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Class D Technology

So I get the obvious strengths of Class D. Efficiency, power output & running cool which allows for small form factors. I also understand the weaknesses somewhat. 1. Non-linear & lots of distortion that needs to be cleaned up with an output filter. 
So my question is, if it weren't for efficiency & power, would there be any reason to own a Class D amp? Do they beat Class A in any other categories that count for sound quality?  
seanheis1
georgehifi's avatar
georgehifi
10,312 posts
 
I read a tip that a portable am/fm radio could be used as a crude detector for any RF radiation emitted by a component.



Yes for smps leakage, should also work not that I tied it for Class-D switching frequency leakage.
Tune down low and try at different frequencies between 500-800khz on the am/band, so it’s off station not getting a station signal just white noise (some portables mute these are no good to use), then switch on the smps/class-d, and go close to it with the radio, and see if you get a change in sound or level.

Cheers George
noble100's avatar
noble100
2,419 posts
 
georgelofi,

     Thank you for the further clarification.  I just tried your suggestion  with an older (non-muting) portable radio in the 500-800 khz am/band range on my amps with results being no discernible change in sound.or level.  Reassuring results.

Thanks again,
  Tim
guidocorona
4,298 posts
 

Hi all, in olden days, with the NuForce and M312, RF leaks were of some concern... My old FM tuner did pick up hash from the amplifiers if when held less than 2 feet from the power supply of the amps. 


However, newer amps like the Merrill Veritas and my current Rowland M925 do not radiate at all.... AM and FM bands are not affected at all, not even if the tuner is placed on top and is in direct contact with the amps.


Without making a broad generalization, I suspect that FM leakages might today be less common than in the past. Perhaps more of historical interest than anything else.


Worth checking out though, particularly when testing older class D amps.



Regards, G.

 on the

kijanki's avatar
kijanki
4,477 posts
 
There is about 1% of switching voltage noise on the speaker cable since filter is not perfect but, as I said before, 1/300 wavelength antenna won't radiate.  In addition, electricity in speaker cable flows in both directions canceling the most of RF (if any).  When you place radio directly on the wire you might get some capacitive coupling, but I doubt it.  Many speaker cables are twisted making it completely inefective (better than shield) for electromagnetic radiation or capacitive coupling (both ways - from cable or to cable).
cleeds
6,275 posts
 
kijanki
...  electricity in speaker cable flows in both directions canceling the most of RF (if any) ...
There's nothing inherent about an AC circuit that makes it immune to RF, so it isn't clear what your point is here.  
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