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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 3rd February 2018, 07:09 AM   #21
audeo is offline audeo
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If you compare the STA326 datasheet with the datasheet of its original design by Apogee you may notice that the output filter was supposed to use different inductors for different speaker impedances. It appears that D8 uses a castrated version of the filter intended for 8 Ohm speakers. I can only hope that ST Microelectronics did their homework when calculating their own version of the filter as seen in their datasheet, since it is different from the one given by Apogee and does not mention various options for various speaker impedances.
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Old 5th February 2018, 11:00 PM   #22
forestsgump is offline forestsgump
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D8 uses STA328 (datasheet dint offer additional inductors values, although specs-table indicate support 4~8ohm speakers impedances), while STA328 application design reference 8ohm speakers
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Old 6th February 2018, 05:05 AM   #23
audeo is offline audeo
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Quote:
Originally Posted by forestsgump View Post
D8 uses STA328 (datasheet dint offer additional inductors values, although specs-table indicate support 4~8ohm speakers impedances), while STA328 application design reference 8ohm speakers
I don't see much difference between them in those datasheets. Are you sure your amp uses STA328? Some French guys disassembled theirs and showed STA326 inside.

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Old 6th February 2018, 04:12 PM   #24
forestsgump is offline forestsgump
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As mention, though STA328/STA326 datasheet specs 4~8ohm, but test application (pg 7) dint offer any inductors options. However Apogee test application has inductor options for 4/8ohms.

Alientek D8 specs pages shows using STA328. I would not want to dismantle , otherwise results STA heatsink's screws markings showing tampering.
(until i can test use device is functional without hardware defects)
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Old 8th February 2018, 01:01 AM   #25
gilster is offline gilster
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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.
Can you please make a picture? I'm new here and not skilled
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Old 8th February 2018, 03:27 AM   #26
forestsgump is offline forestsgump
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Audeo, if you happen to have on-hand your D8 mod picture of snubber, other missing from Apogee part circuitry, possible to share...i know that likely looks very messy ~~ wld be useful as reference in tracing D8 schematic. anyway - pls dont feel oblige
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Old 9th February 2018, 04:02 PM   #27
guentir is offline guentir
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Default Different D8 Versions

Hi,

there exists different Versions of the Alientek D8:

Click the image to open in full size.
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Old 9th February 2018, 04:02 PM   #28
audeo is offline audeo
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Quote:
Originally Posted by forestsgump View Post
Audeo, if you happen to have on-hand your D8 mod picture of snubber, other missing from Apogee part circuitry, possible to share...i know that likely looks very messy ~~ wld be useful as reference in tracing D8 schematic. anyway - pls dont feel oblige
This won't happen anytime soon for I'll have to dismantle, disconnect and disassemble a lot of gear to make such photos. And they will not help much anyway, because my adding stuff to the board made tracing anything on it even harder.
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Old 9th February 2018, 04:10 PM   #29
audeo is offline audeo
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Default Alientek D8 firmware

Alientek D8's firmware is not total crap, but it has a nasty habit of unpredictably muting and unmuting the speakers for no apparent reason. I originally thought that maybe some broken signal triggers STA326's auto-muting feature, but it surely does not have anything resembling auto-unmute. Which leads to a simple conclusion that it is the host controller and its firmware that is at play here.

If anyone can get its source code, please publish it. I think it can be dug out somewhere near this Chinese forum, but I lack enthusiasm and language skills to dig there.
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Old 9th February 2018, 06:44 PM   #30
audeo is offline audeo
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Quote:
Originally Posted by guentir View Post
Hi,

there exists different Versions of the Alientek D8:

Click the image to open in full size.
Mine says "Panel-V1.6" and "OLED-1.3" on its front panel PCB. I don't see any version number on the main board. Are these firmware folders? Can you get whatever is inside?
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