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Re: [Amps] stero to mono

To: amps <>
Subject: Re: [Amps] stero to mono
From: Ron Youvan <>
Date: Sun, 09 May 2010 12:51:37 +0000
List-post: <">>
Hi  Frank  ÖñáãêéáäÜêçò Ðáíáãéþôçò:

> 1) I want to bridge a stereo amplifier (solid state ) 2 absolutely separate 
> channels to one
> 2) this one channel I want to drive a modulator transformer for anode 
> modulation
> QUESTIONS                            (spelling corrected)
> a) any schematic for the bridge? (input and output)
> b) what way to modulate in order to protect the transistor amplifier
> c) any schematic for an audio (final) amplifier with tubes push pull perhaps??

   First; you need an input AUDIO transformer to go between the ONE audio 
preamplifier and the two x 
500 Watts transistor amplifiers that has a single primary winding that matches 
the output impedance 
of the audio preamplifier and has a single CENTER TAPPED secondary winding that 
HALF of the 
secondary winding matches the input impedance of ONE audio 500 Watt amplifier, 
so the two 500 Watts 
amplifiers are amplifying signals that are 180 degrees out of phase.  (the 
center tap would be 
grounded, to create a single 1,000 Watt "bridge amplifier")  An input AUDIO 
transformer with two 
single secondary windings would also work.

   Second; you need an OUTPUT AUDIO transformer to go between the ONE 1,000 
Watt "bridge amplifier" 
and the plate power supply (and screen power supply {if there is one} possibly 
through a high 
Voltage capacitor, the screen Voltage may have to go through an audio choke 
coil) and the R.F. choke 
of the 2,000 Watt R.F. amplifier (this is over about five time the PEP power 
allowed in the United 
States and their territories) and must provide an AUDIO Voltage about half of 
the supply D.C. 
Voltage.  The secondary must be insulated for slightly over two times the D.C. 
Voltage.  This is a 
modulation transformer.  (with no leakage to the laminations (iron) or the 
primary winding)

   We HAMS have not been building high level modulated A.M. transmitters for 
many years (A.M. 
transmissions suffer from heterodyne interference which becomes horrific in a 
crowded HAM band) so I 
recommend you refer to HAM handbooks dated from the late 1940s to 1970 or so 
for more information 
about high level modulated transmitters.

   We are open for more questions.
    Ron  KA4INM - The next election, I know what is going to happen, I'm going 
to help.
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