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Bridging mono amps

So, here is a strange question: How can I bridge 2 mono amps?

I am trying to optimise the sound from all the equipment I have. I am currently running 2 systems with identical amplification - each has a Musical Fidelity MVT preamp and 4 MA-50 monoblock Class A 50w poweramps, vertically bi-amped. The bedroom system is using Acoustic Energy AE-1s, while the listening room is using Proac Response 3.5.

So, since I have 8 identical MA-50 mono amps, I am wondering if I can bridge pairs of them to increase power to the Proacs.

BTW, does anyone have an MVX or MX preamp stashed away that they'd sell?

Thanks, Samir.
gofast
eldartford
4,262 posts
 
Jumper the Lo (black) posts together.
Wire your speaker across the Hi (red) posts.
Drive one amplifier with an inverted signal. (How to do this is your problem).
gofast OP
19 posts
 
Thanks very much. . Driving the amps w/ an inverted signal is easy..the preamp has 2 pairs of outputs, 1 pair is inverted.

How do I figure out the polarity of the speaker wires? Does the red go to the amp thats getting the regular non-inverted preamp out?

Any thoughts on the advisability of doing this? What sonic benefits and tradeoffs should i except?

Samir.
plato
1,543 posts
 
Don't do it! Sell one set of 4 amps and replace them with a pair of more powerful amps...
ar_t
165 posts
 
Bridging mono amps is easy, especially since you have inverting outputs. You would notice a bigger difference if you tried to bridge a stereo amp that shared a power supply. The monos may actually sound a tad worse, as the supply rails will now have to deal with twice the voltage swing on the output.

If they are true Class A, the differences may not be as audible in either case. But since they are bridged, the effective load impedance is now half of what it was, and they probably do not operate in Class A all the time now.
eldartford
4,262 posts
 
Gofast...Regarding polarity: just do both channels the same. If you worry about "absolute" polarity connect the inphase signal amp to the Red speaker post.

Although you may want to experiment, Plato's comment is worth consideration. One of the benefits of bridging a stereo amp is that the draw on the power supply is more even, because one amp draws positive voltage while the other draws negative. Many amps will deliver more power when the two channels are driven out of phase. With two Mono amps this does not apply.
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