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Class D Switching Power Amplifiers and Power D/A conversion

FDA: Alientek D8
FDA: Alientek D8
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Old 5th November 2017, 09:57 AM   #11
the hound of sound is offline the hound of sound
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FDA: Alientek D8
I should mention that, in my relative ignorance, if the clocks are different by some factor/multiple,
I'm thinking it might be possible to adjust the XMOS (DIYINHK board) driver source code to
subdivide the MCLK output signal.
I am in the process of setting up the driver development environment.
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Old 8th November 2017, 01:23 AM   #12
the hound of sound is offline the hound of sound
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FDA: Alientek D8
audeo?!
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Old 8th November 2017, 05:11 AM   #13
audeo is offline audeo
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Originally Posted by the hound of sound View Post
audeo?!
What? Currently I have no info re. your musings. Maybe if I finally decide to try enabling audio input to PC through D8's ADC connected to its AUX terminals (the XMOS board seems to support bidirectional digital traffic), then I'll disassemble it again and measure some stuff, but this won't happen very soon. Sorry.
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Old 29th November 2017, 11:18 PM   #14
the hound of sound is offline the hound of sound
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FDA: Alientek D8
I've been mulling over getting a 'aliexpress special' logic analyzer/oscilloscope
but just decided against it - can't be sure I won't need a quality manual / instructions !
I'll wait on that next disassembly. thanks.
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Old 2nd February 2018, 02:56 PM   #15
forestsgump is offline forestsgump
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Originally Posted by audeo View Post
Okay, I finally killed that nasty hiss of my D8 and not by restoring the STA326 filtering circuit to its datasheet glory (although I did that too), but by inserting an inductor, as large as I could immediately find which turned out to be 15uH torn out from some dead piece of hardware, between the input power line and the 5V DC-DC converter (it operates at 2 MHz). So, the chief culprit appears to be the usual one - a dirty power source, in this case dirt is produced by D8 internally, hence it can't be eliminated by using even the best possible external power supply.
Audeo, mind sharing some actual pictures of D8 improve mods you did?
can list partlist as well? Thks

globulegl mentioned snubber filter on tp1 it s a very good idea. I guess you are referring pictures provide by Audeo. Does Tp1 refers to Test Point 1 on PCB? Does D8 mods snubber filter refers the 660p Ceremaic cap & 10R resistor? What wattage is suitable for the resistor

Any other mods beside Tp1 is needed?
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Old 2nd February 2018, 03:15 PM   #16
audeo is offline audeo
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Originally Posted by forestsgump View Post
Audeo, mind sharing some actual pictures of D8 improve mods you did?
can list partlist as well? Thks
Those pictures would be really ugly if I were to take them: everything is so crammed and twisted there due to lack of space. The spot where I put an inductor is marked with an X on the attached picture and all other parts are marked red in the schematic I showed previously. I used some film caps and they were not tiny.
Attached Images
File Type: jpg inductor_placement.jpg (383.0 KB, 202 views)

Last edited by audeo; 2nd February 2018 at 03:19 PM.
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Old 2nd February 2018, 06:16 PM   #17
forestsgump is offline forestsgump
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Thks Audeo for helping, what does Tp1,Tp2,Tp3,Tp4 refers to ? where is it on the PCB?
also what wattage is the resistors used?

I can imagine the mod messing-up; that wld be my challenge as well, as I have no idea where are exact location to solder on, if without actual mod PCB image. Did you also did the blueline connection?
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Old 2nd February 2018, 06:34 PM   #18
audeo is offline audeo
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Originally Posted by forestsgump View Post
Thks Audeo for helping, what does Tp1,Tp2,Tp3,Tp4 refers to ? where is it on the PCB?
also what wattage is the resistors used?

I can imagine the mod messing-up; that wld be my challenge as well, as I have no idea where are exact location to solder on, if without actual mod PCB image. Did you also did the blueline connection?
That schematic was taken from the STA326 datasheet and has nothing in common with Alientek D8 except the chip itself. "TP" must be "test point", I presume (and those do not matter here), and blue lines, as I said in my message accompanying the schematic, indicate not my doing, but that of our Chinese friends - it is what must be undone by some sheer and brutal cutting. You better find the STA326 datasheet and compare it to your actual board layout. You might well find some more discrepancies which were not there in my case. Resistors' wattage does not matter much, I think, because none of them carry any substantial current. I used some smallish SMD resistors everywhere, big enough to be easy to hold and solder.
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Old 3rd February 2018, 12:10 AM   #19
forestsgump is offline forestsgump
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Quote:
Originally Posted by audeo View Post
Okay, I finally killed that nasty hiss of my D8 and not by restoring the STA326 filtering circuit to its datasheet glory (although I did that too), but by inserting an inductor, as large as I could immediately find which turned out to be 15uH torn out from some dead piece of hardware, between the input power line and the 5V DC-DC converter (it operates at 2 MHz). So, the chief culprit appears to be the usual one - a dirty power source, in this case dirt is produced by D8 internally, hence it can't be eliminated by using even the best possible external power supply.
So snubber filter at tp1 & tp3 dint help to remove the hiss?

Oh... I think wld just insert the 15uH inductor:
"Input power line" refers to the +Vin from the DC socket, and "5V DC-DC" refers to the 5V regulator +Vin, am i correct?
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Old 3rd February 2018, 05:38 AM   #20
audeo is offline audeo
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Quote:
Originally Posted by forestsgump View Post
So snubber filter at tp1 & tp3 dint help to remove the hiss?
Even if it did, I did not notice it.

Quote:
Originally Posted by forestsgump View Post
Oh... I think wld just insert the 15uH inductor:
"Input power line" refers to the +Vin from the DC socket, and "5V DC-DC" refers to the 5V regulator +Vin, am i correct?
Actually, the larger the inductor the better, I put a 15uH one there only because I had one at hand. But make sure your inductor can withstand current of 3A or more, just to be on the safe side. "Input power line" here is the wide lane immediately after the diode at the DC socket and "5V DC-DC" can be seen on the photo as a 6-pin SMD chip marked "IV7GK". See attached some schematic from Aliexpress showing its typical application.
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