FDA: Alientek D8

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.
 
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.

Amplificateur_Classe_D.jpg
 
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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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
 
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.
 
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.
 
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?

@audeo,

Sorry for confusion, this picture is from openedv.com; Protel is a PCB-Designer Software, now "Altium Designer".
So i think, there exists some D8 with STA326 & the newer D8 with STA328.

For me, the important thing is to modify the output filter, because my loudspeakers are 4 ohms and the filter is designed for 8 ohm speakers (refered to DDX-2051, 8 Ohm - 22uH 470pF).
Ampli_ADC.jpg


I think, the Noise-Problem is related to the Auto-Mute/Auto-Power-Off.
If the D8 wakes up from Powersave, then there´s a hearable noise. Pressing one-time "Source" on the Remote, the hiss is gone.
Other Solution is to deactivate Auto-Mute/Auto-Poweroff.
 
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Can you help confirm if hiss/noise is hear on all inputs (Digital, Analog)?

my D8 noise-floor is found only at aux, but hiss could be hear for gain +1, ard 1 meter on my 6 ohms 86dB. (at gain +0 the speaker is cut-off) However it is quiet on toslink digital-inputs; guess D8's ADC path was affect by smps V-reg noise?
 
Can you help confirm if hiss/noise is hear on all inputs (Digital, Analog)?

Can confirm, only on AUX there is a VERY low hiss/noise.
Connected to AUX is a Phono-Preamp.

MY speakers: 4 Ohms/90dB @2.83V

I have to put my ear close to the tweeter to hear the noise.
Nothing special, all good.

BUT:
If the D8 is switched to AUX and goes standby, after wakeup i hear a "relative loud" noise.
Pressing SOURCE on the remote (D8 stays on AUX) the hiss dissapear.
 
Normally STA326 shorts speakers to ground (as it does at volume=0) when its input contains only zeroes, which it does for all digital inputs unless you feed something non-zero there, like some very quiet music.

I am not sure guentir does mean hiss for D8's Aux or hiss at Digital input?

my case is D8's source to Aux has hiss imply 2 possibility:

1- Noise from SMPS (which that is why audeo's mod add inductor to +Vin SMPS)
2- D8 Aux ADC -- AK5358 analog inputs are single-ended.

But since hiss did not get louder when increasing gain, then it would seems 2nd possibility is not likely.

Also guentir suggest deactivate Auto-Mute/Auto-Poweroff solves the hiss problem -- audeo can you confirm? noise would still exists for Aux if it is from D8's SMPS
 
Also guentir suggest deactivate Auto-Mute/Auto-Poweroff solves the hiss problem -- audeo can you confirm? noise would still exists for Aux if it is from D8's SMPS
I don't know a way to turn off auto-muting function without altering the firmware, hence in my case it is always on. And this function masks hiss by shorting the speakers to ground when the amp input is set to a digital source without signal.
 
I don't know a way to turn off auto-muting function without altering the firmware, hence in my case it is always on.

on Page 23 - Alientek D8 English user manual allows you to turn-on/off the auto-muting function; but currently does not think noise is caused by auto-muting function.

And this function masks hiss by shorting the speakers to ground when the amp input is set to a digital source without signal.

Just tried again, found something interesting:
Without connecting any audio inputs to the D8 & using remote control, switching input channels: Found most of the time Digital inputs masks hiss (even gain at least +01), HOWEVER ton some rare occasions hiss are also heard on Digital inputs as well (Optical/Coax/USB gain at least at +01 - when use remote to cycle a few rounds on input channels), so mask hiss on digital does not 100% always works. On such situation: the Hiss on Aux Analog seems abit more obvious than Digital inputs

...BUT: If the D8 is switched to AUX and goes standby, after wakeup i hear a "relative loud" noise.
Pressing SOURCE on the remote (D8 stays on AUX) the hiss dissapear.
Tried what you did: Aux on D8, hiss... it goes to standby, then Aux audio input wake-up with hiss return, then pressing SOURCE on remote --- HISS still remain there (not gain +00, but gain at least +01).

So after these round cross checking guetir & audeo trying out as well:-
Personal conclusion: Hiss does not originate from Aux path alone (ie. not from D8's Aux ADC AK5358's analog single-ended inputs). This means hiss originate as overall situation on D8's circuits - which has to do with what audeo think could be cause by DC mains supply.
 
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Regarding Digital Direct path (DDX) and Bypass Equalizer (EQ), what to set on Equalizer settings?

on D8 amplifier control menu, pg 18,19,21 of D8 English manual, and the quick toggle on Remote Control "Normal" button (pg 7).

I am confused which D8 EQ menu seeting ("Tone", "Normal", or "Flat"), bypasses EQ & allows DDX path? Also what about the Remote Control "Normal" button - it toggles between Tone & EQ menu pre-selected mode.

Personal conclusion is: only "Tone" bypasses EQ allows DDX path.
 
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A minor correction: this "DDX" thing is related only to the output PWM and has nothing to do with any processing or lack of it before output. So, yes, "Tone" is the only setting in D8 which bypasses the internal DSP, but "DDX" can be switched on or off in firmware regardless of the DSP settings. I suppose, in D8 it is always on.