BillFitzmaurice.info

Just saw this video...a car audio amp with no power inputs?

https://www.youtube.com/watch?v=6bK7CQFuiM4[/youtube]

http://www.rockfordfosgate.com/products/details/pm100x1

Its a marine amplifier, not for cars. Thus everything is protected and all the inputs and outputs are probably routed through the common watertight connection.

Yes it has a power input, you can't get something for nothing. If it didn't, it couldn't rightfully be called an "amplifier".

If you look on the specifications tab, there is a power wire guage spec, it says it needs 8-4 gauge.

Edit: It might not need a 8-4 guage wire like the spec says, its probably just a cookie cutter spec page. But I think what they are saying is it takes power from the same + DC wire that powers the head unit.

Ryan A wrote:Its a marine amplifier, not for cars. Thus everything is protected and all the inputs and outputs are probably routed through the common watertight connection.

Yes it has a power input, you can't get something for nothing. If it didn't, it couldn't rightfully be called an "amplifier".

If you look on the specifications tab, there is a power wire guage spec, it says it needs 8-4 gauge.

Edit: It might not need a 8-4 guage wire like the spec says, its probably just a cookie cutter spec page. But I think what they are saying is it takes power from the same + DC wire that powers the head unit.

Nope, it takes takes the power and the signal from the speaker outs of the head unit. It does have an optional power wire in case your headunit is low power and can't provide enough juice. The way it can make more power than the head unit is by storing excess juice during quiet passages and then using that stored energy for the peaks. The way it can suck juice during quiet passages (and loud ones) is by lowering the impedance to draw lots of current but the unit is also current limited to prevent the head unit from sensing a short and going into protect mode. Very cool idea to boost power without having to run any wires through the car. It wouldn't boost power for sine waves, but for dynamic power of most music it works fine.

CoronaOperator wrote: The way it can suck juice during quiet passages (and loud ones) is by lowering the impedance to draw lots of current but the unit is also current limited to prevent the head unit from sensing a short and going into protect mode.

Ok so it lowers the impedance to draw more power. Essentially the same thing could be done by hooking up another set of speakers in parallel to the head unit.

When used without a power wire, Would it not be more rightfully called a transformer, seeing as how it's drawing more current to create higher voltage? It only becomes an amplifier once you put more power in by way of a power wire.

The head unit is doing all the work one way or another, when used without the power wire.

That's what I couldn't figure out...where the 'extra' power was coming from....
So, for example, it might present a 3 ohm load to the head unit, when connected to a 4 ohm speaker, and storing the difference?