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Class D "digital" amps. Opinions on performance

#321
seamonkey said:
There isn't any trades offs, science has known for 50 years what humans can hear.
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If that were entirely true, MPEG and other encoding schemes would've gotten developed a lot faster! ;)

Science has had a good grasp for 50 years of what humans can hear, but there are always details to learn.

Every once in a while at an AES convention there will be a panel session or two involving audiology, neurology, psychoacoustics, etc. It doesn't really have much to do with my work, but the stuff is fascinating.
 
#322
just to clarify:

Class I is 'technically' Class I. That's what it says on the amp, to differentiate it from the other amps they sell which are class D.

An engineer(or PR guy, or something) for a competing company holds the opinion (opinion, not fact) that the tech is not sufficiently different from a class D amp to warrant a different designation.
 
#325
seamonkey said:
...There isn't any trades offs, science has known for 50 years what humans can hear. It's a science...
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Bob Lee (QSC) said:
If that were entirely true, MPEG and other encoding schemes would've gotten developed a lot faster! ;)

Science has had a good grasp for 50 years of what humans can hear, but there are always details to learn.

Every once in a while at an AES convention there will be a panel session or two involving audiology, neurology, psychoacoustics, etc. It doesn't really have much to do with my work, but the stuff is fascinating.
Click to expand...

+1 agree with Bob Lee on this crucial observation of science in its learning in the past 50 years!

As a scientist myself, science is only a tool and not an explanation of/for everything.

We all know that tools can be limited by the one(s) using them.....myself included!!
 
#327
projectMalamute said:
The first points to the fact that this is a different topology, whether you like it or not. The second to how you are intentionally trying to gloss over this fact.
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You seem to have the false impression that "topology" = "amplifier class"

It doesn't.

There are numerous different topologies one can use to implement an amplifier of a given class.

Heck, the first PWM based amplifier patent dates to about 1959 and used tubes to implement everything... but it was still class-D.
 
#331
projectMalamute said:
So you would argue that a CA9 is 'basically' the same topology as an SVT?
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No.

It's a different topology but the same class.

Like a Fender Champ and Nelson Pass Zen are both class A, but completely different topologies. The Fender Champ uses a 6V6 to drive a single ended transformer and the Pass Zen uses a mosfet to directly drive the speaker... but they're both class-A amps.
 
#334
projectMalamute said:
It's not a straw man argument.

A class I amp is a different topology than a class D amp. You have described some of the differences yourself. Whether you feel these differences rise to the level of giving it a different name is immaterial. You are not supreme dude in charge of making those decisions.
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No - the definition of the amplifier class is the "supreme dude in charge of making those decisions"... and those definitions have nothing to do with topology.

They have to do with conduction angle of the input signal through the output device(s).
 
#336
projectMalamute said:
So why do we have a different term for class H?
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Why do we have a different term for dog and wolf if they're both canines?

Link Removed

"Class G is a modification of some other class of amplifier (normally Class B or Class AB) to increase efficiency and reduce power dissipation."

"Class H is similar to Class G but takes the idea of increasing efficiency one step further than Class G. Class H also uses another class of amplifier, typically B or AB and possibly Class A, with power supply modifications to increase efficiency and reduce power dissipation."
 
#337
NoFretsNoWorry said:
+1 agree with Bob Lee on this crucial observation of science in its learning in the past 50 years!

As a scientist myself, science is only a tool and not an explanation of/for everything.

We all know that tools can be limited by the one(s) using them.....myself included!!
Click to expand...


I read it in a Ethan Winer paper. I'll search for it if you need a reference.

Science knows more and can measure more in audio than many other fields. Audio measurements are beyond what humans can hear. And I'd be glad to read anything on new science that corrects the old. i.e. Science works, it corrects itself.

I don't think we need to drag in codec into this. :D
 
#339
Bob Lee (QSC) said:
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.)
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I read the white paper at Crown's website about the Class I implementation and their "new" PWM generation method. This is how DC motor drives have been using PWM for over 30 years. :hmm:
The PWM generation is done in exactly the same manner.

The claim of reduced switching losses due to the effective doubling of the PWM frequency is also misleading, since the implementation requires twice as many switching devices to achieve the doubling of effective switching frequency. (half the switching losses in twice as many devices is not a reduction in total switching losses!)

Maybe I'm missing something here or perhaps all is not being revealed in their description for proprietary reasons, but I don't see anything new with the Class I implementation and PWM strategy they describe. It has been in use for over 3 decades (albeit in a different industry).
 
#340
Mod Insert:

I'm done with coming in here and nicely asking for some of you to lay off the personal attacks.

Next one who does gets a vacation: clear enough?
 

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