Mixing: disadvantage to using 2 separate bridged mono amps verses one 2-channel amp?

[666666]

For critical mixing, I've always used one single 2-channel stereo amplifier to power my monitors.

I may be trying out some larger monitors soon, will need more power, and am considering picking up two separate amps (of identical make, model and power rating) and running them as two separate bridged mono amps, one for each monitor. I can potentially get a good deal on two smaller used amps (which will be plenty powerful when used together as separate bridged mono channels) verses one good ultra high power stereo amplifier.

Any reason not to do this? Might there be a greater chance of ultimately having a sonic mis-match between the two channels? Stereo imaging issues? Is there anything "bad" about running an amp in bridged mono in general?

Thanks

[seriousfun]

Originally Posted by 666666

... Is there anything "bad" about running an amp in bridged mono in general?...

Never anything wrong with more headroom.

The only potential problem is that when bridged, many amplifiers lose their ability to drive low impedance loads. If you are running two 4 Ohm speakers, for example, many amplifier will be happy when running stereo but they will not work when bridged on anything less than 8 Ohms.

[666666]

Originally Posted by seriousfun

Never anything wrong with more headroom.
The only potential problem is that when bridged, many amplifiers lose their ability to drive low impedance loads. If you are running two 4 Ohm speakers, for example, many amplifier will be happy when running stereo but they will not work when bridged on anything less than 8 Ohms.

Thanks for the info, man.

Very good point about the impedance. I didn't think of that. I DID notice though that the amps I was looking at did NOT give a 4-ohm wattage spec when bridged in mono... only an 8-ohm spec... and I was wondering why... now I know.

So now I'll just have to consider the impedance spec of whatever speakers are to be used.... either that or just stick with a single high-power 2-channel amp that can be run 8 or 4 ohm.

[TornadoTed]

My tech told me that a bridged amp has twice the distortion. I am not a tech so don't know why but I have no reason not to believe him!

[danharr]

Hi-
I spent a lot of time in high end audio many years ago, so my info is old, but (I think) still correct... I think that not only impedance is a problem, but damping factor is reduced too- resulting in reduced transient response when you bridge amps. I used to hear there were also high frequency phase shift issues because of circuitry variables from channel to channel, and I remember hearing a distinct smearing/roll-off of high frequencies too...

I would bi-amp by using a solid state amp, like a Krell on the bottom and a vacuum tube amp like a conrad-johnson on the top, but of course you need biamp-able speakers for this. I ended up with quality tight bass and smooth transformer-coupled highs, and more overall power too.

[TonyBelmont]

Originally Posted by TornadoTed

My tech told me that a bridged amp has twice the distortion. I am not a tech so don't know why but I have no reason not to believe him!

This is true. Although not necessarily twice the distortion, a bridged amplifier will typically exhibit more distortion.