Pabo said:
hello Pabo
good question.
do you heard about the AES17 filter?
most of testing class-d by ap system must insert this filter between ap system and class-d AMP
why? because the EMI, the The residual amplitude will make the input stage of AP system err.
you can take a look at our test. we have not connet the AES17 (same like).
MCD is the only one class-d amp can Measurement same like class-AB AMP
we can test the THD at 80k bandwidth, no other class-d can, because they must insert a 20~20khz bandwidth filter (AES17 same like)
rg
fumac
Eva said:
yes eva, your are right
all my job is base on god,
one day ,two years ago,
when i Pray at a cave, : "God help me please, give me a class-d amp,give me a class-d amp..."
Suddenly, a pcb droped to my head.
then i got MCD,
here is the picture what happened that day
An externally hosted image should be here but it was not working when we last tested it.
Eva said:
yes you r right, eva,
after one year ago,
i goto there again,
i Pray at a cave, : "God help me please, give me a class-d amp, more power full, more power full..."
Suddenly, a new pcb droped to my head.
then i got MCD-V,
An externally hosted image should be here but it was not working when we last tested it.
Eva said:
yes you r right, eva,
after one year ago,
i goto there again,
i Pray at a cave, : "God help me please, give me a class-d amp, more and more power , more and more power ..."
not Suddenly agian, a new pcb droped to my head.
then i got mhzpower-4,
An externally hosted image should be here but it was not working when we last tested it.
fumac
The AES17 filter is not there to filter out EMI. The AES17 filter is a software filter simply there to filter out the harmonic components outside the audible band.
The AUX0025 filter on the other hand is a filter provided by Audio Precision to filter out HF noise from the signal before it is sent into the AP.
The radiated noise I am referring to is at a very high frequency. If you are using fast modern MOSFETs it usually occurs around 100MHz. Have you measured radiated noise according to CISPR22 or EN55022? If so please provide measurement data to convince me.
I am sorry I started filing replies here as you seem to be on a level much too low to listen to critisism with an open mind.
The AES17 filter is not there to filter out EMI. The AES17 filter is a software filter simply there to filter out the harmonic components outside the audible band.
The AUX0025 filter on the other hand is a filter provided by Audio Precision to filter out HF noise from the signal before it is sent into the AP.
The radiated noise I am referring to is at a very high frequency. If you are using fast modern MOSFETs it usually occurs around 100MHz. Have you measured radiated noise according to CISPR22 or EN55022? If so please provide measurement data to convince me.
I am sorry I started filing replies here as you seem to be on a level much too low to listen to critisism with an open mind.
Pabo said:
hi
S-AES17 Low Pass Filter
S-AES17 is a hardware filtering kit for optional installation in System Two, System Two Cascade or Cascade Plus that satisfies
the AES17-1998 specification for a standard low-pass filter for THD+N measurements of digital-to-analog converters (DACs) which exhibit high-level out-of-band noise.
APWIN 2.20 and later versions support the use of this filter. The filter can be set to either of two bandwidth selections: 20kHz or 40kHz. The S-AES17 Low-Pass Filter Option improves upon the capabilities of the earlier S2-AES17LP filter, which is no longer available.
please goto here
http://www.audiotech.com.tw/AES17 Filter.htm?
aux0025 is a new filter for class-d
http://www.tti.co.uk/products-resale/ap/aux0025-1.htm?
we have no this two filters too, no any filter between class-d and AP system
we are testing our finished AMP to pass CE, and FCC, when it ready , i will post it for you
rg
fumac
fumac
Yes, I know what the AES17 filter spec says. I just thought you where referring to the one inside the audio precision software.
Anyway, I am not saying that it is impossible to switch at 1MHz or above. I am just saying that if the flanks are very fast and you switch at such a high frequency you will generate much more radiated noise. This noise is of course possible to handle but at a higher price and with more time spent to do it.
I would certainly like to see your emissions between 30MHz and 1GHz. Specify the measurement setup when you post the result so that it is easily comparable.
Yes, I know what the AES17 filter spec says. I just thought you where referring to the one inside the audio precision software.
Anyway, I am not saying that it is impossible to switch at 1MHz or above. I am just saying that if the flanks are very fast and you switch at such a high frequency you will generate much more radiated noise. This noise is of course possible to handle but at a higher price and with more time spent to do it.
I would certainly like to see your emissions between 30MHz and 1GHz. Specify the measurement setup when you post the result so that it is easily comparable.
fumac
I see what you where saying about the AES17 filter. I do not know how the Audio Precision modules is made in detail but I was assuming that 60dB attenuation from 20kHz to 24kHz with less than 0,1dB attenuation at 20kHz was mode in the digital domain.
I was wrong there and I will need to study how that is done.
I see what you where saying about the AES17 filter. I do not know how the Audio Precision modules is made in detail but I was assuming that 60dB attenuation from 20kHz to 24kHz with less than 0,1dB attenuation at 20kHz was mode in the digital domain.
I was wrong there and I will need to study how that is done.
Pabo said:
if you do with one well know class-d amp , when you use 2 modules in one case, and when you put the two modules nearby each other,
that will found the noise floor goto very high. sometimes beep.
i have no this class-d amp modules, all this is one of our oem user told us,
they just can place the two module at two side of the case.
but our modules can place nearby each other,
and the noise floor same like stand alone, MCD nevre beep.
perhap this will let you know about the emi of mcd.
after all, i will post the test after ready
nice to meet you, and the post of the god is not for you.
sorry for it
rg
fumac
Pabo said:
more info about aes17 filter
Audio Performance Measurement
Audio measuring equipment with an AES17 brick wall filter, such as the Audio Precision AP2, are necessary. However a classic audio analyzer like the HP8903B can be used with appropriate pre-stage low pass filter is applied. The important consideration here is that the output signal of a Class D amplifier still contains substantial amount of switching frequency carrier on its waveform, which causes a wrong reading, and those analyzers might not be immune enough to the carrier leak from a Class D amplifier. Figure 9 shows an example of a filter.
here is the link
http://csoneone.bokee.com/6538503.html
pdf from IR
http://www.irf.com/technical-info/appnotes/an-1071.pdf
darkfenriz said:
hello darkfenriz
yes , that's science
show you a picture
An externally hosted image should be here but it was not working when we last tested it.
you can find it at this link:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=116053&perpage=25&pagenumber=1
rg
fumac
darkfenriz said:
sorry, dont ask about this,
i'm making living on it, i have read about >3000 types mosfet datasheet, and test >100 types mosfet, then select <10 types for our project.
and i can show you the TDH+N, testing at 80k bandwidth 8 ohm load ,mhzpower-4 module
An externally hosted image should be here but it was not working when we last tested it.
rg
fumac
Wow, I don't know if the amp does, but at least people on this topic are overheating a bit xD
Well, your amp is nice but shows a quite small SNR don't you think?
Fumac, would you please fix your website? I'd be interested in your amps, but I need to have a look at SNR & THD measurements... as well as prices of the amp.
If it works well, and is simple in the sense of few components (at least does it looks like), it should lead to a fair cost. Which is very interesting ^^
Well, your amp is nice but shows a quite small SNR don't you think?
Fumac, would you please fix your website? I'd be interested in your amps, but I need to have a look at SNR & THD measurements... as well as prices of the amp.
If it works well, and is simple in the sense of few components (at least does it looks like), it should lead to a fair cost. Which is very interesting ^^
The snr is prolly due to that the amp itself have quite low gain so i have a preamp on it that gave quite high gain.
maybe the AF error feedback resistor and audio input resistor should be equal in resistance, or the input resistor shoiuld be smaller, or maybe ther preamp opamp should be included in the feedback loop, or it could be that its a low power amp running off only 15V as well as beeing single rail and having input and output dc blocking caps, what do i know.
Its a work in progress.
Heres the scopes noisefloor: Link
maybe the AF error feedback resistor and audio input resistor should be equal in resistance, or the input resistor shoiuld be smaller, or maybe ther preamp opamp should be included in the feedback loop, or it could be that its a low power amp running off only 15V as well as beeing single rail and having input and output dc blocking caps, what do i know.
Its a work in progress.
Heres the scopes noisefloor: Link
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