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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 26th November 2017, 09:24 PM   #21
Mark Whitney is offline Mark Whitney  Netherlands
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It is the first thing that I would fix and it does cause the type of problem you are having.

You want the solder to flow through the hole. When this doesn't happen there is a good chance that the solder will crack or not connect to the colder surface. I like to use a high temperature and work fast so that the heat doesn't transfer to the component.
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Old 26th November 2017, 09:33 PM   #22
Wungun is offline Wungun  Canada
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Quote:
Originally Posted by Mark Whitney View Post
It is the first thing that I would fix and it does cause the type of problem you are having.

You want the solder to flow through the hole. When this doesn't happen there is a good chance that the solder will crack or not connect to the colder surface. I like to use a high temperature and work fast so that the heat doesn't transfer to the component.
Thanks Mark...
There's no doubt that any issue I'm having is due to workmanship... Be it my own or the manufacturing...
I'll start with my work!
Fingers crossed
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Old 27th November 2017, 10:06 PM   #23
reggieSf25 is offline reggieSf25  United States
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i was considering purchasing the same assembled board and was wondering if the sound quality of the China DAC was worth the risk? $200 for a $2000 sound?
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Old 27th November 2017, 10:12 PM   #24
Wungun is offline Wungun  Canada
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Originally Posted by reggieSf25 View Post
i was considering purchasing the same assembled board and was wondering if the sound quality of the China DAC was worth the risk? $200 for a $2000 sound?
I bought mine unassembled because I'm using my own PSU... Also Burson opamps on the one side. I also have a discrete crystal clock board I've yet to implement. All other components on the board are very nice quality...
My ears wouldn't be able to tell (I hope) between a $2k dac and this one... If I get it built properly!
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Old 28th November 2017, 01:10 AM   #25
Wungun is offline Wungun  Canada
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Okay... Reflowed some solder, mostly from the top side, directly to the resistors and caps, using a tiny bit of flux at each joint. And the components I couldn't reach from the top, I reheated and Reflowed from the bottom.
And.... Sweet Lord, it's fixed! Sounding very nice, and crisp in comparison.
While taking some measurements while playing some audio, I noticed the mono opamps running very hot. These were the dual 2114D JRC's I dropped in after initially running the dac. Apparently they AREN'T compatible with mono opamp layouts...?
Can't believe everything on the internet I guess.
Id still like to upgrade them, however. Maybe go full discrete with some Burson singles to match my duals...

Thank you everyone for your help! Much appreciated!
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Old 1st December 2017, 12:57 AM   #26
Wungun is offline Wungun  Canada
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I guess I spoke too soon!
So went to listen to some tunes tonight, and back to square 1...distorted left channel and almost nonexistent right channel (heavily distorted)...

Trying to think what's different from when it ran fine, and the only thing I can come up with is that the DAC has been powered up already for a few hours.
So I checked the 317 voltage regulators (which are heatsinked) and they are very, very warm...
Disconnected power and metered it... My 9v rated transformer is putting out almost 11.8VAC.

Could these regulators be thermaling? Dying? I think Ultimately, that's too much voltage they're trying to regulate...
Better solution?

I'll have to check the schematic, but I'm not sure what output the processor wants (3v or 5v?).
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Old 1st December 2017, 04:13 AM   #27
nezbleu is offline nezbleu  Canada
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Built a Chinese dac... Distortion and power issues..?
Stop guessing and measure the DC voltage drop across the 317s, and try to find a series resistor to measure the current. What about your shunt regs, are they producing the expected voltage when things stop working? Is it possible that something is oscillating? Have you considered building it per spec then modifying one thing at a time?
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Old 1st December 2017, 10:22 AM   #28
Wungun is offline Wungun  Canada
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Originally Posted by nezbleu View Post
Stop guessing and measure the DC voltage drop across the 317s, and try to find a series resistor to measure the current. What about your shunt regs, are they producing the expected voltage when things stop working? Is it possible that something is oscillating? Have you considered building it per spec then modifying one thing at a time?
Youre right, I have to stop guessing...
Just trying to find help with diagnosis.

The shunts aren't used in my setup... Separate psu for the opamp/output.
The power circuit for the rest of it uses 2 separate lines...
A single 317 and two 317's...
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Old 2nd December 2017, 02:25 AM   #29
phase is offline phase  United States
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Since you are talking about power supplies, I noticed a nice improvement from adding a 4.7uf 50v across the rails on my discrete op amps in two different DACs. I used some surplus Elna ARS I had here.
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Old 2nd December 2017, 08:26 AM   #30
Wungun is offline Wungun  Canada
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Originally Posted by phase View Post
Since you are talking about power supplies, I noticed a nice improvement from adding a 4.7uf 50v across the rails on my discrete op amps in two different DACs. I used some surplus Elna ARS I had here.
I have some 0.1uF caps on the Burson's...
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