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

[Rob Fell]

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