Class D Efficiency: How far will it go?

[audiobass10]

I just read a thread on another forum with a guy who's running one of the new Hifonics Brutus amplifiers rated for 1600x1@1ohm. He explains how he's running an 80A stock alt and a Blue Top under the hood and recieves NO light dimmming. He's wondering why as I am myself, unless he's full of it. He brought up the point that the amp was Class D and perhaps that's the reason he recieves no dim. With two 90a fuses and the power that things rated for there is no way efficiency could compensate for all that current draw. Even if the amp was 100% efficient, wouldn't it still be pulling way more current than the alt can supply? If he is indeed recieving no dimming lights, i'm guessing the symptoms of a lacking electrical system are hidden and the alt is still taking a beating. Right now, i'm running a MTX 1040D rated for 560x1@4ohms bridged and I get dimming lights off a 90A alt. Things just don't seem to match up. Even if the Brutus weren't putting out rated power It still should be putting out more than the alt should be able to handle. Also, when an alt recieves stress like this from a large amplifier does the amp become less efficient? Just a couple of things i'm pondering on a bit.

[Ryan from Ohio]

This is a rather easy one.

He just upgraded his battery.

Here is what is happening in a nutshell. He just upgraded his battery and its new and fully charged. When the system is on and playing at high volumes it sucks the alt clean dry. The alternator TRIES to put out more current which it may to an extent. Voltage usually goes up also (mine was up to and over 15 Volts...). After all this any remaining amperage not generated comes off that new battery. Until that battery dies or the alt pukes.

If this system has been in operation for a good period of time he may not always have the system cranked or gives the battery time to charge...

[audiobass10]

This is a rather easy one.

He just upgraded his battery.

Here is what is happening in a nutshell. He just upgraded his battery and its new and fully charged. When the system is on and playing at high volumes it sucks the alt clean dry. The alternator TRIES to put out more current which it may to an extent. Voltage usually goes up also (mine was up to and over 15 Volts...). After all this any remaining amperage not generated comes off that new battery. Until that battery dies or the alt pukes.

If this system has been in operation for a good period of time he may not always have the system cranked or gives the battery time to charge...

What about amplifier efficiency? Does efficiency usually drop without the proper elect. system? I would assume the battery does help a bit like you said, but it should only be a matter of time until somethin takes a dump. I still can't understand the guy having no dimming issues. Hell, my headlights dim with that damn MTX although it is Class A/B.

[GlassWolf]

class D. 80% efficient. at full output the amplifier will draw upwards of 160A of current @ 1 ohm.

now keep in mind that's with a signal generator.
look here for an example:
http://www.zedaudio.com/products.html

current draw is 20A with a sine wave. 6A with music. <1.5A @ idle.
he's playing music, and not at absolute full output, so his current consumption is far less than the peak 160A draw. Remember every time he reduces the volume from absolute peak output to half the perceived volume, he's reducing the current draw by a factor of between 4 and 10 times. I have no idea why the bozo used a blue top though. That's a MARINE application battery. Not a car application.

[audiobass10]

class D. 80% efficient. at full output the amplifier will draw upwards of 160A of current @ 1 ohm.

now keep in mind that's with a signal generator.
look here for an example:
http://www.zedaudio.com/products.html

current draw is 20A with a sine wave. 6A with music. <1.5A @ idle.
he's playing music, and not at absolute full output, so his current consumption is far less than the peak 160A draw. Remember every time he reduces the volume from absolute peak output to half the perceived volume, he's reducing the current draw by a factor of between 4 and 10 times. I have no idea why the bozo used a blue top though. That's a MARINE application battery. Not a car application.

Blue Top's a Marine battery? Didn't know that. From what i've heard it's very similar to a yellow top (maybe identical). I've heard of other people using them in car applications as well. Not sure if anyone has seen a benifit of using them in car over the yellow or red tops.

[William from NOLA]

You can get it wet -a benefit :)

[GlassWolf]

http://www.optimabatteries.com/publish/ ... _info.html

http://www.optimabatteries.com/publish/ ... arine.html

Technically I guess he could use blue top batteries, but I really hope that's not his primary starter battery. At best he should have a bank of those, isolated, just for teh audio system.