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my DAC design - pup1 DAC - Page 29

post #421 of 656
7/15/12 at 9:04am
It lives! plugged in and powered up - made music right away. Very very nice! I just brought up a BIII build yesterday and have been listening to that. While PupDAC certainly isn't at that level (BIII, PH Regs throughout, eXD PCM/DSD board), it's amazing how well it does next to it. Great detail, dynamics and tone. This is a personal first for me too. It's my best (in laying down components and success) smd build so far. Thanks cobolmute/tomb for making this possible for me.
Quote:
Originally Posted by Mullet View Post

No I actually meant opa2365, which is the I/V opamp in the Gamma2. I had an extra that I temporarily used when I was having initial trouble. I've used two different opa2865s before the 2365. Both produced the same puttering noise. The 2365 didn't. Then I just got the LMH6643, which appears to be working fine. I'll eventually try swapping it back out for the opa2835. I have at least one virgin lying around. wink.gif I do like the sound of the LMH6643 definitely better than the 2365. The 2365 seemed to have more glaring uppermids. The 6643 is definitely smoother. Let's hope the next 2835 works out.

Good luck Misterrogers! Next up to bat is "The Wire"!
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post #422 of 656
7/15/12 at 9:19am

Yay!!! biggrin.gif

 

Bringing it up in the same sentence as a Buffalo III is very high praise, indeed.  If you figure in the cost differences, it's even more outstanding.


Edited by tomb - 7/15/12 at 9:21am
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post #423 of 656
7/15/12 at 9:31am
Absolutely! Cost/Performance ratio is off the charts for this little guy. In listening, it achieves something often not found with small bus powered DACs; notes have body and weight. Regarding the build, I found it very straight forward, with no out of the norm steps needed. It is tight and I was dreading having to reflow some of the larger chips due to the higher elevation components around them - but the DIY gods were gracious this time. I'm sure that means my next project will be a 'custer' of highest order. Hmmm, better do a throwaway before the wire :-)
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post #424 of 656
7/15/12 at 12:17pm

Man, oh man, with every new review I get more and more excited!

 

I mentioned a few pages back about the $25 Linux boxes about the size of a CMoy, someone is working to use one as a squeezebox player:

http://www.head-fi.org/t/616427/raspberry-pi-diy

 

Add in a Pupdac and you'd have one heck of a music player.

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post #425 of 656
7/15/12 at 1:56pm

I'd say if you had a 6"x6" case you could fit everything in it. If you needed a smaller enclosure, I'd say the GrubDAC is a better bet as it's 1/3 the size of the Pup.

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post #426 of 656
7/17/12 at 10:37am
Thread Starter 
Any of the recent pupDAC builders have any suggestions for board changes that I may want to look at?

I know tomb has asked that the pads for the two PCM chips be made a little larger and I have done that.
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post #427 of 656
7/17/12 at 11:00am
Honestly, the only change I can think of may not be feasible; and that would be to keep the PCM chips away from the taller caps. Just to make it easier to reflow if necessary. Not a huge sea - given the all other tradeoffs, it's pretty spot on and reasonably easy to build.
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post #428 of 656
7/17/12 at 11:10am

I agree with both Tom and MrR -- more space for traces and possibly those caps. The ladder is probably going to be too difficult though. Other than that the right and left channels are reversed. The right output is on the left side and the left output is on the right side. To fix this would require a complete redesign so it looks like it is the way it is.

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post #429 of 656
7/17/12 at 11:27am
Thread Starter 
Ideally the caps should be close to the part that they are working with. So not a lot of options there.

As for the side of the output, I take them straight off the chip to the the edge of the board. I could flip the RCA outputs around, but then the traces get long.
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post #430 of 656
7/17/12 at 1:39pm
Exactly. So considering those design realities, I think you've pretty much nailed it. Can't tell you how much I'm enjoying my PupDAC!
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post #431 of 656
7/17/12 at 3:15pm
Quote:
Originally Posted by cobaltmute View Post

Ideally the caps should be close to the part that they are working with. So not a lot of options there.
As for the side of the output, I take them straight off the chip to the the edge of the board. I could flip the RCA outputs around, but then the traces get long.

 

Sounds good. I agree with MrR, this DAC sounds great. Definitely a few steps above the Grub, which is also an awesome DAC for its footprint.
 

Don't bother swapping the RCAs if it's going to hinder the quality of the DAC.

 

Can't wait for my FPE panels order!

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post #432 of 656
7/17/12 at 4:23pm

Suggestion:

 

Drive the LED off pin 11 on PMC2706/7.

The LED will only light when there is communication with the computer.

This will serve as a diagnostic as well as a power light...

 

I did that on my USB DAC.

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post #433 of 656
7/17/12 at 6:16pm

I agree with everyone else, too - sounds like some great ideas!  It seems we're just talking a few tweaks, too - nothing very significant.  I think cobaltmute mentioned offline that he would just go without the 3.5mm output option.  I think that makes sense, too.  A DAC this good should really just be used with RCA's, anyway.

 

What sort of worries me is supporting builds in the future from the inevitable newbies.  I'm going to try to super-detail the construction sequences, maybe suggest what Misterrogers and I did - save the building for several sessions, take your time, etc.  Any more suggestions for special strategies in building/troubleshooting would be most welcome.

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post #434 of 656
7/17/12 at 7:34pm

Here's a few that come to mind (In addition to, and along the lines of taking your time):

* Do the PCM's and smaller multi-pin parts first (understood) but resist the urge to move on to the next point until you've visually inspected each pin, looked for bridges and have reflowed to insure a good joint. 'Going back' incurs a real penalty with small SMD builds.

* Order a couple extra of the small 'chicken feed' caps/resistors. You're likely to loose some as you adapt to the task at hand. At the minimal cost, it isn't wise not to.

* I've found that the technique of liberal flux, tinning one pad, positioning the component, flowing the solder, adjusting then soldering to be very effective. For the PCM's and package parts, a makeshift 'holder' of a coax crop, a bic pen without the ink tip and a rubber band does a great job of holding the part in place while I tack it down. With the right gear (fine tip, right solder, good magnifying glass, etc.) I'm starting to prefer SMD to through-hole.

 

I have more, but they're mostly 'good practice' stuff that I'm just now developing as habit. I'll leave that level of instruction to old hands like you Tom :-)

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post #435 of 656
7/18/12 at 4:40am
Thread Starter 
Quote:
Originally Posted by Avro_Arrow View Post

Suggestion:

Drive the LED off pin 11 on PMC2706/7.
The LED will only light when there is communication with the computer.
This will serve as a diagnostic as well as a power light...

I did that on my USB DAC.

If I'm reading the datasheet right, it appears that this pin only get driven high during music playing. Is that what it does on your DAC?

I like the idea, but I'd have to move stuff around as pin 11 is "trapped" right now by traces on both sides of the board.
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