[islubio]

I m use windows 7.
It happens on both my netbook and my gf's desktop. Both windows 7.(distort at start)
It seems that every time where there's when there's a pause or stop in output to the dac. Distortion will come on when sound/music resumes
Over at my gf place the grub gets knock offline pretty often i got a feeling it's cause of her powerline or her old receiver.
the grub only gets knock offline when i turn on or off a power socket that is in parallel to the socket that is powering my adapter for my netbook.

 

[Fishline]

I've finished all the soldering, but ran into some problem.  I'd very much appreciate help!
 
At first I can get the PC (WinXP Pro) to recognize the DAC, but no sound came out.  I did get 3.3v at the test point.  I tried re-flowing some solder joints, and now the PC doesn't even recognize the DAC.  I don't get any voltage at the test point, either.  All I get is the LED.
 

 

[tomb]

The solder looks a little thick on those IC's.  I suspect that you may have several bridges.  It sort of explains why you can get some of it to work, then not.  Keep re-flowing - without solder - and try to reduce that solder  build-up on the pins.  Refer to this description and the pics for a review of the technique needed on the pins with your soldering iron:
 
http://www.diyforums.org/GrubDAC/GrubDACsolder.php
 
P.S. That low-pass filter does nothing without the capacitors on the output.  Just having the resistors there will most likely really degrade the sound.  Also - please use the second ground lead, if you can.  It will make it more reliably quiet. 

 

[cobaltmute]

Quote:

P.S. That low-pass filter does nothing without the capacitors on the output.  Just having the resistors there will most likely really degrade the sound.  Also - please use the second ground lead, if you can.  It will make it more reliably quiet. 

The low pass filter caps are the ones on the bottom

 

[akgfan]

Quote:

Also - please use the second ground lead, if you can.  It will make it more reliably quiet. 

Could you please explain why? I don't have very good results in RMAA in stereo crosstalk which I find weird.

 

[tomb]

 
Quote:

The low pass filter caps are the ones on the bottom

Oops - sorry I missed that!
 
 
Quote:

Could you please explain why? I don't have very good results in RMAA in stereo crosstalk which I find weird.

 
Maybe it's because you don't have a sufficient ground connection?  OK, so I blew it on seeing the SMD caps on the bottom of your PCB.  Still, IMHO you're asking for trouble just using one ground wire.  Any "dodgy" connection whatsoever in that single ground wire and your whole output quality goes putz.

 

[Spacehead]

I have problems with my latest GrubDAC. It gets recognized sometimes, but mostly it is an unknown device. I lifted one or two pads in the pin 31 and scratched to the first layer in 25 and 26.  I just wonder, that when those are only ground connections, do I have other problems in there or should I just make sure the ground connections are good? If I need a jumper wire, where should I connect 25 , 26 and 31 ?
In my opinion the other components are properly soldered, but I guess I could try reflowing them all. I just hope that the PCM2706 has not burned.
 
P.S. I lost one PCM2706 somewhere. Such a large IC...

 

[Ikarios]

Quote:

The low pass filter caps are the ones on the bottom

On a somewhat-related note, what is the difference between using the MKP box caps in those positions vs. SMD? I had SMD caps in the GrubDAC that was in the SSMH I used for quite some time because they were 5 cents cheaper, and easier for me to solder/more convenient to clean. I have regular box caps in the one I'm currently building. I suppose the box caps will sound better but how big is the difference?
 

 

[akgfan]

 
Quote:

Still, IMHO you're asking for trouble just using one ground wire.  Any "dodgy" connection whatsoever in that single ground wire and your whole output quality goes putz.

This was my first test:

 
Now I use the same in this box:

 
But results in RMAA are still the same:

 
However, sound quality is much better than soundcard.
 

 

[Spacehead]

akgfan , don't worry about it. GrubDAC tests abnormally low on RMAA for some reason. Maybe it starts to oscillate or something. And, if it outputs 2V, then it would need attentuation before going to soundcard IMO
 
Could somebody help me with my problem? The chip is possibly OK, because it first gets recognized, and then is lost, and gets unknown.
I don't usually do such bad soldering job, but now I have a lot of stress that distracts me.
 
Pics:
http://dl.dropbox.com/u/7337908/Grubdac/IMG_8263.JPG
http://dl.dropbox.com/u/7337908/Grubdac/IMG_8264.JPG
http://dl.dropbox.com/u/7337908/Grubdac/IMG_8265.JPG
 

 

[Ikarios]

Well, for one... R5 is missing. I would also try cleaning the board thoroughly with isopropyl alcohol (especially between the pins of the ICs), check with a flashlight to make sure no bridges are being made, and carefully scrape between pins to remove bits of solder and other crap that might be making a bridge.

 

[Ikarios]

Is there any harm in cleaning a completed board with acetone? I did it last time after I had soldered the sealed SMD parts but before I placed the through-hole parts and capacitors. I didn't clean my board very thoroughly this time (lack of tools and time) so I completed my board before cleaning off any flux before placing capacitors and other stuff. I know acetone is a pretty strong solvent but will these solid polymer and film caps be affected?

 

[tomb]

 
Quote:

akgfan , don't worry about it. GrubDAC tests abnormally low on RMAA for some reason. Maybe it starts to oscillate or something. And, if it outputs 2V, then it would need attentuation before going to soundcard IMO

I agree that someone should not worry about it.  I don't think it's oscillating, though.  After years of messing with RMAA, I'm convinced that it does not respond well to anything without a feedback loop.  Put a cheap amp or DAC with an opamp feedback loop on RMAA and it will test beautifully.  Put anything that sounds good (great?) without a feedback loop and it will test like cr*p.  None of that is indicative of the actual sound quality.  I think RMAA is valuable for tweaking a final design - trying new components to lower distortion, etc., or pinpointing noise in certain areas of the audio band, etc. - but that's only when comparing with before and after tests of the same device.  Using it as some sort of absolute standard of comparison among different designs is very problemmatic.
 
Quote:

 
Could somebody help me with my problem? The chip is possibly OK, because it first gets recognized, and then is lost, and gets unknown.
I don't usually do such bad soldering job, but now I have a lot of stress that distracts me.
 
Pics:
http://dl.dropbox.com/u/7337908/Grubdac/IMG_8263.JPG
http://dl.dropbox.com/u/7337908/Grubdac/IMG_8264.JPG
http://dl.dropbox.com/u/7337908/Grubdac/IMG_8265.JPG

 
Quote:

Well, for one... R5 is missing.  I would also try cleaning the board thoroughly with isopropyl alcohol (especially between the pins of the ICs), check with a flashlight to make sure no bridges are being made, and carefully scrape between pins to remove bits of solder and other crap that might be making a bridge.

R5 is only for the LED.  If he's not using an LED, then there is no need for it.  I agree with the rest of your suggestions, however.  The joints actually look cold to me - maybe turn the temperature up on the iron and try some re-flowing to clear some of those pins?

 

[cobaltmute]

Quote:

On a somewhat-related note, what is the difference between using the MKP box caps in those positions vs. SMD? I had SMD caps in the GrubDAC that was in the SSMH I used for quite some time because they were 5 cents cheaper, and easier for me to solder/more convenient to clean. I have regular box caps in the one I'm currently building. I suppose the box caps will sound better but how big is the difference?
 

In my personal builds, to my ears, in my system,  the ceramic caps sounded a bit more "bright" than the box caps.
 

 

[Beftus]

 
Quote:

Is there any harm in cleaning a completed board with acetone? I did it last time after I had soldered the sealed SMD parts but before I placed the through-hole parts and capacitors. I didn't clean my board very thoroughly this time (lack of tools and time) so I completed my board before cleaning off any flux before placing capacitors and other stuff. I know acetone is a pretty strong solvent but will these solid polymer and film caps be affected?

Steer clear of acetone. A lot of plastics don't like it. Those film caps might be affected. Stick with isopropylalcohol for flux removal.