Mark levinson Bridge Kit Owners Manual
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2 Bridged Operation Bridging Explained Bridging refers to the act of reconfiguring the circuitry in both the left and right channels of an amplifier to act as though it were a single, much larger amplifier. (Of course, you will need a second bridged amplifier for stereo; more for multichannel sound, as in home theater applications.) Bridging is accomplished by sending a normal signal to one channel and an inverted signal to the other. In this configuration, one channel will always be ÒpushingÓ when the other is Òpulling.Ó By connecting the loudspeaker leads across the left and right red output terminals, the amplifier can now deliver twice the normal voltage to the loudspeaker. Working together this way, the two amplifier channels can deliver almost four times the power to a speaker that a single channel could deliver on its own. Bridged operation is particularly beneficial with low sensitivity, high-imped- ance loudspeakers (8W or higher) that have a greater need for voltage than for current. It is not recommended for loudspeakers that have an impedance sig- nificantly below 4W, as the speakerÕs impedance is ÒsplitÓ by the two halves of the amplifier. Thus the bridged amplifier ÒseesÓ a 2W load when connected to a 4W loudspeaker. Prolonged delivery of high power levels into such a low impedance creates a great deal of heat that needs to be dissipated. (Of course, Madrigal amplifiers are protected against overheating, but having an amplifier shut itself down even temporarily can put a damper on the eveningÕs enter- tainment.) Balanced Bridging If your preamplifier has balanced outputs, use a Madrigal Balanced Bridging Kit for each channel to be bridged. This kit is comprised of two pieces: and input cable that splits the incoming signal (inverting one side only), and a ground bus bar that ties the output ground terminals together and allows ground currents to flow through an extremely low impedance. These cables are wired internally as indicated below: Balanced Bridging Kit 21 3 12 3 12 3 Female XLR Input Pin 1: signal ground Pin 2: signal + (non-inverting) Pin 3: signal Ð (inverting)Male XLR Output (normal) Pin 1: signal ground Pin 2: signal + (non-inverting) Pin 3: signal Ð (inverting) Male XLR Output (inverted) Pin 1: not used (floated) Pin 2: signal Ð (inverting) Pin 3: signal + (non-inverting) Balanced Bridging Input Adapter (pin configuration) Bridging Output Adapter (not drawn to scale) (shield not connected) The ÒnormalÓ leg of the Madrigal Balanced Bridging Kit will be marked with a red stripe on the XLR to indicate positive polarity, while the XLR on the in- verted leg will be solid black to indicate inverted polarity.
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3 The Bridging Output Adapter is simply a bus bar of solid copper (with g\ old over silver plating) used to strap two of the output ground terminals together. This establishes a common ground reference for the amplifier and completes the circuit that includes the loudspeakers. (There are two such bus bars in- cluded in each kit: one appropriate for Mark Levinson 300-series amplifiers, and one appropriate for Proceed amplifiers. Use whichever is appropriate, or heavy guage speaker wire if for some reason the bus bars cannot be used.) Important! Do not attempt to operate your amplifier in a bridged mode without first strapping the black output terminals together.Failure to establish a common ground reference betweenthe two channels can damage your amplifier by forcing significant currents to flow where they do not belong! To bridge your Madrigal amplifier using a balanced input signal, follow t\ hese steps: 1 DISCONNECT YOUR AMPLIFIER FROM EVERYTHING Start with your amplifier totally disconnected from inputs, outputs, and AC power. It is always best to power down an amplifier before changing connections; here you are also changing its basic configuration. 2 CONNECT THE BALANCED BRIDGING INPUT ADAPTER TO THE AMPÕS INPUTS Connect the two male XLRs to the inputs of your amplifier, noting which XLR is marked red and which is black. You may want to standardize on ÒRed is RightÓ to avoid confusion, although it makes no difference\ to the amplifier. The channel with the red, normal input will later be connected to the red, positive terminal of your loudspeaker. Balanced Bridged Input Connection DU L MONAUR L POWER AMP I I R N¼ 3 3 commun cat on por s j k nputs inpu s Madrigal Balanced Bridging Input Adapter from preamplifier loudspeaker terminals Madrigal Bridging Output Adapter inverting non inverting 3 CONNECT ONE END OF THE BALANCED BRIDGING OUTPUT ADAPTER TO TWO SIDE-BY-SIDE BLACK OUTPUT TERMINALS Connect one end of the Balanced Bridging Output Adapter to an upper black output terminal on one side of the amplifier, and then connect the other end to a black output terminal on the other side of the amplifier. (The two connections should be side-by-side rather than one above the other.) Make sure these connection are snug and secure. ( The upper black connectors are used on Mark Levinson 300-series amplifiers since strapping the lower black terminals would inhibit access to the communi- cation ports and AC cord. Electrically, it would make no difference. )