What’s the Difference between Class A, A/B and D Amplifiers

A simple explanation

Class A

Different Classes of Amplifiers

Puting it into terms that everyone can understand; a Class A amplifier is a type of amplifier where the current is always on and sent to the speakers regardless of the musical signal.

You tend to find a warmer sound and higher power consumption as the current is always being converted to heat.

The Bryston BP17 Cubed is an example of a premium Class A preamplifier.

Class A/B

Different Classes of Amplifiers

With Class A/B, power is reduced where there is no signal but as the signal demands it power consumption in increased to meet the demands and dynamics of the music.

It offers a more efficient option to Class A and the sound is typically more reined in so far as smoothness. This is probably the most common type of Audiophile amplifier consequently. An example is the Cyrus Mono X300 Signature mono power amps

Class D

Different Classes of Amplifiers

With Class D, the amplifier is creating pulses related to the original signal, rather than being on all the time, which makes the amplifier very efficient with little heat produced.

As a downside you get high frequency noise created by these pulses which has to be electrically filtered to deal with it.

Class D typically produces a sound that is a bit more pitched up in the high frequencies, although some commentators believe that the sound on the newest amplifiers are similar. I would agree with some of them.

It is typically used in high power applications or inside active powered speakers where cooling might be an issue, for example.

An example of a Class D power amp is a NORD NC500DM MkII Stereo Power Amplifier which uses Hypex power modules similar to the NAD M10

Cyrus’ ONE Cast uses a class D integrated amplifier which sounds very much like a Class A/B amplifier.

Different Classes of Amplifiers

For an article about the differences between active and passive crossovers and speakers click here.

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Written by Simon Price

I'm music lover who shares experiences of faithfully reproduced audio in an ENGAGING way with HIGH VIDEO PRODUCTION VALUES. I enjoy and make reviews as I love audio gadgets, being a voice on audio and producing creative videos that ultimately benefit the industry and new participation. I keep technicalities easy, as I believe great audio serves music and music is inclusive and to be enjoyed by all!

Bristol HiFi Show Film 2020

Bristol HiFi Show Film 2020

The difference between Passive and Active Crossovers and Active and Passive Speakers.