[willco007]

Hi All,
I've just completed by build of a Pup DAC but alas, I've got a problem. I have audio but I have a pulsating noise; like a da-tha-da-tha that sort-of comes and goes.  All my voltage test points are between .1 and .2 volts off of what they should be as well.  I've checked my ICs for bridging and I *think* they are fine, but you never can tell.  Any ideas what could be causing this?
 
EDIT: Also, on my Mac when I adjust the volume it has no effect; it's always full blast.  I'm not sure if the volume buttons are supposed to effect the volume or not, but I thought I'd mention it.
 
Thanks in advance.

 

[willco007]

AND....with a bunch of solder reflowing later, presto, it works. Time to try it out with my SOHA. 

 
Cheers!
 
 
Quote:

  Hi All,
I've just completed by build of a Pup DAC but alas, I've got a problem. I have audio but I have a pulsating noise; like a da-tha-da-tha that sort-of comes and goes.  All my voltage test points are between .1 and .2 volts off of what they should be as well.  I've checked my ICs for bridging and I *think* they are fine, but you never can tell.  Any ideas what could be causing this?
 
EDIT: Also, on my Mac when I adjust the volume it has no effect; it's always full blast.  I'm not sure if the volume buttons are supposed to effect the volume or not, but I thought I'd mention it.
 
Thanks in advance.

 

[adnc]

I've just completed by build of a Pup DAC but alas, I've got a problem. I have audio but I have a pulsating noise; like a da-tha-da-tha that sort-of comes and goes.  All my voltage test points are between .1 and .2 volts off of what they should be as well.  I've checked my ICs for bridging and I *think* they are fine, but you never can tell.  Any ideas what could be causing this?  

Hi,
 
I'm facing the same Problem since the build of my pupDAC. that da-tha-da-tha comes and goes. Sometimes I think it is an issue of pcb position on the desk, but most of the time I do not know what this causes. I've double checked my solderings and measured all possible points. It works great, but if volume is down you hear that particular alternating sound.
 
If someone has any suggestions I also would be interested in any solution.

 

[Avro_Arrow]

 
Does the DAC make the same noise on different computers?

Does the DAC work fine other than the intermittent noise?

 

[willco007]

Hi Adnc,
I think my problem was a bridged pin on the DAC chip itself; specifically on the right side (the side without the orientation dot).  I would triple check they are all clear and check again.  I reflowed all the ICs several times before it started working correctly.
 
 
Quote:

 
Hi,
 
I'm facing the same Problem since the build of my pupDAC. that da-tha-da-tha comes and goes. Sometimes I think it is an issue of pcb position on the desk, but most of the time I do not know what this causes. I've double checked my solderings and measured all possible points. It works great, but if volume is down you hear that particular alternating sound.
 
If someone has any suggestions I also would be interested in any solution.

 

[willco007]

Now that I have mine up and running, could someone verify that the volume controls on a Mac have no effect; is that correct? Is it always outputting a line level volume?
 
Thanks.

 

[christsay]

correct that is how mine behaves, same as the GrubDAC's I've built and a Headroom Micro DAC.
 
-chris

 

[willco007]

Thanks for the confirmation.  My AlienDAC responds to the volume keys, thus the question. Thanks again. 
 
Quote:

  correct that is how mine behaves, same as the GrubDAC's I've built and a Headroom Micro DAC.
 
-chris

 

[adnc]

   
Does the DAC make the same noise on different computers?
 
Does the DAC work fine other than the intermittent noise?

 
Hi,
 
yes, it does make the same noise on different computers and the DAC works really fine except those noises. If I do hear music these noises are not hearable.

 

[Avro_Arrow]

 
I find that mine tends to pick up some noise from the computer.

The noise varies by computer, with my desktop being the quietest and
my Dell laptop being the noisiest. The noise is only audible on the quietest
passages or with no music playing.

 

[tomb]

Hmm ... I have not noticed this at all, neither have any of the ones I've measured shown this. It can be caused by a number of things, though. Regardless, you have something that can improve bad DAC environments quite a bit.*

 
 
* I have come to the conclusion that laptops are just not a good source for USB-powered DACs, period.

 

[Avro_Arrow]

Originally Posted by tomb /img/forum/go_quote.gif
Regardless, you have something that can improve bad DAC environments quite a bit.* 

 
 
* I have come to the conclusion that laptops are just not a good source for USB-powered DACs, period.

 

 

[adnc]

  Hmm ... I have not noticed this at all, neither have any of the ones I've measured shown this. It can be caused by a number of things, though. Regardless, you have something that can improve bad DAC environments quite a bit.*

 
 
* I have come to the conclusion that laptops are just not a good source for USB-powered DACs, period.

Hi,
 
I'm seeing this on the Raspberry Pi where I mainly use pupDAC and also on my Samsung notebook.

 

[tomb]

 

  Hmm ... I have not noticed this at all, neither have any of the ones I've measured shown this. It can be caused by a number of things, though. Regardless, you have something that can improve bad DAC environments quite a bit.*

 
 
* I have come to the conclusion that laptops are just not a good source for USB-powered DACs, period.

Hi,
 
I'm seeing this on the Raspberry Pi where I mainly use pupDAC and also on my Samsung notebook.

Everything I've read about the Raspberry Pi, unfortunately, is that it is problematic in supporting USB audio.  Again as I stated above, the PupDAC perhaps represents the maximum that one can go in USB-powered performance.  Because of that, a laptop/notebook USB connection is probably not going to be enough for a PupDAC in some scenarios.
 
We converted to all laptops with docking stations where I work and frankly, I've been totally astonished at how bad the USB power is in that kind of arrangement.  Unfortunately, even a docking station still uses more or less the same power adapter as the laptop.  A powered USB hub will help, but the power on those is pretty cr*ppy, too.
 
For some reason - I guess the enormous power available in the typical desktop power supply - a desktop PC does not seem to have these issues.
 
P.S. It should be noted that if you follow many of the threads on the ODAC, similar issues have been noted - especially dropping on and off at the drop of a hat.  NWAVGUY put a humongous ferrite bead on the USB input to compensate.  I don't agree with that strategy, but still - more evidence of the issue.

 

[lithoras]

Hey guys,
 
So I build my pupdac, and all the voltages are correct expect one. The 3.3 v at U4 is a 2.02. Now I am not sure wether the chip is damaged or some capacitor somewhere. I reflowed all the joints from J1 to the checkpoint so I think something is damaged. I just don't know what it is. Can someone pls give the correct voltages of the C13, L1, C4, C7, C5, C1 and the X1 output. 
 
 
 
P.S. the chip is recognized by windows, however the right channel does not work, I get clean audio from the left channel though.
 
 
O and it seems that my U5 is heating up like crazy, I burned my finger when I touched it, after it was on for a couple of secs.