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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
mapman's avatar
mapman
22,373 posts
 
A better analogy,at least in teh case of newer BEl Canto amps, is souping up the engine.

With ref1000m amps, they add custom input board for better integration with tube pre-amps and a beefed up powersupply board.

Original ref1000 was just vanilla Icepower in a nice box. I would not even consider using that with a higher output impedance tube pre-amp.

Just goes to show not all Class D is equal, even newer ones so gotta be careful about generalizing there.   
guidocorona
4,298 posts
 

Adding some more info about the Bel Canto REF1000 Mk.2. John Stronczer of Bel Canto added a custom input stage which elevated the input impedance from 8K Ohms to 100K Ohms, to make the amp compatible with those tubed pres that exhibit high output impedance.... As a side benefit, the amp also became much sweeter, immune from audible intermodulation in the treble, and... Quieter to boot.


Regards,    to   

georgehifi's avatar
georgehifi
10,312 posts
 
sonicbeauty

Quite some years ago, I purchased a pair of Bel Canto REF-1000.

It ended up being my absolute worst purchase in my 30+ years in this hobby.

I understand of course that those class "D" designs have much improved since.

Still, I could not bring myself even today to even remotely give D another shot.

seanheis1 OP

Does anybody know what causes the dead silences in songs that is a characteristic of Class D? Is it the output filter or dead time? I really noticed this with my Ice Module and couldn’t figure out if the amp wasn’t allowing for the music to decay or if it was something else causing the inky blackness.


The BC 600 monoblocks we listened to were better than the Ref-1000’s when we a/b them, probably because of the 600’s multiple series up output filters.
But they still had a stripping of the harmonic structure of the upper/midrange and highs, leaving what seemed to be just the fundamental with no decay and an opaque sound with larger than usual "nothing" gaps in the music.

Like I said before the switching frequency needs to be several times higher so then these output filters can do their job properly well away from the audio band without their side effects coming down into the audio band.
A bit like those nasty "brick wall filters" used to do in the early days of CD
Cheers George

bcgator's avatar
bcgator
355 posts
 
@sonicbeauty

I can understand this.  I once owned a Honda Accord that started making this sound that can only be described as sounding like the car was passing wind.   Every time you stepped on the accelerator, that first second of acceleration, it sounded and felt like the car had eaten too many burritos.  Sounds crazy, but it felt and sounded awful, like sitting on a whoopie cushion.  Took it back to two different dealers, both said it was normal.  Dumped that thing, bought a Camry, and have never visited a Honda dealer since.  Logically, I KNOW that Honda makes great cars, I like how they look, but I just can't go back...
seanheis1 OP
629 posts
 
But they still had a stripping of the harmonic structure of the upper/midrange and highs, leaving what seemed to be just the fundamental with no decay and an opaque sound with larger than usual "nothing" gaps in the music.
This is the perfect description of my experience with Ice Power. I have heard others describe this sound as neutral and uncolored, but to me the vocals and instruments sounded stripped. Diana Krall sounded more like Katy Perry. The larger than usual nothing gaps in the music made me focus on the recording instead of enjoying the song. 

It seems like some companies are aware of this and add tube input stages to try and add harmonics and meat back to the bone.  
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