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Old 16th January 2007, 12:22 PM   #1
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Question Why Class A

i would like to know that whats so special with solid state and class A amplifiers that a lot of people are interested in them, Even when a lot of Chip amps are available which delivers more power, are more efficient and dissipates less heat.
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Old 16th January 2007, 12:34 PM   #2
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Put simply, it's all about the sound.
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Old 16th January 2007, 02:38 PM   #3
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The more you experimented with various CCT, you will realize the problem with solid state amp is actually in the output stage, like crossover distortion. Front end (diff, VAS) can only be maximized AFTER you have a good output stage, otherwise you will be frustated Class A guarantees good output stage linearity, at least
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Old 16th January 2007, 02:39 PM   #4
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Default Re: Why Class A

Quote:
Originally posted by kuldeepsingh
i would like to know that whats so special with solid state and class A amplifiers that a lot of people are interested in them...
IMO, chip amps and Class A amplifiers are simply two entirely different approaches to amplification and there are many more topologies too. All kinds of people are actually interested in all kinds of different amps.

In general, comparing the two at similar output power, the Class A is going to be physically larger, more discrete components and obviously require a bigger power supply and some cooling via larger heat sinks and/or forced air. That doesn't mean you can't put a giant heat sink and huge power supply on a chip amp, some people do! I think it would be universally accepted the Class A is more luxurious and indulgent. As for the sound quality, it would depend on the quality of the designs; build quality and the listener's preference. Not to mention speakers and the rest of the shabang.

Quote:
... Even when a lot of Chip amps are available which delivers more power
I have difficulty believing that. I think there are some very large Class A amps out there. I think Nelson Pass has designed & built one or two.

Quote:
are more efficient and dissipates less heat.
In Canada during the winter months Class A amps are a vital necessity to keeping cosy.

Cheers,

Shawn.
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Old 16th January 2007, 03:07 PM   #5
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Default Re: Re: Why Class A

Quote:
Originally posted by TomWaits

As for the sound quality,
it would depend on the quality of the designs;
build quality and the listener's preference.
Not to mention speakers ....

Seems many listen to amplifiers only ( how much sound do these give )
and use not speakers when compare.

After all,
How much better are these advanced amplifiers,
with 0.00017 % THD ( 50% power output!!! )
Compared to a more normal amplifier
with 0.00100 % THD ( 50% power output!!! )


How much better, when it comes to the doing the job
give some thing that sounds as output.

My idea has always been
it is my SPEAKERS co-operateing with MY ROOM
that forms the sound waves.


I love you TomWaits
Good point with BOTH Feet firmly on the Ground ( = GND )


lineup Let's Get Real ... when comparing sound systems
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Old 16th January 2007, 04:06 PM   #6
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Default Re: Re: Re: Why Class A

Quote:
Originally posted by TomWaits
I have difficulty believing that. I think there are some very large Class A amps out there. I think Nelson Pass has designed & built one or two.
Oops! Perhaps kuldeepsingh was refering to the fact that there are more powerful chip amp designs available these days? Yes indeed, and folks are bridging them for very high power.

Quote:
Originally posted by lineup
it is my SPEAKERS co-operateing with MY ROOM
that forms the sound waves.
If the components in the system are not flawed and match well then I agree speaker choice and placement would remain the largest single variable. Here I am in the midst of constructing the Krell KSA50 clone and I truly can't wait to listen to it. I wonder if I will be able to tell the difference? At least the weather is right.

Quote:
I love you TomWaits
Hey! That's way off topic.


Cheers,

Shawn.
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Old 16th January 2007, 04:25 PM   #7
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The following represents my personal opinion and a simplified interpretation :

All solid state devices have non-linearity. The non-linearity is highest at small bias current; a typical example would be the Id vs Vgs curve for a MOSFET. By using a high bias, you are operating the device at a much more linear part of its characterisitcs, and hence you have much better INTRINSIC linearity (i.e. open loop). Any feedback you might choose to use helps to compensate for variable output impedance, but not linearity errors.

The penalty is high heat dissipation, large heatsinks, large power supplies. Or in other words, expensive, both for the cost of hardware and operating costs.

In using Class AB or Class B, one makes the compromise and use the non-linear part of the device characteristics, and compensate (correct) for that using large amount of negative feedback. It is a more practical solution, especially for consumer. And some can sound quite good (I used to have myself a Krell KAV300i for years).

But if you want the ultimate, I personally will go for Class A every time. And yes there is a hugh difference. I would not have believed it myself. I sold my Krell within a week after my Class A 100W were in operation. The decision was made in a day, although I initially planned to keep it alongside for a few months just to be sure.

If one wants efficiency, there is nothing to beat Class D. And there are supposedly nice Class D amps around as well.


Patrick

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Old 16th January 2007, 06:23 PM   #8
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Also depends on the loudspeakers.

Speaking for myself:
electrostats need an output stage with a high current capability because of a low minimum impedance level and large phase shifts.
This translates to a sufficiently large output stage, stepping up to class A is not such a big deal.
Secondly: i do not need a very high power amplifier.
Thirdly: electrostats have the lowest distortion number, and crossover distortion can be heard.

(on an subjective level : class A amplifiers seem faster. Maybe because the current is already running and only needs to be bent off in the right direction. Fluid still is a nice characterization of class A,imo)
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Old 17th January 2007, 07:37 AM   #9
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OK, if i simply compare a 50 Watts Class A Amp and a chipamp (LM3886), which will SOUND BETTER for normal 8 ohm woofers. Now i am asking it seroiusly coz listening good music is my passion more then my interest in sound hardware. But now i am making a 3 way x-over using LM chips to get good sound. DOes a simple 20-40 W class A amp beats a 50 W chip amp in terms of sound quality, punch and dynamics? is the simple answer i want...
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Old 17th January 2007, 07:44 AM   #10
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If sound quality equals punch and dynamics for you, then I think you should stay with chip amps.

But a 15W Class A takes a few hours and say $100 to build. So why not build one and find out for yourself ?

Patrick
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