Re: [linux-audio-user] Re: The famous "Jack Hum" (Can't record and desparate)

From: Rob Fell <rob@email-addr-hidden-egg.org>
Date: Thu Nov 16 2006 - 10:40:58 EET

Carlo Capocasa wrote:

> Can you give me a hint on how to identify an inductor? My notebook case

An inductor is a coil of wire wound (several turns) around some kind of
core. If it's an encapsulated type it may be harder to identify.

http://en.wikipedia.org/wiki/Inductor

> is open right now and the whine comes from a place out of or near the
> CPU. Also, the whine comes when I start Jack at low latencies; I don't

Ok - that's likely the supply regulators.

> quite understand what the purpose of loading the power supply would be;
> I've hooked up my Palm Zire or a USB microphone (which sounded like
> crap, but did load the power supply) and experienced no additional hum
> whatsoever.

You're not expecting additional hum.

An inductor smooths out current flow in circuits by storing energy
magnetically. Because there's a magnetic field (coil of wire and
electric current), there's also a force exerted on the coil (think
electric motor) which _can_ cause the coil to physically move in
sympathy with the current. The physical movement of the coil acts like
a loudspeaker - but this isn't a tune you can dance to.

Do you have a stethoscope? Unload the machine and get that noise back.
Now listen. Can you identify the component?

R
Received on Thu Nov 16 12:15:03 2006

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