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Class D Switching Power Amplifiers and Power D/A conversion

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Old 4th March 2013, 06:31 PM   #41
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Kad did quote RMS but am I correct - That is impossible.
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Old 4th March 2013, 06:47 PM   #42
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Well over five years ago, I built a class D amp utilizing one of the high power Tripath reference design boards configured as a differential H-bridge. I set up the power suppplies so that each amp channel could deliver 200W @ 8 ohms, 350W @ 4 ohms, and around 650W @ 2 ohms, per the reference design board's datasheet. Today, the sound is super transparent, bass has both natural weight and dynamic punch. Cymbals are reproduced with realistic brass tone and air. Bell and triangle strikes sound sharply percussive followed by natural decay. Vocals have natural presense, clarity, and tone. The soundstage will collapse to a nearly pinpoint mono, such as on some old Louis Armstrong recordings, and then, on the next album, expand to an enveloping 3D field extending far beyong the loudspeakers, both laterally and in depth. This wasn't always so.

Initially, the amp sounded about the same as many other mid-fi (circa, $2,500) power amps I've heard. However, being unable to leave well enough alone, I began to tinker with passive component selection. One particular modification of the original Tripath reference design produced a transformative affect on the sound. So much so, that I eventually sold my ARC Classic 120 tube mono-blocks without regret. So, what was that change? It was to substitute the normal single metalized mylar film capacitors in the LC output filter for double-metallized mylar units sourced from BC components. These capacitors are specifically designed for high slew and switching applications. I sometimes still shake my head in disbelief. Your experience may vary.
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Old 4th March 2013, 06:54 PM   #43
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yea and class D still sucks.. except for its efficiency..
just replaced # class D amps with a H and a/b no comparison the a/b/h killed it..
oh yes they were crown macro and K series amps..
haven't heard en Ncores yet.. but since the best is not available in anything but DIY i don't have time to fool with it..
and also being a car guy i've had about every class d car amp powering parts of my home system and they all sound like ****..
now from my guy who has done high speed (20ghz) data aquesiton board work and custom rf equipment here in Tech land for the nuclear facilities and is an audio guy too..
"when the learn what they are doing as far a board layout goes they might get close"
inadequate filtering , incorrect filter principles., etc,
they need a true RF guy to do board layout but the the cost goes way over A/B at that point!
Commercial amps are nothing more than to make money(sq might be second) and what sells now is weight and efficiency..
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Old 4th March 2013, 07:35 PM   #44
xrk971 is online now xrk971  United States
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Quote:
Originally Posted by bnorrish View Post
What is the best place to buy the TI evaluation modules and chips?
From TI directly - pricey at $150 ea but a deal compared to what a class A will cost you for similar performance. I am building it with a custom made pcb and parts from Digikey, I am also building smaller TPA3118D2 using smd dead bug wiring in progress now on another thread. Total BOM about $17 not including $8 ps laptop brick.
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Old 4th March 2013, 09:59 PM   #45
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I try to keep an open mind and I am not sure the arguments for Class D add up. On one hand not too many commercial Class D gets it right - its a different animal, requires different design skills, etc.,etc. On the other end I can on my own, purchase an eval board with a cheap switching PSU and compete with a Class A design? I suppose my Yamaha Aventage does not sound well because it is 2 years old and does not sport the latest chip or Yamaha does not design Class D very well, yet I can beat it by hooking up a TI eval board?
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Old 4th March 2013, 10:59 PM   #46
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I've yet to find a Class D amp that sounds musical. Most sound pretty clinical. It will always be a purely personal choice.
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Old 4th March 2013, 11:19 PM   #47
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Originally Posted by KatieandDad View Post
I've yet to find a Class D amp that sounds musical. Most sound pretty clinical. It will always be a purely personal choice.
Try using a more resonant housing, strike it with a metal rod.

"Musical" amp "sound." Please!
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Old 4th March 2013, 11:29 PM   #48
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Originally Posted by bnorrish View Post
I try to keep an open mind and I am not sure the arguments for Class D add up. On one hand not too many commercial Class D gets it right - its a different animal, requires different design skills, etc.,etc. On the other end I can on my own, purchase an eval board with a cheap switching PSU and compete with a Class A design? I suppose my Yamaha Aventage does not sound well because it is 2 years old and does not sport the latest chip or Yamaha does not design Class D very well, yet I can beat it by hooking up a TI eval board?
Class D is not a whole lot different than the DAC situation. I personally must think that all DACs stink because I still own and use a turntable. DACs are still getting better all the time and the best DAC chips are yet to come. Digital sources must be popular because not many are running turntables these days and yes, I do mostly listen to digital. Absolutely no progress has been made in Class A and Class AB amplification technology in 30 years and in another 15 years, it may even no longer be available because everyone will be listening to Class D. The best chips are yet to come.
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Old 4th March 2013, 11:40 PM   #49
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The remark about class G and H being so much better than class D makes no sense. The real difference between those topologies is that the power supply side can be modulated to match the output, but if I remember correctly the rest of the circuit is the same basic layout.
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Old 5th March 2013, 12:06 AM   #50
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Originally Posted by ssportclay View Post
Class D is not a whole lot different than the DAC situation. I personally must think that all DACs stink because I still own and use a turntable. DACs are still getting better all the time and the best DAC chips are yet to come. Digital sources must be popular because not many are running turntables these days and yes, I do mostly listen to digital. Absolutely no progress has been made in Class A and Class AB amplification technology in 30 years and in another 15 years, it may even no longer be available because everyone will be listening to Class D. The best chips are yet to come.
I thought we would all be riding around in personal spaceships by now.
Maybe an electric car some day will perform better than a Porsche. I guess it is fun to speculate into the future - but we live and play our music only in the present moment.
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