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Class D Switching Power Amplifiers and Power D/A conversion

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Old 4th May 2008, 10:31 AM   #101
fumac is offline fumac  China
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Quote:
Originally posted by soongsc
What I am trying to say is that at 5mW, the noise would not be a dominating factor for the THD + N figure. Rather linearity is still the most dominating factor. Other specs being equal, the better THD + N figure at low levels would indicate better performance in revealing detail.

I think the data you have posted is much thorough than what other manufacturers care to provide, this is a very good start. Lets hop other companies can post more challenging data.


thanks soongsc
you can take a look at the datasheet of ucd and ice
or anyother class-d amp.
and take a look at the noise floor or THD+N at lowest power output.

perhaps you can get more about the smps+class-d

rg
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Old 4th May 2008, 11:02 AM   #102
Pafi is offline Pafi  Hungary
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fumac!

Quote:
do you caculate a dynamic range as mr. song?
No, and I think he didn't calculate dynamic range either! He calculated exactly what he wrote: difference of the highest and lowest level at wich you specified your amp. Obviously this is not the full dynamic range.

Quote:
For example, if the ceiling of a device is 10 dB and the noise floor is 3 dB then the dynamic range is 4.85 dB, since 10 dB−3 dB = 4.85 dB (recall that care must be taken when adding numbers in the decibel scale).
This is from there too:

Quote:
This article may require cleanup to meet Wikipedia's quality standards.
I agree with this. That part is a complete mess. In logaritmic scale dinamic range is difference, in linear scale it's ratio. The 2 method is equivalent, but not allowed to mix them.

soongsc!

Quote:
My guess is, showing THD+N in the lower level range such as 0.1W or even 5mW, if the amplifier dynamic range is good, noise level would still be maybe 40db lower than the signal, and thus have little effect on measurements.
Measurements of what? If noise is much lower than signal (eg. -49 dB), then distortion is unchanged, but if noise is higher then harmonics (eg. -120 dB), then THD+n will be obviously higher!

Quote:
Lower PSRR in class D amps would mean that the efficiency is high. Would this be a correct assessment?
No, there is no connection between efficiency and PSRR.

Quote:
What I am trying to say is that at 5mW, the noise would not be a dominating factor for the THD + N figure.
But it is dominating. 0,01 % THD+n at 200 mV (5mW@8ohm) means 20 uV "error". Do you think output noise is much less then 20 uV?
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Old 4th May 2008, 11:53 AM   #103
Pafi is offline Pafi  Hungary
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Quote:
Originally posted by fumac
Pafi
do you have tested other class-AB and class-A amp?
how about the PSRR of class-A amp?
I have tested ClassA amps, and they have PSRR from 0 dB to 100 dB.

Quote:
our mcd is 71db,
Really? Then why did you say it is low?

Quote:
take a look at this 1$ chip, it have a 120db PSSR. not 65db also not 71db.
Yes, 120 dB from the positive rail, but continue reading! 105 dB from negative rail, at DC! PSRR at DC??? Who cares? It's only war of numbers, without any importance. Compare them at full audio band! UcD have uniform PSRR, while LM3886 starts to fall at 50 Hz. What about yours?
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Old 4th May 2008, 12:43 PM   #104
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by Pafi
...
soongsc!



Measurements of what? If noise is much lower than signal (eg. -49 dB), then distortion is unchanged, but if noise is higher then harmonics (eg. -120 dB), then THD+n will be obviously higher!



No, there is no connection between efficiency and PSRR.



But it is dominating. 0,01 % THD+n at 200 mV (5mW@8ohm) means 20 uV "error". Do you think output noise is much less then 20 uV?
I guess I should have done the numbers before I spoke. So it seems like we really have to try and measure through the noise.
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Old 4th May 2008, 01:28 PM   #105
fumac is offline fumac  China
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Quote:
Originally posted by Pafi


I have tested ClassA amps, and they have PSRR from 0 dB to 100 dB.

Really? Then why did you say it is low?

to me , large than 80db is good ,
please check here, Mr Bgt have test his MCD amp
and he is using a singal supply to drive his mcd-255

MCD-255 amp

Quote:
Originally posted by Bgt
Fumac, the amp stays really cool. Should not be a problem.
BTW the "mosfet side" is closest to the amp. side pieces.
Sound is very..................very nice
Positioning of the modules is done for symmetry.
Crosstalk at 20khz is>100Db at full power/8Ohms/>80W/ch.
rg
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Old 5th May 2008, 02:57 AM   #106
IVX is offline IVX  Russian Federation
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Nihao fumac, you know, 71db PSRR and loop gain "10", whatever db or 10:1, it's mutually exclusive things, there something wrong, and rather your amp has much bigger loop gain, than you like to think.
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Old 5th May 2008, 06:09 AM   #107
fumac is offline fumac  China
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Quote:
Originally posted by IVX
Nihao fumac, you know, 71db PSRR and loop gain "10", whatever db or 10:1, it's mutually exclusive things, there something wrong, and rather your amp has much bigger loop gain, than you like to think.

i just told you the gain of mcd is about 10x
this is gain of our amp.
it just means input a 1v, you can get 10v at output.

have i told you about our open loop gain?
and have i told you that we have Decay at the input of power stage?

we have talked about at the phone,
because you are doing a job at china now , and not so far away from me , so perhaps we can make friends at real life,
but now , i don't think so.

because no one like others to post his personal talking at the Public .
so i will never talk with you again, and please delete my phone No. that i have gave you.

there are about 10 Foreign guys have gone to my lab when they was visiting or working at china,
we know each other at diyaudio, and make friends at real life.
or do biz at real life.
sometimes i drive them to club to have happy hours,
my English is better and better because i can talk with them at real life, this help me great.

most of them are very well know here.
but i have never post the personal MSG at here or another website.
because i know the Privacy right , i will not post their any MSG at public.




rg
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Old 29th May 2008, 10:42 PM   #108
fumac is offline fumac  China
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to now the lowest THD+N of our project.
THD+N=0.00132%(still no test filter )
Click the image to open in full size.
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Old 30th May 2008, 08:26 AM   #109
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Old 30th May 2008, 12:21 PM   #110
-CGL- is offline -CGL-  Finland
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Quote:
Originally posted by fumac
to now the lowest THD+N of our project.
THD+N=0.00132%(still no test filter )
Click the image to open in full size.
You could, if you know how, set up the AP correctly.
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