Message 20414 in TECH.WW
From: G8MNY
Date: Tue, 07 Apr 26 06:44:00 Z
Newsgroups: TECH.WW
Subject: Dual phase AF AMP explained
Message-ID: <56658_GB7CIP>
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated May 06)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
(phase splitter)
The LS sees 2x the voltage of a normal single amplifier arrangement. That is 4
peaks to the LS. Peak crest power = 12 x 12 / 4 = 36W peak, = 18W RMS.
pair of amplifiers in bridged to 8R LS load, to give a peak power of
179 x 179 / 8 = 4kW peak crest power (USA rating), or 2kW RMS. Although this
sounds big they are made this size! But the power rails usually dip a lot under
heavy load, but 4kW peak pulse is what the loud speaker system has to handle!
The phase inverter/splitter could be just this....
1K
1K +
significant following different circuit loads. The bias 220k should be selected
to give about 1/2 the voltage across the transistor. e.g. on a 12V supply
emitter = 3V, collector = 9V, so there is 6V across the transistor, then about
2V peak to peak can be handled.
But it is more usual to attenuate the output of the 1st amplifier by the gain
of the 2nd amplifier & feed it into the inverting input of the 2nd amplifier.
AMP AMP
R2
////
But with this simple method you do get 2x the distortion out of the 2nd
amplifier!
N.B. If on single power rail (eg. 12V car radio) these amplifiers often DC on
the LS rails!
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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