How to reverse polarity

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I am trying to bridge two amplifiers. Neither have a bridging switch. I was told that my amps can in fact be bridged but would need to reverse polarity on one input on each amp. I have searched the internet for countless hours and have not found a single device that will do this. I guess they do not exist. I have two Sumo Polaris amps that I want to bridge. How do I invert the polarity? Can this even be done? Thank you.

Sure can ... super simple Bridge Tied Load circuit below.
 

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Make a Stereo Amp into a MONO BRIDGED AMPLIFIER.
Most amplifiers can be converted, and the load must be then changed to ½ load.
If the amp will drive a 4 Ohm load then when Bridged it will only drive 8 ohm load or larger.
To make the modifications: This modification is the basic step and not for the untrained person.
1. Short the input to the RIGHT AMP.
2. Add a new resistor same as the old feedback type from the OUTPUT to inverting input. This may be 30k to 100k and 1/2w 1%. YOUR ARE TURING THE RIGHT AMPLIFIER INTO A UNITY GAIN INVERTING AMPLIFIER.
3. NOW CONNECT THE OPEN END OF THE NEW RESISTOR TO THE OUTPUT (RED POST TERMINAL) OF THE LEFT AMP.
4. The signal input in now only the LEFT INPUT

You only need one Resistor.
Duke
 
If you wire OR the left and right channels with 1k resistors you can drive stereo into the phase splitter.

You feed the stereo channels, from a pre-amp, one into each of the BTL inverters each inverter feeds one stereo amplifier then each stereo amplifier then feeds one speaker.

Total cost for two of them in a tiny box... about $3.00 ... Wall Wart supply, about $4.00 if you don't have one laying around.

I can't believe I need to draw a picture ...
See the thumbnail...
 

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No, you need one for each amplifier... then you feed the stereo channels, one into each of the BTL inverters each inverter feeds on stereo amplifier then each stereo amplifier then feeds on speaker.

See the thumbnail...

For my mobile disco I just used one amp.
The stereo was simply mixed with 1K resistors into a high power amplifier.
In all the years I was DJing no one ever commented it wasnt true stereo.
 
Rshatz:
The easiest way to bridge two power amplifer (channels) is to use a preamp with a balanced output and then feed the + in-phase signal to one amp and the - out-of-phase signal to the onter.
https://images.squarespace-cdn.com/...reen.jpg?format=1000w&content-type=image/jpeg
So solder (or crimp) Pin 1 & 2 to a RCA jack for amp 1 and pin 1 & 3 for amp 2.
As you can see pin 1 is ground for both amps - whereas pin 2 is in-phase and pin 3 is out of phase.
The connect the speaker between the two positive (red) terminals on the amps.
Good luck.
 
You might have identified a gap in the market...

It's not usually a recommended procedure because of current limitations but any stereo amp that can tolerate 4 ohm speakers can be bridged with an 8 ohm speaker without much danger. It's a simple one transistor (for each channel) circuit, as I posted... stick it in an altoids tin and away you go... change your mind? Just unplug it and hook things back up normally, no harm no foul.
 
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Make a Stereo Amp into a MONO BRIDGED AMPLIFIER.
Most amplifiers can be converted, and the load must be then changed to ½ load.
If the amp will drive a 4 Ohm load then when Bridged it will only drive 8 ohm load or larger.
To make the modifications: This modification is the basic step and not for the untrained person.
1. Short the input to the RIGHT AMP.
2. Add a new resistor same as the old feedback type from the OUTPUT to inverting input. This may be 30k to 100k and 1/2w 1%. YOUR ARE TURING THE RIGHT AMPLIFIER INTO A UNITY GAIN INVERTING AMPLIFIER.
3. NOW CONNECT THE OPEN END OF THE NEW RESISTOR TO THE OUTPUT (RED POST TERMINAL) OF THE LEFT AMP.
4. The signal input in now only the LEFT INPUT

You only need one Resistor.
Duke

I am not sure I follow what you are saying. I thought it was interesting that you mention a resistor on the output because on one of the two amps there is a resistor and I think a capacitor. On the other amp the resistor is absent at the output posts. I've wondered why one amp has it and the other does not. Any ideas why that is?
 

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Rshatz:
The easiest way to bridge two power amplifer (channels) is to use a preamp with a balanced output and then feed the + in-phase signal to one amp and the - out-of-phase signal to the onter.
https://images.squarespace-cdn.com/...reen.jpg?format=1000w&content-type=image/jpeg
So solder (or crimp) Pin 1 & 2 to a RCA jack for amp 1 and pin 1 & 3 for amp 2.
As you can see pin 1 is ground for both amps - whereas pin 2 is in-phase and pin 3 is out of phase.
The connect the speaker between the two positive (red) terminals on the amps.
Good luck.

What I am trying to do is have each amplifier power each speaker independently. Also my amps do not have balanced inputs unfortunately.
 
What I am trying to do is have each amplifier power each speaker independently. Also my amps do not have balanced inputs unfortunately.

What you need is two out of phase inputs ... that is both left and right channels get the same input signal, except, one channel will be driven positive while the other is going negative, then vice-versa. This causes the speaker outputs to create opposing voltages, that are then applied to the speaker.

To achieve this you need to invert the signal in one of the channels.

Splitting a balanced output is one way to accomplish this. My little BTL inverter, posted earlier is another, and you've seen a number of OpAmp based solutions as well.

To my knowledge there is no commercially available product for this, since as Mark pointed out most amplifiers designed with this in mind will include a switch on the rear panel, or jumpers on the mainboard for this purpose.

Also you should be aware of a common misconception that this will make your system twice as loud. It won't. You gain about 3db, twice as much power, which is a barely noticeable increase in loudness. To go twice as loud you need to increase by 10db... which takes ten times as much power.
 
What you need is two out of phase inputs ...

Also you should be aware of a common misconception that this will make your system twice as loud. It won't. You gain about 3db, twice as much power, which is a barely noticeable increase in loudness. To go twice as loud you need to increase by 10db... which takes ten times as much power.

I'm not sure to understand???
Why more power will increase only loundness, not the whole signal ?
Thanks
 
I'm not sure to understand???
Why more power will increase only loundness, not the whole signal ?
Thanks

It means that in order to get a little bit louder music, you need a lot more power.

How loud your music is directly relates to the power of the whole signal.
More power == louder music.

However; we do not hear in a linear fashion and speakers do not produce output in a linear fashion ... the result is that increasing apparent loudness means disproportionately increasing power on a logarythmic scale.

Give THIS a read.
 
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