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Class D Switching Power Amplifiers and Power D/A conversion

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Old 10th December 2003, 05:07 PM   #31
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For more information on Class D amplifier technology, see: http://www.aes.org/sections/la/PastM...003-02-25.html.

BTW, very few Class D amps are actually digital. Most use totally analog means of modulation.
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Old 13th December 2003, 11:43 AM   #32
km is offline km
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hi.

i think that there are several good reasons for using class-d/pwm amplifiers in high power applications , but i also think that there is a lot of hype and that the use of pwm amplifies in hifi/home applications isnt all that obvious.

i have been involved in listening tests comparing 3 different types of pwm amplifiers and a "normal" amplifier too (a current feedback amp like the alexander amp)

no doubt the latter presented the best sound quality of these.

the pwm amplifiers involved were ; icepower , tripath and our own discrete pwm amp.

i do realize that different people hear different things , as an example;

> have now owned a pair of monoblocks based on Ice-power (semi-diy) and I think they are superior in certain areas. I would never buy anything else actually.>

>the trancparency and directness is stunning. Everything alse just sound dull or artificial compared.>

in the mentioned comparison the icepower were sounding quite dull and distant like in other reviews i have read i do think they have the best steady state specs but they could very well have the lowest sound quality (like we found).......

a good reason for sticking with traditional amps for a while is the verdict i read about lc audio zappulse some time ago ; "the sound quality is certainly below hifi standards but they are good at receiving radio , you twist the output inductors to tune in to different stations......"

as for low price i suggest that lars clausen publish the schematic of his low price pwm amp , in this way the diy folks here can make a couple and compare them to the amps they allready have, this i think would give a broad basis of comparisons and very valuable feedback for lars too...

i for one have been a bit reluctant to pay some $350 for what seems to be $20 worth of parts

rgds karsten madsen

ps. i havent heard the zappulse amp so i cant comment on it....
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Old 13th December 2003, 12:06 PM   #33
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Well Karsten, if you can produce our ZAPpulse for 20$: congratulations! You have a job!

Furthermore the retail price is NOT 350$, check your facts Karsten

Lastly i will give you right in your conclusions about pwm (may i use that term?) vs. analog amps for home use.
You were absolutely right about one year to 18 months ago. However evolution works, even in this area. Today i think there are several good pwm amp's available for home use also.

Icepower is (in my opinion) a very good amplifier, i have heard the latest versions, and i can not say anything bad about them.
Maybe you compared with some 2-3 year old modules, and then i might be inclined to agree with you in your conclusions. However the new ones are really good!
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Old 13th December 2003, 01:17 PM   #34
km is offline km
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hi .

thanx lars but i allready have a job

i think you forgot to comment on a few points , dont you think its a good idea to make a pwm amplifier available to the diy community , could be a simple version of your zappulse if you like.

this way your points about comparisons between pwm amps and traditional amps in hifi applications could have some more weight (imho) and on op of that you would get a lot of unbiased feedback helping to improve on the pwm amp topology and giving lots os hands-on experience to those who have opinions about pwm amps based on little (on none) practical experience.

feel free to contact me directly if you want to discuss this further (offline) and/or if you think we could realize a project like this this in some kind of cooperation.

if i may ask , why is the schematic of the zappulse amp secret when you have published schematics for your other amps?

i can only comment on the icepower and tripath boards i have heard and im not sure exactly what version of the icepower modules i have heard , i think its the ones sold through high-fidelity allthough i didnt get them there.

i guess you could say the same about tripath boards, to my knowledge there have been several revisions to them as well.

rgds karsten madsen

ps. my price of $350 seem to be for 2 boards , sorry but i just emembered you had a offer for 2 boards + 12v supply for around $350.....
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Old 13th December 2003, 01:35 PM   #35
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Yeah, that's a good idea. A layuot for a simplified zappulse or a simplified layout for zappulse-like amp would be great. That's just what I need right now
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Old 13th December 2003, 02:23 PM   #36
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km and dylanmrjones: Thanks for the suggestion, it seems like a good idea, however there is one problem. A ZAPpulse can not be implemented with full sound quality on less than a 4 layer PCB. This is because the ZAPpulse does not produce harmonic distortions, but rather random noise. And the only way to keep the random noise down is by the use of a 4 layer board with shielding ground planes, and a lot of HF capacitors.
I think most DIY'ers would try to build their implementation on 1-2 layer boards, and thus get a degraded performance.

But i might be able to find another good pwm amplifier, that is not ZAPpulse, but will give good results as a DIY project. Let me look into it. How about your pwm, km, maybe you can publish that in here??

Have a nice day from rainy and cold Denmark
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Old 13th December 2003, 03:15 PM   #37
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Quote:
Originally posted by Lars Clausen
Jocko: If i understand right Class G is switching between different power supply levels, but using ananalog power stage ... right?

You are right about the distortions in the "********" amplifiers
( don't know what to call them anymore ) Just some don't have distortions harmonic to the audio signal, but random noise instead.
""********" amplifiers", which ones do you mean ?

ClassG or analog in general ?

Bernhard
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Old 13th December 2003, 03:35 PM   #38
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Bernhard: I would not use a term starting with the word: 'Class'.

So what i am referring to is some types (but not every) of 'amplifiers with a coil in the output for making square waves with various duty cycles into an analog audio signal that can feed a loudspeaker' do not produce harmonic distortions but rather produce random noise products instead...

Some people call them Class D. (Others call them other classes).
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Old 16th December 2003, 12:51 AM   #39
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If class AB amps haven't yet killed off class A, I don't think class D will ever replace class AB completely. I could see it getting into the mid-fi section of audio in the next few years, probably suited more towards battery powered boomboxes. I read an article about class D amps finding their way into cell phones and other portable equipment where battery life matters. As far as full range quality goes, I don't think class D will ever get to where AB is. For PA and huge subwoofer amps, class D will always win but I don't think it will completely replace AB.
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Old 16th December 2003, 02:33 AM   #40
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Quote:
Originally posted by Lars Clausen
So what i am referring to is some types (but not every) of 'amplifiers with a coil in the output for making square waves with various duty cycles into an analog audio signal that can feed a loudspeaker' do not produce harmonic distortions but rather produce random noise products instead...
And yet you can measure harmonic distortion at their output.
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