[r0b]

Hello all,

I would appreciate some help figuring out the solution to some strange RF interference I have. At least, I think it's RF interference!

Here's the setup:
- 667MHz G4 powerbook: headphone jack
- inexpensive 3' gold-plated mini-mini monster cable OR the 1' gold-plated cable that came with the headphone amp:
- HeadRoom Total AirHead headphone amp. (battery powered)
- Etymotic ER-4S

Description:
- The laptop and headphone amp need to be turned on to hear it.
- When I have my powerbook on (nothing needs to be playing), I faintly hear some radio station in the background. I hear it more clearly when I turn the headphone amp louder. Its volume doesn't seem to change when I turn the laptop volume up or down or mute it, although I only notice it sometimes.
- It becomes very apparent when I have a 15' (very cheap) extension cable from the headphone jack to an amp/receiver/PC-speakers, etc. The use of the 3' or 1' cable makes little or no difference.
- When I unplug the mini-mini cable from the powerbook and/or the amp, the sound goes away.
- Other sources: I don't hear that sound / radio station / interference when using a cheap radio-shack mini-to-RCA cable from a 1987 Fisher cd player (model DAC-202), even though that cheap cable goes through a tangled web of USB cables. In fact, I don't hear that sound / radio station / interference with any other source (including a cheap PC, a static-filled Aiwa 5.1 dorm-theater receiver, a Pioneer car cd player, or an iPod).

I hope that's enough information that someone may recognize the problem! So...

What is the problem, and how do I get rid of it?

It is very annoying... Another strange thing is that when I first noticed it, it was a mexican-sounding radio station that I can't understand, but more recently it sounds like some American-English sounding soft-rock station.

 

[Jazper]

http://www.radioshack.com/product.as...t%5Fid=273-105

Grab a few of those, chuck them on the cords and see if it makes a difference. Wrapping the wire through the core multiple times makes it more effective. They just snap over the cables, so yeah - easy to use and effective

 

[r0b]

Thanks for the link!

So then I was right in my assumption that the problem is RF interference?

 

[Jazper]

Quote:

Originally Posted by r0b Thanks for the link! So then I was right in my assumption that the problem is RF interference?

yep.. sounds like it

 

[r0b]

k thx! btw, so since it seems to be coming from the laptop's sound card, would a usb DAC be an alternative solution?

 

[Jazper]

Quote:

Originally Posted by r0b k thx! btw, so since it seems to be coming from the laptop's sound card, would a usb DAC be an alternative solution?

yep

but those ferrite cores could be used on powercords or such anyhow.. so there's no harm in getting them anyhow