Any way to Bridge an amp not specifically designed for bridging??

Dan_C

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I have a Marantz MM9000 5-channel amp. I was thinking about bridging 4 of the 5 channels. This amp wasn't specifically setup for bridging but I was wondering if there is any way to DIY. Thanks in advance.
 

Wayne A. Pflughaupt

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Dan,

In order to bridge an amplifier the inputs must be driven out of phase. Normally the bridging switch on the amplifier does this inversion internally.

If the amp does not have such a switch, then it was not designed to be bridged. I guess Marantz figured no one would have a use for a two-and-a half-channel amplifier...

If you’re adventuresome you could make some custom cables to drive the inputs out of phase. One channel must have the signal positive connected to the outer ring of an RCA plug, and the signal negative (i.e, the shield) connected to the center pin.

Proceed at your own risk, because it is dangerous to bridge an amplifier that was not designed to be bridged (if it was designed to be bridged it would have that switch). Don’t be surprised if it goes up in smoke in short order.

Also keep in mind that if you pull this off, the bridged channels will require speakers double the minimum factory impedance rating. Bridged amplifiers are not forgiving of improper loads. So if the amp is only rated for 8-ohms, you will have to use speakers with a nominal 16-ohm impedance rating.

Regards,

Wayne A. Pflughaupt
 

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