Amp Bridging


Gold Member
Username: Arande2

Extreme SQ FTW

Post Number: 1931
Registered: Dec-06
I know on a bridgeable amp you can bridge it for twice the voltage (and half the impedance to each channel), but can you parallel bridge an amplifier to give it lower impedance drive capability (and double the impedance to each channel) so it works the in the opposite manner?

Let's say it's a 1000w x2 channel 2-ohm amplifier. If you were to bridge it the way you usually do, you could drive that 1000w into 8-ohms, correct? If you were able to bridge it the other way, you could then drive that 1000w into 1 ohm, correct? Or am I thinking about this incorrectly? Series-Bridging doubles the voltage, but doesn't affect current capability, and Parallel-Bridging doubles the current delivery capability and voltage stays the same right? As the output stage would be in series to double voltage or in parallel to double the current because if you put the output stages in series they add together doubling the voltage, but if you parallel them, they deliver the same voltage, but then there's twice the output stage for the same amount of voltage, so you can put twice the current through it. That's all correct, isn't it?

I'm thinking of it like this. Let's say you have two 6-volt car batteries with 100 hours life at 1 amp draw. If you hook them in series, the cells in the batteries are in series, and so creating twice the voltage at 12 volts, but still 100 hours with 1 amp draw. If you hook them in parallel, now you've hooked the cells in parallel, so have twice the capacity, and so 200 hours from a 1 amp draw, or 100 hours from a 2 amp draw, so you can draw twice the current and have the same life!

If you had 2 12v batteries with 50hours in parallel you'd have the same power as if you had 2 6v's with 100 hours in series. Also, isn't that what you do when you get more batteries for your amps? You hook them in parallel to have more amp capacity for your amps right? Or alternators, you could do like a 10 alternator setup (why???) with each a 350-amp alt and get 3500-amps (muahahahahah!) capacity so you have less voltage drop because each alternator does less work!

Back to the amplifiers, you could also still get 2000 watts from the bridged amplifier in total either way right? If you went series, you could get it at 4-ohms to make it look 2-ohms to each channel that's bridged, but still deliver twice the voltage of the added output stages for 2000w, correct?

On the parallel bridge, since the resistance looks twice as high to each channel PLUSSSS you have twice the maximum current capability so if you hooked something up that would make it look like 2-ohms to each channel at 1000w you'd still have that extra current capability and so could make it half again to get 2000w, but at lower impedance. This means you can put 1-ohm on there to make it look like 2-ohms to each channel and get 1,000 watts with the same voltage, but still have the extra current capability, so that you can lower the impedance to .5-ohms to use the parallel drive capability and get that 2000w from the extra current instead of voltage. This would be useful in say powering a dual 1-ohm voice coil subwoofer where if you independently hooked up each voice coil you'd burn up the amp, but if you parallel bridged for a low impedance drive capability, you could give .5 ohms giving the sub 2000w instead VCs in series on one channel giving 1000w.

Is that right? If not, correct me please. I think that parallel bridge might still half the resistance to each channel so that you could lower the impedance only to 1-ohm. I'm sure that I was correct with the former idea though. Please correct me if I'm wrong though. I'm trying to get this straight in my head.

Gold Member
Username: Arande2

Extreme SQ FTW

Post Number: 1934
Registered: Dec-06
lol 12 hours later...

Gold Member
Username: Arande2

Extreme SQ FTW

Post Number: 2038
Registered: Dec-06
Like...181.5 (or so) hours later...

Platinum Member
Username: Glasswolf

Wisteria, Lane USA

Post Number: 11723
Registered: Dec-03
please read this page.

this should help you to understand how bridging an amplifier works, and why.
a two channel 2-ohm stereo stable amp would be 4 ohm stable when bridged due to using the negative voltage rail from one channel and the out-of-phase positive rail from the other channel ( or vice versa )
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