file Class AB or Class D for a home theater amplifier

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kyson Posted 5 years 5 months ago
I am planing to assemble a 5.1 channel amplifier. I selected the famous TDA2030(this one ) as the basic element and is simple to proceed. But I have a confusion, whether to use some other Class D amplifier for better quality.Conceptually, a Class D amplifier is considered by some music purists to be less "perfect" in music rendition than a Class AB. This is because at the end of the day, a Class D amplifier generates digital pulses, which are then low-pass filtered to reconstruct the original sound.

However, this distinction is perhaps more a preconception than human-discernible reality. Modern Class D amplifiers like the TPA3125D2 work at high enough oscillator frequencies (300 KHz) that the low-pass filter node frequency can be well above the ability of the human ear to perceive - 60 KHz or higher frequency low-pass filters have been used in DIY audio amplifier designs.

Class AB too can suffer from distortion, especially if the load impedance is not well matched to the design, or the AB amplifier inherently has poor crossover distortion profiles. This is not so evident in "famous" Class AB chip amps such as the TDA2030 or the LM3886, both of which boast excellent Total Harmonic Distortion figures.

Also, Class AB amplifiers can conceivably exhibit distortion at lower frequencies as well, where the human ear is more sensitive to such distortion. Class D distortion is significantly at the top end of the audio band, and beyond.

A bigger cause for concern around audible distortion in DIY audio amplifiers is power-rail voltage droop under load. While the power supply could be designed to comfortably provide sufficient current to exceed the RMS power rating of the amplifier design, the actual power requirement rises to much more than a hypothetical Sqrt(2) x RMS wattage + overhead. Even 4 x rated RMS wattage might be momentarily breached in practice, such as during big drums and cymbals clashing at once.

If the power supply tops out in those moments, and especially if the voltage regulator's protection circuitry takes time to recover, you have harsh distortion, more discernible than any amplifier chip choice would expose you to.

Please share your experience about these classes of amplifiers in the term of their output quality. I really don't care about the efficiency or the size.
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GDHAL Posted 5 years 5 months ago
Hello kyson.

Welcome to the forum, although I'm not sure it is the best source of anwsers to your questions. The class AB versus D scenario is discussed ad nauseam at the audiogon forum . You certainly would want to check that out irrespective of any input you GET (pun intended) here :laugh:

From all I've read and what little I may know about the two, class D is better suited for low end bass reproduction. It is a widely debated issue in general and the camps are rather divided. In my case I have a class AB integrated, however, the powered Triton's use a class D amp.

Best of luck in your search for answers. :)
Golden Ear Triton Reference (pair), Musical Fidelity M6si, Schiit Yggdrasil-OG-B, Oppo UDP-205, Emotiva ERC-3, LG OLED65C9PUA, Salamander Synergy Triple Unit SL20, Audeze LCD-X, GIK acoustic paneling ;
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WayneWilmeth Posted 5 years 5 months ago
Last edit: 5 years 5 months ago by Moderator. info_outline
Yes, Kyson, welcome to the forum!!!!!
Good questions and did I get you correctly? You are looking to build your own amp? You said assemble a 5.1 amp, does that mean you want to build 6 amps, or an AVR with 6 channels? You ask irrespective of power requirements, but I don't think even Santa Claus can answer your needs without knowing more, like what speakers do you want to drive? Any of the GEt speakers we discuss here? They are all pretty efficient, do not require too much power, but my experience is that my towers all love power!!!
GDHAL is very correct that LOTS of places discuss amplifier topology, and I have read a TON of that stuff, my experience and conclusion is that there are good, some REALLY GREAT and many piss poor implementations of all classes!!!!
I run my Tritons on Class A a (you did not mention this, the best of all classes) tube amp, that is awesome. My Ones on Class A tube/transistor hybrid amps up to 20 W and then in Class AB to 200 W RMS @ 8 ohms. But my surround T 2s are powered by Class D Bel Canto eVo 6 amp, which is older technology now, but still sweet and powerful.
When it gets HOT here in Thailand in my home theater, I start really appreciating my class D amps a lot more. They are powerful and run cool/efficient. Are they the best sounding? No, but pretty great.
Hope this helps, or perhaps you could ask more specific questions.
And again, welcome, God Bless,
God bless the child that's got his own.
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