2 Mar
2006
2 Mar
'06
2:03 a.m.
On Wed, Mar 01, 2006 at 10:43:15PM -0600, Paul Winkler wrote:
On Thu, Mar 02, 2006 at 07:09:35AM +0900,
res0u2uc(a)verizon.net wrote:
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.)
On Wed, Mar 01, 2006 at 04:52:33PM -0600, Paul
Winkler wrote:
Or a highpass filter tuned very low - AKA a capacitor in series. Which
almost any modern electronic gear has on its inputs and outputs. 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. --
Paul Winkler
http://www.slinkp.com
--
Joel Roth