On Wed, Mar 01, 2006 at 10:43:15PM -0600, Paul Winkler wrote: > On Thu, Mar 02, 2006 at 07:09:35AM +0900, res0u2uc@xxxxxxxxxxx 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 > http://www.slinkp.com -- Joel Roth
