Classes of Amplifiers

[Whiney]

What does 'class of amplifers' mean?

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[basswiigee]

efficency for the most part... but there is alot to it....

 

[bbeljefe]

It has to do with how the circuitry is designed. But for car audio purposes, efficiency is the most important element, because we have a limited amount of power capabilities in our vehicles.

Class A and A/B amps are usually in the 50-60% efficiency range and class D hover around 65-85%.

 

[trumpet 5,000+ posts]

I don't have facts in front of me to back this up, but Class D tends to be around the same efficiency as Class AB until the output ramps up toward clipping. They get more efficient as the duty cycle increases. Regardless, I recommend Class D full range amplifiers for customers who don't have a preference as they're typically smaller and more powerful than a comparably priced Class AB amplifier.

 

[basswiigee]

I don't have facts in front of me to back this up, but Class D tends to be around the same efficiency as Class AB until the output ramps up toward clipping. They get more efficient as the duty cycle increases. Regardless, I recommend Class D full range amplifiers for customers who don't have a preference as they're typically smaller and more powerful than a comparably priced Class AB amplifier.

really starting to wonder when i see these d/f class amps and up like class h i think i seen....

 

[bbeljefe]

I don't have facts in front of me to back this up, but Class D tends to be around the same efficiency as Class AB until the output ramps up toward clipping. They get more efficient as the duty cycle increases. Regardless, I recommend Class D full range amplifiers for customers who don't have a preference as they're typically smaller and more powerful than a comparably priced Class AB amplifier.

You're correct. It's not unlike the efficiency of a cordless drill running at full tilt or attenuated. When the volume is turned down or when the trigger on a tool is only pulled part way in, the attenuation of that voltage creates, necessarily, some loss.

But then, amplifier efficiency is also affected by impedance, so with lower impedance loads, efficiency goes down and since most amp manufacturer's (if they do at all) rate efficiency at 4Ω, even though most bassheads run at 2Ω or lower... maximum efficiency is almost never seen.

And that is just one more reason why we need overkill on the supply side of the equation.

 

[SounDrive Pro Seller]

I don't have facts in front of me to back this up, but Class D tends to be around the same efficiency as Class AB until the output ramps up toward clipping. They get more efficient as the duty cycle increases. Regardless, I recommend Class D full range amplifiers for customers who don't have a preference as they're typically smaller and more powerful than a comparably priced Class AB amplifier.

I believe a class A/B is much less efficient at low power levels as well. It's something about the switching of the power supply that makes the class D more efficient.. Maybe someone else can go in to more detail.

 

[hispls 5,000+ posts]

I don't have facts in front of me to back this up, but Class D tends to be around the same efficiency as Class AB until the output ramps up toward clipping. They get more efficient as the duty cycle increases. Regardless, I recommend Class D full range amplifiers for customers who don't have a preference as they're typically smaller and more powerful than a comparably priced Class AB amplifier.

Class D does get much more efficient as the output approaches maximum... as does class A (though class A isn't really terribly efficient at any time)

really starting to wonder when i see these d/f class amps and up like class h i think i seen....

All just variations on PWM (Class D).

I believe a class A/B is much less efficient at low power levels as well. It's something about the switching of the power supply that makes the class D more efficient.. Maybe someone else can go in to more detail.

The old Zed manual had a good breakdown of types of amplifiers.

 

[SounDrive Pro Seller]

Class D does get much more efficient as the output approaches maximum... as does class A (though class A isn't really terribly efficient at any time)


All just variations on PWM (Class D).

The old Zed manual had a good breakdown of types of amplifiers.

It's been a good while since I've read it. It's got a ton of information, and I'd recommend anyone wanting to learn more about amplifiers to read it.

 

[gckless 5,000+ posts]

Anatomy of the Power Amplifier

 

[n2audio 5,000+ posts]

Class D's stay relatively efficient at low power -- 60+

At high power most I've seen are 70-85%

A/b's drop to 30-35 at low power and are 60-65 at high power.

 

[neo_styles 10+ year member]

It's been a good while since I've read it. It's got a ton of information, and I'd recommend anyone wanting to learn more about amplifiers to read it.

Each year covers different facts, so don't be afraid to go in and read the 2010, 11, and 12 manuals. I'll try to remember to upload the 2013 manual on MAF tonight when I get home. TONS of good info in there.