Class A--B amps

[squeak9798 5,000+ posts]

i was under the impression that probably 99% of people couldn't tell the difference between a class d amp and a class a/b amp in a blind sound comparison in a car audio enviroment. i think i read about such a test before and the results were very inconclusive.

100% of people tested under scientific conditions have been unable to demonstrate an ability to hear a difference in amplifier topology.

 

[Grinder1989 5,000+ posts]

So under perfect conditions (14.4V & 25% efficiency) a 790w class A amplifier would draw a constant 220A. Good luck with that electrical system //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

**** thats a lot of amps. So how many are class A's good for in a normal setup? 25? lol

 

[Gary S 10+ year member]

Some of the old soundstream amps sounded similar to class A amps because of the softer clipping... but for overall sound quality, a more powerful, less expensive amplifier run below audible clipping levels will always sound better.

I know soundstream advertised some amps as class A... but I have heard hand assembled, made in California class A Adire (not the speaker company, before Dan stole the name) home amps with caps on the outputs, with which I could not hear any audible clipping even with the volume maxed out... the Soundstreams' were never that good, LOL!

 

[helotaxi 5,000+ posts]

Some of the old soundstream amps sounded similar to class A amps because of the softer clipping... but for overall sound quality, a more powerful, less expensive amplifier run below audible clipping levels will always sound better.

Sound while clipping has nothing to do with topology. Pretty much any amp can be made to clip gracefully, but why the hell would you? Amps were menat to be run below clipping.

but I have heard hand assembled, made in California class A Adire (not the speaker company, before Dan stole the name) home amps with caps on the outputs, with which I could not hear any audible clipping even with the volume maxed out

If the guy know what he was doing the amp probably WEREN'T clipping which is why you heard nothing.

 

[JimJ 5,000+ posts]

**** thats a lot of amps. So how many are class A's good for in a normal setup? 25? lol

25% is the theoretical maximum. One of these days I'll clamp the monos and see what they're drawing from the wall...no idea as of now.

The largest Class A (albeit A2) amp design I know of is the 833A triode running in single-ended operation...which I've seen anywhere from 150 to 220 watts depending on plate current/voltage and how much THD was tolerated.

http://www.tubelab.com/833SE.htm

Basically the same concept behind the Japanese WAVAC HE-833 amp that sells for $350,000.

 

[Ge0 10+ year member]

Are you saying Class A Because soundstream did make a Pure Class A Amp back in tha Day.And they are excellent for SQ. IMO

These were the Reference 3.0, 5.0, 6.0, 10.0 and Picasso. Some of the D series were also biased class A

Ge0

 

[Ge0 10+ year member]

Myth buster time.

I challenge you to tell an audible difference between modern day D-class amps such as the Alpine PDX series, Class A, and Class A/B. Distortion figures are so low in all cases that your ear can't discern the difference. They only way you could possibly hear a difference is if you wanted to and your mind tricked you into thinking it did. Therefore, no one can tell for sure unless you do true ABX type testing.

Myth Buster #2

Any class A/B amp can be run pure class A if biased properly. You know that little pot on the amp that says DON'T TOUCH! Well, this sets the bias of the output stage. Crank it up so the output devices operate midway into their linear range and you now have a class A amp. Just make sure the amps heat sink can handle the thermal load. Class A amps dissipate the most power at idle.

There was NO difference in the amps output stage design between the Soundstream reference series and Class A series. The only difference was the voltage available at the power supply rails. The class A amps were lower power since the heat sink could not tolerate operating at the same power levels as a identically designed class A/B amp.

And there you have it...

Ge0

 

[helotaxi 5,000+ posts]

Myth buster time.
I challenge you to tell an audible difference between modern day D-class amps such as the Alpine PDX series, Class A, and Class A/B. Distortion figures are so low in all cases that your ear can't discern the difference. They only way you could possibly hear a difference is if you wanted to and your mind tricked you into thinking it did. Therefore, no one can tell for sure unless you do true ABX type testing.

Hi, welcome to several years ago.

Myth Buster #2
Any class A/B amp can be run pure class A if biased properly. You know that little pot on the amp that says DON'T TOUCH! Well, this sets the bias of the output stage. Crank it up so the output devices operate midway into their linear range and you now have a class A amp. Just make sure the amps heat sink can handle the thermal load. Class A amps dissipate the most power at idle.

And you would probably have a ton of notch distortion and a fully redundant set transistors.

There was NO difference in the amps output stage design between the Soundstream reference series and Class A series. The only difference was the voltage available at the power supply rails. The class A amps were lower power since the heat sink could not tolerate operating at the same power levels as a identically designed class A/B amp.

The "Class A" Soundstreams were not trimmed to run as Class A's. The input stage was Class A. They were low voltage high current amps. Typical cheater amp of the day. They didn't get hot like a Class A would and they didn't draw constant current like a Class A either. Why not? because they were not Class A amps. Why on earth would a company design and produce a Class A/B amp and then trim it to run as a Class A. Not sound from an engineering standpoint and not nearly sound from an economic standpoint.

 

[Audio Master 10+ year member]

steg make a proper class A amp its called the CLASSE' A MSK

 

[Audio Master 10+ year member]

but back in the real world Orion dude if you buy any amp it will be class ab except in the case of monoblocks where the majority is leaning towrds digital if you want pure sound quality id suggest buying better than soundtream for a start and go with steg or audisson or gennisis or a handful of other top end brands then also find some speakers to match like the Dynaudios or the focal utopias or AD600rs and the mm series also hertz and lotus seas there is alot you will have to do a lot more research before you jump intpo straght up SQ as also there is class a/b monoblocks to think about aswell do ytoui go fully active ar do you run passive whats your budgethow much and har far do you want to go is it for you or are you compeating the reason i say this is you can get a system using the best gear in the world and it wil cost like 300k but it might not sound very good to you go to the shop and listen to everything you can from el cheap to the most expesive on the shelf then go to another shop and do the same try as many as you can and get as many opinions as you can then decide what you like and go for it

 

[helotaxi 5,000+ posts]

Yes, you should get good speakers. No the amps don't matter nearly as much and pretty much any amp will sound like nothing if set up and used properly.

 

[squeak9798 5,000+ posts]

steg make a proper class A amp its called the CLASSE' A MSK

Keep in mind that amplifier is a class A/B amplifier. It is NOT a pure class A amplifier.

And I've yet to see any measurements indicating Soundstream amplifiers are not capable of the same "sound quality" as any other amplifier on the market.

And please don't refer to class D amplifiers as "digital".

 

[Megalomaniac 5,000+ posts]

Is this why Audisons lrx 5.1k only uses Class A on the tweeter channels...because of the bad efficiency but better sound on high frequencies?

 

[helotaxi 5,000+ posts]

^^^The idle current is listed at 3A. Sorry, still not Class A. Just the high freq channels would idle close to 30A. There is no sonic difference between a well designed and built Class A/B and a good Class A. It's all marketing.

 

[Ge0 10+ year member]

Keep in mind that amplifier is a class A/B amplifier. It is NOT a pure class A amplifier.

And I've yet to see any measurements indicating Soundstream amplifiers are not capable of the same "sound quality" as any other amplifier on the market.

And please don't refer to class D amplifiers as "digital".

I'm interested. Please elaborate. What do you consider a PURE class A amplifier?

I think people are confusing single ended and complimentary designs.

"And please don't refer to class D amplifiers as "digital""

Agreed!!!

Ge0