can someone define Class-A preamp?

Leeking

Leeking

New member
I have listened to this "class-A" term for quite sometime.... never really bother about it cos it usually means $$$$ ;)

But I do hope one day I'll be able to own one of these babe... :)

I made a quick search on this forum but can't really find a definition on class-A pres.... can someone enlighten me? :)

Is the RNP considered class-A stuff?

I have a VC3Q at the moment... hopefully one day I can own a $1000 preamp... that's quite a sum for a third world country guy like me. :(
(currently eyeing on the Sytek MPX4A, not so convinced on the RNP yet... )

so, your comments are appreciated! :)
 
I've never heard anybody even discuss these classes with preamps. They are only discussed when it comes to power amps, and the reason is that a class-A amp will use a lot of power and a class-A poweramp will get hot, so you need much bigger transistors, much bigger coolers, a bigger transformer and so on.

A class-A poweramp is therefore more expensive than a class-B poweramp, but typically sounds better.

However, a class-B amp uses twice the amount of transistors/tubes. So in a preamp, where power isn't an issue, a class-B amplifier would not only sound worse, but also be more expensive. Making a class-B preamp would be pretty strange.

As to definitions:

A class-A amp uses one transistor as amplification for all of the signal. You design the circuit so that the most linear part of the transistor amplification curve, giving a linear amplification.

A class-B amp uses two transistors, one amplifying the positive part of the signal and one negative. This gives distortions around the zero-point, and you are not typically using the most linear part of the amplification curve, again giving distortions.
 
From the December issue of Recording Magazine:

A Class A amplifier is one where the tube or transistor conducts throughout the full cycle. For conservative voltage or current swings centered within the conducting range, amplification is highly linear. Class A operation is highly inefficient, however.
That's because with no signal present, the tube or transistor is still drawing about half its maximum current, wasting power that's not contributing to the output. We rarely see Class A amplifiers outside the audiophile world since it's expensive to throw away 50 watts much of the time in order to get linear operation over about a 10 watt range.

"For a small signal application such as a microphone preamp, however, the power involved is small enough that we can afford to take a hit in efficiency in exchange for linear operation and simple design...

"A class B amplifier is biased so that it conducts over half the cycle and is cut off for the other half. By itself, this is a sure recipe for distortion, but by operating a second amplifier fed by the same input signal with the opposite polarity and combining the two outputs (this is called push-pull operation) we can make an amplifier much more efficient because it doesn't waste power at lower levels...

"A Class AB amplifier is biased so that it draws less current than Class A but more than Class B.

"There's a Class C also, biased so that the amplifier conducts for less than half a cycle. Class C is common in radio transmitters where it's necessary to amplify only a single carrier frequency. The distortion caused by the extreme clipping is easily filtered by a resonant circuit."
 
And what on earth makes you think that is a class B preamp?

Could it be this:
"EMC Complies with: EN 55103-1 and EN 55103-2
FCC part 15, Class B
CISPR 22, Class B"

Nah, that can't be it.
 
regebro said:
And what on earth makes you think that is a class B preamp?

Could it be this:
"EMC Complies with: EN 55103-1 and EN 55103-2
FCC part 15, Class B
CISPR 22, Class B"

Nah, that can't be it.
Click to expand...


Ah, haste makes wastes....

Neve 1081
 
Seems like some types of 1081 indeed was Class A/B, although some of the was Class A. Quite surprising...
 
"class c is like a mesa boogie."

No, Mesa produces class A and B , A/B amps.who knows maybe C also but They aren't into comunications last I checked.Unless they are building AM/FM transmitters,and using class C amplifiers to increase the RF power level to rectifier standards

PS Don't talk about us anyway...???
 
That magazine left out guitar amps, which also fall into that exsesivly distorted class. But I suppose you kids have alot to learn about rock n roll.

All microphone preamps are class A and A/B. As far as I know.
 
Amplification classes are not dependent on amplifier application. The article defined amplifier classes in general, using mic preamp as an example.
 
No, thats all depedant on the type of gain you get from the amp. I was just listing examples that anyone could understand.:rolleyes:
 
I have a sugden class a amp that has about 40 watts of power, sounds tremendous and kicks out quite a bit of power, only downside is you need excellent speakers to get full quality and it takes a while to warm up and puts out a ton of heat. its the best for cd's though, because it warms up the sound
 
You must log in or register to reply here.
Back
Top