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FDA: Alientek D8
FDA: Alientek D8
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Old 20th November 2016, 11:25 PM   #1
jean-paul is offline jean-paul  Netherlands
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Default FDA: Alientek D8

Does anyone of you have one ? How is it in sound quality ?
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Old 21st November 2016, 07:03 PM   #2
Dofus is offline Dofus  Sweden
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Im interessted in one aswell, no real info.. some italian sites discuss it but my italian sucks and and google translate doesnt make it any more clear Seems simlar to Q5 Pro / D802
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Old 22nd August 2017, 06:44 PM   #3
audeo is offline audeo
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Default Alientek D8 inside

I've opened my Alientek D8 and discovered (rather unsurprisingly) that it has much less discrete parts than recommended by the STA326 datasheet. In the attached picture those omitted are colored red, those present are green, and in blue I colored some changes in the schematic which I noticed. I did not check SMD capacitors, hence their actual values are unknown to me.

Guys, do you think it's worth trying to restore the scheme to the version intended by ST? Will it improve sound quality and maybe at least lower that horrible hissing noise which is audible a meter away from speakers?

Also, I noticed a little issue with XMOS USB connection. After a dozen seconds of silence the XMOS driver drops USB connection and it takes the driver about half a second to establish it again, which results in a corresponding pause between e.g. some Windows event and its sound. This does not affect any prolonged sounds (like music or games), but it is still pretty annoying. Is there a way around it?
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File Type: png STA326 in Alientek D8.png (165.2 KB, 766 views)
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Old 23rd August 2017, 12:58 AM   #4
Eva is offline Eva  Spain
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This is a low budget solution chip, for teenagers parties or similar, it is function rich, but in the sense of including a digital limiter for protecting boomboxes and budget 2.1 systems from overload, keeping decent sound when loud. It also allows some trade-offs in speaker driver selection with DSP and some biquads per channel.

The datasheet shows 0.1% THD for non-bridged operation, and not better than 0.03% for BTL. High noise was probably allowed in design process. 100dB SNR is stated, but there is no noise floor plot, there could be a rising noise characteristic towards 20khz. Datasheet says something about 3-level modulation, this surely involves a trade-off for increased noise.

The thing they call DDX is also another trade-off for noise, going to analog with a CODEC, and then amplification, achieves 112dB SNR easily without noise increase at HF, so the thing called DDX is involution rather than evolution, for cost reduction.

There is a third factor, there could be HF peaking due to no post-filter feedback, and this could be solved by looking at output with oscilloscope while connected to speakers, feeding 10~20khz from a signal generator, low amplitude, and tuning a series RC in parallel to speaker to flatten the HF portion of the impedance, where success is observed as no peaking when sweeping from 10khz to 20khz.

There could be a fourth factor: Self interference, but being a chip from ST, the self interference limiting factors are probably inside the chip and not in this PCB implementation.

The parts omitted have to do with optional EMI filtering on outputs, but this is far more related to disturbing other equipment than to self disturbance.
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Old 23rd August 2017, 08:15 AM   #5
audeo is offline audeo
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Quote:
Originally Posted by Eva View Post
Datasheet says something about 3-level modulation, this surely involves a trade-off for increased noise.

The thing they call DDX is also another trade-off for noise, going to analog with a CODEC, and then amplification, achieves 112dB SNR easily without noise increase at HF, so the thing called DDX is involution rather than evolution, for cost reduction.
Actually, here and here is what manufacturers say about this "Direct Digital Amplification" a.k.a. "DDX" - it is just a peculiar version of PWM involving 3 states of the output signal (fully positive, fully negative and fully grounded or "damped") instead of two.
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Old 23rd August 2017, 08:50 AM   #6
Eva is offline Eva  Spain
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Lests call it "increased THD, increased noise floor, and no damping factor, for saving DAC and some more silicon" for boomboxes. Because consumer electronics is no longer hi-fi, and that kind of equipment usually mounts tiny lo-fi speakers into loose plastic frame/case used as acoustic enclosure.

At least CRT TVs used bigger speakers and bigger acoustic enclosure, resulting in better LF reproduction. Now even expensive flat screen builtin speakers are setting the standard for bad thin sound, and this produces a thin-brain syndrome too, for the ones using that "equipment" to calibrate their senses... Chinese takeover hahaha
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Old 28th August 2017, 08:26 AM   #7
globulegl is offline globulegl  France
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Originally Posted by Dofus View Post
Im interessted in one aswell, no real info.. some italian sites discuss it but my italian sucks and and google translate doesnt make it any more clear Seems simlar to Q5 Pro / D802
yes the snubber filter on tp1 it s a very good idea. i tested on v200 and on d310. the sound is very much much better.

Click the image to open in full size.
snubber filter
Click the image to open in full size.
v200 tightlight without snubber. with snubber is much better.

v200 tight light tutorial :

<<Amplificateurs FDA, episode II - Page 18>> - 30079872 - sur le forum <<Amplificateurs Integres>> - 1030 - du site Homecinema-fr.com

the best resultat : d310 tweak + snubber :

<<FDA D.Sound d310 - Page 106>> - 30064559 - sur le forum <<Amplificateurs Integres>> - 1030 - du site Homecinema-fr.com
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Last edited by globulegl; 28th August 2017 at 08:28 AM.
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Old 29th August 2017, 01:36 AM   #8
audeo is offline audeo
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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.
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Old 8th October 2017, 10:20 PM   #9
audeo is offline audeo
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I found a way to eliminate the initial lag when using Alientek D8 with XMOS connected via USB: just add a Windows registry key "DeviceStreamingMode" of the type "DWORD" at "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\U SB\VID_20B1&PID_302E\0000\Device Parameters\Settings" and put "2" there. With this key set to 2 a USB connection to the XMOS chip is never dropped hence no more lag.
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Old 5th November 2017, 09:47 AM   #10
the hound of sound is offline the hound of sound
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FDA: Alientek D8
hello folks.
I attempted to link DIYINHK's 8ch multichannel board to the D8 via i2s but it didn't work.
inside the D8 is an XMOS based daughter board taking in the USB signal. I removed this to expose the pins and conveniently found labels for i2s on the underside of the board.
It's been suggested (by DimDim) that the master clocks of the DIYINHK and daughter board
could be different, which may very well be the case because the daughter board is an older generation XMOS.
The DIYINHK clocks are spec'ed at 22.5792Mhz and 24.576Mhz which is 8x the BCLK/SCLK.
I don't have an oscilloscope to check the daughter board MCLK line so I want to
ask for someone here to measure their D8 )
just as with the DIYINHK board the daughter board's MCLK is likely to be an output (to the rest of the D8).
Looking at the unit from the display side (front), the top of the MCLK pin is in the row to the right hand side of the daughter board, 3rd away.

If the clocks are a fraction of the DIYINHK numbers, is it safe to say the D8 simply cannot be driven at those higher rates?

thanks all...
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