A fish named Wanda

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classd4sure

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Joined 2004
diyaudio.com
gpapag said:
marconist
You can put the blame (credibility deficit) on me.
You may very well question the case. Subject is still open and will remain that way. The following
is a valid contribution to the thread.It is an opinion expressed after a subjective listening test and some measurements. If there wil be x tenths of such opinions your opinion will be strengthened. But the questionmark will be still here.
regards
George
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If we're to answer this, and I honestly doubt it'll happen, we'd have to agree on a set of designed tests that are actually meaningful, I don't think his was, but am impressed he tried. It's more than I did.
 
G

ghemink

Member
Joined 2004
Yves Smolders said:
ghemink,

Could it simply be the lower harmonic distortion in high frequencies + lack of crossover distortion (against class AB anyway?)

Yves
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Hi Yves,

I don't think so about the harmonic distortion, with respect to crossover distortion, you maybe right. I have now tried 3 different Class D amps at my home. ZAPpulse, UcD and Tripath. They all for sure have different distortion characteristics, different background noise levels and different frequency response due to difference in feedback mechanisms, however, they all have that certain Class D magic. The ZAP and UcD are better in that respect than the tripath, but still the tripath sounds clearly better than my Class AB amp that has now been sitting idle for more than a year. Anybody interested in an Accuphase E407 (100V Japanese version), the 60 Euro UcD180 easily beats that Accuphase, it's a shame.

Best regards

Gertjan
 
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koolkid731

Member
Joined 2005
class-D sounds better than class-AB?

There're class-AB amps that sound very good, even better than recent class-D amps. However they're expensive to make (using RF transistors and multiple local feedbacks)

UcD, IcePower, and NuForce have very short and fast forward and feedback path to enable them to self-oscillate at high frequencies. Their loop propagation delay (less than 200ns) is smaller than class-AB's therefore their TIM is better, output impedance lower, squarewave response better, etc...

Those are some factors why they would sound better.

I'm not sure they sound better than Halcro amps and other expensive amps, although these have higher output impedance, and their price tag prevent purchases by cash-poor engineers for serious comparative studies.
 
M

marconist

Member
Joined 2005
Hi folks,

I was out for a while. Thanks for your comments and please no praise because the whole thing took me only an hour and a half and I also was probably a bit rough to you all. :rolleyes:
Nasty Dutch habit I fear .....

Anyhow I appreciate the ideas on the quality aspects of any amplifier and indeed also on my Philips UcD as I do not build myself these days anymore.
It was mainly because I do not buy the dither or pre-activation (like in servos) theory. To my opinion if that is the matter than man should also have discovered that analog taperecorders and records sound also better. (Although the fight is still on ;) )

I like the comment of koolkid 731 as it gives me more a sense of reality to me.
Don't expect me to make very smart measurements as I don't have too much equipment. Life was easier in the old days when I worked for HP (now Agilent).

I will stay tuned.
 
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ghemink

Member
Joined 2004
Re: class-D sounds better than class-AB?

koolkid731 said:
There're class-AB amps that sound very good, even better than recent class-D amps. However they're expensive to make (using RF transistors and multiple local feedbacks)

UcD, IcePower, and NuForce have very short and fast forward and feedback path to enable them to self-oscillate at high frequencies. Their loop propagation delay (less than 200ns) is smaller than class-AB's therefore their TIM is better, output impedance lower, squarewave response better, etc...

Those are some factors why they would sound better.

I'm not sure they sound better than Halcro amps and other expensive amps, although these have higher output impedance, and their price tag prevent purchases by cash-poor engineers for serious comparative studies.
Click to expand...

Hmmmmm, square wave response better??? My Accuphase is faster (meaning having a more extended closed loop frequency response than the UcD modules) but the UcDs sound better. Class D just plays with much less effort and can go loud without becoming aggressive, maybe very expensive Class ? amps can do that as well but then maybe you need to invest like 10-??x more to get the same result as with a Class D amp? If that is true, then I think the other classes will be gone in a few years. My far more espensive Accuphase can not match these 60 Euro modules (UcD180 standard version with a few modded capacitors).

Anyway, for me it is pretty clear that Class D is a sound revolution on its own with very high performance/cost ratio.

Best regards

Gertjan
 
Kenshin

Kenshin

Member
Joined 2005
Maybe the surface wave would reduce some nolinearity of loudspeaker cone cloth? Then try it on loudspeaker made of different material?

Another posibility:

class D have low open-loop output internal resistance, and it's immune to the inductive / capative characteristics of loudspeaker.

I once met some faked chips that could power 8 ohm loudspeaker clearly, but 4 ohm cant -- I could not hear a word clear. It could be infer that output characteristics of the amplifier would affect lot on the sound clearity.

As an additional proof: A report in 1980s said that some Hi-END class AB's have 1% distortion on RLC network mimic real loudspeakers.
 
T

Tim__x

Member
Joined 2004
This thread is almost entirely pseudoscience.

I don't know where to start, and I'm not going to cover it all.
I will say I agree with the statement about lack of crossover distortion.
But micro-diodes!? I mean really, conductor non-linearities are hundreds of decibels down, and if dithering was important noisy amplifiers would work just as well as carrier residual.
And fourier transforms don't convert between square waves and sine waves or any thing of the sort, they convert between frequency and time domains.
 
Pjotr

Pjotr

Member
Joined 2002
Tim__x said:
This thread is almost entirely pseudoscience.

I don't know where to start, and I'm not going to cover it all.
I will say I agree with the statement about lack of crossover distortion..........
Click to expand...

Duh, new life for an old discussion?

I can second that Tim. For me, class-D (in my case UcD) sounds very much the same as a good class-A at lo level. IMO mainly because of the lack of cross over distortion. At high level, class-D wins because of much more power headroom. It is all a matter of signals that are not in the music signal NOT being there.

IMHO no need to search for mystical unknown (and unproven) phenomena.

;)
 
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Tim__x

Member
Joined 2004
Oh wow, three years old.
I tend to assume threads on the first page really ought to be there. I don't often check to see if the poster before me might have dredged up some corpse of a thread vivifying it like some forum-ite Dr Frankenstein. And I, acting as an Igor of the forums help continue it.
 
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