Power Amp bridged power rating?

[JMT3781]

Here's a question i'd noramally direct to my old man, however as i am successfully hiding a bergantino NV412 in my wardrobe at the moment, im avoiding questions that would make him suspicious

i have a power amp that is 500w per channel at 4 ohm, and 600w per channel at 2ohm

what power is it achieving bridged into a 4 ohm cabinet????

prizes for the best answer!*









*prize is you can tell my dad ive bought yet another bass cab

[velvetkevorkian]

Depends on the amp. Not all amps will bridge into 4 ohms, in fact most I recall checking only bridged at 8. In any case its not something you can work out by looking at the stereo ratings.

[Dood]

"The bridged power rating is equal to the sum of the power rating for each channel at a load of twice that of the single-channel rating."

For example, an amplifier 750W per channel in to a minimum load of 2 Ohms: The bridge rating is 1500W into 4 Ohms (minimum load). Be sure to check the specification of the amp to ensure it is a.) bridgeable in the first place b.) that you do not exceed the minimum rating. This can cause the amplifer to run hottter, work harder and possibly fail earlier.

[JMT3781]

cheers dood






[quote name='dood' post='813044' date='Apr 20 2010, 09:01 PM']"The bridged power rating is equal to the sum of the power rating for each channel at a load of twice that of the single-channel rating."

For example, an amplifier 750W per channel in to a minimum load of 2 Ohms: The bridge rating is 1500W into 4 Ohms (minimum load). Be sure to check the specification of the amp to ensure it is a.) bridgeable in the first place b.) that you do not exceed the minimum rating. This can cause the amplifer to run hottter, work harder and possibly fail earlier.[/quote]

[Phil Starr]

dood is right but you may want a little explanation.

Two things limit the power of an amp; the voltage it can swing and the power that the power supply can provide. Bridging the amp means that the voltage is effectively doubled, which in turn means 4x the power. However 4x the power means a lot more current is needed from the power supply and must be handled by the output stage of the amp. Which means that the minimum speaker load has to be doubled (usually) to protect the amp and that the power is less than you expect because heating limits the power available from the transformer. What actually happens depends upon the detailed design of the amp and to what extent it is over-engineered. Some designs won't allow you to bridge anyway. You have to check this out with the manufacturers.

[Bottle]

IIRC the QSC range of power amps are bridge-able down to 4Ohms (RMX range and the PLX-xx02 range) - have been looking to replace my older 'Maplin special' POS PS1000 amps for a while

[url="http://www.qscaudio.com/"]QSC Audio[/url]

HTH, Ian

[LawrenceH]

[quote name='Bottle' post='813780' date='Apr 21 2010, 02:06 PM']IIRC the QSC range of power amps are bridge-able down to 4Ohms (RMX range and the PLX-xx02 range) - have been looking to replace my older 'Maplin special' POS PS1000 amps for a while

[url="http://www.qscaudio.com/"]QSC Audio[/url]

HTH, Ian[/quote]

Many amps have quoted specs for 2ohm/ch or 4ohm/bridge operation...but only a subset of these will actually take that kind of abuse long-term without dying. It puts a LOT of thermal stress on the output transistors, which in turn shortens their lifespan. Also as mentioned above they may not be able to supply the power for sustained operation except in brief (millisecond) bursts (detailed specs sometimes reveal this as for the Yamaha P series amps), often too brief to be useful for low frequency output. These problems can be more apparent with bass applications where the driver ohm rating is nominal and actually varies with frequency, dipping lower that the nominal rating on certain bass notes and therefore pulling even more current stressing the amp even harder. Some cabs will behave better than others in this respect.
If the amp is a QSC it should be fine as long as you make sure it has adequate cooling. Budget amps I wouldn't risk it.