CLASS AB Amplifier Vs CLASS D Amplifier

[Bigun]

I have been using one that I designed that switches at 1 Mhz. 18uh output coil
sound quality is fantastic, only problem is slight interference on FM resulting in a lower s/n ratio in stereo mode. This is with the amp 6 inches from tuner.
Monoblock config should solve this problem.

I am very intrigued by your project - I hope you'll make a new thread and tell us more about it.

I got into this hobby with Class AB but I do believe the future is Class D. Even now when I do my Class AB+C projects it feels like I am re-living the technology of the past which is fun by itself.

With the money being invested by the semi-conductor industry in SMPS semi-conductors and i.c.'s there will be continue to be better materials, passives and active devices to support Class D. This is no longer happening in Class AB, which had a hey-day of investment in Japan in the 1980's. The challenge is that Class D can be more difficult to DIY.

 

[waxx]

I tend to choose always for class A or class AB when i listen. Even in blind tests. I know there are very good class d and t amps around, but class a or ab feels more natural in my subjective view. Just like i like vinyl more than hi res digital audio. High res digital audio is objectivly better, but still i prefer vinyl concerning sound.

 

[Pafi]

I have been using one that I designed that switches at 1 Mhz. 18uh output coil
sound quality is fantastic, only problem is slight interference on FM resulting in a lower s/n ratio in stereo mode. This is with the amp 6 inches from tuner.
Monoblock config should solve this problem.

RF radiation is caused by switching transients and transfered to output by parasitic elements of the filter, capacitance of inductor and inductance of capacitor. With proper layout design the effective parasitic inductance can be reduced to under 1 nH, this way I managed to push 1st RF resonance to about 200 MHz, where there is very low energy in the switching event. The result: when I connect output signal of my amp to the antenne of my receiver I notice S/N enhancement on weak stations and nothing else. (No magic, like any passive metal object, it increases the size of the antenne, and doesn't introduce any noise in the 88...108 MHz band.) The result is the same with or without audio modulation.

 

[ErnestoFB]

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

The TPA32xx class D series is much better than the best Class AB IC that I found, the TDA7575:
http://www.mouser.com/ds/2/389/tda7575b-957192.pdf