Class D "digital" amps. Opinions on performance

[seamonkey]

Link Removed

Quotes from the link above:

"Class-D amps are switching amps. The signal is either on or off, not constant as it would be in an analog system. Because of this feature, sound quality is an issue."


"Because of its "all-or-nothing" nature, digital sound reproduction requires extremely rapid signal switching to reproduce sound accurately."

This article also cites references to it's sources of info on the bottom of the page.

This article is a misinterpretation.

Did you look at the references?

Elliot Sound has nothing but good to say about Class-d, it's just not "DIY", unless you buy modules.

And Bryston (Ceo picture above) makes and sells class-d amps. The given link points to a misinterpreted article by Bruno Putzeys who is a well know experts in Audio amplifier designs with many "class-d" like patents to his name.

Please read some articles and papers by Bruno directly. It will open your eyes.

 

[bongomania]

See the cited references on the link at the bottom of the page!

This is how that type of article and citation works:

"Granola is made of broccoli and string cheese"
cite:
The Holy Bible

See how authoritative my statement is?

 

[projectMalamute]

Was that your answer? It was a pretty basic question.

It's a different thing.

Or maybe it isn't, depending on how you want to parse the carefully worded 'advice' of industry experts here and elsewhere.

A Lab Gruppen or an I-Tech is a different animal than any of the type D amps being discussed here. They are only 'basically' class D in the same sense that a CA9 is 'basically' class A/B.

 

[seamonkey]

Crown review on their site:

[Invalid or Expired Link Removed]

"Class-I is like
two Class-D amplifiers in a bridge
configuration, except the load is still
referenced to ground."

 

[projectMalamute]

and class H is like class A/B except it can switch between multiple power supply rails.

So some things are, in some ways, like some other things.

 

[Bob Lee (QSC)]

A CA9 is class H--based on its commuted multiple power rail voltages--and class AB, based on the quiescent bias points being slightly above cutoff.

The Lab Gruppen and I-Tech are indeed class D. Amp designers have developed many ways to implement class D--some fixed clock, some self-clocked; most bistable, but some tristable; etc. Some manufacturers choose to give their particular implementations a name different from the IEEE designation.

 

[Chef]

HEYheyhey:

This was well conducted for a bit.
Let's please get back to making your respective points civilly.

thanks.

 

[Bob Lee (QSC)]

and class H is like class A/B except it can switch between multiple power supply rails.

Class H almost always is class AB, with switching among multiple rails.

 

[projectMalamute]

Apparently some dude who works for QSC is in charge of deciding if products from other manufacturers are 'basically' the same thing as some other products, opinions of the people who designed the things and filed for(and received) the patents notwithstanding.

 

[projectMalamute]

Class H almost always is class AB, with switching among multiple rails.

So you would argue that a CA9 is 'basically' the same topology as an SVT?

That is what you are doing by saying that an IPR is the same topology as an I-Tech.

 

[JimmyM]

I've missed all the pointless arguing over tiny little details...thanks for bringing it back, guys! I know very little about this new fangled technology, but in an argument between a guy who does it for a living for one of the major well-known companies and a bass player who's read a few books, I always side with the bass player who's read a few books. Go Malamute!

 

[bongomania]

Apparently some dude who works for QSC is in charge of deciding if products from other manufacturers are 'basically' the same thing as some other products, opinions of the people who designed the things and filed for(and received) the patents notwithstanding.

The purpose of a patent is to retain a financial stake in a design; the patent office is not a dictionary, industry terminology reference, glossary, etc. It is just a catalog of claims to ownership of ideas that may have market value to the person who paid for the patent process.

 

[Brad Johnson]

It's a different thing.

Or maybe it isn't, depending on how you want to parse the carefully worded 'advice' of industry experts here and elsewhere.

A Lab Gruppen or an I-Tech is a different animal than any of the type D amps being discussed here. They are only 'basically' class D in the same sense that a CA9 is 'basically' class A/B.

I guess that's a step up from the they both make things louder nonsense.


I'm not parsing anyone's advice, I have no baggage in this thread. I'm going by what LG has said about their proprietary designation of TD. I've read elsewhere that it's a form of class D. You OTOH are saying it's not.

Cool.

 

[projectMalamute]

I've missed all the pointless arguing over tiny little details...thanks for bringing it back, guys! I know very little about this new fangled technology, but in an argument between a guy who does it for a living for one of the major well-known companies and a bass player who's read a few books, I always side with the bass player who's read a few books. Go Malamute!

Well, I read those books because the people who do this stuff for a living tend to provide information that will sell product over information that will actually help the users of this stuff understand what's going on.

Good to see you back Jimmy.

 

[BurningSkies]

I've missed all the pointless arguing over tiny little details...thanks for bringing it back, guys! I know very little about this new fangled technology, but in an argument between a guy who does it for a living for one of the major well-known companies and a bass player who's read a few books, I always side with the bass player who's read a few books. Go Malamute!

This doesn't hurt Bob's case:

Invalid Link Removed

 

[Bob Lee (QSC)]

Crown review on their site:

[Invalid or Expired Link Removed]

"Class-I is like
two Class-D amplifiers in a bridge
configuration, except the load is still
referenced to ground."

That's an understatement of what they do. The two sides of each output are not only each a separate class D circuit, but they are clocked in quadrature so they are interleaved. This doubles the effective switching frequency and makes the reconstruction filter more effective without the attendant problems of making the output devices themselves switch at double the frequency. It's quite clever. I think it was Gerald Stanley who came up with that.

It's also a clever way to implement a grounded-bridge topology. Crown had used grounded-bridge in many of their high-power linear power amps as a way to double the output voltage capability of the output transistors. (BTW, they were still class AB--and the "VZ" models were essentially class H, though implemented in an unusual way.)

 

[Bob Lee (QSC)]

So you would argue that a CA9 is 'basically' the same topology as an SVT?

That is what you are doing by saying that an IPR is the same topology as an I-Tech.

Now you're making straw man arguments.

 

[Bob Lee (QSC)]

This doesn't hurt Bob's case:

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Honestly, it doesn't support my case, either.

 

[projectMalamute]

This doesn't hurt Bob's case:

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Sure, but he also works for an amp manufacturer who is still trying to sell a vanilla class D amp to the type of people that are also looking at Crown or Lab Gruppen.

The people who have the budget and experience do not seem to think a class D amp does the same job as a class I amp.

Bob thinks (or at least says he thinks) they are the same thing. Look at the amp racks at a big show and see what those people think.

 

[Bob Lee (QSC)]

Sure, but he also works for an amp manufacturer who is still trying to sell a vanilla class D amp to the type of people that are also looking at Crown or Lab Gruppen.

The people who have the budget and experience do not seem to think a class D amp does the same job as a class I amp.

Bob thinks (or at least says he thinks) they are the same thing. Look at the amp racks at a big show and see what those people think.

Again, straw man arguments.