What makes an amp Class A, A/B etc,

I was wondering,

What makes an amp Class A, A/B and other designation, and do these ratings apply to Pre-Amps and Phono sections ?

Thanks for this and other comments to past queries here on the forum.

Best Regards
Groovey Records

Listening to
Tyranasaurus Rex-Prophets, Sages, Seers and Sages. The Angels of the Ages
Fly Records Reissue Toofa 3/4
With a Class B amp, complementary transistors handle the positive and negative halves of the signal. One output transistor handles the positive half of the signal, another transistor handles the negative half of the signal. Each transistor runs half of the time, which is efficient; however; when one transistor hands off to the other one, the transition is not seamless. Distortion will result.

With a Class A amp, all output transistors operate all of the time. You don't get the distortion that occurs in Class B when one is handing off to the other. However, it is inefficient in that everything is operating all of the time. It produces a lot of heat and needs a good power supply.

A Class AB amp has transistors that hand off to one another for the positive and negative halves of the signal (like Class B), but there is a little bit of overlap in order to minimize the distortion that would otherwise occur when one hands off to the other. In this overlap region, both transistors are operating simultaneously (like Class A).

By the way, there are other classes as well.
Thanks Mark

So Class A has the most power consumption and operates ineffeciently but carries the ? cleanest or least distorted? signal without feedback. or is that too simple.

Also is this related to feedback at all or is that another aspect of amp design.

I have also heard of class d amps.
Are there any references that explain these types of terms as well as push-pull, balanced-unbalanced, feedback and the like

It is a lot to fathom, an idiots guide to amplification theory is what I need !!
if you will!

Thanks again Mark

Groovey Records

Listening to

Thelonius Monk Genius of Modern Music Vol 1 Blue Note BST 81510
Direct Metal Master Pathe Marconi Digiatal Remaster Vinyl
Dear groovey: Feedback is a different subject.

Now, a class A amplifier design it is not always better than a class AB or B design operation. I heard over the time some class A amps that sounds not so good and AB that are really fine, all depends on the whole amplifier design and not only if it is class A/B/D/etc.

Regards and enjoy the music.
Markphd- a furhter definition of CLass AB is that it runs in class A for the first watt or so where most of the music is.
Vacuum Tube Technology Overview

The basic purpose of the audio amplifier is to increase the current, voltage or power of a signal and deliver the signal to the speakers. The three basic types of amplifiers are solid state, hybrid (utilizes tube and solid state) and vacuum tube. Each technology has its positives and negatives. Although the general operational characteristics of the three audio amplifier types are similar, there is a differential in the sound.

There are two basic designs of tube amplifiers. One design is the triode amplifier (also referred to as single ended or Class A) in which one vacuum tube (300B, 2A3) is used per channel to amplify the audio signal. Within the tube, a small signal is placed on the grid which causes a large fluctuation of voltage. Thus, the small amount of signal controls the larger power so that the signal is replicated at a larger level of energy. Another design is the push pull amplifier (Class AB). Rather than using one tube, the push pull amplifier uses more than one tube per channel. One tube will amplify the positive portion of the signal and the other tube will amplify the negative portion. The push pull design provides greater wattage than the single ended amplifier. This is a very simplified rendition of how a tube amplifier works. For the detailed technical operations of audio amplifiers, we recommend engineering web sites.