Class D or AB

[fdeck]

No, they aren't.

Let's look at that wikipedia entry on
"continuous functions" as you suggested and see what it says:
"In mathematics, a continuous function is a function for which,
intuitively, "small" changes in the input result in "small"
changes in the output."

The output of the comparator circuit (what you call the
"modulation duty cycle") defies this description. There is
a threshold on the input that results in a large jump (a step
function) on the output.

The modulation duty cycle is defined as the percentage of time that the output is in one state as opposed to the other. It is a continuous function of the input voltage. The duty cycle, not the instantaneous state of the output devices, is the analogue of the input voltage.

The charge on any node of a circuit is a discrete number of electrons. Does that make any circuit digital? And if you hook up a high speed scope to any digital circuit, you will see continuous waveforms. Does that make all digital circuits analog? Again, look at the properties of digital circuits in the Wikipedia article. The distinguishing features of digital circuits have to do with what the signals represent and the way that information is propagated. For instance a digital circuit has unambiguous rules for what makes a transition from 0 to 1, and the circuits are designed to enforce these rules.

By the way, I am taking this all in the spirit of friendly discussion, and it isn't really a big deal anyway. If we understand how a switchmode amplifier works in detail, then it doesn't matter what we call it.

 

[onosson]

By the way, I am taking this all in the spirit of friendly discussion, and it isn't really a big deal anyway.

Exactly. Thank god this thread isn't about the new iPhone...

 

[agedhorse]

You sure? It used stepped transformer taps smoothed at the final filter. Odd design.

Both... the smaller one was class AB and the larger ones were up to a 3 tier class H (which is also an AB amp with stepped rails) but there was somethig odd done to achieve the top tier... maybe reverse phase control limit of the highest voltage or something like that.

 

[Budbear]

What I learned from this discussion:

The difference between Classes D and AB is not quantum faeries and magic unicorns. (boy, was I wrong!)

Marketing people will say anything to sell a product if they can get away with it.

KJung has an unusual understanding of the concept of "out and unsubscribed".

Thanks, guys.

 

[B-string]

Both... the smaller one was class AB and the larger ones were up to a 3 tier class H (which is also an AB amp with stepped rails) but there was somethig odd done to achieve the top tier... maybe reverse phase control limit of the highest voltage or something like that.

Thanks agedhorse BC always kept the details on the cuff back in those days.

 

[barryaudio]

Just checking in on this thread...

I think FDeck has done a great o job in explaining the differences. One thing to keep in mind that even if you treat an applied voltage as a step function (or treating a threshold as a step), there is an inherent exponential response in all dielectrics on the output that will yield an analog output. A review on dipole polarization is a good way to look at this (here's a chance to use wiki).

back to the topic at hand (amps): IMO, there is nothing "superior" about class AB, D or digital amps in theory. Much of the performance has a lot to do with the actually engineering involved (sample rates, cap banks, etc.) rather than some esoteric knowledge that one class is superior than another.

 

[PrairieDogma]

Am I the only one who HATES car analogies?

Car analogies are like putting fancy wheels and tires on a stock Pinto. All show, no substance!

 

[majortoby]

ARGH

 

[JimmyM]

TC amps are digital and don't sound digital at all. Makes no difference to me.

They do to me, but hey, who am I to judge?

 

[fdeck]

I remember back when CD players became available, the hi-fi manufacturers all rushed to label their amplifiers, speakers, and even signal cables "digital ready." Likewise a famous toy wagon was called a Radio Flyer, because radio was new and cool.

 

[James Simonson]

If there is no digital ADA conversion happening anywhere in the chain, be it pre amp or power amp, then it is analog.

I feel if the preamp is doing any type of ADA converting then it's definitely a digital amp.

 

[seamonkey]

If there is no digital ADA conversion happening anywhere in the chain, be it pre amp or power amp, then it is analog.

I feel if the preamp is doing any type of ADA converting then it's definitely a digital amp.

So all these guys using Line 6 G50 have converted to digital? Don't tell them.

 

[James Simonson]

They will eventually figure it out but only a few milliseconds later!

I remember fighting they latency of the early Pods. I remember being able to hear a pick hitting the string and then the sound responding. Analog amps would never do that.

Here's a question:

Is there any mathematical latency with a Class D amp? Any?

 

[seamonkey]

No latency for class-d, but Class-d is analog

But there's no perceivable latency with the Line 6 or many digital tools used today.

Can you see a millisecond? Look at your eyes in a mirror and move them around, see if you can see them move.

 

[James Simonson]

Exactly, and no I definitely can't see a millisecond.

If there is no latency with Class D then it also supports the argument that it is an analog amp.

 

[seamonkey]

preface an AD followed by a DA and you add on Microseconds
It's the DSP that adds milliseconds. Fast as a Radio Flyer!

 

[dincz]

I'm not trying to be confrontational. This is an interesting thread and I'd be glad to hear warnergt or anyone else respond to my post #87.

 

[agedhorse]

I'm not trying to be confrontational. This is an interesting thread and I'd be glad to hear warnergt or anyone else respond to my post #87.

I thought it was an interesting example... kind of a tri-state digital where there is a single time variant. In this case I would think that it's more digital than analog because there isn't a continuous (or large number of) time variant. Additionally, each letter stands alone as a digital tristate word with sort of a base 3 component to it. Each word could be stored, manipulated and retains it's unique meaning. Additionally each number represented as code could also have operations performed on it such as add and multiply (not the same algorithems as binary but certainly possible).

Just my casual morning coffee thoughts

 

[Bob Lee (QSC)]

I remember back when CD players became available, the hi-fi manufacturers all rushed to label their amplifiers, speakers, and even signal cables "digital ready." Likewise a famous toy wagon was called a Radio Flyer, because radio was new and cool.

Yes, I was just thinking about that. In particular I remember normal headphones with "Digital" or "Digital Ready" added to the packaging.

 

[BurningSkies]

Yes, I was just thinking about that. In particular I remember normal headphones with "Digital" or "Digital Ready" added to the packaging.

Wait. Now you're telling me my headphones aren't digital?!?! Does that mean I can use them when I listen to my records too? Because I've been keeping two pairs with my stereo ever since those digital ones came out.