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my DAC design - pup1 DAC
Mar 25, 2011 at 12:27 PM Post #78 of 675
The quality of this DAC amply justifies RCA jacks.  However, let me emphasize that the 3.5mm jack spec'd on the proto is very robust.  It doesn't feel at all that the spring contacts are going to loosen anytime soon.
 
Mar 25, 2011 at 8:02 PM Post #79 of 675
Whoops, forgot to check up on this thread and didn't get a PM about it. Oh well, maybe it's for the best - I don't expect much free time to test anyway...
 
Mar 25, 2011 at 9:15 PM Post #80 of 675
Well here's hoping!!!
 
Just finished my Crack with Speedball... Very sweet sounding, revealing as heck too.
 
Mar 28, 2011 at 9:42 PM Post #83 of 675
It your pictures you show the same caps for C18, C31, C33. but on the BOM its:
CAP_ELECTROLIT, 330µF
 
SHould I install the 330 ufs or the 47. ALso, so far its not working, and test point 3.3 i get 0.2v and it seems that reg is getting hot. I've went over and over with magnifying glass and dont see any shorts, Idea?
 
Mar 28, 2011 at 9:53 PM Post #84 of 675


 
Quote:
forsakenrider said:
It your pictures you show the same caps for C18, C31, C33. but on the BOM its:
CAP_ELECTROLIT, 330µF
 
SHould I install the 330 ufs or the 47. ALso, so far its not working, and test point 3.3 i get 0.2v and it seems that reg is getting hot. I've went over and over with magnifying glass and dont see any shorts, Idea?
Click to expand...


Only C31 and C33 have been changed to 330uf (in cobaltmute's latest BOM).  C18 is still the 47uf.  Keep in mind that the 47uf series is an organic polymer cap, whereas the 330uf are standard electrolytics.  Physically, they are the same size - more or less (the electrolytics are 0.7 mm taller).
 
Do you have a good pic?  There maybe something else on the rest of the PCB that could be causing the issue.  It never hurts to have an extra pair of eyes.
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Also, it sounds like you may be in progress with the build.  I'm not sure it's a good idea to plug it in and start measuring readings if the PCB is not totally complete.  Techniques used in building amps may not apply with DACs.  Just a thought ...
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Mar 28, 2011 at 10:13 PM Post #86 of 675
one booboo I made was, I plugged it in without the Xtal at first, that was the only part missing, I then installed that and it didnt "boobeedupe" like it does when windows finds a new hardware so I checked and the first voltage was wrong
 
 
Mar 28, 2011 at 10:28 PM Post #87 of 675
Actually, it looks pretty good from here and truthfully, I'm not sure that having the crystal not installed would cause any lasting ill effects.  The DAC chips and opamp look pretty good in those pics.  You did a good job on the slightly-rotated regulator, too.  Just a check - but you did install C1 and L1 on the back side, right?
 
Mar 28, 2011 at 10:37 PM Post #88 of 675
C1 and L1 are installed. I re-flowed all the ICs and now Im getting 0.02v  on 3.3.... argh!! I remember when I was building my alien dac I had the same issue and something just needed a re-flow.  Any ideas?
 
 
 
 
 
Mar 28, 2011 at 10:42 PM Post #89 of 675
What's the voltage at 1A?  If it's good, then you have something shorted on the regulated side of the 3.3V regulator.
 
As for the caps, I use the 330uF ones in my personal build after switching away from the 47uF polymers.  Seemed to add more bass.
 
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