GrandmasterB

The spec sheet says 81A at rated output. Rated output is 75x4 @ 4ohms and 220x1 @ 4ohms. If you take 75x4+220 = 520. 520/14.4 = 36 Amps. So I was wondering if the 81A is peak current draw. Has anyone used this amp? Do I need a cap and/or a deep cycle battery?

D.T.Sealy

Therefore, there will be no need for a deep cycle battery. The battery only powers the amp when the alternator can no longer provide all of the car's electrical components with the current that they demand. I have installed many Sony amps over the course of the past 8 years, and have had two friends that competed with them. They are of high quality, and are reliable. The 80 amp number is the maximum that the amp can draw during transient peaks. Where do they get that number you ask? They probably rate the amp for 150 x 4 @ 2 ohms and 440W x 1 @ 2ohms. This yields a total wattage of 1040W. Divide that by 12.8 volts and you get 81.25. You should consider what you are doing with the amp regarding the battery question. If you plan to run it at 2ohms per channel, you are doubling your needs, and probably should consider buying a new, larger battery. If your headlights are dimming, it is due to the amp's demand on the charging system. A capacitor will provide a rapidly replinishing supply of current for the amp, taking a little strain off of the alternator. While this may seem to fix the problem, it is merely a 'band-aid' for the source of the trouble- the alternator that is too small. I know that they are expensive, and can introduce noise, but if you plan to add more amps in the future, you will inevitably have to upgrade it. Good luck!

GrandmasterB

Here what I'm going to have...
Diamond Audio 5 1/4 components up front
and Diamond 5 1/4 coaxials in the rear deck. Plus a JL 12W3-D2 - terminals wired in series for a 4 ohm load. I plan to have the rears turned pretty low for good front imaging. The Sony XM7557 puts out 75Wx4 and 220Wx1 all at rated at RMS voltages with 4 ohm loads. I'm sure that's too much power for me, but at reasonable volumes do you think my lights will be dimming to the beat if I don't get a cap?

GrandmasterB

If I turn the gains down do I draw less current?