[millerdog]

can someone explain to me the difference between these three different amps?
I know most modern SS amps are op amp based. Right?
I remember that transistor amps were classed into different groups? Meaning the output was linear to the input...hence they were called class C? this was for RF amps though.
what the hell is class A? B? A/B?
tubes...just a mystery to me...I do remember reading about grid and some other stuff..took me long enough to figure out what OTL means and I still don't understand how it applies....
Perhaps a layman can decipher all this tech talk and make it clear for me?
thanks,
md

 

[JMT]

Quote:

what the hell is class A? B? A/B?

Check this out:

How To Speak Ampese

 

[eric343]

Good link, Jon.

But let me put it this way, by making the old apples/oranges analogy:

Dynamic amps == Fruit. Both Apples and Oranges.

Solid state amps == Oranges.

Transistors == Orange seeds. They're the "core" of all solid-state amplifiers.

Op amps == Clumps of orange seeds in a convinient package.

Tube amps == Apples. They're totally different in design, build, etc.

Class A = Using only the better half of the orange seeds in any given orange.

Class AB = Designing your orange so only the better half of the seeds affect the taste, but all the seeds are used. (AFAIK)

Class B = Using all the seeds.

And IIRC the Class A/AB/B thing does apply to tubes, to a degree, but I know very little about tube amps.

 

[KurtW]

There are two basic types of amps, solid state and tube, although there are some designs that have both. Solid state amps often have integrated circuits (ICs), but there are several that have discrete transistors instead, and others that have a combination of ICs and discretes. An IC is just a bunch of transistors connected together on one common substrate and put into one package. Op amps are most always ICs but they don't have to be.

Two basic type of tube amps are those with output transformers and those without (OTL). The output transformer is there to lower the output impedance, which is needed for low impedance headphones. A few tube amps allow you to switch to either type. If you are using only high impedance headphones there can be some advantage to an OTL design, as really good transformers are quite expensive. Cheap transformers have limited frequency response. Solid state designs by nature have low impedance outputs, so some tube amps, notably the Melos, uses a transistor output stage. The Berning MicroZOTL is an amp that is a special case of OTL type output that does have low impedance. Berning has a patent on it so its only used in his products.

If anyone gets anything out of the above explainations, it should be that its easy to over generalize about this stuff.

If you read the link that JMT provided, you can see that the biggest problem with class A amps is the high current that's needed to achieve class A operation produces a lot of heat. Fortunately this is less of a problem with home based headphone amps than it is with amps for speakers that need much higher power. But even for battery operated headphone amps, it can be practical to take the first stage which is used for voltage gain and bias it's output into class A since it doesn't usually need much current to drive the following stage.

As for the term "dynamic", I think this may have been used to to mean it was not an amp designed to drive electrostatic headphones which need a very high bias voltage, usually hundreds of volts.

 

[Dusty Chalk]

Quote:

Originally posted by eric343 But let me put it this way, by making the old apples/oranges analogy: ... Solid state amps == Oranges. ... Tube amps == Apples. They're totally different in design, build, etc.

What about MOSFET amps? Or are those technically solid state? I like the analogy, but it falls apart like an overripe...never mind...

 

[eric343]

LOL!

 

[millerdog]

thanks guys!
as most of you know, I am on a mission!
Thanks for the link, JMT.
I had more questions, but I think I'll leave them for a different thread.
md

 

[Toe]

Quote:

Originally posted by Dusty Chalk What about MOSFET amps? Or are those technically solid state? I like the analogy, but it falls apart like an overripe...never mind...

A MOSFET is actually just a type of transistor. So of course a MOSFET-based amp is solid state.