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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
7 responses Add your response
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...
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.
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.
gofast OP
19 posts
 
Thanks again for the responses. I'll probably try this over the holidays - have all the equipment, so not much to loose, except my wife yelling at me for the mess it'll create.

The history: system generated great sound incl bass w/ my Rogers Studio 1As. With the move to the new house, the bass got sucked out in my new listening room. (I need to do some room treatment too). To compensate, I've moved to larger and larger speakers, currently Proac Response 3.5, which are not as efficient as the Rogers. I'm told that more power might improve the bass..thus this current thread.
dtich
7 posts
 
yeah. get bigger amps. even bridging mono 50Wers in a bi-amped setup is like pissing in the wind when what you really need is 200-300wpc with huge transformers to supply the current. have you ever tried a large stereo amp with the 3.8s? you might mess yourself at hearing the difference. imho.
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