What class is a gainclone?!

[CJ900RR]

Just curious.

Is it A, AB or what?! It would be nice if someone could explain the different classe's.

Thanks...

[tiltedhalo]

The LTP and drive are all class A the drivers and outputs are class B Qausi-complimentary, all the transistors are NPN. Actually internally the chip is a pretty simple class AB amp.
Actually I think the drive stage runs A with a current source also,I have to go have a look at the internal schematics.

[phn]

Isn't the chip A and the amp A/B?

Using non-tech speak here. Class A is faster than A/B. 30W Class A means 30W, always. There's no "lag time." Class A/B handles power surges better. A 30W Class A/B amp might be able to produce as much as 300W in very short bursts.

The Gainclone is already fast. There's no need for biasing.

[tiltedhalo]

Class A means the transistors are saturated all the time, huge amounts of heat due to the constant power dissipation, very linear low TID over all better sound. Class AB is a the middle ground between A & B, usually the voltage gain stage sets the bias points at good level to help eliminate cross over distortion when the NPN swings to the PNP.
Class B has no bias applied therefor most often has large notch distortion, but are much more linear then class C, class C are used most often as RF amps .
The chips are AB, low bias AB, but AB.

[HFGuy]

Class A == Conducts for 360 degrees, the transistor is biased so that it is always on. By changing the reference from gound to ahigher voltage we can get an AC swing.

Class B == conducts for 180 degrees, two transistors one for the positive swing and one for the negative swing. The problem is that the transistors dont turn on right away (a threshold voltage or diode drop much be exceeded first) so you get what is called "crossover distortion".

Class AB == A bit a of a hybrid between A and B as the name implies. By biasing the amp so that the two transistors (the one doing the positive and the one doing the negative swing) so that they are just on they will never turn off and dont waste power like class A.


Almost always the classes of amps refer to output stages, the magority of other stages in an amp are just called linear amps.

As far as sound i think its up to the specific implemenation and its a bad idea to make gross generalizations such as Class A is always best.

[HFGuy]

Originally posted by tiltedhalo
Class A means the transistors are saturated all the time,
The chips are AB, low bias AB, but AB.

Sorry forgot about this but this is both true and untrue. For BJTs a class A amp the transistors operate in the active region, if they were saturated the amp is massively clipping. For MOSFETs they will operate in the saturation region, funny naming but the same situation.

[awpagan]

[QUOTE]Originally posted by HFGuy
[B]

Class AB == A bit a of a hybrid between A and B as the name implies. By biasing the amp so that the two transistors (the one doing the positive and the one doing the negative swing) so that they are just on they will never turn off and dont waste power like class A.




class AB
Biased on by a few mv's to 100mv's
This is class A region (very small).
over this one transistor will have to switch off.

or have i got it wrong?

allan

[Leolabs]

Why dont you guys ask them at National Semiconductors???

[HFGuy]

Originally posted by Leolabs
Why dont you guys ask them at National Semiconductors???

Because we dont need to.

[phn]

Doh! As a non-techie I always get lost in the details. Should know better.

You could bias the chip and see if class A always is better