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Class D Switching Power Amplifiers and Power D/A conversion

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Old 23rd July 2012, 04:59 PM   #141
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Quote:
Originally Posted by The golden mean View Post
I disagree, most people get headaches from listening to music through a class D amp!

Seriously, I still disagree to the categoric statement above and BTW its noting wrong to use a tube amp or vinyl records if you like it this way.
Quote:
Originally Posted by MrKTrout View Post
If you are getting a headache from listening to a class D amp, try a different amp or different headphones.

MrkTrout.
You are totally missing my ironic twist, please do not qoute in an inappropriate way....this should be clear if one goes back to the first few pages!
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Last edited by The golden mean; 23rd July 2012 at 05:07 PM.
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Old 28th January 2014, 05:51 PM   #142
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Well... very interesting discussion indeed.

I am in the process of building a small scale PA system for community cultural programs (small auditorium or large party room). I tried a 300W+300W TAS5630 based Class-D. I bought this from sure-hifi on ebay and powered with 50v dc from a toroid and I must say that the quality of sound is OK (read good) but not as good as an old Pioneer VSX815 which is a medium consumer grade home-theater receiver. A few years ago I had a Panasonic SA-XR55 (again a common consumer grade and inexpensive Class-D home-theater receiver) and it was very tiring to listen to music on that. We tend to say, "Can you please keep that volume down?". The speakers in both these cases were 8 Ohm Natalie-P (Parts Express/Dayton). You don't need golden ears to distinguish the difference as my hearing stops after about 15 kHz

So, for my own purpose I am going to use the Class-D for low frequency (below 1200Hz) on an active cross-over along with LM3886 chip-amp for high frequency.

In my experience Class-D is adequate for most purposes but not quite as good as my old 2N3055 based DIY amplifier (Class AB) built as published in an old Elektor. It is hard to convince that to an audience who says MP3 songs played on a tablet or ipod sound good enough!

Last edited by hanair; 28th January 2014 at 05:55 PM.
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Old 28th January 2014, 06:27 PM   #143
dewardh is offline dewardh  United States
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Quote:
Originally Posted by kct View Post
What is the general magnitude of THD of a Class D at lets say 20kHz at rated power ?
Why would I care? I couldn't hear 20kHz. even if it was present on any of my source material, which it isn't, and I certainly couldn't hear any harmonics.

What Class D offers is what Class A offers . . . freedom from crossover distortion (which becomes increasingly noticeable and obnoxious at the lower power levels where amplifiers are operating most of the time). Some Class AB amps avoid it too . . . a notable example being the LM3886 . . . but too many don't, especially as bias "drifts" with time and temperature.
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Old 28th January 2014, 06:33 PM   #144
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Old 29th January 2014, 06:10 AM   #145
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Quote:
Originally Posted by dewardh View Post
Why would I care? I couldn't hear 20kHz. even if it was present on any of my source material, which it isn't, and I certainly couldn't hear any harmonics.

What Class D offers is what Class A offers . . . freedom from crossover distortion (which becomes increasingly noticeable and obnoxious at the lower power levels where amplifiers are operating most of the time). Some Class AB amps avoid it too . . . a notable example being the LM3886 . . . but too many don't, especially as bias "drifts" with time and temperature.
AS a Lifelong Audiophile I find I am unable to listen to any Class D amplifier they make me feel ill and I have to turn them off even if hearing them in another room. Well designed Class AB amplifiers are excellent with no listening fatigue. Anyone not into High Fidelity could probably use a Class D amp but not me.
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Old 21st April 2015, 09:38 AM   #146
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I had a Skoda with a 12-channel class-D amp rated at 360W. However, when you listen to the music you feel the output to be around 50W overall!

I have my serious doubts on power delivering capabilities on the Class-D amps. Similarly goes for the Sony home theater systems (the compact ones) vs AVR!
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Old 21st April 2015, 10:17 AM   #147
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Quote:
-Originally Posted by dewardh
Why would I care? I couldn't hear 20kHz. even if it was present on any of my source material, which it isn't, and I certainly couldn't hear any harmonics.

What Class D offers is what Class A offers . . . freedom from crossover distortion (which becomes increasingly noticeable and obnoxious at the lower power levels where amplifiers are operating most of the time). Some Class AB amps avoid it too . . . a notable example being the LM3886 . . . but too many don't, especially as bias "drifts" with time and temperature.

Any ... and especially a large class AB , has a considerable class A
"first watt" ( some- first 5 W ) !
NO X-over distortion.
After this , some faster AB designs with advanced thermal biasing and
really advanced compensation can even cancel out the class B switching
distortion down to PPM levels.
A 200 watt class AB amp @ <50ppm with a 250khz bandwidth is common
on the forum now.

The LM3886 sucks (tested one) - no headroom , push it and it shuts down.
It does not "avoid" any of the issues in the larger amps - in fact , compared to them - It sucks !!!
Bias "drifts" .... WHAT ??? .... just opened my amp after 3 months , still 60ma
bias , 5C to 35C ... still 60ma.

LM3886's and (most) class D is to benefit cheap chinese walmart junk , NOT
for SQ.
PS- a phillips 5 channel HT system with 6- 3886's was most listenable as compared to a sony walmart class D chinese "junkbox".

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Old 24th April 2015, 11:41 AM   #148
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My experience with different amp classes is that they can all sound good if they are put together right. Many manufactures have looked to class D to cut cost. When cost is their biggest consern they cut down on component quality and psu capability aswell. In my diy class D experience it delivers a lot more grunt than AB amps with the same psu capability. Also class D is relatively new to most people which reflect extremely poor layout in many class D pcbs for diy. It looks that many designers don't fully grasp the high frequency effect in class D. Crusial components are placed to far away from were they should be,caps high frequency esr is more important, bootstraps filters are placed too far away, oscillating problems cause of skipped snubbers, mismatch between speakers and class D output filter etc. There is a lot of pitfalls in class D.
A good example of a optimum class D card is the wiener 3118 made by Gmarsh. If one reads Ti's design guide you could see that all the design guides points have been achived, no wonder it sounds really good. Looking at many of the el'cheapo cards out there makes me think that they haven't even bother to look into design guide for the Ti's chips. I think this is true for most of the cheap class D cards with their overdone heatsinks and crappy layout.
Perhaps Class A gives a tiny bit better sound quality but my experience with class D is that it delivers good sound and power cheaply. The new Pioneer surround receivers is class D and has way better bass than the previous models.
In car use I now only use class D. In my living room is mostly use the tpa3116/8 and sometimes my diy AB tube amp which is quite costly to use since the tubes now cost a fortune. The tube amp has its own sound which I like but I can't say thats its a true reproduction of the source material.I think all classes have their usefulness but I think class D is going to be the "go to" class for most applications in the future.
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Old 24th April 2015, 12:13 PM   #149
Cresnet is online now Cresnet  Germany
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Class-D for your low frequency driver, Class-AB for your HF driver.

use a DSP to split the Xover point, and enjoy the ultimate sound quality.

No evidence that class-d performs better in the HF area, unless some one can show same output signal from a Class-D compared to a Class-AB amplifier, for example a 15K square wave, or 15K sine wave, once both waves LOOKS exactly the same, no distortion, no noise, same slew rate, then OK

Else, god knows!
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Old 27th April 2015, 09:40 PM   #150
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Im about to tackle this one.. very rare.. very vintage.. then the test. Probably the highest quality Class D I will ever listen to.

www.davidsaudio.com/Infinity_DSP.pdf

If I can get it working again.
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Last edited by jakelm1975; 27th April 2015 at 09:42 PM.
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