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Class D Switching Power Amplifiers and Power D/A conversion

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Old 15th December 2010, 08:43 PM   #21
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Originally Posted by Saturnus View Post
You're confusing two things I think. Power supply efficiency and amp efficiency.

In class G (or H) that's the same thing but in a class D amp the power supply is seperate. In both efficiency should theoretically scale according to output level but some SMPS's lose efficiency faster than they theoretically should so that at very low volume levels a class G (or H) amp is more efficient. Also because in class D amps there are 2 seperate units that each draws idle current.

If you use a trafo (which have a pretty much constant 98% efficiency) or battery supplies for the class D amp it will always be more efficient.
That isn't my point - my point is that Class D is thought to be very efficient, but it ain't at low volume which you often are in HiFi. There is switching losses - don't forget.
Let us see your loudspeaker - it could be interesting...
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Old 15th December 2010, 08:47 PM   #22
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Originally Posted by Robert GS View Post
That isn't my point - my point is that Class D is thought to be very efficient, but it ain't at low volume which you often are in HiFi. There is switching losses - don't forget.
Let us see your loudspeaker - it could be interesting...
Do me a favour and google "Boominator"

That's of course not my home speakers, there I use an FE206E based BLH.
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Old 15th December 2010, 09:05 PM   #23
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I can see the point in your "Boominator". Are you also using Class D for your high efficiency full-range horn loaded home system? Tripath? Sub? EQ?
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Old 15th December 2010, 09:06 PM   #24
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Originally Posted by Robert GS View Post
I can see the point in your "Boominator". Are you also using Class D for your high efficiency full-range horn loaded home system? Tripath? Sub? EQ?
Same amp, yes, and with a solar cell backed up battery supply (yes, it works all year round even in Denmark). No sub or EQ used.
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Old 15th December 2010, 09:07 PM   #25
ontoaba is offline ontoaba  Indonesia
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Originally Posted by lorylaci View Post
Class H amps can be made without switching power knowledge. So this would predict they are easier to design. Apart from this you can see more simple Class-D designs than Class H designs in this forum.

If somebody likes amps with low Damping Factor (i really don't, thats not what i would consider as HiFi), just put a big power resistor series with the load. Low DF viola.
You suggest anyone to connect resistor in very wrong way. Connecting resistor in series with loudspeaker makes it less control and wrong damping. The resistor should connected in parallel with loudspeaker in current driving, or use active damper (negative feedback).
You don't know anything about loudspeaker driving technique and designing classD are easier than the others because it doesn't care how the loudspeaker move will be.
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Old 15th December 2010, 09:17 PM   #26
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Hi guys, take a look here, another SMALA:

The Composite / Hybrid- Linear + Switching Power Amplifier
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Old 16th December 2010, 01:48 AM   #27
ontoaba is offline ontoaba  Indonesia
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Um.. Just found this. It says that classD efficiency are fakes and they going to combine all classD+G+H.

Exploding the Efficiency Myth of Class D Amplifiers | ECN: Electronic Component News

pdf:
http://www.newelectronics.co.uk/arti...076/p21-22.pdf

I don't know which one is true here, but the most efficient I ever achieve is using forward converter, not soft switching but it really reach high efficiency in all the way, nothing gets warmed also no warming inductor at 100W output into 8ohm, the only problem is its reversing plus minus polarity. The key is discharge all the inductor current always to zero for each cycle.
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Old 16th December 2010, 06:30 AM   #28
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Originally Posted by ontoaba View Post
Um.. Just found this. It says that classD efficiency are fakes and they going to combine all classD+G+H.
If you know anything about electronics you really don't need to read further than this sentence to file it under fairy wings and karma improved input caps.
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Old 16th December 2010, 06:52 AM   #29
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Quote:
Originally Posted by ontoaba View Post
Um.. Just found this. It says that classD efficiency are fakes and they going to combine all classD+G+H.

Exploding the Efficiency Myth of Class D Amplifiers | ECN: Electronic Component News

pdf:
http://www.newelectronics.co.uk/arti...076/p21-22.pdf

I don't know which one is true here, but the most efficient I ever achieve is using forward converter, not soft switching but it really reach high efficiency in all the way, nothing gets warmed also no warming inductor at 100W output into 8ohm, the only problem is its reversing plus minus polarity. The key is discharge all the inductor current always to zero for each cycle.
Can we agree that Class D hasn't high efficiency at low levels? Should be possible.
Interestingly is that Class D is pretty good at high level, but at clip level they very often sound terrible because of poor power supplies again because of the designers thought of high efficiency ! Their ultimate purpose is often in PA and here you often see IcePower modules that doesn't perform that convincing. One of the many companies that use IcePower is RCF for their Line-Array systems, but you will discover that fans are employed to cool the amps! Recently I were at a demo of a RCF TTL55 with subs and it was quite okay at levels between -60dB and -10dB full level, BUT above -10dB it was scary bad

And when measuring Class D it's allow to filter the output with low-pass filters - this isn't allow for the other Classes !
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Old 16th December 2010, 06:59 AM   #30
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