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Class D Switching Power Amplifiers and Power D/A conversion

How 'Green' is Class D compared to other amplifier classes?
How 'Green' is Class D compared to other amplifier classes?
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Old 9th October 2007, 06:39 PM   #31
DcibeL is offline DcibeL  Canada
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Like combining Class-D and Class-H? I like the idea, but would a class-D amp suffer from the switching noise that has plagued the class-H topoligy? Would the added cost and design complexity be worth it for a few less watts of power consumption?
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Old 9th October 2007, 07:31 PM   #32
noah katz is offline noah katz  United States
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George,

Thanks for the links.

DcibeL,

"Like combining Class-D and Class-H? I like the idea, but would a class-D amp suffer from the switching noise that has plagued the class-H topoligy? "

Yes, that's the idea.

I wasn't aware that class H had a noise problem. Isn't that what Carver and NAD designs are?

Is it audible, or just visible on a 'scope?
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Old 9th October 2007, 08:26 PM   #33
gni is offline gni  United States
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Sound quality aside:

Class D

After a little research of Class D modules(not including PS losses):

At idle:
Brand A: less than or equal to 14w/module
Brand C: 6.5watts/module to 10w/module
(Values for Brand A read from graph so are approximates)

Class A or AB draw considerably more power at idle than a Class D.
Again, power supply losses will increase this (35watts); switch-mode
will be more efficient than linear power supplies.

At 50% efficiency Brand A module:
14 watts total (7watts into 8ohms) [7watts used by amplifier]
26 watts total (13watts into 4ohms) [13watts used by amplifier]

At 80% efficiency Brand A module:
85 watts total (68watts into 8ohms)[17watts used by amplifier]
156.25 watts total (125watts into 4ohms)[31.25watts used by amplifier]

At 92% efficiency Brand A module:
163 watts total (150watts into 8ohms) [13watts used by amplifier]
298.9 watts total (275watts into 4ohms) [23.9watts used by amplifier]

Class A

At Elliott Sound Products this discussion covers Class A amplifiers
having an efficiencies between 13% to 40% at full power; efficiency
will fall as power output is less than maximum.

http://sound.westhost.com/efficiency.htm

A 35watt Class A amplifier running at full power:

At 13% efficiency:
269 watts total (35watts into 8ohms)[234watts used by amplifier]

At 40% efficiency:
87.5 watts total (35watts into 8ohms)[52.5watts used by amplifier]

Efficiency will be lower as power output is lowered.


Class AB

Class AB amplifiers will be in the range of 35% to 55%; theoretical
maximum of close to 78% isn't achievable due to losses in power
supply and circuit inefficiencies.

http://en.wikipedia.org/wiki/Amplifier

A 40 watts Class AB amplifier at full power:

At 35% efficiency:
114 watts total (40watts into 8ohms)[74watts used by amplifier]

At 55% efficiency:
73 watts total (40watts into 8ohms)[33watts used by amplifier]

Conclusions

How 'Green' is Class D compared to other amplifier classes?

Class D offers the most efficient power transfer ratio of all the
classes; at low wattages a Class D amplifier efficiency drops to
less than 10% (maybe even lower).

Class A and Class AB amplifiers also have poor efficiency ratings
at very low power output; these values can easily fall below
2% at 1 watt output.

Overall, Class D amplifiers consume less idle power than Class A or
Class AB amplifiers at idle; and most Class D amplifiers use less
power internally to output full power than Class A or Class AB
amplifiers use at their idle.

From a pure 'watts used' standpoint: Class D is 'greener' than Class A
or Class AB amplifiers at idle. With increased power output, all
amplifier classes increase efficiency as they get closer to their
maximum power output. I would rather pay the electric bill for
a Class D amplifier plugged in 24/7 than any other amplifier class.

Class D amplifiers will be most efficient if using switch-mode
power supplies; Class A and Class AB amplifiers could increase
efficiency by using switch-mode power supplies.

As far as electronic components used in the different classes of
amplifiers: they both use chemicals in their making that you would
not want in your house; they also use about the same amount of
raw materials -- except if using large transformers (more copper).

The 'greenest' way to go would be to use the smallest, most
efficient amplifier for the task that sounds good to you. A close
look at loudspeaker efficiency shows that they are even worse
than Class A amplifiers(watts to dB SPL); improvement could be made
in this category.
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Old 9th October 2007, 08:28 PM   #34
Brett is offline Brett
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Quote:
Originally posted by raintalk
I think this thread started with an important topic.
Bollocks. This thread started with someone who markets a product using an underhanded way to justify and market it.
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Old 9th October 2007, 08:36 PM   #35
gni is offline gni  United States
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Regardless of who posted the original question, we can state with
certainty that Class D amplifiers use less wattage.
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Old 9th October 2007, 08:47 PM   #36
Brett is offline Brett
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Quote:
Originally posted by gni
Regardless of who posted the original question, we can state with
certainty that Class D amplifiers use less wattage.
Since when was D efficiency ever a topic for disagreement?

It's still marketing and a reason for some tosspots to feel better about themselves.
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Old 9th October 2007, 08:55 PM   #37
The golden mean is offline The golden mean  Sweden
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From the Mackie M-2000, M-3000, M-4000 advertising. These are linear PA-amps.

"Adaptive Slewing circuitry allows M-Series amplifiers to pass the fastest transient attacks—like kick and snare drum, or any bass player trying to imitate Marcus Miller—while minimizing Class-H switching distortion. As a result, the M-Series have the lowest distortion of any Class-H amplifier on the market. And no matter how hard and fast you thrash, the M-Series amps are gonna be a couple of steps ahead, making sure the output is clean."

When using a digital storage system for musical reproduction such as CDP, DVD, hard disc it seems possible to store the information in a buffer there analyzing the amplitudes coming and calculate the need for power; given the efficiency of the loudspeaker and average listening level. If the music leaves the system with one second of delay, I donīt care.

If multiple amps are used (bi- or triamping ) the amps have to receive their signal in a synchronized manner, or even at slightly different times to compensate for differences in the drivers phase response. Goldmund of Switzerland have done some promising research about compensating (in the time domain) both loudspeakers with conventional and active crossovers.

There may have been some intention of promotion when starting this thread, but letīs forget about this if the discussion has clearified a few other things...(or made us more confused).
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Old 9th October 2007, 08:56 PM   #38
gni is offline gni  United States
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tosspot?

I'm sorry, I came into the thread late and after further reading
I see that the original poster does seem affiliated with a company.

But, that shouldn't make the original question any less valid.

I think any discussion of quality of sound from the different classes
of amplifiers should be in their own thread. Some good thread
topics I would like to see would be:

Class A tubes sound better than Class D amplifiers.

Class AB amplifiers use less complex circuits than Class D amplifiers.

Class AB amplifiers can be made more efficient.

Class D amplifiers are used in at least one stage of the music
we hear everyday.
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Old 9th October 2007, 09:01 PM   #39
gni is offline gni  United States
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Quote:
Originally posted by The golden mean
From the Mackie M-2000, M-3000, M-4000 advertising. These are linear PA-amps.

When using a digital storage system for musical reproduction such as CDP, DVD, hard disc it seems possible to store the information in a buffer there analyzing the amplitudes coming and calculate the need for power; given the efficiency of the loudspeaker and average listening level. If the music leaves the system with one second of delay, I donīt care.
That is a real benefit of being all digital. . .the amp can get ready
for the upcoming signal. A big plus to increasing efficiency. I wish
I had though of it. There might not even be a 1 second delay. . .it might
be less that 50mS given how fast processing is today.

And with a linear power supply. . . voltage rail switching. . . slick
technology. . .would certainly make the linear power supply more
efficient.
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