[linux-audio-user] Re: Digital Fidelity

res0u2uc at verizon.net res0u2uc at verizon.net
Wed Mar 1 17:09:35 EST 2006

On Wed, Mar 01, 2006 at 04:52:33PM -0600, Paul Winkler wrote:
> On Thu, Mar 02, 2006 at 06:47:19AM +0900, res0u2uc at verizon.net wrote:
> > On the subject of the direction of signals in cables, I
> > think I can offer to put the issue to rest by reminding
> > all parties that audio signals from a microphone or to a
> > loudspeaker are carried by the AC (alternating current)
> > component of electron movement. Thus the direction of the
> > electric current reverses many thousands of times each 
> > second, more or less depending on the pitch.
> thanks, I was going to say much the same thing.
> The only exception I can think of is when there's a
> DC offset to the signal of sufficient voltage to force the
> signal always be positive (or always negative).
> But that would mean something's broken :)

Not necessarily broken. Class A amplifiers do their work
with sufficient DC offset that the signal never changes
direction. Even so, the music is carried by an AC
*component* which is present, and may be separated out by
using a transformer.

It is also a conceptual jump to appreciate how a DC signal
can include an AC component. 

I balance my relative familiarity in this area with my
abundant ignorance on the subject of music and recording!

> -- 
> Paul Winkler
> http://www.slinkp.com

Joel Roth

More information about the Linux-audio-user mailing list