# How to bridge an amplifier



## imbeaujp

Hello,

Is it a way to bridge a stereo amplifier to on channel ? The amplifier that I would bridge does not have that feature (switch) ?

Thanks !


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## Hakka

I'm pretty sure the amp needs to support bridging.

Hakka.


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## F1 fan

imbeaujp said:


> Hello,
> 
> Is it a way to bridge a stereo amplifier to on channel ? The amplifier that I would bridge does not have that feature (switch) ?
> 
> Thanks !


Assuming the amp is not a high powered unit using a balanced(bridged) output configuration for each channel already( as some do),you would need an external circuit incorperating an inverter that would invert the phase of one channel.Im not aware of any such commercial unit so it would likely need to be done DIY.


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## jerome

The amplifier you're going to bridge definitely needs to support this feature. Which amplifier is it?
Ask the amp. manufacturer first, as you could damage it if bridging is not supported :thumbsdown:

Also take a look at you user guide. If bridging is supported then it will probably be described there.


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## drf

it can be done, however you need to know: 

What impeadence is the amp rated down to? once bridged you must double the minimum rated impeadence of the amp.
And what style of amp it is? you will be hard pushed to properly bridge an amp if its output circuitry has unusual topologies that require modification.

If it is a run of the mill Class AB and it can handle a low speaker impeadence then in order to bridge it you only need to make a small inverting preamp for one of the channels.



Hope this makes sense.


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## tonyvdb

bridgeing an amp that is not designed to do so can cause many problems,
1) a total failure
.....causing damage to the internal components of the amp
2) Heat overload
.....running less than the minimum ohm's it can handle
3) damage to speakers
.....in some cases it can damage a speaker if there is some sort of failure in the amp causing clipping.
If the amp doesn't have a bridge switch or at the very least a bridge label under two of the four speaker terminals I dont recommend it.


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## imbeaujp

Thanks for your input guys.

I think that I will need an external device to do that.


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## threadlock

Is it possible to bridge two identical monoblock amps?


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## lcaillo

As a service tech I have to counsel against bridging amps, particularly those that are not designed to be bridged. I have seen enough damaged amps to view it with concern. Heat is the enemy of electronics, and current generates heat. You will be pulling more current through the outputs with the same load, as noted above where impedance is mentioned. EVen with good heat sinking and ventilation or fans, you will be stressing most amps when bridged.


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## vantec

I agree, make sure your amp supports bridging. I would assume you are thinking of doing this for a subwoofer. Most of the newer amps we used in cinema sound were designed to be bridged. We did this for subs and also this is where we had the most failures. Initally make sure you have ENOUGH amp for the job.


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## tonyvdb

threadlock said:


> Is it possible to bridge two identical monoblock amps?


No, Amps will clearly be marked if bridging is allowed.


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## threadlock

So that means that is safer to just power each coil of a dvc driver with two monoblock amps?
I was told that doing a config like this might damage the driver if the voltage given by each mono-amp differs even by a small margin. Is it true?


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## lcaillo

I would simply not use two amps in either way. Get the right amp for the application or just use one of them. You may be able to make it work, but it is outside the intended design of the amp.


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## ampire

threadlock said:


> So that means that is safer to just power each coil of a dvc driver with two monoblock amps?
> I was told that doing a config like this might damage the driver if the voltage given by each mono-amp differs even by a small margin. Is it true?


Ive done that before with a cheaper car audio subwoofer and two 500 watt monoblocks. I ran a 50 hz test tone (that i typically use for gain setting with car subwoofer amplifiers) and checked to make sure the voltage was the same (i don't trust the gain knob positioning on the amps even if they were two of the same model). One amp per coil.

It could damage the driver but I doubt it.

Ive ran a pair of drivers with just a single coil driven each so Id have 4 ohm per driver with two dvc drivers rather than 2 ohm per driver and that increases the driver's throw and seems to make the driver more distorted but is relatively harmless. I did this because my monoblocks were not 1 ohm stable. It would seem to me that would be even worse than having one coil getting slightly less power. Given that even running a stereo amp unbridged (with left to one coil and right to one coil is a popular way of powering dvc subs in car audio) is relatively harmless even with different left and right signals.

With car audio, there are advantages to running DVC drivers with a single coil. 1) you could get more power out of an amp that is low ohm stable 2) if the coil blows you can always run the other coil until that one blows 3) you can pair up different combinations of drivers to get different load at the amp.

Of course, running a mono signal off of a single amp is definitely preferable. It would sound a lot better.


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## rselby

so what could anyone recommend for a device to invert the audio input signal to the amp, or amps?? have a few amps I would like to do this with( they are common ground amps) and can handle the lower impeadiance as well, thanks


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## 8086

threadlock said:


> Is it possible to bridge two identical monoblock amps?


Your best bet is to get a bigger set of monoblock amps.


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