Class A--B amps

[bonesninja 5,000+ posts]

I figured that response was just too stupid to be serious.

i figured that as welll......but he seems so sincere

 

[Ge0 10+ year member]

There is no such thing as a digital amplifier.
And for the record, there is no recognized Class T amp either. That is a name stuck on amps that use a Tripath chip to control the switching modulation.

They use a noise shaping algorithm to minimize disortion on the switched output. Still considered Class D, but, since they do things a little differently with signal manipulation after modulation, why not call it T //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif? Similar strategy to ICEPOWER, but, in my opinion ICEPOWER (licensing now owned by B&O?) does a better job at it.

Ge0

 

[Ge0 10+ year member]

A pure class A amplifier is an amplifier that never "falls out" of class A operation.
That Steg does not operate in class A for it's entire output range. At some point (it's claimed after 50w per channel in the literate) it falls out of class A operation. That's not a pure class A amplifier. It's a class A/B amplifier with a high bias.

I would actually like to see some independent tests of that amplifier as they claim they have developed a system to raise the efficiency and lower the current consumption of the class A operation dramatically allowing for the high class A power output of 100w which is unusually high for class A. I would be interested if it truly operates in class A up to 50w per channel as claimed. The only test I could find is not in English //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

First of all, you spend WAYYY too much time in this forum //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif.

Not saying you are right nor wrong. Just for clarification, PURE CLASS A opearation means the output transistor(s) never turn off. This is irrelevant of topology.

Everyone can argue other facts until they are blue in the face. The point is, does it matter?

Ge0

 

[Ge0 10+ year member]

First of all, I'm not responding to argue with you or flame. Just trying to check my own ideas and possibly learn something in the process.

Hi, welcome to several years ago..

Don't knock me for stating the obvious. Obviously the point has not sunk in...

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

Tons of distortion. Perhaps not. Define tons... Redundant transistors. Maybe. Depends on the goals of the design.

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.

Give me a break if I don't get this 100% accurate. It's late and I've been drinking //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif. The SS class A series was not trimmed to run class A from the factory. BUT, these amps were the only in the REF series to have the bias POT populated. The others were fixed. You could trim it to class A if you wanted too. At least up until a certain point AND if you ran a reasonable load. I.E. not cheater loads. That was SS's marketing gimic...

Correct me if I am wrong. I am not a professional amp designer. **** near every amp that is designed using a descrete input stage vs. integrated circuit is class A. ALL soundstream amps that I have ever looked at use the same input stage. This is the same type (though not identical) of input stage that is used in **** near every amp I have ever looked at (100+). Could this also be part of the marketing ploy?

Why would a company bias a class A/B design to run class A? Seems like a waste right? It makes perfect engineering sense to me. Use the same basic board throughout your product line and make a few component substitutions/tweaks prior to shipment. This saves money believe it or not. You save money when ordering in volume. An odd ball design at the schematic and physical board level (which may have a lower component cost) will cost you more than if you modified a design you order in higher volume (that has a higher component cost). I deal with this stuff on a daily basis. I believe that I at least have a basic apprehention...

Ge0

 

[Ge0 10+ year member]

Delete this post. DUPE.

 

[buildmeabox 10+ year member]

Can't we all agree to dis=agree? I've never heard of a "class A " amp producing more than 15 watts, but that doesn't mean one might not exist. A "class A/B" amp is only class A the first few watts then switches to class B. In order to take full advantage of a class A amp's output you need high sensitivity speakers.

As for the digital, class T's, N's and what ever the industry tries to shove down our throats, its like re-inventing the wheel...

Regardless of what type, brand or size the majority of amps today are built in China. Smoke and mirrors boys smoke and mirrors...

 

[JimJ 5,000+ posts]

I've never heard of a "class A " amp producing more than 15 watts, but that doesn't mean one might not exist.

I know of a bunch of them //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

In order to take full advantage of a class A amp's output you need high sensitivity speakers.

Indeed. Which is why they're not really suited to in-vehicle use.

 

[squeak9798 5,000+ posts]

First of all, you spend WAYYY too much time in this forum //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif.

//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

Not saying you are right nor wrong. Just for clarification, PURE CLASS A opearation means the output transistor(s) never turn off. This is irrelevant of topology.
Everyone can argue other facts until they are blue in the face. The point is, does it matter?

Ge0

I understand what class A operation is.

Does it matter ?

Well, if someone is marketing an amplifier as "class A", when it is infact a class A/B I personally think it does matter as I'm not a big fan of inaccurate marketing.

 

[Ge0 10+ year member]

//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif.

Sorry, should have explained myself. I meant this as a light hearted joke with some amount of respect implied. With 24,000 some odd posts, you are not simply a forum member, it a lifestyle //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif.

I understand what class A operation is.

Does it matter ?

Well, if someone is marketing an amplifier as "class A", when it is infact a class A/B I personally think it does matter as I'm not a big fan of inaccurate marketing.

As far as inaccurate marketing is concerned. Well, there will always be that factor. I've learned simply to ignore it and take it for what its worth. Although, one that still bugs me is "digital ready speakers".

Ge0

 

[helotaxi 5,000+ posts]

Why would a company bias a class A/B design to run class A? Seems like a waste right? It makes perfect engineering sense to me. Use the same basic board throughout your product line and make a few component substitutions/tweaks prior to shipment. This saves money believe it or not. You save money when ordering in volume. An odd ball design at the schematic and physical board level (which may have a lower component cost) will cost you more than if you modified a design you order in higher volume (that has a higher component cost). I deal with this stuff on a daily basis. I believe that I at least have a basic apprehention...

With an education in economics, if fully get where economies of scale would factor into the equation for amp production. There's a reason that OEMs are out there using the same board in tons of different brands of amps with only component tweaks making them different. The problem with this is that if you are trying to sell two different topologies of amp using the same circuit design, which design gets compromised? As a reputable amplifier company (the Soundstream of old was one of the most reputable, IMO) you wouldn't compromise on either, especially in an era when you could pretty much charge whatever you wanted for an amp and people would pay. From that point of view, it makes no sense to build a Class A/B amps an then trim it to run as a Class A. It results in a design compromise for the "higher end" design. I'm quite sure that the reason that the trimmer pot was populated on the Class A series boards was to allow the QC engineer to optimize the bias for the higher end amp in an attempt to minimize/eliminate any notch distortion and tune it for the actual transistors in the amp rather than designing to specs and then accepting the tolerances of the batch of components used. All the MS series PG amps had the same pair of trimmers, BTW.

 

[DBfan187 5,000+ posts]

Sorry, should have explained myself. I meant this as a light hearted joke with some amount of respect implied. With 24,000 some odd posts, you are not simply a forum member, it a lifestyle //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif.

It's called having a job that enables you to be on the internet all day. //content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif

 

[Ge0 10+ year member]

It's called having a job that enables you to be on the internet all day. //content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif

Heh, that and screw around on it too boot...

That's a fuggin hilarious avatar!

Ge0