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From: jsf007@trsvax.UUCP
Newsgroups: net.audio
Subject: Re: Son of Ampzilla bridge - (nf)
Message-ID: <2980@uiucdcs.UUCP>
Date: Sat, 24-Sep-83 23:03:48 EDT
Article-I.D.: uiucdcs.2980
Posted: Sat Sep 24 23:03:48 1983
Date-Received: Tue, 27-Sep-83 03:14:52 EDT
Lines: 15

#R:tekid:-154600:trsvax:55100012:000:763
trsvax!jsf007    Sep 23 08:02:00 1983

The way bridging works is seperatly amplifying the positive and negative
parts of the input through different amplifiers.  Since most preamp out-
puts use common ground (i.e. unbalanced outputs), it is hard to do the
conversion to balanced outputs with a simple passive circuit effectivly.  
An active circuit is a fairly trivial matter, however.  Two opamps per
channel are required.  One is configured as a voltage follower, the other
as a voltage inverter.  The outputs of each of these opamps are fed into
the unbalanced inputs of your amps.  The speakers are connected across
the positive outputs of the amps with the two negative outputs wired together
(this may be unnecessary if your output stages are common ground).
			Steve Fintel
			...trsvax!jsf007