Re: [linux-audio-user] Re: Digital Fidelity

From: <res0u2uc@email-addr-hidden>
Date: Thu Mar 02 2006 - 08:04:29 EET

On Wed, Mar 01, 2006 at 10:43:15PM -0600, Paul Winkler wrote:
> On Thu, Mar 02, 2006 at 07:09:35AM +0900, res0u2uc@email-addr-hidden wrote:
> > On Wed, Mar 01, 2006 at 04:52:33PM -0600, Paul Winkler wrote:
> > > 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.
> Or a highpass filter tuned very low - AKA a capacitor in series. Which
> almost any modern electronic gear has on its inputs and outputs.
Hmm. Well, my knowledge here isn't great, but I think having
a capacitor at the output of a Class A amplifier would
prevent it from operating with a DC offset.

You're right about most gear using capacitors. Most
transistor amps are Class B or AB which output AC. Older
tube amps, however are usually Class A to reduce the number
of tubes, and like my dad's old Heathkit, have a big
transformer on the output.

(Which, sad to say he threw out one fine day. The only
problem with that amp was that there would be a zhuuum
zhuuum sound pulsating with a period of a couple seconds.
Replacing one tube in the power amp would fix this for a
number of hours.)

> --
> Paul Winkler

Joel Roth
Received on Thu Mar 2 08:15:06 2006

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