whats makes sense to have class A amp?

[space2000]

Hi All,

Base on my own practical experience. I can be wrong too. Pls comments on this thread.

I always heard about Class A amp so I made one class A amp. It’s working fine. I had listened for many hours and compare with my class A/B amp. I am very much confused about the sound quality differences. Class A doesn’t have much low bass power only have high frq and mid nice but not very much different with class A/B. Their are very minor difference I found in practical. When I listened same song using this two amps. Class A and class A/B not really much difference but A/B has more power to drive nice bass and treble too where class A is really failed to do the job in low frq. There is a question about class A watts too. mine is 30wrms. I am still very much confused why many are talking about class A amp, Class A amp is very good? i am not telling it is bad. As I am not electronics engineer, I could be wrong.

Pls write your comments. I want to understand, whats makes sense to have class A amp. whats the great difference in this two amp?

i will not stop to making my class A amp, i have to understand the logic behind.

Thank you
Michael

 

[analog_sa]

Can you describe exactly what amplifiers you are comparing including the power supplies? General statements like "Class A doesn’t have much low bass power only have high frq and mid" while entertaining are not very useful.

 

[AndrewT]

I would expect the ClassA to sound better in the bass not worse.
I wonder what you have done wrong?

 

[sreten]

Hi,

Good Class A ( ~ 20w) vs. Good Class AB (lots more power) ?

Really good midrange on complex difficult material.
Bass end is a complete joke, not enough juice.

What I found for :
Sugden A21 or Kelvin Labs (both 20w) vs. Audiolab 8000A

🙂/sreten.

 

[philpoole]

So that was the Sugden and Kelvin with good midrange and comical bass?

 

[space2000]

Can you describe exactly what amplifiers you are comparing including the power supplies? General statements like "Class A doesn’t have much low bass power only have high frq and mid" while entertaining are not very useful.

hi,

Class A bass is not very bad but wk, not like AB very strong. i just made aleph-3, 30wrms for testing prpose. my power supply have more then enough ampire as its require. its only require 2.5ampire to 3 but mine is 10 ampire huge power supply. i am using 29v dc.

 

[Mooly]

Hello Michael,
The quest for knowledge continues I see.
When you are comparing totally different amps it's very difficult to say whether any difference is down to the class of operation or other details totally unrelated.
I think I am correct in saying Doug Self published a design a few years back that could be run in all three classes, A, AB and B.
Perhaps something like this would be of use as you are listening to the same amp but running in whichever Class you want.

 

[analog_sa]

just made aleph-3, 30wrms for testing prpose.

Have you considered the possibility that you (or your speakers) don't like single ended bass rather than class A? How much capacitance do you have in the PS?

 

[analog_sa]

I think I am correct in saying Doug Self published a design a few years back that could be run in all three classes, A, AB and B.

Let me guess: all three sound bad 🙂

 

[space2000]

Hi mooly,

Thanks for comments. yes, its true. i was wondering what is the great dfrnce in btwn this two amps. if the dfrnce is only very minor then whats the point to have class A right? i am not expert but i was very much curious about it so i made it and still learning.

My friends are telling me to make one class A as they have one. so i was thinking to make one and see.

class A amp:
Clearity = good
high freq= good
mid = good
low = not good


class AB amp:
Clearity = not so bad
high freq= not very good
mid = good
low = very good

PS 40000uf as i have enough power in transformer.


thank you
michael

 

[tschrama]

I think Class A amplifiers are popular because they alow for simpler circuits, they don't need much open loop gain or FB as they are inherently more linear

 

[Mooly]

But seeing as you come to mention it 😀 .
I have said it before and will say it again. They don't sound "Bad" they are -well- just very good HiFi very very good actually, but something is missing. They are very clear, very detailed, very dynamic, and oh yes, they DON'T make "The music come alive" It's that indefinable factor. Once you have experienced that, all mere talk of technical details goes out the window, it's something I could not live without.
Michael knows what I am on about --- don't you 😉 ---
I used the new Sugden A21SE as a benchmark for my own design, and have even had a tour of the factory --- amazing place, nothing at all like you would imagine, but they genuinely care about how the final product sounds, they listen to and evaluate individual components as well.
Michael, ultimately in my opinion the Class of the amp does not matter, there are plenty of poorly executed Class A designs out there, it's how it sounds, does the music "move you". If it does, the amp has done it's job and you can concentrate on the music, as I am about to do now.
The Philharmonia Orchestra playing Mussorgskys "Pictures at an Exhibition" are waiting for me to take my seat.

Ta-ra for now.

 

[CBS240]

class A amp:
Clearity = good
high freq= good
mid = good
low = not good


class AB amp:
Clearity = not so bad
high freq= not very good
mid = good
low = very good

This is relative to design. The latest class AB amp I made can amplify 400 KHz with no problem. Highs and mids are just as strong and clear as bass even with complex program material. This is with KLH linear dynamics speakers (very flat response curve) and the amplifier source is a simple CD player line out and a pot voltage divider for volume control. Most of the distortion related to class AB is from output crossover, which can be alleviated using linearization techniques, if your willing to deal with the added complexity.

 

[sreten]

So that was the Sugden and Kelvin with good midrange and comical bass?

Yup. Fantastic and then some some bass comes along and it falls apart. 🙂/sreten.

 

[wg_ski]

class A amp:
Clearity = good
high freq= good
mid = good
low = not good

PS 40000uf as i have enough power in transformer.

thank you
michael

You're not running the output through a 1000 uF coupling capacitor or anything, are you? All the power supply in the world won't help you then.

30 watts isn't very much, and you may be subject to clipping. Class A amps will clip fairly gracefully, but if you're flat-topping every kick drum hit the bass will sound weak.

 

[Nordic]

it is actualy scary how many class a designs out there have way too small caps on the output.... even at 4700uf you are still seriously affecting bass roll of into 8 ohms... something I learned from headphone amp buiding.

 

[adason]

there is big difference in sound quality between tube classA and solid state classA amps
I have built three solid state designs from 3-20 watts
and bulit/restored three tube classA amps 2-5 watts
I personaly preffer sound of tube amps

 

[adason]

and they are all used only to run mid/tweeter sections

 

[analog_sa]

PS 40000uf as i have enough power in transformer.

Enough power in transformer? This sounds like some real nonsense.

Aleph 3 is designed to use 170000uF and one can easily imagine the bass suffering with less than a quarter of this capacitance.

 

[wakibaki]

Maybe it could be a GOOD class AB amplifier and a CRAP class A amplifier.

Stranger things have happened at sea...

w