CLASS AB Amplifier Vs CLASS D Amplifier

[nkdecibels]

Hi all,

Iam planning to build a two Way plate amplifer. For the LF Section iam planning to use a Class D Amplifier Module the power is 400W @ 4 Ohms.

For the HF sction which amplifier type would be best. The Wattage of the HF is 100W.

Some people say that CLASS AB Module is better for HF section and some people say CLASS D Module will be good.

So please advice me on this whether to use Class AB or Class D module for the HF Section.

Help me on this:confused::confused::confused:.

Thankx

[Saturnus]

Modern class D amps rival and surpass most class AB amps in sound quality at a much lower price and vastly lower power consumption.

Class AB amps are in my opinion a relic of the past, gone the same way as tube amps, vinyl records, and AM radio. Sure, some people will still swear to them but they're more an oddity having no value in themselves beyond nostalgism.

[The golden mean]

Originally Posted by Saturnus

Modern class D amps rival and surpass most class AB amps in sound quality at a much lower price and vastly lower power consumption.

Class AB amps are in my opinion a relic of the past, gone the same way as tube amps, vinyl records, and AM radio. Sure, some people will still swear to them but they're more an oddity having no value in themselves beyond nostalgism.

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 it´s noting wrong to use a tube amp or vinyl records if you like it this way.

[nigelwright7557]

I have designed class AB and class D amps and to be honest cant tell the difference just by listening.

The class d amp has the benefits of using less power and requiring a smaller heatsink and using fewer components.

[Saturnus]

Originally Posted by The golden mean

Seriously, I still disagree to the categoric statement above and BTW it´s noting wrong to use a tube amp or vinyl records if you like it this way.

A categoric statement usually don't start with: "In my opinion..."

[gychang]

Originally Posted by The golden mean

I disagree, most people get headaches from listening to music through a class D amp!

I listen to class D amp, many different kinds mainly from Helder's. I get no headaches and sounds excellent IMHO. I am not into tubes, exotic stuff, just mainly vocal/jazz/small group classical...

[nigelwright7557]

Originally Posted by gychang

I am not into tubes, exotic stuff, just mainly vocal/jazz/small group classical...

I have a class d amplifier with a tube front end, best of both worlds.

[tinitus]

I would suggest to build two stereo amps, one each channel

or you could 3 smaller amps of equal design
bridge two of them for LF
and the other for HF
this way you get a high power and a low power amp running on the same voltage

though, a bridged amp into 4ohm may be a tough one

[opc]

Hi nkdecibels,

From a performance and sound quality standpoint, there's no question that a class AB, or better yet a class A amplifier would be your best choice. The only reason to use class D is high power density and better efficiency.

Class D pros:
1. Higher power density (both in size and weight)
2. Higher efficiency
3. Potentially lower cost

Class D cons:
1. Limited power Bandwidth
2. Lower SNR
3. Higher THD
4. Response that varies with load
5. Higher circuit complexity
6. EMI/EMC related issues

So in short, if you're building a powered monitor for portable PA use, then you'd be a fool to use anything but class D. For any application where sound quality is a primary concern, class A or class AB are the way to go.

I know there will be some who disagree, but I would like for them to show just one sound quality related area where a class D is better. I have yet to find one, and used to design class D amps for a living!

As a side note, are you sure you need 100W for your tweeter? That's a lot of power to be feeding into a tiny driver. Dropping that requirement would allow you to use something like an F5 which would really be the cat's meow.

Cheers,
Owen

[kristleifur]

opc, may I humbly suggest that there have been developments in Class D that elimiate any of the disadvantages you mention:

Originally Posted by opc

Class D cons:
1. Limited power Bandwidth
2. Lower SNR
3. Higher THD
4. Response that varies with load
5. Higher circuit complexity
6. EMI/EMC related issues

1 - Not that I know of. Perhaps I don't understand. Can you elaborate?
2 and 3 - Here are some measurements of a good, clean Tripath TA3020 amplifier, the 41Hz Amp15 which gives 0.008% THD+N at up to 74Wrms, and a noise floor below -120dBV. (And the IMD performance of good Class D is excellent too!) It is possible to reduce the distortion figure further, and increase power, with modifications / choice of chipset. I suspect that the Hypex NCore will then be significantly quieter and cleaner.
4 - Not likely to matter significantly in practice. Furthermore, Hypex UcD and NCore, and other designs, do away with this limitation entirely.
5 - Not likely to matter in practice. Secondly, Class D amps are much more efficient, and a populated board for a high-power Class D amp with very high sound quality is possibly going to be much cleaner and smaller than a similar Class A; Also more reliable due to less heat, and more quiet due to less stray inductance etc. in the signal path.
6 - If the design is done properly, then Class D amps don't need much shielding. Add minimal shielding and the environment is as good as EMI-free.