gain turned down = less watts?

[KnighTWolF]

Rookie question I am sure but here goes. My amp is 400w bridged if I have the gain turned up only 1/4 would that mean I am only pushing 100w? I am looking to buy 2 subs with 400rms each. And want to run them in parallel would this work or am I not putting enough power to the subs?

[geolemon]

The real answer is "yes and no"...
...but not how you are picturing it. ;)

The gain knob is a doorway. You adjust this "input level" to match the RCA voltage (your head unit's "output level" ;)) coming down the line.

If you set it "too low", you can use this as a tool to harmlessly throttle back how much power comes out of your amp.

The more dangerous risk is if you set it "too high" - in other words, if you set your doorway smaller than the signal that's being shoved though it. What happens is "clipping" - you literally lop the top and bottom off the electrical signal, not only distorting the waveform, but the resulting squared-off shape of the waveform is bad, bad both for the amplifier and the subwoofers that are connected to it.

With any waveform, the voltage level rises and falls very quickly, cycling up and down at some frequency (whatever frequencies are in the music). It is only supposed to reach peak voltage for the briefest of instants - at which point the subwoofer reaches the peak of it's excursion (and therefore loudness).

When you clip the amp, that voltage rises to peak levels and stays there for a longer and longer duration :eek: ...which is harmful to everything, not just sound quality. The amplifier will heat up disproportionately, compared to how much power it's actualy producing (it can't EVER make more power than what it's designed for - once you reach that clipping point, no more power is made). Worse, the voice coil on the subwoofer will heat up just as disproportionately - resulting in seriously elevated levels of heat energy going through the subwoofer, compared to how much actual power is going through it.

And since the power ratings on subwoofers are thermal ratings - how much power the subs can take without thermal damage - you can technically blow a subwoofer with an amp that is technically perfectly sized for it (or even undersized), by misusing the amp, clipping the signal, and causing more heat energy to be created than is supposed to be.

It's not "more" in terms of quanitity - it's "more" in terms of duration... the 'power is on' for longer each cycle, even though the amplitude isn't one bit higher. And that's abusive and harmful... as well as sounding bad to some degree. ;)