#1
Ive always heard that a class a amp will sound louder than a class ab amp of the same wattage. Is there a rule, so to say, as of how much louder it will sound?

For example, a 30 watt class a amp will sound as loud as a _____ watt class ab amp?

Thanks
My Gear:
MIM Fender Strat HSS

My Influences:
1) David Gilmour
2) SRV
3) Jimmy Page
4) Jimmi Hendrix
5) Slash
#2
Any amp with more than like 10 watts is AB. Some amps stay class A to a point, but once they're turned up so far tho go to class AB. If I'm no mistaken AB is more efficient, therefore louder.
I don't give a shit if you listen to me or not
#3
30 watts class a= 30 watts class ab. 30 watts is 30 watts. class a just means all the power tubes are running all the time (i think) so an amp with 1 tube will always be class a. class ab is usually more efficiant then a class a amp though ( amp with 2 power tubes class a would be less wattage then an amp with 2 power tubes class ab)


EDIT:
Quote by Kevin Saale
Any amp with more than like 10 watts is AB. Some amps stay class A to a point, but once they're turned up so far tho go to class AB. If I'm no mistaken AB is more efficient, therefore louder.


false. mesa lonestar special is class a and it's 30 watts. there are plenty of more examples i just dont feel like listing them.
#4
The difference between class A and AB amps is largely BS as far as marketing is concerned. Any amp with a single power tube is class A. Any amp with two or more is class AB. Some amps, like the AC30, clain to run in class A at lower volumes, and AB at higher volumes. I'm not enough of a techie to you if that's true or not. I can tell you that those big "Class A" labels on the Palominos 15W and larger are complete BS.

Many amps claim to be class A if they're cathode biased. Generally a cathode biased amp will put out less than a fixed bias amp. Which would be the opposite of what you heard.

My advice? Don't worry about it. Assume that any amp with more than one power tube is class AB, and pick an amp based on it's sound.
You Don't Need a halfstack.

You Don't Need 100W.

Quote by jj1565
i love you slats.
#5
I saw this one class A amp which was 40 watts.
It was one freaking expensive one though.
Call me Wes.
Gear:
Fender American Deluxe HSS Strat
Chicago Blues Box Roadhouse
Bad Cat Cougar 5
1957 Gibson GA-5
Ceriatone 18w TMB Combo
Hughes & Kettner Tube Factor
Various Ibanez TS9s
Weber MASS Attenuator
#6
Quote by slatsmania
The difference between class A and AB amps is largely BS as far as marketing is concerned. Any amp with a single power tube is class A. Any amp with two or more is class AB. Some amps, like the AC30, clain to run in class A at lower volumes, and AB at higher volumes. I'm not enough of a techie to you if that's true or not. I can tell you that those big "Class A" labels on the Palominos 15W and larger are complete BS.

Many amps claim to be class A if they're cathode biased. Generally a cathode biased amp will put out less than a fixed bias amp. Which would be the opposite of what you heard.

My advice? Don't worry about it. Assume that any amp with more than one power tube is class AB, and pick an amp based on it's sound.


thanks for clearing that up.

I wasn't asking to make a decision on any particular amp. To tell you the truth, i cant even tell the difference between amps that claim to be class a vs those that are ab.
My Gear:
MIM Fender Strat HSS

My Influences:
1) David Gilmour
2) SRV
3) Jimmy Page
4) Jimmi Hendrix
5) Slash
#7
Quote by bigreno
thanks for clearing that up.

I wasn't asking to make a decision on any particular amp. To tell you the truth, i cant even tell the difference between amps that claim to be class a vs those that are ab.


Part of the reason for that is that most amps billed as class A are not.
Here's a good way to tell:
Amps with only one power tube are class A;
Amps with more than one power tube are almost never class A. An easy way to tell is the wattage: class A is not nearly as efficient as AB. For instance, the AC30 would be around 12 watts if it were actually class A. The lonestar that mrchow mentioned is in fact class AB.

+1 to slats though, the class does not matter.
#8
Quote by slatsmania
The difference between class A and AB amps is largely BS as far as marketing is concerned. Any amp with a single power tube is class A. Any amp with two or more is class AB. Some amps, like the AC30, clain to run in class A at lower volumes, and AB at higher volumes. I'm not enough of a techie to you if that's true or not. I can tell you that those big "Class A" labels on the Palominos 15W and larger are complete BS.

Many amps claim to be class A if they're cathode biased. Generally a cathode biased amp will put out less than a fixed bias amp. Which would be the opposite of what you heard.

My advice? Don't worry about it. Assume that any amp with more than one power tube is class AB, and pick an amp based on it's sound.


Well my amp is a 2xEL34 amp and it's class A. First Orange claims this, but that doesn't make it true, doesn't it? No, but in my Orange catalougue they have a small section explaining Class A and Class A/B, which explains very good how Class A and Class A/B differs, in technical terms, so its not just some marketing schem from them.
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

My band

Recognised by the Official EG/GG&A Who To Listen To List 2009
#9
Nearly all guitarists don't know the difference between (those two) classes, and IMO there's no point in knowing it either, unless you're planning on going into amp design. That's why my BS alarm immediately goes off when someone claims to like class A better than AB (it's never the other way around, is it?). The people that do know what they're talking about, would also know enough to not say things like that.

I don't know how it started, but my guess is that one (or several) companies started using the 'class A claim' in their advertisements; after which others started doing it too. Somewhere down the line, this started happening with non-class A amps as well. Now it's even gone so far that any particular 'class A' amp is more likely to be class AB. So does it even matter? I'd say no, but all this class A BS is convincing a lot of people that AB is somehow inferior.
#10
^^ Yeah, I knew I was going to get into trouble by generalizing. If it puts out only 30W on two EL34's, it's almost certainly a true class A amp. No wonder it's so different from the Rockerverb 50, which puts out a sizzling 50W out of four 6V6's. You can only do that in class AB.
You Don't Need a halfstack.

You Don't Need 100W.

Quote by jj1565
i love you slats.
#11
Quote by Gabel
Well my amp is a 2xEL34 amp and it's class A. First Orange claims this, but that doesn't make it true, doesn't it? No, but in my Orange catalougue they have a small section explaining Class A and Class A/B, which explains very good how Class A and Class A/B differs, in technical terms, so its not just some marketing schem from them.


So it's a single-ended amp? Does it have a phase inverter?

30 watts from two EL34s sounds like it could be class AB with cathode biasing, but what the hell do I know?
Last edited by mr_hankey at Feb 25, 2008,
#12
i agree with roc, slats and hankey.

it is possible to bias it for class A with more than one power tube (i think) but it's extremely rare. an ac30 isn't class A, at least not when it's overdriving the power amp. yet the marketing frequently talks about the "sweet sound of class A power amp overdrive".

Which. Is. Wrong.

Class A versus Class A/B distinctions are measured before the amp clips. there's no such thing as class A overdrive, in other words.

I think.
I'm an idiot and I accidentally clicked the "Remove all subscriptions" button. If it seems like I'm ignoring you, I'm not, I'm just no longer subscribed to the thread. If you quote me or do the @user thing at me, hopefully it'll notify me through my notifications and I'll get back to you.
Quote by K33nbl4d3
I'll have to put the Classic T models on my to-try list. Shame the finish options there are Anachronism Gold, Nuclear Waste and Aged Clown, because in principle the plaintop is right up my alley.

Quote by K33nbl4d3
Presumably because the CCF (Combined Corksniffing Forces) of MLP and Gibson forums would rise up against them, plunging the land into war.

Quote by T00DEEPBLUE
Et tu, br00tz?
#13
The Peavey Valveking 212 I own got a weird thing class A-A/B power structure changer. They do sound a bit different from each other.
#14
yup. the $65,000 question, though, is whether that's actually changing between A and A/B, or doing something else, which also changes the tone.

I have no idea.
I'm an idiot and I accidentally clicked the "Remove all subscriptions" button. If it seems like I'm ignoring you, I'm not, I'm just no longer subscribed to the thread. If you quote me or do the @user thing at me, hopefully it'll notify me through my notifications and I'll get back to you.
Quote by K33nbl4d3
I'll have to put the Classic T models on my to-try list. Shame the finish options there are Anachronism Gold, Nuclear Waste and Aged Clown, because in principle the plaintop is right up my alley.

Quote by K33nbl4d3
Presumably because the CCF (Combined Corksniffing Forces) of MLP and Gibson forums would rise up against them, plunging the land into war.

Quote by T00DEEPBLUE
Et tu, br00tz?
#15
Quote by mr_hankey
So it's a single-ended amp? Does it have a phase inverter?


It does. BUT!

Class A can use a Phase Inverter:
http://www.aikenamps.com/SingleEnded.htm

Quote:
"A push-pull stage can be biased class A, where current flows in both tubes for the entire input cycle (but in opposite directions in the output transformer, so they sum in-phase in the secondary winding while the DC offset bias current cancels out, to prevent core saturation and allow use of smaller, ungapped cores), or class AB, where current flows alternately in both halves, but less than a full cycle in each"
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

My band

Recognised by the Official EG/GG&A Who To Listen To List 2009
#16
When you actually look at the facts surrounding amplifier classes, you'll find that a class A amplifier uses 100% of the input signal 100% of the time. This means that the power section is running full tilt all the time.

A class AB amplifier requires the use of pairs of power tubes and each tube in this pair (ideally) amplifies for only half of the wavelength. In reality this is a bit more complicated. Due to a necessary degree of latency when turning each tube on/off you get gaps in the wave called "crossover distortion" which is dealt with (via a process called biasing) by leaving each tube barely on during it's off cycle instead of turning it completely off during it's off cycle.

Because class A is running full voltage and full current at all times, it's significantly less efficient than class AB and therefore you can only suck comparatively limited amounts of power out of one. Whereas a quartet of EL34's will give you a theoretical 100 watts in class AB, the same quartet will give you only about 30 watts in class A and will burn out much sooner.
ESP LTD EC-256 and a Fender Deluxe VM
#17
Quote by Gabel
Well my amp is a 2xEL34 amp and it's class A. First Orange claims this, but that doesn't make it true, doesn't it? No, but in my Orange catalougue they have a small section explaining Class A and Class A/B, which explains very good how Class A and Class A/B differs, in technical terms, so its not just some marketing schem from them.


Could you link me that orange explanation? I can't find it. I'm not really convinced the RV is class A- the wattage is still too high for two EL34s, and Orange claims the AD30 is class A, which it is definitely not.

It's an interesting topic, but I still think it's pretty silly that we spend so much time on class A vs class AB. I vote we change the names to class East and class West just so people stop caring.
#18
Quote by Roc8995
Could you link me that orange explanation? I can't find it. I'm not really convinced the RV is class A- the wattage is still too high for two EL34s, and Orange claims the AD30 is class A, which it is definitely not.

It's an interesting topic, but I still think it's pretty silly that we spend so much time on class A vs class AB. I vote we change the names to class East and class West just so people stop caring.
xD

Yeah, I've been reading up on Class A and A/B for some time, and the thing is most of what marketers put out is BS.

For example, the Orange Rocker 30 may well be Class A although the maximum theoretical plate dissipation for a pair of EL34s is 25w, but 30 is a nice title and overdriven it probably puts out much more than 30w anyway.

The Laney VC30 and AC30 aren't Class A... You can tell because they deliver about 30w clean RMs wheras in Class A 4x EL84 theoretical maximum is 24w, and they both give a lot more than that.

The reason people say Class A amps are louder is because they tend to emphasise much more harmonic distortion than their AB counterparts, but again a lot of this is due to the push-pull output section in most AB amps cancelling out much of this extra dirt.

So to sum up, a Single Ended amp has to be Class A. Push-pull amps can be Class A, but there is no actual benefit as it will run hotter and have less output, so often they market it as Class A and actually run it in AB to minimise breakdowns, increase power output.... There's no massive difference at the end of the day.
The Laney Thread are big and clever. No exceptions.
#19
Quote by Toolshed#9
The Peavey Valveking 212 I own got a weird thing class A-A/B power structure changer. They do sound a bit different from each other.


+1, though all I've noticed is that the gain range goes down and it gets quieter.
...
#20
Quote by Roc8995
Could you link me that orange explanation? I can't find it. I'm not really convinced the RV is class A- the wattage is still too high for two EL34s, and Orange claims the AD30 is class A, which it is definitely not.

It's an interesting topic, but I still think it's pretty silly that we spend so much time on class A vs class AB. I vote we change the names to class East and class West just so people stop caring.


It's not on their website, but in a catalouge I have from them. it says:

"Class A and Class A/B Explained
Class A or Class AB describes how a type of amp circuit works. But to discuss Class we need to first explain push-pull. To achieve more power, a preamp signal is split into two halves by a circuit called a phase inverter. One half goes to each output valve, then the two halves are combined in the output transformer which drives the speaker. As one valve pushes half the signal, the other waits to pull it's half, hence push-pull. to get more power, extra pairs of valves are added. In a Class A amp, both valves conducts current all the time, at or near maximum whether or not a signal is present. The audio flows seamlessly from half to the other. Orange Class A circuitry is self biasing and therefore finds its own optimum performance curve giving greater harmonics with tones that are warm and sweet. The note compresses as you dig into the string, responding expressively to the individual style. In Class AB, one of the output valves is biased to turn on 25% before its opposite number cuts off. This leaves a small amount of residual harmonic, which is enhanced using negative feedback circuitry. All Orange amps 50 and over use Class AB. This class of operation suits these powerful amplifiers the best when it comes down to response, overall tone and size. Class AB has the fullnes of Class A but has a more driven edge and is more suited to rock."

I know some is standard advertising BS, but a lot of it is true, explaining what Class A and AB exactly what they are. Also they don't act like Class AB is inferior to Class A.
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

My band

Recognised by the Official EG/GG&A Who To Listen To List 2009
#21
Quote by Gabel
It does. BUT!

Class A can use a Phase Inverter:
http://www.aikenamps.com/SingleEnded.htm

Quote:
"A push-pull stage can be biased class A, where current flows in both tubes for the entire input cycle (but in opposite directions in the output transformer, so they sum in-phase in the secondary winding while the DC offset bias current cancels out, to prevent core saturation and allow use of smaller, ungapped cores), or class AB, where current flows alternately in both halves, but less than a full cycle in each"


agreed.

push-pull is often confused with A/B (i know i've confused the two before). They aren't the same thing; a push-pull amp can be class A, and (if you bias it strangely, i think- this could be completely wrong, and I admit it sounds far-fetched- i just remember someone in that long-dead 18-watt forum valve junior thread saying that you could bias the valve junior for class A/B, and he knew a lot more about electronics than most of us) a single ended amp can be approaching A/B. I think. This is moving outside my comfort zone, though (haha, anything beyond "the valves light up" is beyond my comfort zone).


Quote by Roc8995
Could you link me that orange explanation? I can't find it. I'm not really convinced the RV is class A- the wattage is still too high for two EL34s, and Orange claims the AD30 is class A, which it is definitely not.

It's an interesting topic, but I still think it's pretty silly that we spend so much time on class A vs class AB. I vote we change the names to class East and class West just so people stop caring.


i don't want my amp named after those commie soviets...

kidding, obviously, but nomatter what you call it, one will sound "better" to some people. Though obviously class A and B is extremely misleading.

http://en.wikipedia.org/wiki/Valve_amplifier#Decline was flicking through wiki and found this. LOLWUT? apparently valve guitar amps are in decline too. o_O
I'm an idiot and I accidentally clicked the "Remove all subscriptions" button. If it seems like I'm ignoring you, I'm not, I'm just no longer subscribed to the thread. If you quote me or do the @user thing at me, hopefully it'll notify me through my notifications and I'll get back to you.
Quote by K33nbl4d3
I'll have to put the Classic T models on my to-try list. Shame the finish options there are Anachronism Gold, Nuclear Waste and Aged Clown, because in principle the plaintop is right up my alley.

Quote by K33nbl4d3
Presumably because the CCF (Combined Corksniffing Forces) of MLP and Gibson forums would rise up against them, plunging the land into war.

Quote by T00DEEPBLUE
Et tu, br00tz?
#22
Quote by Toolshed#9
The Peavey Valveking 212 I own got a weird thing class A-A/B power structure changer. They do sound a bit different from each other.


That knob in no way changes the circuit from class A to class AB. I think it just lowers plate voltage.

Dave- I know they'll always sound different, but people gravitate towards class A as though it's better. Manufacturers play this up and claim that a lot of amps are class A when they are not, which confuses the matter further. It's hard to 'like class A more' when 75% of amps claiming to be class A are not.
#23
oh, i agree wholeheartedly, giving them letters is very confusing. of course, scientists tend to use letters or numbers for things as it allows them to be categorised much more easily.

I'm an idiot and I accidentally clicked the "Remove all subscriptions" button. If it seems like I'm ignoring you, I'm not, I'm just no longer subscribed to the thread. If you quote me or do the @user thing at me, hopefully it'll notify me through my notifications and I'll get back to you.
Quote by K33nbl4d3
I'll have to put the Classic T models on my to-try list. Shame the finish options there are Anachronism Gold, Nuclear Waste and Aged Clown, because in principle the plaintop is right up my alley.

Quote by K33nbl4d3
Presumably because the CCF (Combined Corksniffing Forces) of MLP and Gibson forums would rise up against them, plunging the land into war.

Quote by T00DEEPBLUE
Et tu, br00tz?
#24
I'm an electronic engineer at Purdue and have built small class A and class AB amplifiers in lab. Take what i say with a grain of salt because I got a D in ECET 257 hehhehe. This is from what I remember. We used MOSFET amplifiers in a high side switch configuration for a class A amplifier. It was around 60V max and made about 10W.

Our final project used 2 MOSFET amplifiers to create a 120 V 30W amplifier. This configuration was Class A/B because it used multiple MOSFETS to dissipate heat and share the load. This configuration vocally had the same output on the Peavey 2x12 we powered thorugh an audio IC. The class is just the way the power is amplified. It is the same signal getting amplified just in different ways. I think the only way the tone changes is the tubes, speakers, and maybe the quality of some of the components of the amp. But in my experience with these amplifiers, they are the same.
Peavey VK112
Fish&Chips EQ
Ibanez TS9DX
Jackson Warrior JS30 upgraded EMG 81/85
Epiphone Silverburst 1966 Reissue G-400
Washburn D12N

Playing since 03-11-07
........Uber Noob Skillz