soongsc said:
because the noise floor ,
we can guess the noise floor at the 10mW point of Curve of thd+n vs output power
if an AMP have a low thd+N at low power output (10mW)
that means the noise floor is also very low.
if an amp have a high thd+n at low power output
that means the noise floor is high .
the low floor noise can give us very good dynamic.
we can find the Curve of thd+n vs power same like a "V"
the mini No. of THD+N at the Curve of thd+n vs power
the left side is N>THD, the right side is THD>N
this is the datasheet of mhzpower-2
you can read the THD+N of mini power ,5mW at 8ohm or 10mW at 4ohm
http://www.class-d.net/mhzpower-2.pdf
rg
fumac
Pafi said:
yes , eva is right, infact i agree with her talking from books
but , can you tell me , why most of good class-d amp is running at >300khz?
and not running at 100k?
as she said, she can make a 100k class-d amp 3~4x better than 400k,
ucd-400 THD+N :0.004% 20~20K 1W 8OHM.
EVA need to make a 100k D amp same like :
THD+N :0.001% 20~20K 1W 8OHM.
ok show it to us , we are waiting
Pafi said:
yes you are right, thd is not thd +n
infact thd+n is higher than THD.
"very difficult to measure " is not "no one can measure "
rg
fumac
Looks more and more interesting!fumac said:
Looks like the Power supply section takes the transformer outputs rather than DC? I've found that transformer performance really has a very very significant effect on class-D amp performance, why not just design a SMPS instead?
I think we should make the tone less provoking. Eva has shared much of her work on this forum. I have learned a lot from her posts.fumac said:
Anyway, I think GedLee mentioned some techniques to measure through the noise which involved syncronizing and averaging data to reduce noise effects, hope we see some tools out there that do that in the future.
fumac!
Not really. This means that either noise or distortion is high.
And actually noise floor is a different thing, it is used to describe spectral density of noise.
In your datasheet once you say 1 MHz sampling freq, then 1 MHz switching freq, however they are not the same! In one period a ClassD amp takes 2 samples! 1MHz=2MS/s!
This was what I was talking about: she don't need, because she told that about only power section, not the entire amp with feedback!
Not really. This means that either noise or distortion is high.
And actually noise floor is a different thing, it is used to describe spectral density of noise.
In your datasheet once you say 1 MHz sampling freq, then 1 MHz switching freq, however they are not the same! In one period a ClassD amp takes 2 samples! 1MHz=2MS/s!
This was what I was talking about: she don't need, because she told that about only power section, not the entire amp with feedback!
soongsc said:
about smps +class d ,
many people like to try it ,
but now , most of the smps +class d at the world can't get a very good measure to us.
because the noise floor is higher than translator + class-d.
this is also happened at smps + class-AB
you can easy download the datasheet of one Famous smps+class-d module.
and you can take a look at the thd+n vs power.
then you can get the answer.
rg
fumac
Pafi said:
thanks for your Advice, and we will change the word: samples to switching freq.
but , she need to proof her saying, because she said : 100k is 10x better than 1mhz.
just remenber, don't make a bassboost 🙂 or just stop at talking!
a class-d amp for hifi, not just a class-d technoledge can do,
and no one just heard about the "only power section" (as you said)
we need a full design of hifi audio, not just a "power section"
we need to know about that the Target is hifi audio,
the Target is not just class-d technolege.
talking about any AMPs is not just talking about one side of it , it is a full section. you can't seperate them just like one setion or the other setions.
we need to balance all the setions then we can get a very good amp.
we are waiting
talking is quite easy then doing
thanks
rg
fumac
Where? In what aspect?
I don't agree with you fully, because there are some amps without feedback, where you can hear the quality of power section directly, but this is not really important. Analyzing power section alone is part of a method of understanding and designing amp. The fact that nobody ever seen a real circle (in mathematical meaning), doesn't mean that PI is meaningless thing!
Separation is one of the most useful thing in science and engineering.
Without separation you can't balance consciously.
Pafi said:
hi Pafi
please read this topic again,
many topic about feedback and no feekback
also at clas-AB amps
but to now , noone agree each other.
does feedback really make the sound worst than no feedback?
feedback is one technoledge at morden design. it is used any where,
if continue talk about feed back, will begin another fighting.
dont forget, most of moden class-d have feedback loops.
and THD not just from deadtime , also will product THD from the output filter.
perhaps we need to let tekko keep on his topics.
sorry tekko ,
i think you can make your class d better and better.
just keep trying. you are same like us at that days.
rg
fumac
fumac!
Sorry, I can't read the whole topic again for this!
Feedback is neccessary, I agree, I told just: 1.: still there are some ClassD amps without it, 2.: we can separate it in mind for analysing purposes.
Sorry, I can't read the whole topic again for this!
Feedback is neccessary, I agree, I told just: 1.: still there are some ClassD amps without it, 2.: we can separate it in mind for analysing purposes.
A little calculation says 5mW is 49db below 400W, is the dynamic range of power amps that bad? Such that noise has effect on test levels 49db below max?fumac said:
My stereo amp is now undergoing a major rebuild power rail wise. From beeing a single supply amp, it is beeing rebuilt to accomodate split supply, just a quick test without changes to the board reveals that it works much better than running single supply.
Soldering station, here i come
Soldering station, here i come
soongsc said:
you calculation wrong,
at 4ohm:
the thd+n at 10mW is 0.015%,
and thd+n at 400W is 1%
not just can output 5mW mini.
calculat again please
rg
fumac
Tekko said:My stereo amp is now undergoing a major rebuild power rail wise. From beeing a single supply amp, it is beeing rebuilt to accomodate split supply, just a quick test without changes to the board reveals that it works much better than running single supply.
Soldering station, here i come
yes, seperate power supply is better than single one.
because the low pssr of class-d
rg
fumac
fumac!
soongsc's calculation is not wrong, just he calculated a different thing from you (didn't). 10*lg(400/0.005)=49 indeed. (The question is what did he want to tell with this. Maybe that THD should be specified at low power too.)
Class-D don't have PSRR. It's only a Class! Amplifiers have. Eg. "MHz amplifiers" have low PSRR, some others (eg. Hypex UcD) have higher PSRR.
soongsc's calculation is not wrong, just he calculated a different thing from you (didn't). 10*lg(400/0.005)=49 indeed. (The question is what did he want to tell with this. Maybe that THD should be specified at low power too.)
Class-D don't have PSRR. It's only a Class! Amplifiers have. Eg. "MHz amplifiers" have low PSRR, some others (eg. Hypex UcD) have higher PSRR.
My MHz amp hums, even tho its behind dual regulated supplies, yes the power is regulated twice, first to 2x15v then to 2x8v, but it still hum when i activate bass boost on the preamp.
soongsc said:
Pafi said:
i don't know what are you saying
do you caculate a dynamic range as mr. song?
that's right? so funny
-----------------
Audio
The dynamic range is defined as the difference between the minimum and maximum amplitude a given device can record. 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).
------------------
from wikipedia
http://en.wikipedia.org/wiki/Dynamic_range
Mr song:
you need to caculate the max output voltage and the noise floor level,
then you can get the dynamic range.
5mW, not the noise floor,
5mw also not the minimum amplitude at MCD.
you can find the noise floor picture or No. at our datasheet.
we have posted more test pictures than others.
mhzpower-2 we got a noise floor at 22uV (tested by ap syetem. )
22uV to 4ohm is 121pW, ----this is the noise power output.
you can do this caculate:
the thd+n= 0.015% at 10mW 4ohm
10mW to 4ohm is 0.2V rms
0.2vX0.015%=0.00003V=30uV
is meaning :THD+N is 0.00003V. also is 30uV
------------------
30uV is THD+N, 22uV is N, so , you can verify them yourself.
rg
fumac
That is exactly what I'm trying to understand. I my guess is that most amplifiers on the market will show THD+n for higher levels, and mostly in the linear range. 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. If this is true, then the THD + N measurement at 5mW would represent how linear the amplifier is at low level signals, which should be a good indication how good the amp will reproduce detail information.Pafi said:
Lower PSRR in class D amps would mean that the efficiency is high. Would this be a correct assessment? Thus the more effecient amps rely on better power supply to obtain best performance.
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.
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.
fumac said:
Pafi said:
Pafi
do you have tested other class-AB and class-A amp?
how about the PSRR of class-A amp?
when you know the PSSR of class-A , you will know all the class-d to now have a poor PSRR .
your point out that the class-d amp , they have pssr at 65db (from the datasheet of them)
our mcd is 71db, which one is better?
65db and 71db are poor also.
many many class-A power amp have a >120db PSSR
please take a look at the datasheet of 3886
http://www.jaycar.com.au/images_uploaded/LM3886.PDF
take a look at this 1$ chip, it have a 120db PSSR. not 65db also not 71db.
and this link will told you about :
Closed-loop Class-D power amp delivers improved sound, PSRR
http://www.automotivedesignline.com/products/206900612
if you do know class-d , and comparator class-d with class-ab and class-A,
you will never told others, very good PSSR at class-d.
any class-d have a poor PSSR now. including Closed-loop Class-D.
PSSR of Closed-loop Class-D is better than the openloop class-d,
but also not very good
please comparater with class-A or AB,not just stare at the class-d
any class-d will be better when they use seperate powersupply.
this also happened at UCD and MCD
rg
fumac
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