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difference between amp types (1 Viewer)

George Anderson

Oct 27, 2004
ok, ive read the basics and this didnt really help me.
my question is, what is the differences between classes and the like?

class A-G, A/B
single ended

im no electrical engineer by any means. can someone help me out?

i want good amps for my HT but cant see spending that much for a new one. want to hit the local pawn shops for good amps but want to know which is which.


Stunt Coordinator
Aug 25, 2003
I'll give you a bit of info on each that I know, which isn't a lot really.


Metal Oxide Semiconductor Field-Effect Transistor. A type of Trasistor. Pioneer likes to use them on some of their amps and they claim a "warm" sound as if from a tube amp. The jury's still out if the mosfet offers any benefit in output stage of your amps, but it's certainly not a bad thing.


Usually associated with a Transformer and not a transistor at all. Toroidial are round, I think there is actually a brand name that uses that name for their transformers. In any even it's usually "marketed" as a good thing in manuals so I guess it's okay but I wouldn't believe it's the end all GOTTA HAVE A TOROIDIAL!! But for certain a nice beefy transformer is a good thing in an amp because the transformer dictates the total capacity of current your amp can enjoy (if I'm wrong surely someone here will jump on this one).

class A-G, A/B

I've heard of A/B and they represent the efficiency of the amps themselves. Someone else can explain it better because I'm not sure which is which exactly (without looking it up) but... one is more efficient and tends to find its way in more expensive gear and the other is less efficient (produces more head) and is found in 99% of all consumer electronics gear. There is also the little voice that says that use of A or B amp is not necessarily indictative of the quality of your amplifier.


There is a new breed of digital amp out there... somewhere. They scare me. I am in denial. I've heard they're only good for digital sources and that Panasonic makes one. There, that's all I know about digital amps, for now.

single ended

Hmmm.. don't know, you really got me there. But I can say this, if "single ended" is what you're looking for don't ask a politicians questions because I assure you won't get anything single ended.

Kevin T

Jul 12, 2001
single ended is a type of tube amplifier (single ended triode - SET for short). while tube amps sound better than solid state amps (just my opinion), i would advice against using a SET amp for home theater use. these types of amps are usually very low powered (~10 watts). if you want to use tube amps for home theater use, i'd look into push-pull tube amps. honestly though, i would advise against using tube amplification for home theater only use. i use a pair of tube monos in an integrated home theater, but it's out of necessity and space constraints that don't allow me to use solid state amplification.

kevin t

Dave Milne

Supporting Actor
Jul 2, 2001
A few more details and corrections:

MOSFET: Wayde got it right. MOSFETs are voltage-controlled transistors rather than current-controlled like conventional (bipolar) transistors. A number of amplifier brands use MOSFETs. Not necessarily "better" or "worse" than bipolar devices, although they have fallen somewhat out of favor for output stages conventional amplifiers in the last dozen years or so. Still widely used in switching power supplies and Class D amplifiers.

Torroid: Core shape of the power transformer. A Torus is a "donut" so Torroidal transformers are donut-shaped. Generally preferred over conventional "double-d" laminated steel cores, but not a huge deal.

Class A-G, A/B: Generally refers to the bias point in a push-pull output stage. Pure class A is biased at roughly the midpoint of the transistors' operating current span. The transistors never shut off. This results in huge idle current and low efficiency, but many feel sounds the best. Pure class B is zero idle current. "Push" and "pull" transistors are both off at zero signal. This is the most efficient, but results in audible nonlinearities and crossover distortion. A/B is somewhere between these extremes - which most amplifier designers use. Class D is reserved for digital switching amplifiers. Classes G and H involve adjusting the power supply rails "on the fly" to minimize the inefficiencies of high bias current Class A or A/B designs. Classes C, E, and F refer to non-audio amplifier types.

Digital: Class D amplifier. Radically different approach involving output transistors that switch fully on or fully off hundreds of thousands of times per second. Very efficient but difficult to get full bandwidth without distortion or switching frequency artifacts. Up until recently, Class D was reserved for subwoofer amplifiers. In the last 5 years, the technology has evolved to the point where some decent full-frequency Class D amplifiers are available.

Single-ended: Type of output stage using only one power supply rail and one transistor (or group of paralleled devices) - as opposed to push-pull. Can be transistor or tube but in either case are very inefficient. Many feel they offer the best sound quality by eliminating crossover distortion.

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