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Class D Switching Power Amplifiers and Power D/A conversion

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Old 14th December 2012, 02:33 PM   #3041
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thanks dear friend
i buy the 1% resistor for change your amp FREQ but i dont know how and dont know value.
sorry
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Old 15th December 2012, 11:14 AM   #3042
chago25 is offline chago25  Philippines
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Originally Posted by andrewlebon View Post
Hi Nano
greetings do you have this file to make
warm regards
andrew lebon
hi sir can u share this file? tnx
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Old 16th December 2012, 06:29 AM   #3043
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Hi, gents, I am not pouring cold water over this hot topic. But, I am struggling to understand how could this Class-D technology be applied to make Hi-Fi amps, given the high level RF noise at the output. From the schematic at post1#, I figure out that the L&C forms a LPF, that would prevent most of the carrier getting into the spk system. However, I think this is only a 12db/oct LPF and there will be significant residual RF pass the LPF and get into your speakers. For a rough calculation, if you make the switching freq. at 400kHz, and you measure how much carrier get though the 12db/oct LPF at 20kHz, then you will get (-12)*log(400000/20000,2) = -51.86db, which is about 0.255%. That is to say the THD+S/N at 20kHz must be greater than 0.255%. Even if you push the SW freq. into 1MHz, very unrealistic though, the residual at 20kHz would still be -67.7db, which is equal to 0.04%. If the above calculation is correct, A 40 year old JLH class-A design can easily beat the class-D in terms of THD+S/N.

Neverthless I think this class-D design is good enough for a sub-woofer amp. If using the same switching freq. at 400k, you will get only -131.59db noise at 200Hz.
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Old 16th December 2012, 08:25 AM   #3044
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Hi to all
i waiting for your email sir manoj
thanks
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Old 16th December 2012, 09:58 AM   #3045
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by jazzclassics View Post
Hi, gents, I am not pouring cold water over this hot topic. But, I am struggling to understand how could this Class-D technology be applied to make Hi-Fi amps, given the high level RF noise at the output. From the schematic at post1#, I figure out that the L&C forms a LPF, that would prevent most of the carrier getting into the spk system. However, I think this is only a 12db/oct LPF and there will be significant residual RF pass the LPF and get into your speakers. For a rough calculation, if you make the switching freq. at 400kHz, and you measure how much carrier get though the 12db/oct LPF at 20kHz, then you will get (-12)*log(400000/20000,2) = -51.86db, which is about 0.255%. That is to say the THD+S/N at 20kHz must be greater than 0.255%. Even if you push the SW freq. into 1MHz, very unrealistic though, the residual at 20kHz would still be -67.7db, which is equal to 0.04%. If the above calculation is correct, A 40 year old JLH class-A design can easily beat the class-D in terms of THD+S/N.

Neverthless I think this class-D design is good enough for a sub-woofer amp. If using the same switching freq. at 400k, you will get only -131.59db noise at 200Hz.
there's not a lot of tweeter that's able to play high frequency over 20khz. even then, most people won't be able to hear it anyway.

THD alone don't reflect the actual sound quality. my advice is, build it, test it on your own and deduce your own conclusion. i've built a few of the designs posted in this thread and while i won't personally use them as the resident amp, it does sound quite musical.

heck it sounds even more musical than some single ended class a tube amp that i've heard before.

i'm personally running the irs900d for months now as my subwoofer amp.
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Old 16th December 2012, 01:02 PM   #3046
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I agree with you that THD along does not reflect sound quality. In most of time, I am trying to be objective. That is why I looked at the schematic and theoritical effect first. I am trying to understand why such an advanced technology is yet to be accepted by the Hi-Fi audience. I know that the renowned Jeff Lowance has, after making some successful Class-D amps, reverted to a class-AB approach.

I am using a pair of Fostex FE166En full rangers which has a response well extended to 22kHz, and even that speaker is suggested, by the Fostex in the manual, to accompany with a super tweeter. Nowadays the Hi-Fi is really going to "Hi-Freq". Looking at the spec for some flagship speaks, I have got the idea that a flat response to 40-50kHz is a de-facto standard for the hi-end speakers.
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Old 16th December 2012, 01:40 PM   #3047
exflaco is offline exflaco  Armenia
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Default Thanks you are correct way Jazz..

Quote:
Originally Posted by jazzclassics View Post
I agree with you that THD along does not reflect sound quality. In most of time, I am trying to be objective. That is why I looked at the schematic and theoritical effect first. I am trying to understand why such an advanced technology is yet to be accepted by the Hi-Fi audience. I know that the renowned Jeff Lowance has, after making some successful Class-D amps, reverted to a class-AB approach.

I am using a pair of Fostex FE166En full rangers which has a response well extended to 22kHz, and even that speaker is suggested, by the Fostex in the manual, to accompany with a super tweeter. Nowadays the Hi-Fi is really going to "Hi-Freq". Looking at the spec for some flagship speaks, I have got the idea that a flat response to 40-50kHz is a de-facto standard for the hi-end speakers.
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Old 16th December 2012, 02:38 PM   #3048
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Sorry in the post3046 I meant Jeff Rowland instead. The "Jeff Lowance" was a mistake. The Jeff Rowland used to make class-D amps such as the model 201, but nowadays, its amps are almost all class-AB.
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Old 16th December 2012, 03:29 PM   #3049
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by jazzclassics View Post
I agree with you that THD along does not reflect sound quality. In most of time, I am trying to be objective. That is why I looked at the schematic and theoritical effect first. I am trying to understand why such an advanced technology is yet to be accepted by the Hi-Fi audience. I know that the renowned Jeff Lowance has, after making some successful Class-D amps, reverted to a class-AB approach.

I am using a pair of Fostex FE166En full rangers which has a response well extended to 22kHz, and even that speaker is suggested, by the Fostex in the manual, to accompany with a super tweeter. Nowadays the Hi-Fi is really going to "Hi-Freq". Looking at the spec for some flagship speaks, I have got the idea that a flat response to 40-50kHz is a de-facto standard for the hi-end speakers.
class d have a general character of being bright and clinical. if paired to a loudspeaker that have extended HF tweeter they might sound thin and bright. and they do sound thin and bright on my main speaker, rated to extend to 30khz (iinm).
but when paired to a cheap speaker that i have in my study room, they sounded nice as the tweeter have a natural slope above ~12khz.

that being said, when absolute efficiency and low heat output are critical, hard to beat class d. if the designer absolutely must reduce the carrier freq as much as possible, then it's always possible to use much steeper slope.
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Old 17th December 2012, 10:15 AM   #3050
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Originally Posted by manojtm View Post
Hi Hadi,

yes ETD29 . it can go up to 500KHz no problem.but i am using 250KHz only.after testing i will send to you.

Regards
MANOJ
i am waiting sir manoj
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