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Old 26th November 2005, 07:19 PM   #1
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Default The real difference between Class T and Class D?

Quote:
Quote of Tripath's technology white paper:
Class-A and Class-AB amplifiers have long dominated the amplifier marketplace. These
purely analog devices have low power efficiency, and most integrated circuit Class-AB
amplifiers fall short of true high-fidelity audio quality. Another class of amplifier, Class-D,
solves the efficiency problem by using switching pulse-width modulation (PWM) technology.
However, this produces audio output quality that is inferior to Class-A or -AB, so efficiency is
gained at the expense of signal fidelity. As a result, these amplifiers are generally used only
in low-frequency subwoofer applications where the audio fidelity performance level of PWM
amplifiers is acceptable.
Most readers of this forum having a level of insight, would most probably regard this content as 'hot marketing air'. And much of the rest of the white paper is in the same category.
You can download it here: http://www.tripath.com/tech.htm

But what makes me wonder is, that clearly Tripath want to distance themselves from Class D.

Is there in reality any difference between Class D and Class T ??
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Old 26th November 2005, 07:47 PM   #2
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Although I don't know the exact differences on a detailed technical level, they do have similar roots. Tripath uses a variable switching frequency that varies according to output level. The switching frequency is rather high, up to 1MHz, which allows smaller filter components to be used at the expense of switching loss.

My guess as to why Tripath wanted to distance themselves from class D is because when Tripath was founded, 1995, class D wasn't yet a viable and accepted full range amplification technology. Skip to 2005 and we have several companies making great full range class D amps.
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Old 26th November 2005, 07:59 PM   #3
Tweeker is offline Tweeker  United States
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I think the Tripath Amp is what some other companies call class H, its the powersupply rails that switch here IIRC.

Seems I dont recall correctly.
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Old 26th November 2005, 08:10 PM   #4
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Tripath is a swithing amplifier and it's not class H. Class H involves rail voltages that step between different vaules depending on the power delivered to the load. This does not describe a Tripath amplifier.
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Old 26th November 2005, 08:23 PM   #5
Tweeker is offline Tweeker  United States
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If its not class D and not class H, then what is it?
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Old 26th November 2005, 08:26 PM   #6
Tweeker is offline Tweeker  United States
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Nm, its fancypants class D.
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Old 26th November 2005, 08:43 PM   #7
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Most self oscillating Class D amplifiers varies in frequency with load, just like Tripath. And today 9 out of 10 Class D amplifiers are actually self oscillating.

So is Class T just a variation of (more or less regular) Class D, only with the difference that it is marketed by Tripath?
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Old 26th November 2005, 09:47 PM   #8
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Quote:
By Gerald R Stanley, Senior V.P. of Crown Corp. in an article on the definition of classes of audio amplifiers:

"Class D is a subset of all possible switch-mode amplifier topologies that is typified by use of the half-bridge (totem-pole) output stage that has two interconnected switches operating in time alternation. The paradigm is that of Loy Barton's class B, but uses the statistics of conduction angle to produce amplification (PWM). There are many subclasses within class D that describe the origins of the modulation. Class D is at least as old as 1954 when Bright patented a solid-state full-bridge servo amplifier U.S. 2,821,639."
I think this general definition of Class D covers the Tripath technique very well.
So it seems strange that Tripath's marketing dept. are trying to distance themselves from this definition.

It's kind of like saying: over here in San Jose we are not breating regular air, but a special mixture of oxygen, nitrogen, methane and other exotic gases.
By this time it's so technical that maybe some people don't get the fact that is actually IS regular air.

By now turning into 'Hot air' [joke]

The class definitions can be found here: http://forum.soundillusions.net/arch...e/t-29820.html

Somebody also copied theme here:
http://members.tripod.com/Eli47/Page2.html
and included Class T, but unfortunately just a copy of Tripath's own advertisement material. So no real information to be found here
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Old 26th November 2005, 09:49 PM   #9
IVX is offline IVX  Russian Federation
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Quote:
Originally posted by Lars Clausen
Class D, only with the difference that it is marketed by Tripath?
Rather question is why they took decision to change old name? Maybe it's attempt to save them money from the spend to reabilitation of the class D reputation, which was not so good in 1998.
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Old 26th November 2005, 10:15 PM   #10
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IVX: I think it goes like this:

The marketing people want to get the best sales, and traditionally that is accomplished by trying to show that you have a unique product. This same strategy is used for everything from soap and toothpaste to any other consumer product. Of course this strategy relies on the consumers to be intelligent enough to interest themselves in the 'difference', and also ignorant enough to not be able to see through the story.
For example we have here in Denmark a commercial for a toothpaste, that is special because it's without 'triclosan'. As a consumer i am simply too stupid to see if this is true, or if it is of any significance. Probably like 99.9% of everybody else.

In technical stuff like an amplifier, its all to easy to illude the consumers with this strategy.

So my guess is that, when Tripath wanted to market their Class D amplifiers, the marketing dept. came up with the idea: why not make a whole new class instead of class D, so it looks like it's very unique. Since nobody can look inside our chips, they will never find out the truth.

B&O Icepower also fell into the same pit when they started with the Icepower modules: No no we are not making just Class D, but Class BD (Very special!!! )
See here: http://www.classd.org/oem_products/products/b_o.htm
But then later they came to their senses, and now it's all Class D, like everybody else...... (Ups: except Tripath of course .. )

BTW: My own regular toothpaste also doesn't use Triclosan
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