Built a Chinese dac... Distortion and power issues..?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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.
 
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
 
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!
 
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!
 
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?).
 
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?
 
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...
 
Yanked the DAC out and powered it up in the bench. And immediately smoked this....
20171205_091821.jpg
 
Something bad going on with the 317's or blocking diodes or caps...
Did some solder reflow in and regulator closest to the edge got hot, other 2 cold....
Did some more soldering...
317 in the middle gets VERY hot, other 2 warm....
Maybe now the resistors are pooched as well.
Was able to measure 1.2V on all three on legs 1 and 2, and roughly 5V on legs 2 and 3.
317 closest to edge was 12v then 8v on legs 2 and 3....

I think I probably now have $150 worth if junk....
:( 20171205_095634.jpg
 
Maybe try and put together a lightbulb tester for your efforts.
A small wattage bulb, maybe 15w, in series with the hot leg of your ac will give you a visual as to what the load is on your power supply. It will light up bright at first, then dim down after the caps suck up power. If it stays bright, then you have a problem and can pull the plug hopefully before any meltdown.
You can test a known component with a similar power consumption first so you can get an idea of what to expect.
 
Maybe try and put together a lightbulb tester for your efforts.
A small wattage bulb, maybe 15w, in series with the hot leg of your ac will give you a visual as to what the load is on your power supply. It will light up bright at first, then dim down after the caps suck up power. If it stays bright, then you have a problem and can pull the plug hopefully before any meltdown.
You can test a known component with a similar power consumption first so you can get an idea of what to expect.
Thanks... Damage may already be too much....
I'm thinking it might be better to build my own 5V regulator/ rectifier and tap into the board...
I don't understand why the board uses two separate 9VAC inputs on the one side? One a 3VDC and one a 5VDC?

Or maybe cut my losses and buy a built board and mess with small upgrades.
:(
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.