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KB2VXA > TECH 22.07.03 04:21l 46 Lines 1910 Bytes #999 (0) @ WW
BID : 10717_WT3V
Read: DB0FHN GUEST OE7FMI
Subj: Re: G6MNY > Dual phase AF amp
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Sent: 030721/2313 10717@WT3V.#CNJ.NJ.USA.NOAM $:10717_WT3V
From: KB2VXA@WT3V.#CNJ.NJ.USA.NOAM
To : TECH@WW
Hello John and readers,
Your circuits are simply push pull amplifiers but unfortunately many
don't understand how they work. Thanks for the idea, so here is just a
bit more albiet less technical information on them.
The typical juke box amplifier uses a rather unique method of delivering
that thundering bass without undue distortion. Simply stated it is a push
pull push pull wiring arrangement. Each channel is a standard push pull
output, but here's the twist.
One input is wired backward putting that channel 180 degrees out of phase
with the other. The midrange and tweeter are likewise wired backward
reinverting the phase so the sound output is in phase, normal. The
resulting push pull output is fed to the woofer, doubling it's output.
So, being each channel has a push pull output stage, when strapped in
this manner the bass output may be said to be push pull push pull.
Many audiophiles make a big mistake when strapping the channels of a
stereo amp and using two of them for stereo sound. They simply strap the
inputs together and also the outputs putting the channels in parallel
which accomplishes nothing. What needs to be done is to invert the phase
of one channel at the input and connect the loudspeaher between the two
"hot" output terminals which will result in the out of phase signals
being applied to the load. Again you have a push pull push pull amplifier.
Oh, one more thing. This is a common internal arrangement for medium and
high power output transistors and modules. Some may be surprised to learn
that it's called a Darlington amplifier (device).
73 de Warren, KB2VXA@WT3V.#CNJ.NJ.USA.NOAM
E-MAIL: kb2vxa@juno.com
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Message timed: 23:20 on 2003-Jul-21 GMT
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