MadSci Network: Engineering

Re: Is it possible to bridge 4 channels of sound into 2 for more total power?

Date: Thu Oct 5 03:32:41 2000
Posted By: Bruno Putzeys, Staff, Electrpacoustics and Analog Electronics, Philips ITCL
Area of science: Engineering
ID: 969260853.Eg


That depends on how the amplifiers are connected internally. Most power 
amplifiers have the red plus terminal "hot" (i.e. carrying the amplified 
signal) and the black minus terminal connected to ground. In that case, 
the amplifiers can be bridged by supplying one channel's input with an 
inverted version of the input signal that goes to the other channel. The 
load is then connected across the red terminals only.
Keep in mind that a bridged amplifier effectively puts out twice the 
output voltage compared to normal use. To make sure that output current 
does not double also, the rated minimum load impedance must be doubled. If 
the amplifier states 4 ohms minimum load, you shouldn't connect less than 
8 ohms to it when it is bridged. Otherwise it would be delivering more 
than twice its rated output power which is no longer safe.

Some amplifiers are internally bridged by default. This means they already 
consist of 2 amplifiers each feeding an output terminal and no terminal is 
grounded. In that case further bridging is not possible. It can be checked 
simply by turning the amplifier off and measuring (using an ohm meter) if 
the black terminals are connected internally [and to ground].

The phase invertor can be made using a standard -1 gain op-amp circuit.

Regards and good luck,

Bruno Putzeys

Current Queue | Current Queue for Engineering | Engineering archives

Try the links in the MadSci Library for more information on Engineering.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2000. All rights reserved.