked wonders on my brother's HTS. He had the ground buzz really loud through the speakers and the Isobar cleared it up. Meanwhile, we used one of the oldschool 3-prong -> 2-prong adaptors and left the ground disconnected on the outlet while we waited for the bar.
Incedently, Isobar is made by Tripp-lite.

You probably have really bad power ground at your place or bad ground in the amp.

Does the FM change or any buzzing if you touch the amp case or the cord?

 

[SiBurning]

Every amplifier I ever built picked up WNYC classical radio. At least until I found the loose connection. Never did figure out if it was the FM or AM station, since WNYC existed on both. i hope this isn't the problem.

The simplest thing to try is a ferrite ring.

A quick web search for "ferrite rf interference" came up with many web pages, such as:
http://www.mp3car.com/vbulletin/showthread.php?t=51978
http://www.ce-mag.com/archive/02/11/may.html
http://audiosystemsgroup.com/SAC0305Ferrites.pdf

I seem to remember something about these being tuned to particular frequency ranges. If that's so (might not be) you need the right one for FM (or AM or whatever). You can do the research as easy as me, so...

 

[Lad27]

What you hearing is demodulated audio that is picked up from strong FM transmitter (or one not so strong but somewhere very close; any ham radio operator there?). To get signal demodulated (getting rid of high frequency carrier wave) all you need is a diode - in old radio ages it was germanium based diode, but silicone diodes of modern age will also do with lesser effect. That of course wouldn't be enough, you also need antena and as in your case really strong radio signal (which you no doubt have).
Wiring in your place could act as antenna, also you'll have at least four diodes in amps power supply rectifier. You said that Belkin didn't fix it, I' would try ferrite core as suggested here. If that + Belkin won't help you might consider that FM is picked up by amp itself.
It is not as far fetched as it sounds - there is more diodes (semiconductor P-N junctions) that you can count, board copper track can act as a stub antenna. Now, if amp case was full metal enclosure and have good ground (thus creating a Farraday cage) it would be shielded from radio frequency.
What I would try next is to attach a piece of wire somewhere between amp case and case screw. You need a good metal-metal contact here though. Then connect another end to a ground (please don't do it on your power point unless you are absolutely sure that you know which one is live). The plumbing pipes (not PVC of course) should do. Again, good metal-metal connection is needed. See whater FM disapperas or at least gets muted.

BTW, is your sister's flat close to your place? If your amp is silent there, doesn't mean that her wiring is better, she might be just out of the transmitter's close proximity.

 

[Uncle Erik]

Try shielded interconnects. You're probably picking up the RFI there.

 

[tbonner1]

I have had this problem. You have two good and simple ideas that really work:

1-Shielded interconnects.

if that does not work go to

2-Ferrite rings on your interconnects. You can add these on or buy them with ferrite rings built in.

 

[jules650]

Thanks for the many replies; I've been busy this week so I haven't had time to check in on this thread..

Quote:

Originally Posted by SiBurning /img/forum/go_quote.gif The simplest thing to try is a ferrite ring.

I'll give that a shot. Thanks for that suggestion; I've always wondered what the heck those things were around my power cables.

Quote:

Originally Posted by Paragon /img/forum/go_quote.gif Does the FM change or any buzzing if you touch the amp case or the cord?

No the buzzing isn't present unless the volume is at zero, and the FM doesn't change when I touch the case or cord.

Quote:

Originally Posted by Lad27 /img/forum/go_quote.gif What I would try next is to attach a piece of wire somewhere between amp case and case screw. You need a good metal-metal contact here though. Then connect another end to a ground (please don't do it on your power point unless you are absolutely sure that you know which one is live). The plumbing pipes (not PVC of course) should do. Again, good metal-metal connection is needed. See whater FM disapperas or at least gets muted. BTW, is your sister's flat close to your place? If your amp is silent there, doesn't mean that her wiring is better, she might be just out of the transmitter's close proximity.

Are you suggesting that I 'ground' my amp? My knowledge of electronics is miniscule. My sister's flat is in a different town.

Quote:

Originally Posted by Uncle Erik /img/forum/go_quote.gif Try shielded interconnects. You're probably picking up the RFI there.

The intereference is present even with the interconnects unplugged. There is no difference between a crappy 6m RCA lead and my 0.5m Blue Jeans LC-1 interconnect.

Thanks again for all the helpful posts, I'll keep you updated.

 

[jules650]

Update:

In spite of my best efforts, this is still a significant problem. I've tried ferrite cores and a new surge protector which haven't made much of a difference. On top of this the volume knob seems to act a bit like a radio tuner so I've concluded that it's the amp itself, not the PSU or the power cable that are causing the interference. The amp runs so quietly when I've used it at a different town so I'm just going to bear with it until I move in a few months time. Sigh.

 

[mrarroyo]

Please do not laugh, go to the kitchen and get a large enough piece of aluminum foil to over the Heed (Top, Bottom, Sides). See if that stops the FM from being picked up. If not you did not loose a lot of money. If it fixes then lets talk.

 

[Chops]

As soon as you said it didn't matter whether you had the ICs connected or not, I fugured it was an internal issue. Might want to find yourself a small sheet of copper and line the the lid and sides of the amp with it (on the inside that is). Possibly pull everything out of the chassis and lay a sheet of copper on the bottom as well.

If you don't want to try any of that, at least open the amp up and make sure all the connections are secure.

 

[Chops]

Quote:

Originally Posted by mrarroyo /img/forum/go_quote.gif Please do not laugh, go to the kitchen and get a large enough piece of aluminum foil to over the Heed (Top, Bottom, Sides). See if that stops the FM from being picked up. If not you did not loose a lot of money. If it fixes then lets talk.

Or that!

A much cheaper, easier and quicker fix!

 

[OldRoadToad]

My son picks up Mexican radio on his guitar amp, but only during the evening. I just ask him to play LOUDER.

El Toado Verde

 

[griff2]

Quote:

My son picks up Mexican radio on his guitar amp, but only during the evening. I just ask him to play LOUDER.

There's much to be said for shielding.