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Built a Chinese dac... Distortion and power issues..?
Built a Chinese dac... Distortion and power issues..?
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Old 25th November 2017, 08:51 PM   #1
Wungun is offline Wungun  Canada
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Default Built a Chinese dac... Distortion and power issues..?

Bought a EBay Chinese kit DAC that uses ES Pro processor... And using my kit built PSU...
Soldered in my Burson discrete opamps, and upgraded the single/mono opamps.
Weird issue is I need to flex the pcb to get it to work! So I'm thinking a power issue/circuit trace to the chip, as a signal issue would reveal itself as a channel problem maybe...
Supply seems solid from the input side...

Also, playing music, there is audible distortion in the audio stream. Sounds like it would sound if I removed half the power to the opamps... Only not as bad...? Or line in was too hot..?

I'm seeing full power from my PSU to the Burson's pin 4/8 but on the single opamps, it seems short by a few volts... I don't know if that's by design or an anomaly.

And suggestions appreciated....

Also, reflowed as best I could, solder to some of the SMD components... No improvement.
20171120_202053.jpg

20171121_211915.jpg
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Old 25th November 2017, 09:22 PM   #2
rayma is online now rayma  United States
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Quote:
Originally Posted by Wungun View Post
I need to flex the pcb to get it to work! So I'm thinking a power issue/circuit trace to the chip
This is likely a bad via or solder joint, it could be the pcb itself. If both channels are bad,
it's probably power supply related. Doing SMD by hand can make bad joints that look good.
Maybe a heat sink is shorting to a trace underneath it. Measure each supply while flexing the pcb.
A schematic would help, is it this one?
ES9028 ES9028PRO /ES9018 ES9018S Q8 HiFi Audio DAC Decoder DIY KIT | eBay

Last edited by rayma; 25th November 2017 at 09:36 PM.
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Old 25th November 2017, 10:25 PM   #3
Wungun is offline Wungun  Canada
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Yes, that's the unit I put together...
Thanks for the reply.

A "via" joint?

I hope it isn't one of the lines to the processor... I don't think I have the skill to reflow that solder!
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Old 25th November 2017, 10:28 PM   #4
rayma is online now rayma  United States
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Quote:
Originally Posted by Wungun View Post
A "via" joint?
A via is a built-in connection between layers, which looks like a smaller pad, and is usually
covered by solder mask. Try pressing around with an insulated tool, or a pencil eraser,
while listening or measuring the voltages.

Last edited by rayma; 25th November 2017 at 10:36 PM.
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Old 25th November 2017, 10:34 PM   #5
nezbleu is offline nezbleu  Canada
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Built a Chinese dac... Distortion and power issues..?
Did you test it before the "upgrades", or did you build it only with the changes? If flexing the board makes a difference, then there is a physical problem.
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Old 25th November 2017, 11:03 PM   #6
Wungun is offline Wungun  Canada
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Quote:
Originally Posted by nezbleu View Post
Did you test it before the "upgrades", or did you build it only with the changes? If flexing the board makes a difference, then there is a physical problem.
I had the Burson's on there from the get go...
Same with my PSU.
The mono opamps came later, but none of these are likely the culprit, AFAIK.
Physical issue for sure, and likely power related.

About the distortion on the output, maybe power related too. I think I should see the same voltage at the single opamps and I do with the duals...?
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Old 25th November 2017, 11:10 PM   #7
rayma is online now rayma  United States
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Quote:
Originally Posted by Wungun View Post
About the distortion on the output, maybe power related too. I think I should see
the same voltage at the single opamps and I do with the duals...?
It appears that all the op amps run off a pair of discrete shunt regulators.
The pcb schematic is the very last photo of the group under the main photo
on the ebay product page.
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Old 25th November 2017, 11:13 PM   #8
Wungun is offline Wungun  Canada
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Except that they don't on my board... I connected my PSU to the pair of caps closest to the opamps. 20171125_191248.jpg
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Old 25th November 2017, 11:34 PM   #9
Wungun is offline Wungun  Canada
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I'll give the schematic a good looking over this week...
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Old 26th November 2017, 12:43 AM   #10
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by Wungun View Post
Weird issue is I need to flex the pcb to get it to work! So I'm thinking a power issue/circuit trace to the chip, as a signal issue would reveal itself as a channel problem maybe...
Supply seems solid from the input side...
I had exactly same issue with a new build IGBT audio amp.
I hadn't soldered a joint and it was just touching the via. If I flexed the pcb it crackled in the speaker.
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