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Decisions Decisions Decisions, Class A, Class AB, Class D

antarctica24

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#1
I dont think I have covered this before, but thought I would for those interested.

The class ratings are all about the power supply designs and amount of distortion the amp puts out at any given point.

The best way to describe how this works is with a water spigot on a sink.

Class A, you basically turn on the water as high as it will go. We are cooking eggs on these amps.

Class AB, you turn on the water as high as it will go, but you move your hand through the water from side to side. These amps run much cooler at the same output levels.

Class D You turn the water on full, and hold your hand in the stream with all your fingers open. These are very power efficient.

Class A is the cleanest you can get but you get clean at a high cost. The power demands for this design are very high and most cars could deal with (1) 2 channel 25 x 2 class a amp.

Class AB is a switching power supply design. That means it is cutting the power on and off all the time. This makes the amp more efficient but at a cost of adding distortion to the sound. There is a night and day difference between the sound quality of a Class a vs Class AB design amp. There is also a night and day difference in the cost.

Class D uses what is called a digital power supply and uses the least amount of power draw to make the same amount of power. The sound quality between the class AB and Class D is negligible. There is a difference but some sacrifices have to be made to accommodate the amount of power you have available to power the amp.

80% of all amps are Class AB and that number is changing in lieu of the Class D design. When Class D first came out it was only good for subs, because anything over 500hertz had massive distortion. That is no longer the case, and class D design from a sound perspective is just as good if not better in some cases than Class AB. While I am not referencing that here, there have been may test to prove this point.

Many audiophiles argue on this point. There are those that live and breath by the tube or class A design. And they would be right, they are the cleanest sounding amps available. The problem your car is not powered by a nuclear generator. Our cars have small alternators and 1 class AB designed amp would probably be ok if properly reinforced, 2 would be pushing it depending on the power output of the amp.

The Class D amps are designed from everyone these days including, ARC aduio, Pioneer, Kenwood, JL Audio, Alpine(My Choice) to name a few.

Additionally, the Class D vs Class AB or Class A are much smaller because of the design requirements. As we have small cars with small charging systems, The class D will suit almost all of the demands you could have for your system.

As an example, the Alpine PDX-V9 Amp, here are the specs, this is a class D design

Power Requirements: 14.4 V.DC (11-16 V allowable)
Input Sensitivity (RCA Input): 0.2 - 4 V (CH1/2, CH3/4), 0.1 - 4 V (Subwoofer)
Input Impedance: >10k ohms
Frequency Response (+0, -3dB: 1W into 4 Ohms) for CH-1/2/3/4: 3 - 100k Hz
Frequency Response (+0, -3dB: 1W into 4 Ohms) for Subwoofer: 3 - 600 Hz
THD+N (10W into 4 Ohms) for CH-1/2/3/4: <0.005 %
THD+N (10W into 4 Ohms) for Subwoofer: <0.006 %
THD+N (Rated Power into 4 Ohms) for CH-1/2/3/4: <0.03 %
THD+N (Rated Power into 4 Ohms) for Subwoofer: <0.05 %
Damping Factor for CH-1/2/3/4: >500 into 4 ohms at 100Hz
Damping Factor for Subwoofer: >1000 into 4 ohms at 100Hz
Signal to Noise (Rated Power into 4 Ohms) for CH-1/2/3/4: 112 dB
Signal to Noise (Rated Power into 4 Ohms) for Subwoofer: 119 dB
Weight: 2.7 kg

This is one of the cleanest sounding amps available by any measure.

Audiophiles also disagree on the point of Class D being as good as Class AB. Every amp I have ever used save one system has been Class AB. Pioneer in their ODR systems offered Class A designed Amp, but even though I owned 2 ODR systems in vehicles, I never used the Class A amps, because of the car I was using and the power requirements of those amps. Everyone I knew that did use the Class A amps, had to upgrade their cars electrical systems with multiple batteries and upgrated alternators with caps.

So when you are going to get an amp for your ride, give the design consideration. It is my opinion, that with the way the industry is going, Class A/B design is going away in lieu of the Class D design.
 


OP
antarctica24

antarctica24

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Thread Starter #3
How do you feel about class g or h amps?
So for a better break down

http://www.audioholics.com/audio-amplifier/amplifier-classes

I’m still a fan of the class d. You can make anything work in our car with enough power. Moving to one class a/b the power supplied buy the vehicle would be sufficient using two starts to present a channel he.

To answer your question, class g and h are hybrids using different voltage rails. One rail works at lower voltage and as demand increases the other rail ramps up to meet demand.

As for One being better read the attached article. Class d seems to me the mother of efficiency. Which al things considered equal would efficiency be the most important thing.

Can you hear the difference?

If you have a trained ear, perhaps. Listening first on a reference system then comparing back to back probably. I went class d and I’ll be running two 5 channel class d amps.

So perhaps my choice helps to answer your question. That’s not to say my choice is the only choice to each their own, right?

Choose what works for you and your wallet. What I would not do is buy a class g or h amp from a company that was not reputable. If it is not a name that has been around for 25 years I would not do it. That means the other companies have not dreamed it worth the cost yet.
 


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Clinton
#4
I already have the amps. In one car i have an arc ks 300.4 and a arc ks 500.1. I have a arc xdi 1200.6 in the closet that i was thinking of putting in the fist. Ive been going back and forth in my mind though with the idea if it would be worth swapping my ks amps for the 1200.6 since the vehicle its in is my baby and the fist is a daily.
 


OP
antarctica24

antarctica24

Active member
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Location
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Thread Starter #5
I already have the amps. In one car i have an arc ks 300.4 and a arc ks 500.1. I have a arc xdi 1200.6 in the closet that i was thinking of putting in the fist. Ive been going back and forth in my mind though with the idea if it would be worth swapping my ks amps for the 1200.6 since the vehicle its in is my baby and the fist is a daily.
What I would look at is the total fused amperage of the 2 arc amps combined versus the 1 6 channel which ever has less is what I would use.
 


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