# my DAC design - pup1 DAC



## cobaltmute

Over here, I showed off the fact that I made some nice looking coasters.

 I'd rather not do that again. So I'd like to get some comments before I send out my boards again.

 Considering that there is some many DIY DACS out there, why do another one? Well, quite simply, there was not one I could find that would meet my requirements:

 1. USB only - for power and digital source
 2. No capacitors at the output.

 At a high level, what I have in my DAC which I'm calling the pup1 is:
 USB -> PCM2707 -> I2S -> PCM1794/1798 -> IV stage

 So in some detail:

 The PCM2707 (U2) accepts the USB signal and converts it to I2S. The chip is running in self-power mode and is configured in a simliar manner to what is done in the gamma1 DAC. I had originally set it up as host powered, but the self-powered mode is a simpler configuration taking up less board space.

 The PCM1794/98 (U4) is setup as to accept the I2S. The implementation is setup as per the PCM1798 datasheet. This is slightly simpler than the 1974 implementation (saves a bit of board space).

 The IV stage is the same as the one used in the ezDAC. All kudos to Evan for his design. The only thing that I have done is change some resistor values to keep the ouput within available voltages (2V p-p). My choice of op-amps at the moment for this stage is either the LMH6643 or the THS4222. 

 Power on this board is a bit of work. USB power is filtered with a ferrite right off the cable. From their there is a 3.3v TPS (U1) regulator to provide the 3.3v sections to the PCM2707 and PCM1794 and a 4.75V TPS (U5) regulator to provide the power for the analog section of the PCM1794. In both cases the power is run through another ferrite post regulation. 

 To provide power to the I/V stage, a charge pump is used to create a negative rail. The charge pump I choose was the TPS60403 (U6) . This provides an unregulated -5V rail from the USB 5v source. Two regulators (U7, U8) are then used (one from the +5V and one from the -5V) to create +-2.5V. It is important to regulate the charge pumps output as the talk alot about the rail drooping under load. Post regulation there is again another ferrite as well as two rail capacitors to ensure that the output op-amp is feed properly.

 Given all that to create clean power, I've added a couple of "test points" to the board. In the default configuration they can be used to check the voltages of the various stages. However, if desired they can also be used to:

 a. run the output unregulated at +-5V
 b. run the entire board on a power supply other than USB.


 As a choice, I was originally going to go through hole like the gamma1. I then decided that certain components were too large, so I changed some of the larger components to 1206 SMD.

 So my PCB looks like this:

 Top:






 Bottom (showing Top silk for reference):





 I've got the schematic as a PDF file, but it is a little messy. It started as the schematic for a more complex design and then I took stuff off so it looks like a bit of a mess. I can attach is someone would like.

 The two things that concern me right now:
 1. The placement of the de-coupling capacitors (C19 and C17) around U4
 2. The fact that I don't have any resistors on the I2S lines.

 To more experienced eyes, am I in any trouble with what I am doing?

 As a final note, I like to says thanks to:
 1. Evan for his ezDAC I/V stage
 2. AMB and everyone who commented on the gamma1 project. Learned a lot just from following the development thread at Headwize
 3. MisterX for the charge pump idea. Took me a while to get to using it, but I got there eventually.


----------



## MisterX

Can't you already purchase a product based on a similar design? 
	

	
	
		
		

		
		
	


	




HIPPOhifi - The Bloat

  Quote:


 Digital music and power is provided from your pc via USB to the Bloat. The digital signal is received by a BurrBrown PCM2707 USB Receiver IC. The digital signal continues into a BurrBrown DAC (Digital to Analogue Converter) PCM1798 (or PCM1794, see upgrade options link below). After the DAC the converted analogue signal goes into the first of the 2-stage amplifiers, also know as the I/V stage. It then enters the second stage amplifer and continues out via the 3.5mm stereo jack to your headphones.


----------



## cobaltmute

Quote:


  Originally Posted by *MisterX* /img/forum/go_quote.gif 
_Can't you already purchase a product based on a similar design? 
	

	
	
		
		

		
		
	


	




HIPPOhifi - The Bloat_

 

I hadn't heard of that one until now.

 But then again I wouldn't learn anything by just buying someone else's product. This is DIY after all. I'll reinvent the wheel if it means that I learn about how the wheel was built. This is about the process as much as the outcome.

 And it's listed at $229US. That's about $287CDN right now. Excluding my screw up from my costs,its about $55CDN for the parts + $10CDN for each PCB board = $65CDN (or $54US) for the whole thing minus case.


----------



## error401

Don't know if you saw dsavitsk's HPDAC2 and 3, they're kinda similar to what you're trying to do. Might take a peek.

 What was the issue with C17,19? They seem fine to me, though I'd move them to the side of U4 to shorten the loop a little. Might take a bit of shuffling for C17, but it shouldn't be too hard. I don't see any glaring issues, but I haven't seen the schematic so...

 Why not go to mostly SMD components if you're going to go as far as you did?


----------



## MisterX

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_But then again I wouldn't learn anything by just buying someone else's product._

 

What are you hoping to learn here? 
 This is like an exact repeat of your last design check thread. 
 What did you learn there? 
	

	
	
		
		

		
		
	


	




  Quote:


 This is DIY after all. 
 

So you won't mind posting the gerbers then?
 (we can only do so much by looking at your images, especially since there is no schematic and it appears you are using something besides Eagle)

  Quote:


 Excluding my screw up from my costs,its about $55CDN for the parts + $10CDN for each PCB board = $65CDN (or $54US) for the whole thing minus case. 
 

Do you get free electric to run the computer you "designed" this on?


----------



## cobaltmute

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Don't know if you saw dsavitsk's HPDAC2 and 3, they're kinda similar to what you're trying to do. Might take a peek._

 

I've seen them. You are correct in that they are very similar. The HPDAC2, which is the closest to what I'm interested in still used the capacitors at the output.

  Quote:


 What was the issue with C17,19? They seem fine to me, though I'd move them to the side of U4 to shorten the loop a little. Might take a bit of shuffling for C17, but it shouldn't be too hard. I don't see any glaring issues, but I haven't seen the schematic so...

 Why not go to mostly SMD components if you're going to go as far as you did? 
 

Having read a couple of articles about the de-coupling, I was curious how much difference it would make if they were not placed right beside the DAC.

 As for full SMD, it really is a bit of a trade off. As I see it so far, if you have a ground plane on the bottom of the board, and you need to do a de-coupling capacitor to ground, you need to get to that plane somehow. It will either be through a via or a a through hole for a part. If you are limiting yourself to 1206 at the smallest size, for small value capacitors with small lead spacing, it would seem to be a toss-up on which is the better part to choose through-hole or SMD


----------



## cobaltmute

Quote:


  Originally Posted by *MisterX* /img/forum/go_quote.gif 
_What are you hoping to learn here? 
 This is like an exact repeat of your last design check thread. 
 What did you learn there? 
	

	
	
		
		

		
		
	


	


_

 

That either a. my approach was wrong or b. it was the wrong place to solicit an opinion as I did not get a single response.

 So I learned a lot in the reading all the datasheets, learning what everything did on the parts, the choices that needed to be made and how to layout the board. What unfortunately I didn't get was any feedback to know if what I thought was correct actually was. And as I said, that may have been due to the way I approached the community.

 And it is not an exact repeat of last time - at least this time you said something.

  Quote:


 So you won't mind posting the gerbers then?
 (we can only do so much by looking at your images, especially since there is no schematic and it appears you are using something besides Eagle) 
 

You are correct in that it is not Eagle. Using Eagle lasted about the length of trying one board.

 Gerbers attached. I'll clean up the schematics and post them sometime later today. They'll still be the same multi-page design as the first time.

  Quote:


 Do you get free electric to run the computer you "designed" this on? 
	

	
	
		
		

		
		
	


	



 

Work laptop, which usually makes it from day to day charges at work, so pretty much yes. In fact spending a number of days staying late to work on the 24" monitor as opposed to 12" laptop display.

 And yes even I would put designed in quotes. Integrated building blocks would be more like it. I still have much to learn. But then again, everyone needs to start somewhere.


 EDIT: I have removed the gerbers as they were incorrect.


----------



## error401

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_Having read a couple of articles about the de-coupling, I was curious how much difference it would make if they were not placed right beside the DAC._

 

Probably not much, but may as well do the best you can if you've got room. You want the cap as close as possible to the power pin you're decoupling, but also the loop that the path back from the corresponding ground pin to the other lead of the cap makes should be as small as possible. Right now it's gotta go around some traces and stuff.

  Quote:


 As for full SMD, it really is a bit of a trade off. As I see it so far, if you have a ground plane on the bottom of the board, and you need to do a de-coupling capacitor to ground, you need to get to that plane somehow. It will either be through a via or a a through hole for a part. If you are limiting yourself to 1206 at the smallest size, for small value capacitors with small lead spacing, it would seem to be a toss-up on which is the better part to choose through-hole or SMD 
 

Size wise you don't always save, but you can manage a more contiguous ground plane and it's less work to stuff the board. You're obviously not scared of SMD from the rest of the board design, so it seems odd to go with half through hole since it offers no real advantages other than no skill required soldering. Nothing wrong with it, it just seems weird.


----------



## cobaltmute

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Size wise you don't always save, but you can manage a more contiguous ground plane and it's less work to stuff the board. You're obviously not scared of SMD from the rest of the board design, so it seems odd to go with half through hole since it offers no real advantages other than no skill required soldering. Nothing wrong with it, it just seems weird._

 

The partial SMD and through-hole is just an evolution thing. It started as the cub1 design at Headwize. As I decided to do the charge pump, I decided to remove the ASRC. Then I got to doing the PCB layout, I decided that to save space, the ferrites should be SMD. The 1uF and the 2.2uF as well became choices for SMD as they better ones seemed to only available int 0.2" lead spacing.

 Now seeing the boards from the first run, it seems tighter in real-life than on the screen. After I build one, we'll see if I was foolish or not.


----------



## cobaltmute

As promised, schematics:

 USB Section




 DAC Section:




 I/V Section:




 And for the record, here is my Digikey BOM. All the parts are listed with their part numbers so you can see what goes where.

 Edit: Just remembered that R19 on the BOM has the wrong value - that is the resistor for the LED and 10 Ohm is quite wrong there.


----------



## digger945

I don't know if this will help, but it might spark some ideas (several different products to choose from, my first idea was a vertical adapter I saw on ebay).
 I don't know what size and/or pin count you have.


----------



## cobaltmute

Well, my boards came in yesterday and I assembled one board. Having a problem with the 3V reg and the charge pump, but I think I may know where those are. 

 Will post pictures later.


----------



## millwood

Quote:


 Having read a couple of articles about the de-coupling, I was curious how much difference it would make if they were not placed right beside the DAC. 
 

I used to have tremendous amount of trouble to power on a 8dip PIC device: one out of 10 times it would power on but others it just sit there.

 it turned out it was a lack of decoupling. I had thought, incorrectly, that it draws minimal current so decoupling wasn't needed.

 i couldn't be more wrong on that. apparently the chip needs consistent Vdd during power on or it hangs.

 so I would say decouple your dac too.


----------



## cobaltmute

Quote:


  Originally Posted by *millwood* /img/forum/go_quote.gif 
_so I would say decouple your dac too._

 

I would suggest you review the schematic and the datasheets. Everything is decoupled as TI suggests.


----------



## cobaltmute

I found the issue on the 3.3v regulator - I had a bridge on the PCM2707 that was sitting behind the pin so it was not very visible. Once I got that straightened out, the board would power up and register as a USB device and then died with Windows reporting a device malfunction. No amount of reflowing the PCM2707 seemed to fix it so I've resigned myself to replacing it.

 Now removing it was a challenge. I tried heating up all sides to get it loose, but that didn't seem to work. I tried wicking off all the solder and then doing the same, with no result. My final attempt has met with reasonable success and I only removed one pad off the board - I simple used a set of wire cutters to cut all the pins and then used my soldering iron to clean off the pads. There is one pad that is in question and it does worry me as it goes the the crystal.

 I need to re-clean the board (as I have no compressed air right now to blow the crud off after I use my flux cleaner) but here is what it looks like:





 My only other issue that I know about right now is that the charge pump (U6) is only putting out -1v as opposed to the -5V that it should be doing. Isolating it from the op-amp stage didn't make any difference for its output nor did re-flowing all the joints around it, so I'm a little puzzled by it right now.


----------



## cobaltmute

IT LIVES!!!! 
	

	
	
		
		

		
			





 Well as well as it can live considering the charge pump is only putting out -1V and the -2.5V reg is then regulating that to -0.25V. As a result to the output op-amps rails are 2.5V and -0.25V.

 Setting Foobar's volume way low, I can listen on my capactively coupled cmoy and it sounds pretty decent. No further comments on the sound until I can get the output rails straightened out and listen to it in my normal setup.

 Things learned in debugging so far:
 1. Reversing Data+ and Data- from the USB won't get you anywhere 
	

	
	
		
		

		
		
	


	



 2. If you want I2S out of the DAC, you need to tell it that.


----------



## cobaltmute

I've now determined that that the -2.5v regs that Digikey sent me are not the right part. Removing them and the charge pump gives me a perfect -5v negative rail.


----------



## cobaltmute

The last post of mine is cow-patties. Turns out that the issue was mine - I assumed that the pins on the negative regulator were the same as the positive ones which is not the case. On the negative regulator the Vin and GND pins are reversed compared to the positive regulators so the issue is on the PCB itself. 

 However, with some creative bridging and placement, I was able to place the regulator on the board and get a nice -2.5V rail. As a result, everything on the board is now working as intended.

 The result (in need of a good cleaning):





 To my ears, this board sounds very good with the LMH6643 as the output op-amp. I'm not going to try to compare to the other USB DACS (gamma1 and AlienDAC) I have since as much as I try I'm going to be biased. 
	

	
	
		
		

		
		
	


	




 Someone else will need to build one to be the judge of the outcome.

 My next build of this is going to try unregulated rails with a THS4222 as op-amp


----------



## cobaltmute

I've had a chance to slowly complete my second board now. My original intentions for this second board was to use the THS4222 as it seemed like to would be a good fit. Aside from the op-amp, the only other change from my BOM were that the C31 and C33 were replace with larger 120uF Panasonic FM caps.

 The THS4222 is a fairly high speed opamp (950v/uSec slew rate) and it turned out to be somewhat unstable on my board as laid out. While there was no audible distortion, the left channel was experiencing 80mV offest voltage while the right channel only had 1mV offset. Not feeling like fighting with it to get the opamp stable, I replaced the THS4222 with a LME49721.

 So I have two functional boards at this point in time. Proto 1 use a LMH6643 and 47uF UCC PSA caps as C31 and C33. Proto 2 uses a LME49721 and 120uF FM caps. Both boards, to my ears sound really good. Proto 1 has a bit more of an intimate sound - vocals can really sound like you are right there. Proto 2 seems to lose a bit of the intimacy for a bit more bottom end. To me they sound as good as the gamma1, but I am biased. 
	

	
	
		
		

		
		
	


	




 The biggest difference that I have qualitatively tested between the two boards is noise. On both boards, any noise is not noticeable to me at listening levels. If I stop playing music and then crank my Pimeta to the end stop, proto 1 is noisier than proto 2 by a fair margin. I would say that proto 2 is as quiet as my gamma1. I do not have any good tools to quantify this. I am however quite happy that the charge pump does not seem to make any noise into the audio spectrum.

 I'm slowly working to r3 fixing the obvious mistakes and tweaking the board based on what I'm learning and reading. That being said, if anyone wants to try building one of these, PM me. A PCB will be yours for cost + shipping. I can easily describe the three fixes that need to be done to get the board working.


----------



## Nisbeth

Looks good. If I didn't have a handful of USB-dacs already I'd definitely want one 
	

	
	
		
		

		
		
	


	




 /U.


----------



## tomb

Well, I built one over the last few days and it sounds glorious!













  Look to see more of cobaltmute's excellent DAC soon!!


----------



## Lil' Knight

Wow, looks like a nice, little DAC. Any impression between it and the Grub?


----------



## tomb

Quote: 





lil' knight said:


> Wow, looks like a nice, little DAC. Any impression between it and the Grub?


 

 Well, you know I don't like make comparisons in the DIY threads.
	

	
	
		
		

		
		
	


	




  Let's just say that it's not bigger and a bit more expensive for nothing.  Cobaltmute has designed in the same feature on the Pup that exists in the Grub: a charge pump that needs _no_ output coupling caps.  Further, the TI DAC chip is one of the best out there ~130dB SN ratio, among other things.  Almost every voltage source is regulated on the PCB.  The result, IMHO, is an outstandingly clean and detailed sounding DAC. That's really an understatement, but it's probably because I'm very excited about this and am trying not to gush over everyone.


----------



## holland

Nice build.  I take it to mean you are going to pick up distribution of this?
   
  FWIW, lift pin 2, put a switch on it for high/low selection.  It's 5V tolerant and allows selection of the digital filter rolloff on the PCM1794/PCM1798.


----------



## 00940

While I'm not a fan of the passive I/V section (in my experience, active I/V stages sound better with the pcm179*), I must admit that it makes a lot of sense for such a compact DAC.
   
  The whole implementation is very interesting and I've no trouble to imagine it sounding absolutly wonderful. Are you planning to sell boards ?


----------



## tomb

Quote: 





00940 said:


> While I'm not a fan of the passive I/V section (in my experience, active I/V stages sound better with the pcm179*), I must admit that it makes a lot of sense for such a compact DAC.
> 
> The whole implementation is very interesting and I've no trouble to imagine it sounding absolutly wonderful. Are you planning to sell boards ?


 

 Yes - kits, too, we hope.  I'll have to talk to cobaltmute, but we may be interested in a few prototype builds from volunteers.  I understand he has a few PCB's left and I know I'm building a second one.  In its present form, it's a perfect fit for the Hammond 1455C801 with no wiring required.


----------



## cobaltmute

I do have a few boards left over and it would be nice to get a couple of other opinions as I rework the board.
   
  That being said, if you're considering putting your hand up, I want to be up front:

 The board has two part layout defects.  Very easy to overcome, but want you to be aware.
 The layout around the op-amp is "marginal".  The feedback loop is too long and you may experience issues.  With the high speed, best sounding op-amp, I have seen offset issues by doing something as simple as mounting the resistors on the bottom of the board.  That can be fixed by swapping out for a slower op-amp, but it is definitely a trade-off in sound.
   
  That being said, follow the BOM, don't do anything crazy and you'll have something very nice sounding.
   
  If you can't accept those points, wait for the rework.  Either way, its worth building, in my utterly biased opinion.


----------



## tomb

#1. is a piece of cake, IMHO - not a problem.  Yes, it's not perfect, but it's a prototype.  The fixes (2 of them) are easy with only moderate SMD soldering skill.  One of them you can easily see in my pics above and requires only a through-hole-skill simple fix.  There are two resistors on the left USB side of the board that are vertical with their leads looped over a resistor crossing underneath.  The other is a small TPS-style regulator at the bottom right (toward the 3.5mm output jack).  It needs to be angled slightly in order to be offset on the pads.


----------



## Spacehead

I would like to have one board. Do I have to pay something for it?


----------



## cobaltmute

tomb will think me nuts for this as he has heard the DAC, but given that a) I don't remember what I paid for the boards, and b) the issues with the board, I will give the extras away for cost of shipping.
   
  So $5 Canadian gets you a board in an envelope mailed to your address anywhere in the world.  To ensure fairness, I'm only putting one board per envelope.  You want more than one, you pay extra.
   
  All I ask in return is that you give your opinion of the DAC here in the thread afterwords.
   
  PM me for a board.  First come, first served.  Spacehead is first on the list.
   
  And of course, it is rather silly to post this right now, as I'm packing to go away for the weekend.  So I won't be replying until Monday.


----------



## Lil' Knight

Just wondering if this can be configured to feed the Carrie like the Grub?


----------



## cobaltmute

If you look at the picture of the board, point 1A is the 5V USB taken after the ferrite and right next to it is a ground.
   
  So I suspect that yes it can.  I haven't read all the latest on the Carrie, but I know that there was some start-up issues that were happening if you didn't take the power off the bottom of one of the caps on the grubDAC, so I can't say 100% that it would work.
   
  And also the pup1 is the full length of the 1455C801 case.  You'd have to look at something like the 1455C1201


----------



## MrDavis

Exciting!  Looking forward to buying a kit when it comes out.


----------



## mugdecoffee

Does the IV opamp put out enough power to drive headphones directly do you think?  Is the power supply robust enough to handle such a load?  This would make a really cool single board solution for portable listening.


----------



## tomb

Quote: 





mugdecoffee said:


> Does the IV opamp put out enough power to drive headphones directly do you think?  Is the power supply robust enough to handle such a load?  This would make a really cool single board solution for portable listening.


 

 You'll have to wait for cobaltmute to answer that one.
   
  Meanwhile, for those of you who commit to building one of these, I can perhaps supply some of the TI chips.  Since it's for prototyping, the TI sample program should apply.  Just be aware that if I supply you with the chips, you can't eventually sell the device except for a price that will only recoup your miscellaneous parts investment (not the chips).  Those are Head-Fi rules, anyway.
   
  I'll coordinate with cobaltmute on those of you who have requested a PCB and send you what I can.  I'm pretty sure I can supply the DAC chip and perhaps some of the TPS's.  I'll take stock tomorrow and we'll see.


----------



## forsakenrider

SOunds awesome TOMB, I hope I can get in on this!


----------



## cobaltmute

As I've said, I'd deal with the PMs on Monday, but everyone that has PM'ed me will get a board.
   
  So that you can have this before you commit, this is an up to date Digikey BOM:
http://dl.dropbox.com/u/630887/bom-r1-lmh6643.xlsx
   
  I only have a BOM for Digikey for this project.  It is complete, short the Hammond 1455C801 case.


----------



## forsakenrider

Thanks cobalt! I'm looking forward to this!!


----------



## forsakenrider

It looks like two of your items are non stocked:
CMF10.0KQFCT-ND
296-15276-5-ND
   
  do you have alternate recommendations?


----------



## tomb

Quote: 





forsakenrider said:


> It looks like two of your items are non stocked:
> CMF10.0KQFCT-ND
> 296-15276-5-ND
> 
> do you have alternate recommendations?


 

  
  Hmm ... looks like they'll have the 10K resistor on 3/23.  In the meantime, this one should work: P10.0KCACT-ND
  As for the PCM2707, I think DigiKey has stopped stocking them altogether.  Let's just assume that I will provide you with those, along with the DAC chip.  I don't have the opamps, but may be able to supply a lot of the TPS chips, too.  Once cobaltmute gets me a count of the PCB's he's going to distribute, I'll get a better idea what I can supply and announce it here.


----------



## cobaltmute

Quote: 





mugdecoffee said:


> Does the IV opamp put out enough power to drive headphones directly do you think?  Is the power supply robust enough to handle such a load?  This would make a really cool single board solution for portable listening.


 


 If your tastes involve listening at quiet to moderate levels, you could likely get away with it.  Higher impedance cans would also be a better choice.
   
  The charge pump for the negative output rail only outputs 60mA and this is used for both channels.  Low impedance cans will likely draw more than this design can output.
   
  That being said, I'm listening to "Buena Vista Social Club" at -20dB in foobar with my HD650 and it sounds great.


----------



## cobaltmute

For that that have PM'ed me, work killed me today as we were short staffed and I'm behind on a lot of stuff.  I will respond to you all within the next day,  Wednesday at the latest.


----------



## holland

take your time, cobaltmute.  there's no rush.  work gets the better of all of us.


----------



## cobaltmute

As an update for the prototype team, tomb is going to send me the PCM chips to me to include with the boards when I mail them out.  I will ask for the money for shipping and the addresses of those that are getting protos when I am ready to ship. 
   
  I've been asked about op-amp rolling, and here are my thoughts on that.
   
  So far, I've attempted to use three DACs on the board

 THS4222 - extremely high speed, but was not stable at all
 LMH6643 - this is the current choice for me.  Personally, I think the board sounds so good with this, I haven't seen the need to try others
 LME49721 - this is a "slow" opamp and seems to be stable when the other start to be unstable and show offset issue.
   
  There is two choices for the rails and this can affect your choice of op-amp

 Regulated - using the BOM parts, you get +-2.5V on the rails.
 Unregulated - don't install the regulators, and jumper 1A to 1B and 2A to 2B.  You have to understand what you're dealing with though.  USB input power can be 4.75 - 5.25V.  The charge pump will invert that to equivalent negative voltage.  The issue comes that the charge pump droops as it gets more loaded.  The rail will droop up to 0.5V, so the negative rail could end up at about -4.25V.  When considering op-amps, for safety, I would consider +-4V as working, but they need to be able to handle +-5.25V.
   
  If you are looking at the regulated option, consider rail-to-rail output amps to ensure that you don't have issues.
   
  As I mentioned in the initial post for prototypers, the layout of the board, may be prone to offset issues.  My board is stable with the LMH6643, but I have built one (where I put the output resistors on the bottom side) and it had offset issues on one channel (150mV IIRC).  You will need to check your build for offset, and if it is excessive, the easy fix is to replace the LMH6643 with a LME49721.
   
  Minor offset, depending on your setup, you can live with.  If there is any stage that is AC coupled, you are good,  If you have a DC servo in your signal chain, you are also likely good depending upon its range.  If you are full DC coupled with no servo, you'll have to look at the offset and your gain and decide upon your risk tolerance.


----------



## tomb

Mine is only 20mV from USB ground to the Left channel output, and 29mV on the right.  Measuring from Left and Right output to the output Ground was only 3mV and 5mV, respectively - not an issue at all, IMHO.


----------



## cobaltmute

As promised, here is a picture of the first error portion on the proto boards. The issue here was that I had D+ and D- reversed on my inital footprint for the USB connector

  To make the board work, you need to install the resistors as shown. R1 = Red, R2 = Yellow and R3 = Cyan.  The through hole for R3 is large enough to take the leads for both R1 and R2.


----------



## cobaltmute

Second error portion on the board:
   

   
  The issue here is that this layout is for a positive regulator, when it should be a negative one.
   
  The fix is to install the regulator at an angle, as my wonderful graphics shows.  Place pin 1 of the regulator on the pin 2 pad, and pin 2 of the regulator on the pin 3 pad.  Pins 4 and 5 on the other side of the regulator stay on their pads.  And most importantly, *bridge pins 2 and 3* of the regulator.  Pin 3 of the regulator needs to be tied to pin 2 to enable it.


----------



## c12mech

Those look to be pretty easy fixes.  Should be no trouble at all.


----------



## Gotez

Yes, That should be doable.
   
  Looking forward to the build!!
   
  DigiKey tells me that P1.00MCACT-ND (RES METAL FILM 1.00M OHM 1/4W 1% ) is obsolete. Any tips for replacements?


----------



## tomb

Quote: 





gotez said:


> Yes, That should be doable.
> 
> Looking forward to the build!!
> 
> DigiKey tells me that P1.00MCACT-ND (RES METAL FILM 1.00M OHM 1/4W 1% ) is obsolete. Any tips for replacements?


 

 My DigiKey says NRND, but they have 34,086 available.  I would not hesitate to go ahead and order it on that basis.  If those get sold before you need to order, pick another 1M, 1/4W 1% resistor.  There are several:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=RNF14FTD1M00CT-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PPCQF1.0MCT-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=1.00MXBK-ND
   
  I haven't checked each one of those for physical dimensions, but you get the idea: there are others available.  I'm not sure of this, also, but perhaps cobaltmute can confirm: typically, a 1M resistor is not usually in a critical part of a circuit.  It may be that the 1% spec could be relaxed a bit for that resistor and that would open up a lot more resistors to pick from.


----------



## cobaltmute

At quick check, the ones that tomb has listed are all too large.  There is a Xircon from Mouser that is compatible.
   
  But the with 34,000 in stock we should be good for a little bit.


----------



## Gotez

You're right.
   
  I should have looked better


----------



## c12mech

I was looking at the original post and saw that both PCM1794A and PCM1798 dacs can be used.  What is the major difference between the 2 besides the $16 price difference.  I have the data sheets for both and don't see a whole lot of difference.


----------



## 00940

The PCM1794 has a stronger analog output (twice as much ma) and a better digital filter.
   
  The only practical implication is that you have to adapt the I/V resistors accordingly (not to exceed 0.6V or so because the internal protection diodes would mess up your signal).


----------



## tomb

Yes, cobaltmute and I agree that the 1794 is the better chip.  My understanding is that's the chip he will focus on in refining the design based on the prototypers' experience.  That is the chip I'm supplying along with the PCM2707 to most of the prototypers.


----------



## c12mech

I figured there was a big difference just was not sure what it was, thanks 00940.  In the bom that was posted the 1798 was what came up under the digi-key p/n given.  I was one of the latecomers to ask for a board and so will not be getting the chips.  I have them ordered as samples from TI but they seem to be on perpetual back-order.  I'm really looking forward to building this just to see the difference out of both my pc and Macbook pro.


----------



## tomb

Quote: 





c12mech said:


> I figured there was a big difference just was not sure what it was, thanks 00940.  In the bom that was posted the 1798 was what came up under the digi-key p/n given.  I was one of the latecomers to ask for a board and so will not be getting the chips.  I have them ordered as samples from TI but they seem to be on perpetual back-order.  I'm really looking forward to building this just to see the difference out of both my pc and Macbook pro.


 

 PM me when you receive your PCB.  I may be able to supply you one by that time.  TI indicated an availability date of 3/20, if I remember correctly.  I'd be surprised if cobaltmute gets the chips and is able to deliver those and the PCBs well before that time.  He's not in the states, btw, so it's not like 3 days delivery, after all.


----------



## c12mech

Thanks tomb.
   
  I'm not in the states either.  I live on Guantanamo Bay Naval Station.  The US mail is unreliable at best, 42 days once for a package.  I have all my important stuff sent to an address in Fort Lauderdale to be picked up by the planes I work on.  Sometimes I get it pretty quick and sometime it can take a week or so for them to get up there.  Just depends on scheduling.  If I have not received my chips by the time the board gets here I will send you a pm.


----------



## cobaltmute

The chips are in US mail from tomb to myself.  Let's all hope for faster than slower delivery.  Shortest I've seem from tomb is 5 days and longest has been 28 days.  We'll see what happens.


----------



## forsakenrider

Very excited for this!


----------



## nightanole

SO how do we get one these? Hmm i got 2 other usb dacs, but no current out/capless.


----------



## cobaltmute

Well, my stock of boards is assigned to prototypers.
   
  So at this moment, you'll have to wait for the next revision of the board.


----------



## chakija

Hi guys. This is my first post on this forum so i want to say THANKS because i found much helpful advices and tips. I just hope that i will be able to contribute somehow.
   
  My first post on this forum and i already have ignorant question. Cobaltmute i am very interested in building your proto-dac. I already have some pcm2707 and pcm1794 so i decided to build pup1. Would it be a problem to you to upload BOM in .pdf ? 
  I was also wondering, will the output stage give enough power to drive my gainclone with lm1876 chip ?
  I also want to build pcb  and  i was wondering could i use prints given on the first page (with applied modification that you mentioned later) ?
   
  EDIT
  Please forget uploading .pdf file. I menage to convert xlsx file.


----------



## cobaltmute

@chakija - I suspect any image that I posted will not work as scale would be off. My best advice it wait a little while till I get the revision of the board done.
   
  @Those who I have acknowledged as getting prototype boards:
   
  I got a package with chips in it from tomb today. So the next steps:
  1) PM your address formatted in the PM in address label format to get the envelope to you. I will be copying it and printing it out to tape directly on the envelope. This is the simplest way to ensure that correct addresses on are envelopes.
  2) In the PM include a PM that I can send the Paypal request to.
   
  I will pack up the boards and chips and then send you the Paypal request. Once that is paid, I will drop the envelope in the mail. I'm hoping to have them all packed tomorrow night, but if not, given what my weekend schedule is already calling for, they will be completed on Monday night.


----------



## 00940

I was just having a look again on the schematic...
   
  If you're going to do production runs, it might be a good idea to add a 22 or 47r resistor at the output of the opamp. Ultra low output impedance isn't needed for a DAC and it would shield the opamp from cables' capacitance, etc.


----------



## chakija

@cobaltmute
  Thank you very much for your reply. I will wait for your revision of pcb. I also would gladly buy it from you if i was living in a Canada...
  In meantime, i will collect all parts from BOM file. I hope that changes made on layout wont affect it.


----------



## cobaltmute

don't collect all the parts for the next revision yet, unless you like extras.  Some of the parts (mailing resistors and ceramic capacitors) will be changing to surface mount.


----------



## cobaltmute

There are three people who I confirmed would get protos that have not PM'ed me their address yet.
   
  It would be very nice to have that information by this evening for me so that I can finish packing all the boards at once.


----------



## c12mech

I believe that I sent you my address with the information for the pup1 dac.  If you need it again just let me know.


----------



## cobaltmute

Wall of ??:  Spacehead, tcpoint and Aflac need to send me addresses.


----------



## cobaltmute

For those that have sent me addresses, your envelopes went in the mail today.
   
  There are two that have not e-mailed me a postal address.  If they don't in the next few days, I'm going to release the boards allocated to them for others.


----------



## Avro_Arrow

I would take one if no one else does...


----------



## Billyk

As always, I'm up for a proto, sorry I missed the initial prototype call!I can be patient too, thanks for this one, it looks great!!


----------



## forsakenrider

Quote: 





cobaltmute said:


> For those that have sent me addresses, your envelopes went in the mail today.


 


  I hope that means I will get it tomorrow!!! My digikey order with all the parts will be in tomorrow, I sure hope I can build it this weekend!!


----------



## cobaltmute

Okay, one week to wait for an address from active people on the forum is long enough.  Releasing the last two boards to others.
   
  Going from order of interest postings, chakija and nightanole get first shot if they want the two boards.  They will ship with the PCM chips.  PM your address and paypal email and I will ship them to you.
   
  If they don't take them Avro_Arrow and Billyk are the next in line.


----------



## forsakenrider

Canadians should get priority... Hahha just kidding!
   
  One question, why did you go with 3.5mm output instead of RCA or just pads for wires?


----------



## cobaltmute

It seemed reasonable at the time to use the 3.5mm.
   
  You should be able to pull wires off the holes to mount what you want.
   
  Next version will have RCAs.


----------



## tomb

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.


----------



## Ikarios

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...


----------



## Billyk

Well here's hoping!!!
   
  Just finished my Crack with Speedball... Very sweet sounding, revealing as heck too.


----------



## forsakenrider

odd, why are my two caps (C31, C33) different then your guys?? Im almost finished...


----------



## cobaltmute

Not sure what you mean about the caps - what are yours?
   
  And don't forget the "correct" way to install R1,R2,R3 and the negative regulator.


----------



## forsakenrider

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?


----------



## tomb

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?


 

 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.
	

	
	
		
		

		
			




   
  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 ...


----------



## forsakenrider




----------



## forsakenrider

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


----------



## tomb

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?


----------



## forsakenrider

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?


----------



## cobaltmute

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.


----------



## forsakenrider

1A is 4.79v.  Is there are list of what all teh voltages should be somewhere?(2a, 2b, 1b..etc) My neg 2.5 is correct but 2.5 is above 4v


----------



## cobaltmute

1A = USB 5V
  1B = 2.5V
  2A = negative of 1A
  2B = -2.5V
   
  Other points are labelled.


----------



## forsakenrider

Sorry to be such a hassle!
   
  1A =4.78
  1B =4.15
  2A = -4.75
  2B = -2.52
  4.75 = 4.7
  3.3 = 0.09
  2.5 = 4.16
  -2.5 = -2.52
   
  also U1 gets super hot very rapidly!


----------



## cobaltmute

Your 3.3 regulator is passing too much current.  As I said, follow the traces from it and check for shorts to ground on everything.  As a simple check, check the resistance on the output of the regulator to ground.
   
  For the 2.5V regulator, it is not regulating.  Check for a short between 1A and 1B.
   
  All the other points I'd be happy with.


----------



## forsakenrider

Ok, trying to icolate the problem. Ive removed L3 and L4and now 3.3 is 3.3! so I guess maybe U2 has a short? I really cant see where, I've gone over it with Desoldering Braid and a solder sucker. ALSO now 1B and 2.5 are giving -0.81. all other points check out. Ideas? Im all out of them.


----------



## forsakenrider

Does anyone have a good picture of an unpopulated board? that might help me better then the images on page one of this thread.


----------



## forsakenrider

Ok, it gets weirder! I changed U7 and now my 2.5 is back up to 4.15ish. I removed L3 and L4, re-installed L3 and U1 seemed to be fine, and my computer reconized it! ok, I thought its all better, installed L4, boom 3.3 back down to 0.81. removed L4 and its the same, removed L3 and its back to 3.3. Soo Iim guessing theres a short on U2 but I have no idea where or how to remove it now.


----------



## cobaltmute

I'm fairly busy at work right now, but I'll take a look at what you are saying tonite.


----------



## c12mech

I just got my board today and was planning to take pictures as I go.  I'll try and get some good close shots and post them later tonight.  This board is huge compared to the skeleton dac board.  Most all the parts I ordered are sitting in Florida waiting to be picked up on the next run to the states that the guys here do.  Hopefully I will have all of it by the end of the week.


----------



## forsakenrider

OK more, I've gone over this thing like a mad man (I dont work today) and I think VDD is connected to ground somewhere... and I think it shouldnt be. yes? no? maybe? *3.5ohm <EDIT EDIT EDIT*


----------



## c12mech

Hopefully this helps forsakenrider.  Best I could do at the moment.


----------



## forsakenrider

welli fried  my last 2.5 reg i think...but heres a weird discovery, i have no u9, L3, U7 and C34 installed. voltage at 1B started around 4.5 and is droping  0.01v per 2 seconds.
   
   
  EDIT: I guess thats just a cap bleeding down, wow I'm really looking too hard.


----------



## cobaltmute

Quote: 





forsakenrider said:


> OK more, I've gone over this thing like a mad man (I dont work today) and I think VDD is connected to ground somewhere... and I think it shouldnt be. yes? no? maybe? *3.5ohm <EDIT EDIT EDIT*


 


  Vdd which is 3.3v should be higher that 3.5 Ohm to ground. 
   
  You have a short.  Which is why the regulator is not regulating - it is current limiting.


----------



## cobaltmute

Quote: 





forsakenrider said:


> Ok, it gets weirder! I changed U7 and now my 2.5 is back up to 4.15ish. I removed L3 and L4, re-installed L3 and U1 seemed to be fine, and my computer reconized it! ok, I thought its all better, installed L4, boom 3.3 back down to 0.81. removed L4 and its the same, removed L3 and its back to 3.3. Soo Iim guessing theres a short on U2 but I have no idea where or how to remove it now.


 


  Okay.
   
  Seems like you have some weird shorts.
   
  I check for bridges by looking at the pins I want to check and then tilting the PCB to look down between the pins (rather then from above).  I also find it helps to have the board turn so the row of pins is perpendicular to your body rather than parallel.  I have had bridges deep behind the pins, which the only way to fix was to add more solder to touch to bridge and then wick it all off.


----------



## cobaltmute

Quote: 





forsakenrider said:


> welli fried  my last 2.5 reg i think...but heres a weird discovery, i have no u9, L3, U7 and C34 installed. voltage at 1B started around 4.5 and is droping  0.01v per 2 seconds.
> 
> 
> EDIT: I guess thats just a cap bleeding down, wow I'm really looking too hard.


 

 You are correct on the cap - it is C31.
   
  What are you using as the ground when you measure 1B?


----------



## forsakenrider

All my measurements use one of the corners for ground or the spot beside 1A.
   
  Could the short be because of my trick? I usually use a little bit of thermal paste to hold the larger IC's in place when soldering. It says its not conductive to electricity.
   
  I have looked from all angles, I guess I will cover all the pins with solder and wick it all away.


----------



## tomb

One trick that works for me sometimes is to use an X-acto knife to "slice" between the pins.  That can get some of those bridges that might be underneath and hard to see.  For lack of a better description, think of it as using a comb to clear anything between the pins.  Also, try to be cautious about removing/replacing many more things before you get a handle on it.  These boards are fairly robust with the double ground plane, but they're still protos and may not take much abuse.
	

	
	
		
		

		
			




   
  EDIT: Just thought of one other thing - you may need to be patient with the connection to the PC.  Mine took awhile to register for some reason, but I've had no trouble with it since.
   
  Anyway, don't give up and good luck.


----------



## forsakenrider

Yeah ive tried the xacto comb. I dont know. I re flowed U2 and U4 and used desolder braid and flux to suck as much away as possible. Tomorrow I work so I will put a litt Acetone around the chips and blow it with the compressor. Acetone is ok isnt it? as for the boards and their strength, yeah Ive already lifted one pad at U7 but i should be able to make it work anyway. First step is to try and figure out with the 3.3 reg over heats with L3 installed. If I measure the RIGHT pad of L3 to ground without L3 installed I now get 0.6 ohms so I think I've only made the short worse tonight


----------



## cobaltmute

If that compound you are using is actually conductive, you could have an issue with U4 - look at the board and you'll see three ground plane vias right under the chip - one of which is close to 3.3V pins.
   
  Yup right pin of L3 to ground should no be 0.6 Ohms - you've definitely got a ground short.
   
  And as tomb mentioned - these are protos.  It can be rather easy to lift a pad.


----------



## forsakenrider

Heres a quote from the site, do you think this could be my problem?:
   
  "Not Electrically Conductive:
 Arctic Silver 5 was formulated to conduct heat, not electricity.
 (While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is *very slightly capacitive* and could potentially cause problems if it bridges two close-proximity electrical paths.)"


----------



## cobaltmute

Based on that quote, I'd say you should be good.
   
  So now it is time to hunt the bridge.


----------



## forsakenrider

I brought it to work and blew it out with the air compressor. no solution. I'm starting to get frustrated with this little guy!!!
   
  I really cant figure out where the short is. Could it be the actual dac chip?


----------



## cobaltmute

How high of magnification are you using to look at it?
   
  I use an 8x loupe (something like this: http://www.amazon.com/dp/B000RB3FPE/ref=asc_df_B000RB3FPE1485372?smid=AG275D7O3JJ72&tag=dealtmp9995-20&linkCode=asn&creative=395105&creativeASIN=B000RB3FPE ) that I bought for $8 at a local shop.  It shows more than clear enough so you can check each and every pin.


----------



## forsakenrider

Probably not high enough! Im frustrated so I will have to find me a loupe like that! thanks for the idea.


----------



## particleman14

k mines up and running.  all voltages check out and I'm getting about 2.5mv offset on L and -6.5mv on R.
   
  I managed to compare a few songs to my gamma-2 (fed to CKK3)... So far,  the Pup1 sounds pretty good... while I'm listening to some pink floyd and fleetwood mac  First thing that sticks out is gamma-2 seems to have more "depth"  than the Pup1 which sounded kind of "thin" in comparison.  However, both sounded great in the classic rock department(def leppard, foreigner). 
   
  Comparing various electronic/pop music, the Pup1 does a good job.  But, I think the I am liking the bass on this thing the most, it's nice and fat with just as much clarity as the y-2.  To my ears, the overall presentation of the y-2 is better, but I am also reminded it's about 4x the cost as this Pup1. 
   
  I wonder if finding a way to use a THS4222 would change the sound dramatically?  Anyways, I am pleased with this little guy (esp. for the price)., I'll compare it to the grub later this week if I can.


----------



## cobaltmute

Quote: 





forsakenrider said:


> Probably not high enough! Im frustrated so I will have to find me a loupe like that! thanks for the idea.


 

 This just brings up a very good point:  I'd say you need magnification to build SMT.  You need some to build the PCB (I use a ring light with a magnifier in the middle), but lots of magnification is important to check the board.
   
  Personally for any part with three or more legs, it comes out of the vise and gets checked thoroughly before I move onto the next part.  I've still missed bridges, but I was always ultimately able to find them with good magnification.


----------



## cobaltmute

Quote: 





particleman14 said:


> k mines up and running.  all voltages check out and I'm getting about 2.5mv offset on L and -6.5mv on R.
> 
> I managed to compare a few songs to my gamma-2 (fed to CKK3)... So far,  the Pup1 sounds pretty good... while I'm listening to some pink floyd and fleetwood mac  First thing that sticks out is gamma-2 seems to have more "depth"  than the Pup1 which sounded kind of "thin" in comparison.  However, both sounded great in the classic rock department(def leppard, foreigner).
> 
> ...


 

 Nice to hear about a successful build.  With the dc servo on the CK2III, you should have no worries about the offset from the pup1.
   
  On the next version of the board, better layout around the op-amp should increase the choice of op-amps.


----------



## forsakenrider

I used a similar light as you to build it, and I still feel and I can see really deep. To me it looks perfect, but theres obviously something I'm missing.
   
  Other then the short for the 3.3 reg, what could be causing my 2.5 not to work? In goes 4.85-4.9v and out comes 4.2. I fried atleast one of them carelessly shorting too pins, and maybe even the other so I will have to order extras when I order parts for the Skeleton.
  What could be causing this? or rather, where should I look for something wrong?
   
  Jeeze, this is getting embarrassing! I've never had a problem assembling something from plans


----------



## cobaltmute

It seems like something is bridging across the output of the 2.5V reg.
   
  So if you remove L5, what are you getting on the 2.5V point?
   
  You can always try running unregulated rails for the op-amp, but I'd want to make sure there is nothing else wrong.


----------



## forsakenrider

FINALLY! we have progress. so it wasn't a solder bridge on one of the DAC chips! it is somewhere before or L5. removing L5 and the dac is recognized by my computer. I will have a little something to eat and see what we can get! I just hope my two 2.5v regs arent burnt out!


----------



## forsakenrider

ok, I *THINK *everything is solved. its like there was a bridge under L5 or C31. I didnt see anything but removing and reattaching both all is well, except the 2.5+ because I burnt both my 2.5 regs! (well I assume they are burt since I saw a little magic smoke and they both put out exactly what they take in). So what can I do now? I will order new reg's but is there something I can do in the meantime? will the opamp take the +5~v if I bridge pins 1 and 5? Will I need to do the same on the Negative side? or is there a way to connect the negative 2.5v reg (I have one extra) to the positive (funky pin change?).
   
  One other thing, sometime it shows up as "Unrecognized USB device", not sure why and I cant repeat it, it seems random. Other wise it shows up as "USB Audio Dac".


----------



## cobaltmute

So your 3.3V is good and you just need to worry about the +2.5V?
   
  If your -2.5V is good, you can take a wire and attach 1A to 1B and run with an unregulated positive rail (assuming you have no 2.5V regulator on the board).  Might have a bit more noise, but it will work as the LMH6643 is spec'ed to run at up to +-5.


----------



## forsakenrider

would I be better to connect the positive sides of C22 and C28 together? (maybe a little more smoothing?) Yes all other voltages are right on the money!!!
   
  Jeeze, I wish I could understand what was wrong!


----------



## forsakenrider

ok I connected 1A to 1B as you suggested, 2mV offset of one channel and 3.2 on the other. But no sound!?? what can I check? Ive set it up as default, set it up in ASIO4ALL, I dont get it.


----------



## cobaltmute

What's your voltage at the 4.75V point?
   
  So Windows has recognized and you can select?
   
  Just to the left of U4, you will see three via's very close to each other.  None of these should be connected to ground.  There is also a trace just above those.  That should not be connected to ground either.


----------



## forsakenrider

Man this is getting tough! Ok, looks like there was a short there! I re flowed and now 3 out of 4 seem great, the center of the 3 is ~3ohm to ground, I scraped and re flowed and nothing! cant get that to go away. anywhere else thats connected (other then on U2, checked there)


----------



## forsakenrider

and youre right! short at U4, damnit, where did that come from!


----------



## cobaltmute

The short could be on U4 or on U2. Those are the I2S bus lines that provide the signal to the output DAC. Follow the traces.


----------



## forsakenrider

OMG that took forever!!! but, im hearing music now!! lets see if it holds up. litterally hours resolder over and over, finally I thought, heat the pin up where the invisible short is a tr and blow the short away, seems to have worked!!


----------



## forsakenrider

Ok so for the last two hours its been working and not working randomly. just now it was working for about 30 minutes and then crackled a little then nothing. It seems like the i2s lines are really sensitive or something, its not in a case and I wonder if it has to to with the non regulated + voltage. I guess I will take it to work tomorrow and blow it out with the air compressor. Maybe theres something in there or maybe the thermal paste is in fact effecting it.
   
  Either way, this has been the hardest thing I have ever built! I swear it had some perfect looking solder joints but I guess they just werent good enough. Gotta remember to check, double check, and triple check next time!


----------



## forsakenrider

I AM IN HEAVEN FINALLY! so I woke up this morning with a new idea. I held the corner of the dac over a stove element to heat it up and then gave it a tap to shake off excess solder (we do this when tying and soldering spokes on a bicycle wheel, although a lost art). all better! Its been playing for an hour now!
   
  SO, i think I can give a first impression while I enjoyed some tunes and had a coffee. One word comes to mind every time I upgrade my sound system, and that is detail. I heard clicks and taps I have never heard before in songs. I even played one song twice just to make sure I wasnt crazy! It feels like a big improvement over the Aliendac for sure, but time will tell!


----------



## cobaltmute

The sweet sound of success?
   
  Glad it is working.


----------



## forsakenrider

very sweet sound. Now if my adapters for my wheels came in at work so I can build my new bike this day would be perfect!


----------



## c12mech

Glad you got it working.  Now if my parts will only get here.  I've got the 2707 mounted and that's it.  All the other parts are waiting to be picked up in Florida next time a flight goes there.


----------



## Gotez

I received my board today and have started building. Lots of tiny parts!!! Will update soon!!


----------



## tomb

Quote: 





forsakenrider said:


> I AM IN HEAVEN FINALLY! so I woke up this morning with a new idea. I held the corner of the dac over a stove element to heat it up and then gave it a tap to shake off excess solder (we do this when tying and soldering spokes on a bicycle wheel, although a lost art). all better! Its been playing for an hour now!
> 
> SO, i think I can give a first impression while I enjoyed some tunes and had a coffee. One word comes to mind every time I upgrade my sound system, and that is detail. I heard clicks and taps I have never heard before in songs. I even played one song twice just to make sure I wasnt crazy! It feels like a big improvement over the Aliendac for sure, but time will tell!


 

 YAY!!


----------



## mugdecoffee

Just got my board today and ordered my parts.  When I got the board today with the two chips, I realized I only paid $5CDN for the whole package.  Do I own someone another paypal payment?
   
  EDIT: also the 1Mohm resistor spec'd in the BOM is now obsolete. I forgot to replace it with something but I'm sure I can find something that'll work around school.


----------



## cobaltmute

Quote: 





mugdecoffee said:


> Just got my board today and ordered my parts.  When I got the board today with the two chips, I realized I only paid $5CDN for the whole package.  Do I own someone another paypal payment?
> 
> EDIT: also the 1Mohm resistor spec'd in the BOM is now obsolete. I forgot to replace it with something but I'm sure I can find something that'll work around school.


 
   
  No you don't owe anybody anything more for the package.
   
  You can either try sticking a larger resistor in the holes for the 1M or you could leave the leads long on the crystal and solder the resistor to leads.


----------



## forsakenrider

Ok, I am really enjoying this DAC! for the size, and price (assuming I actually had to pay for the board and chips, thanks cobaltmute and tomb!!!) this is amazing bang for buck! I am haveing a couple friends over to listen to my new Open baffle speakers and this dac tonight!


----------



## Gotez

Ok, my scores are:
   
  All measured from point to ground
  (1a) = 5.11
  (2a) = 0.63
  (1b) = 2.47
  (2b) = 0.76
  (4.75) = 4.7
  (2.5) = 2.45
  (-2.5) = 0.76
   
  There seems to be something wrong with the negative side.
   
  Any ideas on where to search for mistakes or broken parts? Or do you need photo's?


----------



## cobaltmute

Your 2A voltage implies that the charge pump (U6) isn't doing its job.  Check for shorts around that.


----------



## Gotez

I can see no clear shorts (not saying there aren't any). Are there any more measurement I could make?
   
  BTW: I did not include the LED light ( I hate those ), but I did add everything else, including the resistors next to the LED.


----------



## Spacehead

oh people have got their boards? PM me then.


----------



## forsakenrider

ANd I would say add photos, always helps to have more eyes.
   
  For me the key to find shorts was to remove L3, L4, L5, and L6. That separates the power supply components from the dac (I think) and then you can see if the issue is in the PSU or the chips, mine was in the chips


----------



## cobaltmute

Quote: 





gotez said:


> I can see no clear shorts (not saying there aren't any). Are there any more measurement I could make?
> 
> BTW: I did not include the LED light ( I hate those ), but I did add everything else, including the resistors next to the LED.


 

 I would double check that you got the parts in the right places.  Did you reverse U6 and U8?
   
  What is the lettering on the top of U6?


----------



## mugdecoffee

Quote: 





cobaltmute said:


> No you don't owe anybody anything more for the package.
> 
> You can either try sticking a larger resistor in the holes for the 1M or you could leave the leads long on the crystal and solder the resistor to leads.


 

  
  Well a huge thanks to tomb then.  I think those two chips saved me $30 on my digikey order not to mention the time it would have taken to ship from backorder.
   
  Leaving the crystal leads long is a great idea.  Would make a surface mount resistor possible which would be a bit cleaner.


----------



## tcpoint

I was looking at the schematic and noticed that FSEL is left floating.  Shouldn't it be tied to ground for I2S mode?  It is tied to ground in the grubdac.


----------



## cobaltmute

Quote: 





tcpoint said:


> I was looking at the schematic and noticed that FSEL is left floating.  Shouldn't it be tied to ground for I2S mode?  It is tied to ground in the grubdac.


 


  You are correct, and it is set that way for the next revision of the board.


----------



## Gotez

Quote: 





cobaltmute said:


> I would double check that you got the parts in the right places.  Did you reverse U6 and U8?
> 
> What is the lettering on the top of U6?


 

 U6 = PFNI (very difficult to see)


----------



## cobaltmute

PFNI is the correct chip.
   
  With the power off, what is the resistance between 2A and ground?


----------



## Gotez

Quote: 





cobaltmute said:


> PFNI is the correct chip.
> 
> With the power off, what is the resistance between 2A and ground?


 
  infinite


----------



## cobaltmute

So that implies no short on the output.
   
  Have you tried to re-flow the joints on U6?


----------



## Gotez

getting the right voltages now, but is not seen by the pc yet. Should I anything else but plug it in?


----------



## cobaltmute

Just plug it in.
   
  If you are using a Windows 7 machine, driver installation time can be long.
   
  But to verify, you installed the resistors as posted earlier?


----------



## Gotez

Yes, they make a nice little tower.Is there a way to test the chips?
   
  ah, the (3.3) point has no voltage. I will check around that area.
   
  NEW: Device is found. I get the unidentified device message. Still no 3.3 on the (3.3) point. I get 5 volts on pin 1 of U1, and 3.7 on the opposite pin, but nothing on the 3.3 point. Does this mean that C7 is wrong?


----------



## cobaltmute

So you get output from the regulator, but nothing at the 3.3 point?  that is strange.
   
  Check the resistance from 3.3 to ground. 
   
  Also what to you get at the right side of L3 (the side away from the label) - both voltage, and resistance to ground?


----------



## Gotez

I resolderd a bit and now for both:
   
  Voltage is 2v
   
  Resistance is infinite.
   
  My pc says: USB device not recognized.


----------



## forsakenrider

when I had the USB not recognized it was the i2s lines had a short. check them for resistance to ground.


----------



## cobaltmute

Quote: 





gotez said:


> I resolderd a bit and now for both:
> 
> Voltage is 2v
> 
> ...


 

 What is happening is that the 3.3V regulator is supply enough power to get the device recognized as being there, but the PCM2707 is not powered up properly.
   
  2V is still to low.  Something is still the issue.  I would re-flow and check all your joints that are attached to the 3.3V lines.


----------



## Gotez

Quote: 





cobaltmute said:


> What is happening is that the 3.3V regulator is supply enough power to get the device recognized as being there, but the PCM2707 is not powered up properly.
> 
> 2V is still to low.  Something is still the issue.  I would re-flow and check all your joints that are attached to the 3.3V lines.


 
   
  Been busy trying to find the short. Resistance is now 28k. Voltage is still 2. Device is still not recognized. I’m going to keep trying.
   
  Could solder flux residue be the cause of this?
   
  Anyway, thanks for all the help, I’ll post pics as soon as it works!!


----------



## Gotez

IT LIVES!!! I
   
  After many hours of measuring and resoldering I found that the ground conncetion for U1 was not solder properly. After doing so it magically came alive.
   
  Can’t comment on the sound yet, I have to listed some more first. I can say that is drives my IEM and senn HD121pro simultaneously a bit to easily and is very, very loud. It can make my ears bleed!
   
   
  ’ll post some pics soon.
   
   
  And thanks for all the help!!!


----------



## cobaltmute

Glad to hear it works.
   
  I've been surprised by the challenges that people are having as they all seem to be in the 3.3V section, which is essentially the same as the one for the grubDAC.


----------



## mugdecoffee

Just finished soldering mine together.  The build went well for the most part except I spent some time resoldering the PCM1794 over and over until some pin finally got soldered and sound came through the output.  While I've only listened to it a bit, its much much better driving headphones than my laptop or iPad.  I've tried it with my AKG K240s (600ohm) and Grado HF2s (32ohm) and it does a great job with both.  It has a clear sound with crisp highs and some solid, full bodied bass.  I don't have my amps with me at school so I can't compare it to anything decent but it sounds good.  Kudos to cobaltmute for the great design.


----------



## Gotez

As promised:
   

   

   

   

   

   

   

   
  As you can see, photography is not my strong suit....
   
  It drives my MS1 with ease, and sounds very fine. I'll listen some more for some in-depth review. My low end IEM buds do pick up a lot of static noise, could grounding the dac to a case help with this?


----------



## cobaltmute

I do not really endorse driving IEMs direct from the pupDAC.  You could be getting some issue with the current limits on the negative rail charge pump.


----------



## mugdecoffee

A couple suggestions I forgot to mention:
   
  First, when resoldering the right side of the PCM1794 chip, I had a lot of trouble getting the pins with the capacitors in the way.  I'm not sure how critical the locations of C18 and C20 are but if they could be moved a little to the right, the pins would be much much more accessible.
   
  Secondly, the caps for C24 and C26 on the BOM had leads that were a little too wide.  I had to force them in a bit which caused some of the through-plating to get scraped off and I was a little worried about shorting the pads to the ground plane.


----------



## Gotez

I’ve listened to this dac for a couple of days now and it is time to share my thoughts on the performance.
   
  First of all I would like to thank Cobaltmute for the boards and Tomb for the dac chips. This made it all a lot easier.
   
  I’ve never written anything like this before, so please forgive my complete lack of audiophile terminology.
   
*The build *
   
  Sourcing all products was easy. The bom provided is clear and all items are for sale at digikey. The only bad this was that the shipping price to the Netherlands was just as expensive as the items themselves. I was able to buy all items in the Netherlands but this would not have been cheaper. The build is straight forward and simple enough. I did encounter some hiccups (as seen earlier in this thread) but I was able to troubleshoot these and get the dac to work. The tiny parts were posed a greater challenge than my earlier builds, but it was fun to do, and a learned a great deal. My hiccups were all due to me not soldering well enough and this cannot be blamed on the dac or board. Luckily the board provides enough measuring point and this helped me greatly in finding my errors and fixing them.
  As to the layout of the board: U4 could use a little more room. This would improve the ability to fix any problems one might encounted after soldering this chip. I would also like to add that RCA connectors would be better. And perhaps a possibility to add a USB-b connection or a standard USB connection.
   
*The sound *
   
  I used my MS1 as headphone for listening. At first I connected it straight to the dac output. It is more than capable of driving 32 ohm headphones and there is little to no hiss.
   
  To keep it short: the dac sounds fine. It has a bright and clean sound. It’s strengths are its clarity and its powerful performance. Overall it is a very capable dac and it delivers lots of bang for buck. It does tend to sound a bit ‘sharp’ in the high end and can be fatiguing when listening to longer periods. Also the bass does lack a bit of slam and compared to more ‘sophisticated’ dacs it does miss a certain refinement. This is not meant as a negative, it is just my personal taste in sound.
   
  The dac really comes to life when fed to my millitt minimax headphoneamp. The tubes give a bit of warmth to the sound that make it a lot more enjoyable. I really enjoy listening to this combo. I believe that this combination is where the dac can really shine. The clarity of the dac and the sound signature of the hybrid amp make it a very pleasing and enjoyable setup, one that I will listen to for many more albums to come.
   
*Summary*
   
  It is a very good build. The sound is very good, and considering the price probably unbeatable. Especially if paired with a hybrid or tube amp.


----------



## c12mech

I have not finished mine yet, waiting for a few parts, but I have a question.  Would it be possible to by pass the amp section and just run rca's out by wiring directly to C24 and C26?  Just a thought.
   
  I would like the option to go with headphone out or rca depending on the situation.  If it is possible is it something that could be added to the production board, there seems to be enough space.


----------



## cobaltmute

Quote: 





gotez said:


> *The sound *
> I used my MS1 as headphone for listening. At first I connected it straight to the dac output. It is more than capable of driving 32 ohm headphones and there is little to no hiss.
> 
> To keep it short: the dac sounds fine. It has a bright and clean sound. It’s strengths are its clarity and its powerful performance. Overall it is a very capable dac and it delivers lots of bang for buck. It does tend to sound a bit ‘sharp’ in the high end and can be fatiguing when listening to longer periods. Also the bass does lack a bit of slam and compared to more ‘sophisticated’ dacs it does miss a certain refinement. This is not meant as a negative, it is just my personal taste in sound.
> ...


 
   
  I'm going to sound like a broken record, but while the pupDAC *can* drive headphone, I don't think it *should* drive headphones.  The charge pump puts out 60ma max.  That current has to be split between the two channels for 30ma per channel not providing a great amount of current, especially into low-impedence phones.
   
  The sound that Gotez has described driving headphones direct is what I have also heard with the grubDAC direct.  Load the output too heavy for the design and something starts to give.  This is why we build headphone amps and the pupDAC was designed to be a DAC not a headphone amp.
  
  Quote: 





c12mech said:


> I have not finished mine yet, waiting for a few parts, but I have a question.  Would it be possible to by pass the amp section and just run rca's out by wiring directly to C24 and C26?  Just a thought.
> 
> I would like the option to go with headphone out or rca depending on the situation.  If it is possible is it something that could be added to the production board, there seems to be enough space.


 

 Remember that the PCM1794A is a differential DAC.  You could try to run off C24/26 if you were going to drive something balanced off each end. *DO NOT* try to go single-ended off these points - you will find offset at the output.  The amp stage converts the output to single-ended and deals with the offset.
   
  Run your RCAs from the headphone out positions.  On the next revision board I'm working on, I am placing positions for RCA and 3.5mm outputs.


----------



## forsakenrider

I think you should do away with the 3.5mm jack completely. As I do agree the bom spec part is very robust, it seems to be deceiving people into thinking this is a headamp/dac combo. I cant agree with Gotez's comments at all, but thats probably because I havn't run headphones with it. My pup1 goes into a pre amp/selector which has a unity gain jisbos buffer in it, and then out to a head amp or my gainclone driving full range, open baffle speakers. For me as I have said before this thing has WONDERFUL detail for such a small package.
   
  This weekend I will case it and the skeleton dac up, and do some listening. But so far I love it! its really that extra boost over the alien dac I was looking for with out investing crazy amounts of time/effort/and $.


----------



## Gotez

My comments were not meant as a negative, and I think Cobaltmute has a  good point in stating that it is a Dac, not an amp. I will continue using it for my Millitt Minimax amp and enjoying it.I would love to build any new projects your working on Cobaltmute, keep us posted!


----------



## tomb

Quote: 





gotez said:


> My comments were not meant as a negative, and I think Cobaltmute has a  good point in stating that it is a Dac, not an amp. I will continue using it for my Millitt Minimax amp and enjoying it.I would love to build any new projects your working on Cobaltmute, keep us posted!


 

 Don't sweat it.
	

	
	
		
		

		
			








  Just remember that offering reviews always opens you up to criticism.
	

	
	
		
		

		
		
	


	




  Please keep doing them, though.  People appreciate one's thoughts - as long as you don't make direct comparisons with competing products, IMHO.
   
  At the risk of piling on - but this may be a good remedial for others - remember that outside of cobaltmute's recommendations, low impedance phones like Grado's are very tough to drive correctly with many smaller amps.  Back in the day, user Apheared was compelled to create the first buffered CMoy (A47) because of the original CMoy's limitations with supplying sufficient current to Grado's.  So, if a battery-powered CMoy has an issue with Grado's, a USB-powered DAC is going to have even more.
   
  As for the 3.5mm connection, I'm not sure that I agree it's misleading.  The PupDAC as currently configured is a very convenient size to mate up with smaller amps such as the Mini3 (or CMoys, etc.) and the ability to have a very short, 3.5mm patch cord connecting the entire arrangement is a good thing to have.  As for RCA's, I'd like to have them, too (and would use them primarily), but would vote to keep the package refinement the same - as in, no requirement for wiring.
	

	
	
		
		

		
		
	


	




  So, if cobaltmute adds pads for RCA jacks, my preference would be to use PCB-type.  Who knows, we might even come up with a custom case for it - or at least the endplates.


----------



## Beftus

tomb said:


> Who knows, we might even come up with a custom case for it - or at least the endplates.




That would be really good news for people not adept at doing case work. I like the 1455C801 formfactor for this DAC, as it would match the Mini³ perfectly. This DAC is becoming more interesting with every posting!  Can hardly wait for kits showing up on Beezar...


----------



## c12mech

Thanks for clearing that up for me.  I figured that there was a reason that it was done that way.  I will use it with the 3.5mm jack out as it is easier and I already have 3.5 to rca cables made up.


----------



## forsakenrider

So im ready to case up my Pup1 and I've got the longer version of the hammond case because I wanted ample room for RCA's. So I'm wondering is theres and improvements I can make and use up some extra space. I know its not "needed", as this DAC already sounds amazing, but maybe larger capacitors somewhere for filtering? or is nothing really worth it here unless changing to external power?


----------



## tcpoint

I put it all together and found a short on U7 (the 2.5 V voltage regulator).  While trying to fix it, I wrecked the chip (Grrrr...).  I am placing an order for it tomorrow.  My Ubuntu box recognizes it just fine.  I'll give you my impressions of the sound, later in the week.


----------



## cobaltmute

Quote: 





forsakenrider said:


> So im ready to case up my Pup1 and I've got the longer version of the hammond case because I wanted ample room for RCA's. So I'm wondering is theres and improvements I can make and use up some extra space. I know its not "needed", as this DAC already sounds amazing, but maybe larger capacitors somewhere for filtering? or is nothing really worth it here unless changing to external power?


 

 Not a lot I would change.  I'd already done the majority of them on the BOM that you built from.


----------



## forsakenrider

Thats what I thought. Would more capacitance help on the 3.3, 4.7, 2.5 or -2.5 rails? the 2.5 and -2.5 are what you changed from your original, correct? I have some Oscon 1000uf that I could put on the +/- 2.5. would there be any ill effect to adding capacitance to any of the rails after or before the regulators?
   
  Heres how it is now!


----------



## Beftus

Cool idea for the power LED! Is the plexiglass clear or is it colored red of its own?


----------



## forsakenrider

Thanks! It's clear acrylic, the led is embedded in the center.


----------



## cobaltmute

very nice build forsakenrider.
   
  Hammond actually has blue and red end panels for the 1455C801, but to try to get them in small qty is a problem.
   
  As for the caps, you could up the ones after the +-2.5V regs.  They are the ones I upped compared to my original BOM and they seemed to help with the bass.


----------



## Beftus

forsakenrider said:


> Thanks! It's clear acrylic, the led is embedded in the center.




Just so you know, if this "puppy" ends up available in kit form @ Beezar I'm gonna steal your idea!
_"Imitation is the sincerest form of flattery"_ 
Thanks for sharing.


----------



## Gotez

Nice build!! Good idea to use the acrylic to 'break' the led light.


----------



## c12mech

I asked earlier about about running wires directly from c24 and c26.  Cobaltmute pointed out about the fact of DC offset  unless I were to go balanced.  I started looking at the data sheet for the PCM1794a and it shows a balanced ciruit but it looks like it only goes to one xlr plug.  If I wanted to make this a balanced output dac can I just go straight off c24 and c26 with their respective grounds to two xlr plugs?  I'm still getting myself a little confused as to how to implement the balanced part.  I'm working on a balanced amp right now and would like to see how far I can take this dac design.


----------



## cobaltmute

The circuit you may be thinking of in the datasheet is for mono-mode using  PCM per channel (Figure 26).
   
  Look at page 24 - The first two op-amp (the ones above each other) perform the current to voltage conversion and created the balanced signal.  The third op-amp performs balanced to single ended conversion.
   
  In the pupDAC, I to V conversion is done via resistors to ground.  C24/C26 acts like a filter by making the high-frequency common and then the op-amp does balanced to single ended conversion, along with gain.


----------



## MrDavis

Any news on when a production board might be coming out?


----------



## cobaltmute

I've started laying out the next version, but have been a little distracted lately with the r1 so it will be a couple of weeks for me to finish off the lay of the revised PCB.


----------



## c12mech

I finally got all my parts in and finished this project tonight.  I've been listening to random songs that I know very well and I can honestly say that this is the best I've heard any one of these songs sound.  This is by far the best thing I've built yet for improved sound quality.  
   
  Cobaltmute, first of all thanks for this design.  I am now wandering if there is any way to make a direct SPDIF in for this dac?  I imagine it would take a dedicated power supply also but would it be possible?  I've seen the 1794 used in an SPDIF only version somewhere else  but can't seem to find it now.  If it's not possible that's fine I'm just curious since I'm working on another project that is SPDIF out only.


----------



## cobaltmute

To make it SPDIF, you could hack something onto the I2S lines, bypassing the USB input and putting your own SPDIF input.  I'd suspect that it would be quite challenging.
   
  I've run through a lot of ideas about what to do with the revision of the board, but I have settled for updating the existing layout.  The beauty of the board is that it is relatively simple for very good sound.  Down the road I'll do something that has SPDIF input.


----------



## c12mech

I think I'm going to give it a try just to satisfy my curiosity.  After looking at the datasheet for a while it looks as though I could just tap into pins 5 and 8 for the data in and data ground.  I will be wiring it directly to the data out and ground from the board of my cd transport.  This is just an experiment to see if I can get it to work.  I'll let you know how it goes.
   
  I've got a couple of different TI dac chips that I am working on right now in regards to an SPDIF dac.  I'm still trying to get a handle on using eagle to put the circuit together.  I can do it a whole lot faster on paper but that makes it a little harder to get the pcb layout done.  As I get farther along I'll start my own thread about it and ask for input from the group here.


----------



## Avro_Arrow

I can help you with that.
   
  Quote: 





c12mech said:


> I think I'm going to give it a try just to satisfy my curiosity.  After looking at the datasheet for a while it looks as though I could just tap into pins 5 and 8 for the data in and data ground.  I will be wiring it directly to the data out and ground from the board of my cd transport.  This is just an experiment to see if I can get it to work.  I'll let you know how it goes.
> 
> I've got a couple of different TI dac chips that I am working on right now in regards to an SPDIF dac.  I'm still trying to get a handle on using eagle to put the circuit together.  I can do it a whole lot faster on paper but that makes it a little harder to get the pcb layout done.  As I get farther along I'll start my own thread about it and ask for input from the group here.


----------



## c12mech

Thanks Avro_Arrow.  As I get a little farther along I will be in touch with you.  My ultimate goal is SPDIF input and balanced output using as few parts as possible.  This will be to compliment the cd transport project I'm working on.  
   
  Back on topic, the more I listened to this dac last night the more I liked it.  There seems to be more separation between instruments and there placement in the sound stage.  On the live recordings I listen to it actually sounded "live" which I had to get used to at first.  I'm really enjoying this thing.


----------



## forsakenrider

My stopped working today! D'oh! what happened? when I turned on the computer this morning the dac wasn't recognized. U1 is getting hot again and theres 2.2ohm to ground on the 3.3tp. Darn, how could a short come the far in?


----------



## cobaltmute

That is really strange.  Never seen an issue where I board that has been running for a while goes bad. 
   
  The electrolytic is the right way around? 
   
  Not sure what else to check other than looking at everything attached to that power trace.


----------



## forsakenrider

All the capacitors are correct. When I remove L3 everything goes back to normal voltages. so I just theres a short somewhere after that. Its not the i2s lines this time, its not C13, so I Maybe U3 or some pins on U2. Either way, after another 2 hours of searching and frustrated! the board is getting in bad shape from all the playing.
   
  Whens V2 coming


----------



## MrDavis

Any updates on the production version?


----------



## cobaltmute

I'm still working on it.
   
  Spring/Summer is here and this year it mean not only mountain biking but triathlon training as well.


----------



## forsakenrider

Just wanted to say that I've gotten mine back up and running. I had the two dac IC's removed by someone with a hot air re-work station, I cleaned it up and re soldiered. I can only guess that the thermal paste I put under the IC's was somewhat conductive. Either way, after swapping out the Skeleton dac in my system for this one I have been pleasured with amazing sound. This fairly simple USB dac is LEAGUES ahead of the other more simple dacs, its quite the improvement in detail, especially in the low end.
   
  Cant wait for V2


----------



## MrDavis

Quote: 





forsakenrider said:


> Cant wait for V2


 


  Same here.


----------



## cobaltmute

I'll start working on the revision again in the next month or so.
   
  I started doing triathlon this year and have two more in the next three weeks...


----------



## MrDavis

Any news on the revision?
   
  And, did you do well in those two triathlons?


----------



## cobaltmute

Just moved over all my development tools to a new home machine from the work laptop and am just starting to get back into the rhythm.

Both of those triathlons I did as I expected. Towards the bottom of the middle of the pack. Not too bad considering I need to lose about 50-60 pounds.


----------



## anddy78

Please, don't let it die!!!


----------



## cobaltmute

I may be slow, but it won't die.


----------



## tomb

Quote: 





cobaltmute said:


> I may be slow, but it won't die.


 

 That's great news.


----------



## forsakenrider

Excellent news, I still love mine


----------



## tomb

Quote: 





forsakenrider said:


> Excellent news, I still love mine


 

 forsakenrider -
  This is a digression (a big one), I know, but I keep seeing that Lil' Satan hanging on your wall!  Here's the creator - Larry Scarinzi - getting ready to launch the grandaddy of the entire design family (Super Satan).  The girl was well known at the time - Dawn Cosmillo - and was a Junior National Champion in Combat.  I was able to get my girlfriend (she's now my wife) launch mine every once in awhile, but she never flew one herself:
   



   
  This was the caption at the time:
_"... Cover photographer Ron Scalera captures the excitement of Combat in action. Larry Scarinzi holds his Super Satan ready for release while Nationals Champion Dawn Cosmillo (the plane's pilot) separates the control lines. Her opponent, already in the air, is awaiting the start of action. His plane and streamer are just a blurred streak in the background ..."_
   
For some reason, this pic captures just about every boyhood fantasy I had at the time.




  More details here: http://www.jitterbuzz.com/MAN_1967_09.HTML
   
  Fuel was anywhere from 10 to 25% nitromethane under pressure from a baby pacifier - sort of fuel-injection to the extreme.  We'd blow up the baby pacifier like a balloon with a horse syringe - kept that engine running under extreme G's when the plane would turn at 125+ mph.




  Again, sorry for the digression - it _is_ DIY, just not electronics (you couldn't buy any of this stuff - it was all hand-made 'cept for the engines).


----------



## forsakenrider

Very cool Tomb. Always funny to see how people share all sorts of various hobbies. I still love DIY audio, and airplanes for the same reasons; tweaking, designing, trying, crashing, burning, and mostly LIVING! I dont fly the control line much any more but still have a few electric and nitro R/C planes.
   
  For me its audio in the winter (cold up here in canada) and planes in the summer!


----------



## tomb

Quote: 





forsakenrider said:


> Very cool Tomb. Always funny to see how people share all sorts of various hobbies. I still love DIY audio, and airplanes for the same reasons; tweaking, designing, trying, crashing, burning, and mostly LIVING! I dont fly the control line much any more but still have a few electric and nitro R/C planes.
> 
> For me its audio in the winter (cold up here in canada) and planes in the summer!


 

 Yep - I know some people get frustrated sometimes building this stuff, especially SMD work like the excellent PupDAC.  However, at least you don't have to worry about crashing it once you get it built and working!


----------



## dBel84

Thanks for steering me to this tomb..dB


----------



## cobaltmute

Updated board still on my to do list.
   
  Crazy work for the last month has kept me really, really, busy.


----------



## tomb

Quote: 





cobaltmute said:


> Updated board still on my to do list.
> 
> Crazy work for the last month has kept me really, really, busy.


 










 but you're trying ... that's great news.
   
  The PupDAC sounds wonderful on the Dsavitsk/Beezar Torpedo.


----------



## tcpoint

Just cased my pup1 dac, this evening.  I'm going to give it some extensive listening this week.  Thanks for the great project.  I hope this ends up with a new revision, soon (with a kit with panels).  Those mini usb jacks aren't fun to cut out.


----------



## tomb

Quote: 





tcpoint said:


> Just cased my pup1 dac, this evening.  I'm going to give it some extensive listening this week.  Thanks for the great project.  I hope this ends up with a new revision, soon (with a kit with panels).  Those mini usb jacks aren't fun to cut out.


 

 Hmm ... we'll keep the case idea in mind.  I know what you mean - I would never try the exact shape by hand and have only used a rectangle when I've done it.
   
  I understand cobaltmute may be sort of close to finishing the new revision.  The Pup has been my primary listening source for many months now.


----------



## cobaltmute

I finished the revision of the board recently and am sitting on it right now. I find giving myself a break and then coming back to it after a week or so helps to sanity check on the layout.


----------



## Beftus

That's great news. I had almost given up on this puppy. Will Beezar be selling complete kits of this DAC (just like the GrubDAC) in the near future?


----------



## tomb

Quote: 





beftus said:


> That's great news. I had almost given up on this puppy. Will Beezar be selling complete kits of this DAC (just like the GrubDAC) in the near future?


 

 That's certainly the hope.


----------



## cobaltmute

This just went out to have a set of prototype PCBs made:


----------



## tomb

Yay!!!


----------



## dBel84

excellent, glad I subscribed to this thread or else I would have completely forgotten about it..dB


----------



## Beftus

Nice touch, having added a puppy! I'm glad to see there's still progress.


----------



## cobaltmute

It is embarrassing how long it has taken me to get to this point. Hopefully you all feel it is worth the wait.


----------



## Avro_Arrow

I'm in for a prototype board when they are ready....


----------



## tcpoint

I'm in for a prototype board, too.


----------



## tcpoint

I can only compare this dac to the grub dac, gamma 1, bantam dac and alien dac.  The pupDac is clearly in a different category.  It's very detailed and I just enjoy the music.  I'm building a gamma 2 and it will fun to compare the two.  Thanks needs to go to cobaltmute and tomb for a fun project.


----------



## tomb

Quote: 





tcpoint said:


> I can only compare this dac to the grub dac, gamma 1, bantam dac and alien dac.  The pupDac is clearly in a different category.  It's very detailed and I just enjoy the music.  I'm building a gamma 2 and it will fun to compare the two.  Thanks needs to go to cobaltmute and tomb for a fun project.


 
   
  Thanks for those kind comments!
   
  I got notice that the PCB's shipped last night, so I'm thinking I'll have them by Thursday at the latest.  I'll post some pics when I have them.  Cobaltmute suggested that I supply the jacks, since they're the only thing that has to be ordered from DigiKey.  I have those already in hand as of yesterday.
   
  Also, we haven't "officially" asked for prototype volunteers as of yet, but those of you who have volunteered will definitely be asked first.


----------



## Misterrogers

I'd love to be considered too when you get to that point.
  
  Quote: 





tomb said:


> Thanks for those kind comments!
> 
> I got notice that the PCB's shipped last night, so I'm thinking I'll have them by Thursday at the latest.  I'll post some pics when I have them.  Cobaltmute suggested that I supply the jacks, since they're the only thing that has to be ordered from DigiKey.  I have those already in hand as of yesterday.
> 
> Also, we haven't "officially" asked for prototype volunteers as of yet, but those of you who have volunteered will definitely be asked first.


----------



## cobaltmute

Just for everyone that is asking, prototypes won't go out until I've had a chance to build and test one. I won't let anyone else spend money on parts etc until I've confirmed that I didn't make any mistakes in the layout of the PCB. 

As well for anyone considering building a prototype, there is a lot of SMT on this board. You need to be comfortable with your ability to get parts down. 

That being said, I'm comfortably optimistic that the little changes I've made should add to the sound quality.


----------



## cobaltmute

tcpoint said:


> It's very detailed and I just enjoy the music.




There are many times when I don't listen to music because I know I'll get sucked in and not do the work I'm supposed to be doing. For me, the pupDAC presents the music the way I want to hear it - clear, detailed and exact. 

Thanks for the compliment.


----------



## tomb




----------



## tcpoint

Sweet!!!


----------



## Gotez

Still enjoying the old version!! Good to see progress.


----------



## geofftnz

Quote: 





tomb said:


>


 

 I am totally in for a kit if/when they're up on Beezar! (Got a grub on the way, but would upgrade to a pup)


----------



## tomb

Quote: 





geofftnz said:


> I am totally in for a kit if/when they're up on Beezar! (Got a grub on the way, but would upgrade to a pup)


 

 Rest assured, it's "when," not "if."


----------



## Avro_Arrow

I thought you were getting tired of stuffing little parts into plastic bags...
	

	
	
		
		

		
		
	


	



  
  Quote: 





tomb said:


> Rest assured, it's "when," not "if."


----------



## tomb

Quote: 





avro_arrow said:


> I thought you were getting tired of stuffing little parts into plastic bags...


 

 I think I have memory loss and don't remember pain very well.  The bad thing is for you guys, I usually don't settle on the price until _after_ I've stuffed all the little bags ... when the pain is quite fresh.
	

	
	
		
		

		
		
	


	







  Seriously, this one is worth every bit of the suffering.
   
  BTW, I've shipped everything cobaltmute needs to build the first one, so the pressure's on him (and the Canadian mail).


----------



## geofftnz

Look, all you have to do is find an old pick-and-place machine and put a bag in place of the board. Problem solved!


----------



## cobaltmute

Given schedule for the next few days, I'm hoping to have the prototype tested to my satisfaction by the end of the weekend.


----------



## Misterrogers

Thanks for the update - anxiously awaiting a chance to build your DAC 
	

	
	
		
		

		
		
	


	



  
  Quote: 





cobaltmute said:


> Given schedule for the next few days, I'm hoping to have the prototype tested to my satisfaction by the end of the weekend.


----------



## forsakenrider

As I've been listening to mine every since day one many months ago, you can count me in on this new revision, weather it me prototype or kits.
   
  I love my pup1


----------



## tomb

Just a bit of an update - I hope cobaltmute won't mind.  He is busily working on the prototype V2 that he built last week.  He reports that the sound quality is excellent and better than our first versions.  Everything worked the first time!  There is a bit of a problem with DC voltage offset in one channel from the opamp, though.  Remember, there are no output coupling capacitors.  It's an awfully trivial amount, but a DAC is a source that gets amplified and that will increase the offset effect.  So, he's doing his best to get it lowered.  He's been partially successful so far, but is waiting on some new parts to try out.
   
  Meanwhile, I've been bogged down by the IRS.  I expect to build one fairly quickly after next Monday (IRS deadline) and will let you all know if I have the same issue.  I'm sure cobaltmute will get it solved, though.  Like he said, he wanted to be sure to get a good working version before we share the PCB's with the rest of you, so please be patient.


----------



## cobaltmute

So as tomb has said, my new version prototype is working. And as tomb has said, I do think it sounds excellent. I am running the new version with a very nice pair of RCAs versus a 3.5mm mini to RCA cable with the old version, so it isn't a total apples to apples comparison. That being said, I do think, as a *system* including the cables, it sounds better than the first version.

However, I am trying to track down an offset problem with my build. It appears to be something specific with the op-amp as I've replaced many of the parts around it While the offset is higher than I would like on one channel, it is still in spec for what the maximum allowed for the chip. I'd ordered new chips late last week, that I should be able to get on Thursday. I've also ordered an alternative part that has better offset specs, at the trade-off of a bit less output drive.

So a little more patience and I think we'll be able to release the prototype board to you all very soon.


----------



## forsakenrider

sounds like its going great!! keep up the work.


----------



## c12mech

I'm still listening to the first one and would be happy to prototype this version and offer a comparison.  The new layout looks like it should be a little more soldering friendly.  Are the pads longer for the dac chip this time.  I remember that being an issue with the first board.  I look forward to seeing how this one compares.


----------



## scootsit

Tomb,
  Are you still looking for people to prototype? I would definitely be interested. If not, I'll just wait for it to show up on Beezar.
   
  Thanks guys!


----------



## tomb

No, if you read the last several posts in the thread, there is an offset issue on cobaltmute's build.  I'm hoping to build one tomorrow - I've been backed up in orders with Beezar since doing my taxes, but I'm just about caught up. 
	

	
	
		
		

		
			




   
  Anyway, I guess if my build(s) confirm cobaltmute's findings, we may need to modify the layout a bit to reduce offset from the opamp.  So, hang loose and give us a chance.  We fully expect to let several of you prototype the PCB, but not until we have a better handle on this.
   
  Keep in mind, cobaltmute has indicated that this version sounds even better than the first.  If you apply it to an amp that has input coupling caps, output coupling caps, or input/output transformers, there will be no issue at all.  However, we want it to work well with any amp.  So, there may be some changes with the PCB design ... or not.  We'll just have to see.
   
  We will keep you updated. 
	

	
	
		
		

		
		
	


	



   
   
  EDIT: For those of you who may not be familar with "offset", it's some remaining DC voltage that can be measured at the signal outputs of the pupDAC.  These readings are in the single-digit micro-Volts, but understand that as a source, it means those micro-Volts will get amplified when connected to an amp.  The result might be (might be) that the output at the amp will be an amount of DC voltage that could possibly - in the worst scenario - be a cause for concern.  We are working to get that down to a safe range.


----------



## scootsit

Oops, sorry I missed the last page. My bad. I'm excited to see how it works out.


----------



## scootsit

Quote: 





tomb said:


>


 

 I was just looking at this, and I could very well be wrong, but aren't the silkscreens on the top-side backwards at the output? Isn't the TRS, tip=left, ring=right, sleeve=ground? Here, it appears that left and right are switched. Again, I assume I've made a mistake, but I just thought I'd ask.


----------



## Yoga Flame

Looks like the TRS jack's pcb pins are just wired that way.


----------



## scootsit

Oh, weird. My mistake. I forgot to check the BOM.


----------



## Avro_Arrow

I would take one of the boards that has some offset if you are just going to throw them
  out anyway...the amp I'm prototyping now has a servo.


----------



## cobaltmute

avro_arrow said:


> I would take one of the boards that has some offset if you are just going to throw them
> out anyway...the amp I'm prototyping now has a servo.




We are waiting for tomb to build his protos to see what they do before we offer anything. Even if tomb's has issues like mine,we will still offer them out (with a very large disclaimer about the offset).

The offset issue only seems to be affecting the left channel on my board. I've gone through 4 different op-amps and the right channel has been good but the left has been between passable and atrocious.

I'll admit to not having spent a lot of time with it the board over the last few weeks. I'm 4 weeks out from a triathlon and there is a bet with friends on it, so between trying to do normal stuff, training and recovery, I'm more than just a little tired. It's only the beginning of May and I've been on the bike for more distance this year than I rode all of 2011.


----------



## Avro_Arrow

Hey, if it's any consolation, my Chinese HiFiDIY PCM1793 DAC has about 20mV offset on one channel no matter
  what op amp I put in the output filter.
   
  Good luck in the triathlon!


----------



## Mullet

Looks like a cool project. I'm interested in doing a prototype when you're ready.


----------



## scootsit

By my math, only two weeks til the triathalon, good luck! Hope it goes well!


----------



## Avro_Arrow

I saw a peloton of riders coming through my area up by Lake Simcoe yesterday...I was wondering if one of them was cobaltmute...


----------



## cobaltmute

Not near Simcoe, yesterday. Did my first ever 100km on Saturday and went through Uxbridge/Zephyr.

My knees are still recovering. Getting old is a pain.

It was however a wonderful weekend for being on the bike.

Right now the big wait is for tomb to finish his and see what results he gets.


----------



## Avro_Arrow

Actually, I live just north of Zephyr, in Pefferlaw.
  My wife works in Uxbridge.
   
  Quote: 





cobaltmute said:


> Not near Simcoe, yesterday. Did my first ever 100km on Saturday and went through Uxbridge/Zephyr.
> My knees are still recovering. Getting old is a pain.
> It was however a wonderful weekend for being on the bike.
> Right now the big wait is for tomb to finish his and see what results he gets.


----------



## forsakenrider

Keep on riding Cobalmute! save the DAC work for the rainy days!
   
  I continue to enjoy the rev 1 every day! I am now running it after a USB isolator on some pretty filtered power.... Might even try it on batteries for fun.


----------



## tomb

Well, I've finally got some decent time off this weekend, so maybe I'll get them finished.  (Probably shouldn't have tried to do two at once, but I'm committed, now.)


----------



## tomb

Dang, this pisses me off - I don't have any time anymore!  I've got two of them pretty much populated with the SMD parts.  Hopefully, I'll have the rest finished in a couple of days.  Just an FYI, but I have never seen this amount of discrete regulation on a USB-powered DAC.  Every voltage supply imaginable is regulated - even more so than in the first prototype.  The charge pump is separate, and the opamp chip being located on the back side makes it a bit easier to replace, if needed.  I'm building one with the OPA2835 and the other with the OPA2836 (faster chip, but it may have more offset).


----------



## cobaltmute

tomb said:


> Just an FYI, but I have never seen this amount of discrete regulation on a USB-powered DAC.  Every voltage supply imaginable is regulated - even more so than in the first prototype.




I could add maybe one or two more regulators.....


----------



## tomb

Quote: 





cobaltmute said:


> I could add maybe one or two more regulators.....


 
  Well, if you think it would help ...


----------



## tomb

Finally!  I finished two of these - probably the finest USB-powered DACs I've ever heard and among the finest overall, period, I think (bias admitted).  I made some stupid mistakes along the way, but ended up with both of them essentially working the first time out, except for one particular stupid thing.  The stupid thing was that I was so eager to get them clean and spent so much time rinsing them with alcohol that it left quite a bit of fluid under the chips (unbeknownst to me).  They kept cutting out on me yesterday at random and driving me crazy trying to figure out what was wrong.  Now that they're dry, there's been no hiccups at all - just clean, sterling sound with more bass, more highs detail and resolution than the earlier pupDAC, and that same seductive mid-range.
   
  As for the offset, I think we're saying that cobaltmute's version may be a fluke.  Mine measured 1mV on the left and right RCA jack (referenced from the "GND" test point) with one pupDAC and 0mV left and 1mV right on the other pupDAC.  So, I don't think we have an issue with offset.
   
  My understanding with cobaltmute is that very little will change on the final production versions - just a bit of spacing to work out. The RCA jacks either need to have their front pins sliced off, or you need to carefully roll and force them into position onto the front edge of the PCB (what I did). Also, the Mica capacitors are too big for the lead spacing on the PCB, but I found if you pull the leads with a pair of pliers, you can get them down pretty close to the PCB surface. Finally, the C10 electrolytic is too close to one of the Mica caps, but all you need to do is bend it forward slightly to clear the electrolytic. The pads for the PCM chips have the same clearance as the original, so they are a bit challenging.
   
*Needless to say, these are not beginner builds.* I actually destroyed one PCB before completing these two (OK, I was out of practice, I admit).  I have 5 PCB's left and they will go to 5 of the following people who've already expressed an interest earlier in this thread:
   
  Avro_Arrow
  forsakenrider
  Misterrogers
  c12mech
  scootsit
  Mullet
   
  However, you MUST PM me through Head-Fi and confirm that your interest is still valid, and send me your NAME and ADDRESS.  Price will be $20 plus postage payable to Paypal (the PCB's cost me $15 each from Imagineering), but that will include all three output jacks, since those were the only parts ordered from DigiKey instead of Mouser.  Also, I will attempt to supply all the PCM1794 chips and as many PCM2707 and TPS chips as I can (I have several of each, but not sure if I've got 5 of each).  Note that the PCM1794 is $13.62 at Mouser, just by itself.
   
*First come, first serve!!!*
   
   
*P.S. Many, many thanks to cobaltmute for such an excellent design!!!*
   
*P.S. 2 - Looks like I missed one user, so there's 6 and only 5 PCB's - First come, first serve!*


----------



## c12mech

PM sent.
   
  They look nice Tom.


----------



## lehtinel

Darn, wish I was on the list. Looks VERY good and REALLY interesting!


----------



## Mullet

Good lookin' Tom!
   
  PM sent... can't wait to build this "Puppy"


----------



## Avro_Arrow

PM sent


----------



## c12mech

Quote: 





> The pads for the PCM chips have the same clearance as the original, so they are a bit challenging.
> *Needless to say, these are not beginner builds.*


 
  If this is the same as the first one a bit challenging is an understatement.  I think I remember trying to re-flow both those chips three or four times and still had to play with it some before I got it right.


----------



## Mullet

Quote: 





tomb said:


> Finally!  I finished two of these - probably the finest USB-powered DACs I've ever heard and among the finest overall, period, I think (bias admitted).


 
   
  ...And what DACs are you comparing the Pup to?
   
  I'll be able to compare it to the Gamma-1/2 and GrubDAC, so I'll definitely be posting my impressions.


----------



## c12mech

Is there an updated BOM or is it all the same parts with just a different layout?
   
  I will be able to compare it to the original prototype and a couple of different Buffalo 3 builds I'm doing.  I know the Buffalo is not a fair fight really but it would be nice to how they compare.


----------



## tomb

Quote: 





mullet said:


> ...And what DACs are you comparing the Pup to?
> 
> I'll be able to compare it to the Gamma-1/2 and GrubDAC, so I'll definitely be posting my impressions.


 
  A couple of things here, and I know you meant no malicious intent.
	

	
	
		
		

		
			








  It was my fault for making such a strong statement, but I am excited about the design.
	

	
	
		
		

		
		
	


	



   
  I typically frown away from direct comparisons between _genuine, DIY-based designs_.  That's because we're all operating on a shoe-string budget most of the time (me for sure, anyway) and we are in this business because we enjoy it.  My wife often jokes with me about Beezar - at least it self-sustains my hobby ... _for a change_.  However, nothing that you mention is really an absolute, direct comparison.  I have no issue with stating un-categorically, pupDAC >> grubDAC (_much greater than_ for you non-math types).  They are both designed by cobaltmute for different purposes, though - the grubDAC being perhaps the best available in the 1" x 2" form factor (and perhaps better than some bigger than that).  Cobaltmute will need to correct me if I get this wrong, but I think the pupDAC competes against the pinnacle in a USB-powered DAC, without an added extensive feature set (more options, connectibility, etc.).  PupDAC and grubDAC each fill two distinct market niches and will have a definite price differential commensurate with their performance.  _They will also have a huge difference in difficulty of construction._
   
  As for the Gamma 1/2, both have a superior feature set to either the grubDAC or pupDAC,  plus - if I'm not mistaken, they were specifically designed to minimize the non-through-hole parts.  So they don't really directly compete (IMHO).
   
  For me personally, I won't say what I've heard and what I haven't heard.  Suffice to say that I admitted in that same earlier post that _I'm biased_.


----------



## forsakenrider

Hot damn! If I didnt miss out then count me in!!


----------



## tomb

OK - everyone's accounted for, including an alternate.
	

	
	
		
		

		
		
	


	




  I'll try to send out the payment requests tonight through a Head-Fi PM.


----------



## tomb

PM's sent requesting payment.  I will update you through your Paypal e-mails from now on.


----------



## tomb

Wow - thanks a lot, everyone!  You've all paid already!
   
  I'm embarassed to continue to ask for your patience.  I will do my best to get the PCB's and other stuff shipped out by Friday.
   
  I'll either e-mail the BOM or have it posted by then, too.


----------



## Mullet

No worries man. Glad to be a part of the prototype phase. No malicious intent by the way. I was just fishing for a comparison in terms of sound signature and not feature set. A Gamma 1/2 or fully built Buffalo 3 would win any day in the features dept. If we were to closely compare this DAC in terms of what it sets out to do then I'd compare it to the Pico DAC. Both have similar outputs and is USB powered and should be about the same size. It differs in that the Pico uses a Wolfson 8740 as its DAC chip and isn't DIY. I have no idea if it has bypass caps on the output. That's where the comparisons could be made.
   
  We're all into DIY for different reasons... some for the challenge, some for "thinking" they're saving money, and some because we have nothing better to do. I'm in it for all three. I can see why we wouldn't want to compare for the reason of avoiding pissing contests or bias. It's hard to detach yourself from things sometimes.


----------



## scootsit

The chip on the pup is not oversampling, right?


----------



## Mullet

Here are a few questions...
   
  Because there are both RCA and 3.5mm connections... Is it safe to assume you can supply two amps at the same time?
   
  What's the RMS of this DAC?
   
  Also, I'm in for trying to figure out measurements for a Front Panels Express order. Anyone else interested? I'd say they would cost between $40-50 for a set of two.


----------



## cobaltmute

scootsit said:


> The chip on the pup is not oversampling, right?




The PCM1794A is a oversampling chip.


----------



## cobaltmute

mullet said:


> Here are a few questions...
> 
> Because there are both RCA and 3.5mm connections... Is it safe to assume you can supply two amps at the same time?
> 
> ...




There is both connections, but I wouldn't necessarily drive both at the same time. Depending upon cables and pots in the amp, you could end up loading the output stage a little heavily.

When looking at the output stage, I originally designed it to swing +-2V,


----------



## forsakenrider

Is this going to fit in the same sized Hammond case as the first? Or is there a different case planned?


----------



## cobaltmute

tomb said:


> A couple of things here, and I know you meant no malicious intent.    It was my fault for making such a strong statement, but I am excited about the design.
> 
> I typically frown away from direct comparisons between _genuine, DIY-based designs_.  That's because we're all operating on a shoe-string budget most of the time (me for sure, anyway) and we are in this business because we enjoy it.  My wife often jokes with me about Beezar - at least it self-sustains my hobby ... _for a change_.  However, nothing that you mention is really an absolute, direct comparison.  I have no issue with stating un-categorically, pupDAC >> grubDAC (_much greater than_ for you non-math types).  They are both designed by cobaltmute for different purposes, though - the grubDAC being perhaps the best available in the 1" x 2" form factor (and perhaps better than some bigger than that).  Cobaltmute will need to correct me if I get this wrong, but I think the pupDAC competes against the pinnacle in a USB-powered DAC, without an added extensive feature set (more options, connectibility, etc.).  PupDAC and grubDAC each fill two distinct market niches and will have a definite price differential commensurate with their performance.  _They will also have a huge difference in difficulty of construction._
> 
> ...




Here is my take on it:

If you want to compare designs, build a grubDAC and a USB-only gamma1. They will have very similar schematics and since they both use Wolfson chips, will have a similar sound characteristic. I have both, and I can hear the differences between them. The choice however between them has to be up to someone's personal preferences. 

As for how I think the pupDAC sounds? Let me tell you a story. Over half my life ago, when I was a teenager, I listed to vinyl through HD414's with tone controls engaged with full bass and treble boost. It was cool. It was loud and boomy. As I got older, the tone controls got disengaged and I started to learn that there was detail in the bass. The bass wasn't as fat, but I could hear stuff down there - like the actual notes. As I proceeded to get older, my equipment got better and I could hear more details everywhere through the range. Add a few more years, and better equipment, and I started to hear not just the notes, but the stuff going on between the notes, like the little noises fingers make as they move across the strings. Stuff that is hidden in the background, and it takes good resolution to show through.

That's where I think the pupDAC is. The first generation prototype was pretty darn good about showing you all those details. In fact it was good enough that I did the most un-audiophile thing - I settled on it. I really didn't need or want more. As I said to tomb, I don't know if it was just the layout changes or the RCAs or what, but this second generation prototype (with the LMH6643) seems to resolve just a little bit better. In trying to track down the offset problems in my proto, we tried a different op-amp, the OP2835. It was a step-up in all those things that I like - clear dynamics, clear sound and wonderful resolution.

At this level, personal preference for sound characteristics really starts to take affect.


----------



## cobaltmute

forsakenrider said:


> Is this going to fit in the same sized Hammond case as the first? Or is there a different case planned?



Exactly the same case. I toyed with a lot of ideas before doing the revision, but one of the things I had to keep the same was the form factor.


----------



## c12mech

One more thing, can we get an updated schematic along with the BOM. 
   
  Now that I have some more parts to play with I plan to do a little experimenting.  I've got a lot on my plate tight now but this will be worked on between other personal projects and some builds I'm being paid to do.


----------



## cobaltmute

c12mech said:


> Is there an updated BOM or is it all the same parts with just a different layout?
> 
> I will be able to compare it to the original prototype and a couple of different Buffalo 3 builds I'm doing.  I know the Buffalo is not a fair fight really but it would be nice to how they compare.



Most of the BOM is the same, but there is some differences. Mostly around the fact that instead of using a crystal, there is an oscillator with dedicated regulator.


----------



## Misterrogers

Quote: 





mullet said:


> Here are a few questions...
> 
> Because there are both RCA and 3.5mm connections... Is it safe to assume you can supply two amps at the same time?
> 
> ...


 
  I'd be down for that Mullet. Count me in for a set.


----------



## scootsit

After reading the last few posts, I cannot wait to build one of these!!!


----------



## Mullet

My plan is to definitely use the standard Hammond case and make up a few panels from Front Panels Express. They have a nifty piece of software for the designing the panels for both PC and Mac. Cobaltmute, do you have anything available that would aid in measurements so I can apply that to a FPE project? I can then either provide the project to anyone that wants it and they can individually buy the panels or if it's cheap enough we can do a small group buy if everyone is in. Right now it's just myself and Misterrogers that are in.


----------



## scootsit

Depending upon the price, I may be interested, but I wouldn't be involved until the final board is released.


----------



## Misterrogers

Yep, checked out their application/process this morning; looks very cool. I'm going to try it out for another diy project. Price is a bit high, but to me it's worth it for a good, finished look. I kinda suck at the case work.


----------



## Mullet

I'm in the same boat as you... kinda suck at the case work... well I'm ok, but don't have a good amount of tools to get the job done so I find it easier to deal with FPE. Plus, you know it's gonna look good despite the expense.


----------



## c12mech

FPE does good work but I am not a fan of the software.  It may just be me but I can draw a whole 3D model of a face plate in Sketchup in about a quarter of the time it takes to just get things set up in the FPE screen.  Maybe I completely missed something but I still have not figured out how to put in reference lines for layout.
   
  I may be in for a set of panels also.


----------



## Mullet

Yeah I agree their software is clunky. It's the only way to get decent results though. Anyone know of any other companies that offer such a service? FPE seems like the only kid on the block.


----------



## Forte

http://www.cam-expert.com/


----------



## Mullet

Thanks I'll try them out this time around. If it's easy to get quotes from both companies I'll compare then go with the best price.


----------



## c12mech

Thanks, for the link.  I like that you can upload your own .dxf file for them to use.  That makes things very convenient. 
   
  Mullet, let us know what you find out.  As long as the price is good I'm in.


----------



## Mullet

I've asked for a copy of cam experts software for Mac this morning. Still waiting. It does appear that FPE software can export .dxf as well so I can send the same document to both companies for a quote. I'm wondering if Cobalt has something that would contain measurements on his latest board layout. Not sure if Eagle or whatever software he uses can generate that. Otherwise, I can try and piece together measurements using other projects I've done like the Gamma1 DAC, that uses the same case. I'm assume there will be 2 holes on the back plate -- USB and LED. Then 3 holes on the front plate -- RCA and 3.5mm jack. Plus there is Type for the name of DAC, USB, RCA left and right and 1/8" Output. I don't think LED needs type. I'm assuming I'd need a caliper if I don't have some formal measurements.


----------



## tomb

Quote: 





mullet said:


> I've asked for a copy of cam experts software for Mac this morning. Still waiting. It does appear that FPE software can export .dxf as well so I can send the same document to both companies for a quote. I'm wondering if Cobalt has something that would contain measurements on his latest board layout. Not sure if Eagle or whatever software he uses can generate that. Otherwise, I can try and piece together measurements using other projects I've done like the Gamma1 DAC, that uses the same case. I'm assume there will be 2 holes on the back plate -- USB and LED. Then 3 holes on the front plate -- RCA and 3.5mm jack. Plus there is Type for the name of DAC, USB, RCA left and right and 1/8" Output. I don't think LED needs type. I'm assuming I'd need a caliper if I don't have some formal measurements.


 
  I've got the file from cobaltmute.  I'll try to put up a dimensioned drawing soon.


----------



## tomb

I hope you guys don't mind if I slip the shipping one more day.  I'm waiting on more PCM2707's from TI.  They're supposed to arrive today, but it looks like it's going to be at the end of the day, not before.


----------



## Misterrogers

tomb said:


> I hope you guys don't mind if I slip the shipping one more day.  I'm waiting on more PCM2707's from TI.  They're supposed to arrive today, but it looks like it's going to be at the end of the day, not before.




No worries Tom!


----------



## Mullet

It's all good in the hood.


----------



## tomb

All shipped!
   
  I didn't have as many TPS chips as I thought - I gave you each two of them besides the other stuff.  I also included a BOM in each package.  The BOM was revised to show the OPA2835 opamp - that's the recommended one at this point.
   
  Let us know that you received the package OK and good luck on the builds!


----------



## scootsit

If you don't mind me asking, what is the approximate cost of the full BOM?


----------



## tomb

Quote: 





scootsit said:


> If you don't mind me asking, what is the approximate cost of the full BOM?


 
  With the PCB, about $75.  That's not counting any casework, though.
   
  That may change in production.  I don't have a good feel for the PCB price right now.  It all depends on how many we order, plus, there will be electrical testing charges.  Cobaltmute feels that the PCB is complex enough that electrical testing of the PCB's is warranted, and I agree.
   
  That's a charge in PCB manufacturing that many of us never use on through-hole designs, but is probably critical for this board.


----------



## scootsit

Got it, thanks!
  What exactly does electrical testing entail (forgive my ignorance)?


----------



## Avro_Arrow

Thanks Tom
   
  Quote: 





tomb said:


> All shipped!
> 
> I didn't have as many TPS chips as I thought - I gave you each two of them besides the other stuff.  I also included a BOM in each package.  The BOM was revised to show the OPA2835 opamp - that's the recommended one at this point.
> 
> Let us know that you received the package OK and good luck on the builds!


----------



## Avro_Arrow

Thats where the board house tests each board to make sure it has no shorts or opens in the traces.
   
   
   
  Quote: 





scootsit said:


> Got it, thanks!
> What exactly does electrical testing entail (forgive my ignorance)?


----------



## scootsit

Oh, gotcha.


----------



## Mullet

Thanks Tom!
   
  Got a few projects on the burner so I'm foaming at the mouth here  I'll most likely build this along with "The Wire" amp and then decide to maybe stick the whole thing in one case or do separate casing. Let the fun begin!


----------



## Misterrogers

That's an awesome Idea Mullet! Thanks to your tip, I was able to secure an SE/SE Wire board. It'd be awesome to build these into one case.


----------



## Mullet

I'm trying to keep the case at a minimum size. I just bought one of these... http://glass-ware.stores.yahoo.net/psbilops.html for the power supply because I couldn't get a "Wire" PS PCB. It's 4.5 x 2.2 in so that's going to force my amp to be bigger than I wanted it to be. Add in the pup1 and I'm going to need more space. I think I'd need a case at least 10" wide to make it happen, which negates the "stay small" thang. So that's why I'm on the fence about it. If I do it I'm going to figure out how to add in a switch to go between the pup1 as a source and RCA inputs and use another DAC as my source. Either way with this power supply and transformer it's going to have to be 6 to 7 inches wide to begin with vs. separating the pup1 and using the standard Hammond case. Hrrmmmm.


----------



## forsakenrider

HEY! Im going to try and build the wire along side this as well!! small world


----------



## scootsit

Where can these wire PCBs be found?


----------



## Avro_Arrow

They are all sold out.
   
   
  Quote: 





scootsit said:


> Where can these wire PCBs be found?


----------



## Misterrogers

Yea, I was fortunate to fine someone with a spare SE/SE board they were willing to part with. It's a shame - from everything I read it's suppose to be a fantastic amp.


----------



## Mullet

Got the parts today! Pretty stoked for these upcoming builds. I decided to not case the PupDAC and Wire together. It might cost me a little more in the long run for FPE, Hammond case, etc. but I'll get more versatility out of the DAC.


----------



## Mullet

Misterrogers and forsakenrider what "Wire" PCBs did you get? The rework version?


----------



## Misterrogers

mullet said:


> Misterrogers and forsakenrider what "Wire" PCBs did you get? The rework version?




Yep, mine is a rework.


----------



## Avro_Arrow

I was thinking of doing a version of "the Wire", but I will call my version "the String"..
	

	
	
		
		

		
			




   
  Quote: 





mullet said:


> Misterrogers and forsakenrider what "Wire" PCBs did you get? The rework version?


----------



## Misterrogers

If you do, I'm in!


----------



## scootsit

Quote: 





avro_arrow said:


> I was thinking of doing a version of "the Wire", but I will call my version "the String"..


 

 Would it be identical to the wire? SE or balanced?


----------



## Mullet

The "string"... hehe.
   
  I think the only SE-SE boards left (being hoarded) are the rework version. It's not a big deal... you just need an exact-o knife to cut out a few traces. Then solder in some wire to connect things back up. I'm going to use some ethernet scrap wire to fix things up.
   
  Just ordered parts for both projects. I think the cost for the Pup DAC was around $36 with a Hammond case. The panels will be $40-50 and the order from TomB was $25. So all together with a nice case this should cost around $110. Not bad for a higher caliber USB DAC. It'll be way less if you case it up with something else or drill your own panels.


----------



## scootsit

Quote: 





mullet said:


> The "string"... hehe.
> 
> I think the only SE-SE boards left (being hoarded) are the rework version. It's not a big deal... you just need an exact-o knife to cut out a few traces. Then solder in some wire to connect things back up. I'm going to use some ethernet scrap wire to fix things up.
> 
> Just ordered parts for both projects. I think the cost for the Pup DAC was around $36 with a Hammond case. The panels will be $40-50 and the order from TomB was $25. So all together with a nice case this should cost around $110. Not bad for a higher caliber USB DAC. It'll be way less if you case it up with something else or drill your own panels.


 

 That sounds perfect, I've been looking for something just like that, can't wait for the regular build!!
   
  If someone makes a SE board similar to the wire, I'm in, too.


----------



## tomb

Anyone received their package, yet?  I was hoping at least Mullet had.  He's the closest.  I think Misterrogers will take a day longer.  The rest of you are out of the country (at least off the mainland), so it will take a few days longer, still.


----------



## Avro_Arrow

I recently sent a package down to the southern states and it took almost two weeks...


----------



## Misterrogers

tomb said:


> Anyone received their package, yet?  I was hoping at least Mullet had.  He's the closest.  I think Misterrogers will take a day longer.  The rest of you are out of the country (at least off the mainland), so it will take a few days longer, still.




I might have - I'm away for business and it might be waiting for me at the office. Here's hoping!


----------



## forsakenrider

Hey did the BOM get sent out and I missed it? or how is Mullet ordering his parts!
   
   
  I've got 2 wire rework boards and one bal-se board. I need to order parts for that at the same time at my Pup parts and also some sort of PSU.... Oh the projects are piling up!


----------



## Mullet

I received mine yesterday. Take a look a few posts back. I mentioned it. The BOM is included with the package. Most of the ICs were included with the package. If anyone wants here is the a mouser order sans most of the ICs. They didn't have the red led with the given specs so I went with an orange led with matching specs. The Hammond case is also included.
   
  http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=6a840912de


----------



## Mullet

Quote: 





forsakenrider said:


> I've got 2 wire rework boards and one bal-se board. I need to order parts for that at the same time at my Pup parts and also some sort of PSU.... Oh the projects are piling up!


 
  I know the feeling. I've also got a EHHA Rev A in the wings. I mentioned a power supply for "The Wire" a few posts back. I also ordered this transformer from Digikey, which is supposed to be really good and small. The caveat is it's expensive. TE62043-ND. I'm looking at spending about $150 on my "Wire" when all is said and done.
   
  TomB - Do you happen to have those measurements on hand? At this point, I'm definitely going to have panels made at FPE or CamXpert depending on who is cheaper.


----------



## cobaltmute

tomb is waiting on getting set of DXFs from me that Autocad will actually read to do the dimensions. For some reason the exports that I'm sending him aren't working, and I haven't had the time in the last week to go digging to figure out what is going on.


----------



## Mullet

No worries. I'm sure they will be shared once everything is ready.


----------



## scootsit

I saw this today and thought it would make a GREAT electronics case...never have to worry about heat sinking again!
  http://www.thinkgeek.com/computing/accessories/96b3/
   
  A bit more seriously, I also saw some inexpensive hard drive enclosures somewhere recently, and was thinking that using one of those as a DAC case might work well, because there's no pesky drilling or milling the USB plug, and some even have a simple (albeit un- or poorly regulated) power supply to augment the USB, given that every supply on this board is regulated, it might supply some extra current.


----------



## c12mech

Just chiming in to let Tomb know that my board and parts arrived today.  I plan to add the needed parts to a mouser order this weekend.  Hopefully I can get it up and running in the next few weeks.


----------



## tomb

Great!


----------



## Avro_Arrow

Got my box today, thanks Tom!


----------



## forsakenrider

Got my box today too!! thanks everyone! cant wait to get this going!.


----------



## Misterrogers

Me too - thanks Tom!


----------



## forsakenrider

Anyone thats already done it, would it be possible to get the BOM? I'm feeling a little lazy to type in all those part numbers.....


----------



## Mullet

I'm about a third of the way there... Did all ICs including U9 on the bottom. As always the 0805s are a pain in the arse. A few went flying across the room. Luckily I didn't lose any. I'm always worried about solder bridges for the 0805. Let's hope in the end, I avoid this. I hope to have the board completed tonight.

   
  Forsakenrider -- there is a semi complete mouser order that I posted within the last page or so. It's missing some of the ICs that I already had, the 3.3v and 4.75v regs. It's also missing whatever TomB sent you.


----------



## tomb

Quote: 





mullet said:


> I'm about a third of the way there... Did all ICs including U9 on the bottom. As always the 0805s are a pain in the arse. A few went flying across the room. Luckily I didn't lose any. I'm always worried about solder bridges for the 0805. Let's hope in the end, I avoid this. I hope to have the board completed tonight.
> 
> 
> Forsakenrider -- there is a semi complete mouser order that I posted within the last page or so. It's missing some of the ICs that I already had, the 3.3v and 4.75v regs. It's also missing whatever TomB sent you.


 
  Heck - you've got all the hard stuff done!  Looking good!


----------



## Mullet

So I just finished this puppy  Sounds quite good. I'll give more of a listen tomorrow before I post more impressions. Had a little hiccup when I first fired it up. My computer wasn't recognizing the DAC but it was getting power. All voltages checked out. I reflowed the USB chip and all is fine. I'm noticing a wierd pulsing noise when the volume is low or if I put music on pause. It's weird it sounds like a puttering noise. It can be softer and then get louder. Perhaps, I need to reflow the DAC chip. Any ideas on what this might be? Anyways, some pics to come tomorrow evening.


----------



## Misterrogers

Awesome Mullet! I'll be diving into mine this weekend. Hope you get to the bottom of the 'puttering' noise.



mullet said:


> So I just finished this puppy  Sounds quite good. I'll give more of a listen tomorrow before I post more impressions. Had a little hiccup when I first fired it up. My computer wasn't recognizing the DAC but it was getting power. All voltages checked out. I reflowed the USB chip and all is fine. I'm noticing a wierd pulsing noise when the volume is low or if I put music on pause. It's weird it sounds like a puttering noise. It can be softer and then get louder. Perhaps, I need to reflow the DAC chip. Any ideas on what this might be? Anyways, some pics to come tomorrow evening.


----------



## Mullet

The plot thickens. Still have correct voltages at test points, but now no audio. Using the flood method ie dab a bunch of solder and use a solder wick to clean each pin, I've reflowed both the DAC chip and USB to no avail. There are a couple of reasons this could be happening. After reflowing I cleaned the board with isopropyl alcohol and washed the board with warm water. I thought this would be fine -- apparently not. I might have a bridge somewhere too. With a magnifying glass I don't see anything out of the ordinary though. I'm going to try reflowing again and see if it does the trick. Measurement wise I've also measured the OPA2835 on Vin1±  and Vin2±. I get .119VDC for all readings. I don't get any readings on Vout1 and Vout2. Do these readings make sense? Also what pins should I be testing on the DAC chip?


----------



## Mullet

I'm getting .127VDC out of the DAC for both IoutL± and IoutR±. Also I'm getting the proper supply voltage for the opamp. Weird. Maybe my DAC chip is borked.


----------



## cobaltmute

Leave the board overnite to dry might be a first thing I would do.

I do not remember what the voltages would so at the output of the DAC. They are a function of the fact that the DAC is current output + the I/V resistors.

Are you measuring with music or without?


----------



## Mullet

I was measuring with a 1k sine wave. I usually measure in AC to measure what I assume is pseudo RMS readings on output at the 3.5mm jack. I get no readings in AC. In DC I get readings until the output of the opamp. What's weird is I'm getting readings and they are equal for both L and R channels. I'll let the board dry. In the meantime I decided to get some DAC and opamp samples from TI just in case. . I should maybe order the surrounding parts around the DAC chip for good measure. I've already almost ruined C17.


----------



## cobaltmute

Check te digital side - both PCMs

The 1794 seems to be outputting. Its balanced output is not centered on zero so the fact that you are getting voltage there indicates that it is working.


----------



## tomb

I would emphasize the drying part.  That drove me crazy just with alcohol - random failures, etc.  I can't imagine what it may be like with water.  It takes quite a while to dry out beneath those chips.  If you spray with a duster and see liquid staining the PCB on the other side, that tells you there's still moisture underneath.  It was a day later before mine quit acting up and there was no residue under the chips.


----------



## Mullet

I'm getting back to where I started... worked on the digital side of things and now I have audio again. Phew! So now it's time to figure out what this pulsating/puttering noise is. It seems like it has something to do with grounding. If I pick up the Pup and hold it the pulsating goes away - mostly. If I move the Pup closer to my computer the sound seems to get louder. I've never heard this with a DAC before. There is also an intermittent crackle as well. Back to the drawing board.


----------



## tomb

Quote: 





mullet said:


> I'm getting back to where I started... worked on the digital side of things and now I have audio again. Phew! So now it's time to figure out what this pulsating/puttering noise is. It seems like it has something to do with grounding. If I pick up the Pup and hold it the pulsating goes away - mostly. If I move the Pup closer to my computer the sound seems to get louder. I've never heard this with a DAC before. There is also an intermittent crackle as well. Back to the drawing board.


 
  Stick it under a light bulb (heat-dry) and forget about it until tomorrow.
   
  The crackling could very well be intermittent shorting.
   
  EDIT: I'm sorry to say that several of those chips I supplied are brand new versions from TI.  They are specifically subject to humidity and moisture.  There are moisture strip tell-tales in the packages from TI, with instructions to bake the parts if the tell-tales show a moisture intrusion.


----------



## Avro_Arrow

The moisture content is for manufacturing purposes where they use a re-flow oven.
  If the chips have too much moisture they crack during the process.
  This is not relevant to hand soldering.
   
  Quote: 





tomb said:


> Stick it under a light bulb (heat-dry) and forget about it until tomorrow.
> 
> The crackling could very well be intermittent shorting.
> 
> EDIT: I'm sorry to say that several of those chips I supplied are brand new versions from TI.  They are specifically subject to humidity and moisture.  There are moisture strip tell-tales in the packages from TI, with instructions to bake the parts if the tell-tales show a moisture intrusion.


----------



## tomb

Quote: 





avro_arrow said:


> The moisture content is for manufacturing purposes where they use a re-flow oven.
> If the chips have too much moisture they crack during the process.
> This is not relevant to hand soldering.


 
  It may not be relevant to hand soldering as far as cracking, but doesn't that indicate that they will absorb more moisture than other chips?  If so, it seems to me it would still mean that it's harder to get everything "dry" on the PCB - especially if you've rinsed/immersed it.


----------



## forsakenrider

I had a lot of weird issues on my first version and they all came down to solder bridges on the dacs. If you have a hot air station I would almost remove and resolder the chips.
   
  Also, I find using the solder wick method often doesn't leave much solder behind so it could be an intermittent connection. Try lots of flux and adding a little solder to each pin so they have a nice fillet at the back where they join the board.


----------



## Mullet

The solder wick method annoys me too -- especially when you don't have much room to work with caps in the way. I also tend to have to try this method several times before I get it right. The flipside is that doing each pin precisely is not easy and you end up having bridges anyway.
   
  I don't think there are solder bridges. What if I had a bridge or two under those little 0805s? They aren't easy to solder either. I tend to get a blob instead of a nice ramp and this is even using flux. Sometimes it comes out perfect. I have some chipquik and extra chips on the way, so I think I might end up taking off the 2707 first then going from there.
   
  Could it be the crystal that is acting up? D'oh! For the love of DIY.


----------



## cobaltmute

I doubt that it is the Oscillator. If it was, I would expect that it would affect the USB connection


----------



## jdkJake

I actually like the solder wick method. My take is to place a reasonable amount of flux across a row of pins and then go back and forth over those pins with the tip on top of the wick. Move the entire wick back and forth over the pins rather than the tip over the wick. This limits the amount of solder that is taken up by the wick in a single pass. The bridges are cleared away and a reasonable amount of solder is left to mechanically and electrically support the connection. A couple of passes should be all it takes. 

Mullet, I have to say, with 99% pure alcohol, why on earth do you bother to use water? Most water, unless distilled, is loaded with minerals, chlorine and whatnot. The alcohol should be more than enough to disolve and lift the flux into suspension for removal from the board. It will also dry extremely quick. If you must use water, consider blowing off the excess with compressed air or even a hair dryer (cool setting). Standing liquid on the board should be avoided to limit the potential for intrusion.


----------



## Avro_Arrow

I'm going to try the "toaster oven" method on this build.
  Should have everything I need to start next week.


----------



## tomb

I have never had an issue with immersing the entire PCB when building a DAC ... until now.
	

	
	
		
		

		
			





  In fact, I always recommended it and it was part of the documented construction technique, beginning all the way back to the BantamDAC.  Of course, that never included through-hole parts such as capacitors, etc. - or even the crystal/oscillator.  Immersion was done at the end of all SMD work.
   
  If the newer TI chips are more sensitive to absorbing moisture - maybe it's not such a good idea.  No offense, but 90% alcohol (what I use for a buck a quart from Walmart) does not really dry all that quickly - especially if it's underneath a chip.  If these new chips allow the alcohol to soak-in internally, it may take even longer.  I exacerbated my pupDACs because when I had the random problems, I'd re-flow the PCM chips, then splash on the alcohol again to clean up the flux.  The random issues continued and I would repeat the same thing again, to no avail.  I finally gave up and went to bed.  All the problems ended the very next day, when everything had sufficient time to thoroughly dry.  Both of them have been running dependably ever since.


----------



## Avro_Arrow

Parts question.
   
  C2, 9, 16, 19 - 667-EEU-FC1J120
   
  Is this _really_ supposed to be a 63 volt cap?
   
  Edit:
   
  Wouldn't something like this be more appropriate?
   
  Edit:
   
  Or maybe this then.


----------



## tomb

Quote: 





avro_arrow said:


> Parts question.
> 
> C2, 9, 16, 19 - 667-EEU-FC1J120
> 
> ...


 
  I don't think voltage was a pre-requisite for the cap selection.  I believe cobaltmute referenced some recent tests that indicated normal electrolytics may actually be less noisy, but I'll let him explain it for sure.
   
  The BOM caps certainly work well enough
	

	
	
		
		

		
		
	


	




 and they're very cheap.


----------



## Mullet

Quote:  





> Mullet, I have to say, with 99% pure alcohol, why on earth do you bother to use water? Most water, unless distilled, is loaded with minerals, chlorine and whatnot. The alcohol should be more than enough to disolve and lift the flux into suspension for removal from the board. It will also dry extremely quick. If you must use water, consider blowing off the excess with compressed air or even a hair dryer (cool setting). Standing liquid on the board should be avoided to limit the potential for intrusion.


 
   
  With regard to alcohol, I was using 70% because the good stuff was at work. I know we discussed not needing water in another thread, but I thought there wouldn't be a harm in it as long as I let the board sufficiently dry. I was going by TomB's directions for the GrubDAC, which states that you can use water. I know to avoid it now. Even still, after a few days of letting the board fully dry I still get the pulsing noise and some static here and there.
   
  Like I stated before, if I move the DAC around the loudness of the pulsing varies. Also, if I cup the DAC with my hands the noise actually goes away. At this point, it's probably best to replace a few parts and see what happens.
   
  On a final note, anyone have any extra C6/17 caps? (80-C0805C104K3R7210) I've pretty much fried mine from the flood and suck method. They are .07 a piece and I'd hate to buy 2 or 3 and pay $8 for shipping. If I get no response I'm going to go ahead and buy them along with a few more C2, C9, C16 just in case. They are a lot more resilient to heat than the 0805s, so they're probably fine.


----------



## tomb

Quote: 





mullet said:


> With regard to alcohol, I was using 70% because the good stuff was at work. I know we discussed not needing water in another thread, but I thought there wouldn't be a harm in it as long as I let the board sufficiently dry. *I was going by TomB's directions for the GrubDAC, which states that you can use water. *


 
  Just curious, but I'm seriously wondering if I have a typo on the GrubDAC website?  I have never used water.  The pics on the GrubDAC website show me immersing the GrubDAC into a little yellow butter bowl that has the same old 90% Walmart alcohol (it's actually 91%) that I've always recommended:
http://www.diyforums.org/GrubDAC/GrubDACphoto-build-2.php
  (at the bottom of the page)


----------



## Mullet

TomB ~ My bad. I'm not sure where I picked up that info about the water immersion. I'm going to avoid it in the future.


----------



## scootsit

I was sorta thinking of building some sort of media manager with the pupDAC when I build it, and one of these new $25 computers: http://www.raspberrypi.org/


----------



## tomb

Quote: 





mullet said:


> TomB ~ My bad. I'm not sure where I picked up that info about the water immersion. I'm going to avoid it in the future.


 
  No problem - let's just hope you can get yours fixed!


----------



## tomb

Quote: 





scootsit said:


> I was sorta thinking of building some sort of media manager with the pupDAC when I build it, and one of these new $25 computers: http://www.raspberrypi.org/


 
  Raspberry Pi?  Shades of the Timex Sinclair!  (I had one of those!)


----------



## scootsit

Quote: 





tomb said:


> Raspberry Pi?  Shades of the Timex Sinclair!  (I had one of those!)


 

 Interesting. I'd never heard of that one! I was thinking of the first Apple that Steve Wozniak wanted to sell PCBs to. But hey, I can't argue with $25 computer! It supposedly is a hair too big to fit into an Altoids container...the CMoy of computers?
  Evidently, if the corners were rounded, it would fit into an Altoids container, which is pretty neat!
   
  It also has 10 or so pins of in/out interface, I see huge potential there.


----------



## Mullet

I'm totally bummed. But all might not be lost.
   
  Last nite I tried to replace U1 (PCM2707) and in my extraction accidentally pulled two pads. One was pin 21 - Vdd and the other was pin 30 - Vccr. To my knowledge, pin 30 is a throw away anyways. Not sure about pin 21. I ended up scraping away the via so copper was exposed and bridged the via to pin 21. After firing the DAC back up still pulsing, no audio. So I'll have to apply more solder to get better connections. Hopefully the two pads I pulled aren't too important. The lesson learned here is this is not an easy project even if you've done plenty of SMD soldering before. I've done several Gamma1/2 DACs along with a GrubDAC. It's frustrating, but I'm going to move forward to attempt to fix my issues. If all else fails I'll wait until the PCBs are available to the general public and try again.
   
  The other lesson is I probably used too high a heat on my iron when using ChipQuik. This most likely caused the pads to lift.


----------



## forsakenrider

Bummer mullet! but all is never lost, this is DIY after all!
   
  When I got my first board I gave up for two weeks before I got back and fixed it. Sometimes it just takes a little break I think. The pup1 I'm listening to right now has 2 lifted pads as well, I don't think I've told anyone before...


----------



## cobaltmute

mullet said:


> The other lesson is I probably used too high a heat on my iron when using ChipQuik. This most likely caused the pads to lift.




I hate to say it but this is important. You had to have *way* to hot of an iron for these boards. If the board were from Gold Phoenix I would have expected lifted pads, but on these ones from Imagineering, it is rare. I've changed out the op-amp at least four times and still have a board that is in good shape.

I keep my iron relatively cool. I saw a post from tangent once about his iron temp and it was about 100F cooler than mine was set. I started using a cooler iron (which works well for non-RoHS solder).

IIRC, you were also using flood and suck for the 0805s. Why? Two terminal SMD is the easiest to put down. Put a tiny blob of solder on one pad. Reheat the pad/solder with the iron, slid in the part, remove the iron. That gets one side fixed. Then you can treat the other pad like doing any through hole. Do the ground side of the part first and it is a lot easier. Sometimes you may get a little too much solder on it, but it doesn't matter. Also you will never bridge using this method.


----------



## cobaltmute

avro_arrow said:


> Parts question.
> 
> C2, 9, 16, 19 - 667-EEU-FC1J120
> 
> ...




As long as the rated voltage is above the running voltage, it doesn't matter. IIRC, the reason I put that part on the BOM is that was what was in stock when I made the BOM at Mouser. Mouser's selection of Panasonic caps wasn't quite as good as Digikey's.

If you want to try polymers at those positions, be my guest. That being said, C16 should be keep with the FM/FC. In reading comments of people far more experienced than I, the FM/FC cap is the best choice for that position.


----------



## Mullet

I'm using a variable temp iron. I think I have it set to 600 degrees F. In the future I'll try lower temps and see how that goes. I've read that 600 is fine. Maybe its more about opinion than fact.
   
  I don't believe I was doing flood and suck for 0805s -- only for the PCM chips. I was actually doing the method you describe above. The issue I was having with them is holding them with my tweezers without having them fly across the room. The other issue was that some of the pads seem to blob and not take easily even with flux applied. It might not be a big deal, but it's still an anomaly. Also, the reason I thought there might be bridges is because there was at least one or two that wasn't flat on the board. They were close, but not precisely flat. I was going to investigate that further to see if that was the cause of my issues. Otherwise, I'm assuming my lifted pads (21 and 30) won't cause an issue, right?


----------



## cobaltmute

Pin 30 is no issue. Pin 21 is Vdd which is important.

For the slide method for the 0805 - it makes a big difference if you do the GND side first. You have to heat the plane (even with thermal relief) and it is easier to do that if you have the full pad to work with.

IIRC my iron is around 600F. But it does make a difference if you are using tin-lead or silver solder. Silver seems to need more heat in what I have done.


----------



## Avro_Arrow

I ordered the one in the second edit, the Panasonic FM.
   
  Quote: 





cobaltmute said:


> As long as the rated voltage is above the running voltage, it doesn't matter. IIRC, the reason I put that part on the BOM is that was what was in stock when I made the BOM at Mouser. Mouser's selection of Panasonic caps wasn't quite as good as Digikey's.
> If you want to try polymers at those positions, be my guest. That being said, C16 should be keep with the FM/FC. In reading comments of people far more experienced than I, the FM/FC cap is the best choice for that position.


----------



## Avro_Arrow

I use 550 for my iron.
  I turn it up a bit if I am doing larger mechanical parts or ground planes.
  Maybe 600 to 650 at the hottest.


----------



## c12mech

One thing I learned from the first board was that the two dac chips were a pain.  I must have re-flowed them 4-5 times before I got it to work.  I also found that a decent pair of curved jewelers tweezers are your best friend when dealing with the 0805 parts.  That and a good magnifying lamp.  
   
  I'm with forsakenrider, take a break from it for a couple of days and then come back.  I did the same thing and it all seemed to work just right after that.


----------



## Mullet

That's what's so weird about this. I'm within most others limits as far as iron temps go. I'll have to look up the recommended heat for ChipQuik. This is not the first time I've lifted pads at 600 degrees. Got a new PCM1794 today, so we'll see what materializes. Just in case if I have to jump pin 21 on U1, where does it go to?


----------



## Avro_Arrow

The solder paste I have melts at 361°F (183°C).


----------



## tomb

Not to be contrary, but everyone's methods seem to differ a bit.  I set my iron (Hakko 936) to 650 deg.F., but I'm using a 0.8mm chisel tip and ... my Hakko is getting pretty long-in-the-tooth, now.  I don't think it gets as hot as it used to.  I'm the opposite of cobaltmute on the 805/1206 caps and resistors, too.  I prefer to "prime" the non-ground pad.  I figure the first pad is the one where I've got both hands going with the solder iron in one and tweezers and the chip in the other.  The last thing I want to worry about in that position is whether I can melt the solder.  Better to get the thing soldered down - then you have all day to melt the solder on the other pad.  That goes for the PCM chips, too - I never pick a ground pin as the "anchor" pin.  I messed up an entire PCB this time, though, so maybe I'm doing it wrong.
	

	
	
		
		

		
			




   
  P.S. I never do flood and suck, either.  Seems to me you're daring the solder not to go behind the pins.  If it does, all you end up doing is sucking all the top surface solder that's holding the pins to the pads - before you ever get to the stuff underneath.  I dab a bit at a time on the solder iron tip, then move down the row of pins as long as it looks like there's still liquid solder.  If not, then I put some more on the iron tip.  Once I think there's solder on all the pins, then I "clean up" with a lot of drag-and-wipe's.


----------



## Avro_Arrow

I looked on the website of the manufacturer of the solder I use and
  they recommend a temperature of 650 - 700 F.
   
  The method of rework soldering they taught at Flextronics when I worked there
  was very similar to the method TomB uses.
  With the right temperature, solder and flux, you can drag a little ball of solder
  down the pins of the chip and it will merrily bounce along from pin to pin leaving
  them perfectly filled with no solder bridges between pins. I was able to do it
  at work, but I am out of practice and don't have the correct combination so
  I can't do it at home reliably.


----------



## jdkJake

I am in the ~650 deg.F camp myself with my 936. I only go above that when I am soldering heat sinks of something that takes away large amounts of heat.

So far, I have never lifted a pad (knocks on wood).


----------



## Mullet

So the plot thickens even further...
   
  First I fixed the PCM2707. I needed to use a super small clipping off a lead to bridge pin 21 to its via. Then, I proceeded to successfully replace the DAC chip. I have music again but still have the pulsating sound. So then I decide its time to replace U9 -- the opa2835. Still getting the pulsating sound. I check all resistors and caps to make sure everything looks nice and soldered with no bridges. Also, check to see that I have correct resistors in place. Everything is cool. So then I'm thinking to myself is the opamp oscillating? Is this the noise I'm hearing? I happen to have a spare OPA2365 from a Gamma2 build that I recently had to fix. Lo and behold after replacing the opamp no more pulsating. Music sounds fine. Is this opamp within spec? I think I'm keeping it on there unless there is a more suitable replacement.


----------



## cobaltmute

The OPA2365 should work. I would try the LMH6643 as a chip as the specs are a bit better for this application.

While tomb and I didn't have issue with the OPA2835, and tomb thought it was good, it doesn't surprise me that it may oscillate. With the ground plane right under the chip, the layout is super ideal for the high speed op-amp. I will admit leaving the ground plane under the op-amp was a mistake I did on the proto.


----------



## ostewart

When are kits going to be available and price? As ive been looking for a cheap diy DAC, was thinking of the grub DAC


----------



## cobaltmute

If you have never done SMT soldering before, do a grubDAC first. The pupDAC is not a good first SMT project unless you have *a lot* of patience and are will to spend time checking each part as it goes down.

The kits will be ready when they are ready. Like everything else about this particular project, it is taking time.


----------



## ostewart

Thanks, I may get the grub first then.


----------



## tomb

Quote: 





ostewart said:


> Thanks, I may get the grub first then.


 
  Highly advised.  If you read through just the most recent posts, you'll see the trouble that's had with even experienced builders.  We will improve that quite a bit for the production version, no doubt, with cobaltmute's design skills.  However, as cobaltmute infers, it's doubtful that it will ever attain a beginners' or "first kit" status.  I can tell you right now that the price of a kit will be more than you are willing to invest in just as an experiment.
   
  All that said, it's worth every bit of the trouble and complexity involved in building it, but you need prior experience - period.


----------



## Mullet

As the guy who almost killed his project, I agree with what the fellas are saying. This project is not for beginners. I have to be honest this is the first time after doing a few Gamma-2/1s and a GrubDAC that I've actually not had a DAC not work after firing it up for the first time. Perhaps, my mistakes could have been avoided if I changed out U9 sooner and didn't fuss with the PCM2707. I hope what I've been through can help others with regard to how hot to keep your iron, not to soak a board into water after cleaning it with alcohol, how to not lift pads, etc. I learned that using a solder sucker on these pads for cleaning excess chip quik solder is not the answer and using solder wick is the answer. I still have to obtain an LMH6643 to really complete the PCB and make sure there are no oscillations. The next step for me is to work on properly measured panels. I'm just waiting on more solid board measurements so I don't end up having to order panels twice. 
   
  This is where I got the erroneous info for using soap and water after you use isopropyl alcohol... I knew I wasn't crazy 
  http://www.diyaudio.com/wiki/The_Wire_Headphone_Amp_Build_Wiki


----------



## Avro_Arrow

I'm still on hold for a toaster oven...
   
  I may have to break down and hand solder it.


----------



## cobaltmute

avro_arrow said:


> I'm still on hold for a toaster oven...
> 
> I may have to break down and hand solder it.




Skillet method on the stove works as well for doing the "hard" side of the board.


----------



## Misterrogers

Just an update - making progress on mine. I have the main chips down, waiting on a couple that are inbound from digikey. I have relatives in town; they're in from the east coast - and wake every day right at my 5:30 - 6:00 am 'project' time, chatty as can be. Oey!


----------



## Mullet

Good work! Glad to see someone else making progress. That's a shame you only get a half an hour a day to work on your projects. I'm curious to see if I'm the only with with an oscillating OPA2835.


----------



## Misterrogers

It's usually not that 'constrained' - just with relatives in and all. Timing sucks though; between PupDAC, Wire and a BIII, I could spend all day every day just playing


----------



## geofftnz

If you are hand-soldering the GrubDAC, try approaching the pins end-on with a very small amount of solder. I broke a kit on my first attempt by being a bit sloppy. Some of the vias will punish you with bridges.


----------



## Avro_Arrow

Here is my hand soldering job...I gave up on the toaster oven for now.
   

   

   
  They looked cleaner with the naked eye...


----------



## cobaltmute

avro_arrow said:


> They looked cleaner with the naked eye...



They always do, they always do...


----------



## Mullet

Avro -- How are you getting such great closeups? I'm assuming you're using the crop function of your favorite photo editing software.


----------



## Avro_Arrow

Scanner at 1600 dpi...
   
  Quote: 





mullet said:


> Avro -- How are you getting such great closeups? I'm assuming you're using the crop function of your favorite photo editing software.


----------



## Avro_Arrow

Back to component stuffing today, with any luck I could be listening this evening...


----------



## Mullet

Good luck!
   
  Did some price comparisons for panels... Front Panel Express is the winner by $6 difference.
   
  Here's to hoping with my opamp change to an official opamp -- LMH6643 -- that my oscillations go away.


----------



## Avro_Arrow

Progress so far...
   
  Top:
   

   
  Bottom:


----------



## scootsit

Did you bake it or use an iron?
  Quote: 





avro_arrow said:


> Progress so far...
> 
> Top:
> 
> ...


----------



## Mullet

Lookin' good. Looks to be soldered by hand. Just need to do the through hole stuff and you're in like flynn.


----------



## Avro_Arrow

@ Scootsit: I got tired of waiting for my wife to pick out a new toaster oven so I could use the old one...Hand soldered.
   
  Completed:
   

   
  (that one was taken with my camera, not the scanner 
	

	
	
		
		

		
			





)
   
  Now to see if I built it right.


----------



## Avro_Arrow

Guess what...It worked on the first try!
  Op amp stays cold...no sign of oscillation.
  Now on to some listening tests.


----------



## Avro_Arrow

For offset, I got 1.3 mV on one channel and -0.4 mV on the other.


----------



## tomb

Quote: 





avro_arrow said:


> For offset, I got 1.3 mV on one channel and -0.4 mV on the other.


 
  That's great, Avro!  It seems fairly consistent with the two I built (~1 mV).


----------



## Avro_Arrow

I did some further listening tests today.
  This time using the DAC "naked".
  With my Shure SE215 it did a pretty credible job.
  At lower listening levels I didn't miss the amp at all.
   
  Great job Cobaltmute!


----------



## Misterrogers

Had some free time today, so I put down all my remaining components except for 1! C32 flew across my desk and found that black hole where all such 'chicken feed' parts end up. Sigh. Replacement is ordered, and I wait for a couple more days.


----------



## Avro_Arrow

I know your plight.
  I spent ten minutes searching for one of those little
  chicken feed bits in my carpet. Did I mention I hate
  carpet in my work area? I did eventually find it...


----------



## jdkJake

misterrogers said:


> Had some free time today, so I put down all my remaining components except for 1! C32 flew across my desk and found that black hole where all such 'chicken feed' parts end up. Sigh. Replacement is ordered, and I wait for a couple more days.




Those of us with allergies, well, we feel your pain. 
Tile, hard wood, or laminate make it a bit easier, but, still a challenge.


----------



## cobaltmute

avro_arrow said:


> I did some further listening tests today.
> This time using the DAC "naked".
> With my Shure SE215 it did a pretty credible job.
> At lower listening levels I didn't miss the amp at all.
> ...




Considering those are 20 ohm phones, not the designed for load. I would be guessing that the output on the pupDAC was starting to get current starved and sound quality would have been breaking down.


----------



## Mullet

Got a LMH6643 swapped out the OPA2635 that was previously working and then magic smoke <========>~~~~~~~~~~~!!!!@!@#$$%
   
  Somehow, I guess a short fried my U5 and U7 because both weren't responding with my multimeter. Ordered replacement parts, got them yesterday and replaced all suspect parts. Fired it up and success! Finally, in audio bliss with proper parts and no oscillation or noise. Could the charge pump (U7) have been faulty the whole time?
   
  On a side note, ordered panels from FPE, hopefully I'll have them by next week. I'm keeping my fingers crossed that I got the measurements right.


----------



## Misterrogers

Fantastic news Mullet! My parts landed yesterday - so I'll be powering up later today or tomorrow. It'd sure be great to not get the magic smoke


----------



## tomb

Quote: 





mullet said:


> Got a LMH6643 swapped out the OPA2635 that was previously working and then magic smoke <========>~~~~~~~~~~~!!!!@!@#$$%
> 
> Somehow, I guess a short fried my U5 and U7 because both weren't responding with my multimeter. Ordered replacement parts, got them yesterday and replaced all suspect parts. Fired it up and success! Finally, in audio bliss with proper parts and no oscillation or noise. Could the charge pump (U7) have been faulty the whole time?
> 
> On a side note, ordered panels from FPE, hopefully I'll have them by next week. I'm keeping my fingers crossed that I got the measurements right.


 
  I suppose it's possible.  When you're confident everything is working and you feel good about it, I'd suggest swapping back out to an OPA2835 (I'm assuming you mean OPA2*8*35?). It really is superior and gives no indication of oscillating in my builds or cobaltmute's.  If you actually have an OPA2635 instead, let me know and I'll send you an OPA2835.  I have a few more samples coming from TI.
   
  IMHO, the LMH6643 has more prat, but it's because of bass fog - sort of like what I hear at headphone meets when someone wants me to listen to their super-duper CD/DVD player.
	

	
	
		
		

		
			





  I prefer the clean, pristine sound of a good DIY DAC, instead.*  I think the OPA2835 provides that in spades.
  
   
  * There's just as much bass, it's just that you can hear it cleanly defined just like the midrange and highs.


----------



## korben69

Hi

 I'm following this thread, impressive work 
	

	
	
		
		

		
		
	


	



 Could someone point me to the latest BOM ?
 What are the regs refs used as : U4 - U2 - U5 - U7 - U10 - U8 ?
 Cheers

 Phil (korben69)


----------



## tomb

Quote: 





korben69 said:


> Hi
> 
> I'm following this thread, impressive work
> 
> ...


 
  We supplied the BOM's directly to the proto builders.  Not that it's secret or anything, but we haven't gone to production with the design.  There may be two reasons for not posting the BOM at present: 1) the design may change again, anyway, and 2) I don't think it's possible to build something like this without the PCB.
   
  That said, to answer your question directly:
  U2, U4 - TPS79333 
  U5 - TPS793475
  U7 - TPS60403
  U8 - TPS72325
  U10 - TPS79325


----------



## korben69

Hi Tomb
   
  I've read that MIC5205 are very good regs with very low noise, 150mA.
  TPS79333 noise is 32µV vs 0.26µV for MIC5205, same package SOT23-5.
  MIC5207 goes up to 180mA, same low noise 0.26µV, adjustable Vout version available.
  Links :
  http://www.micrel.com/_PDF/mic5205.pdf
  http://www.micrel.com/_PDF/mic5207.pdf
  Maybe this could help


----------



## Mullet

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.  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"!


----------



## cobaltmute

Quote: 





korben69 said:


> Hi Tomb
> 
> I've read that MIC5205 are very good regs with very low noise, 150mA.
> TPS79333 noise is 32µV vs 0.26µV for MIC5205, same package SOT23-5.
> ...


 
   
  Those Micrel parts require tantalum capacitors at the output to be stable, as opposed to ceramics.  Tantalum are polarized, which would be another thing to try and get right on a complex board, so I don't see an advantage at this moment.
   
  The Micrel part that does use ceramics has no better performance than the TI parts listed, so it is a wash.


----------



## Misterrogers

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.



mullet said:


> 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.  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"!


----------



## tomb

Yay!!! 
	

	
	
		
		

		
			




   
  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.


----------



## Misterrogers

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


----------



## scootsit

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.


----------



## Mullet

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.


----------



## cobaltmute

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.


----------



## Misterrogers

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.


----------



## Mullet

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.


----------



## cobaltmute

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.


----------



## Misterrogers

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!


----------



## Mullet

Quote: 





cobaltmute said:


> 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!


----------



## Avro_Arrow

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.


----------



## tomb

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.


----------



## Misterrogers

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


----------



## cobaltmute

avro_arrow said:


> Suggestion:
> 
> Drive the LED off pin 11 on PMC2706/7.
> The LED will only light when there is communication with the computer.
> ...




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.


----------



## Avro_Arrow

The behavior I get is whenever there is proper communication with the computer, the pin is driven high.
  If the DAC is not properly recognized, the pin stays low. The pin never goes low as a result of being idle.
  I. too. thought it might only light when music is playing but that is not what happens.
  Also, if I just supply power, the pin stays low.
  If you use "disconnect" in the device menu, the pin will go low.
   
  Quote: 





cobaltmute said:


> 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.


----------



## Avro_Arrow

You could use the current limit resistor for the LED to escape from between the traces...
   
  Edit:
  You could also change R10 to PTH, that would give you the room to escape.
   
  Another Edit:
  On third thought...
  It's probably much easier to just re-route the I2S lines under the chip.
  That frees up the room to drop a via to the bottom to escape to the
  LEDs current location.


----------



## cobaltmute

avro_arrow said:


> The behavior I get is whenever there is proper communication with the computer, the pin is driven high.
> If the DAC is not properly recognized, the pin stays low. The pin never goes low as a result of being idle.
> I. too. thought it might only light when music is playing but that is not what happens.
> Also, if I just supply power, the pin stays low.
> If you use "disconnect" in the device menu, the pin will go low.




It is interesting though that the datasheet says on page 27 that on an idle bus that it will drive suspend low.


----------



## Avro_Arrow

Here is another suggestion:
   
  Add some 22R to the I2S lines...
   
  Edit:
   
  And move the bypass caps for the op amp to the bottom.
  They will fit at each end of the op amp.
  Might solve some of the oscillation issues.


----------



## Mullet

Quote: 





tomb said:


> 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.


 
  Please don't drop the 3.5mm option. I've been using both outputs simultaneously for two amps with no issue at all just like I do with the Gamma2. More options = moar betta!


----------



## cobaltmute

At this moment the 3.5 is staying.

I think I have done all the revisions I'm going to do on the board at this point.


----------



## Misterrogers

And truly, there isn't anything wrong with the current design. I know that others would love to have access to it  A co-worker borrowed it other day; I think I'm going to have to hunt him down to get it back.


----------



## cobaltmute

The only thing left to be done is decide if I want to put all the resistors for the op-amp stage on the bottom or just some as is pictured here.



The big changes from the proto board all of you built are:


 slightly larger pads for both the PCM2707 and PCM1794
 removing the ground plane under the op-amp
 moving the op-amp resistors around to shorten the loops around the op-amp
 making cut-outs on the board so you don't have to trim the pins off the RCA jacks.
 pushing some stuff around so there is room for the mica caps. The lead spacing is still a touch narrow, but that is to allow options for that part position.


----------



## Avro_Arrow

I think what is happening is even with no music playing, the bus is still active, monitoring the HID pins.
   
  Quote: 





cobaltmute said:


> It is interesting though that the datasheet says on page 27 that on an idle bus that it will drive suspend low.


----------



## tomb

Quote: 





cobaltmute said:


> The only thing left to be done is decide if I want to put all the resistors for the op-amp stage on the bottom or just some as is pictured here.
> 
> The big changes from the proto board all of you built are:
> slightly larger pads for both the PCM2707 and PCM1794
> ...


 
  I would prefer to leave all the through-hole resistors on top.
   
   
  Looks GREAT!!


----------



## cobaltmute

tomb said:


> I would prefer to leave all the through-hole resistors on top.
> 
> 
> Looks GREAT!!




There are currently four resistors on the bottom of the board. These are the resistors at the output of the op-amp. The idea for having them on the bottom is to have the shortest trace possible to the resistor, to help with stability for the fast op-amp. It also reduces any capacitance effects from the PCB itself.

Nothing says you have to install them on the bottom....


----------



## tomb

Quote: 





cobaltmute said:


> Nothing says you have to install them on the bottom....


 
  Wouldn't they be reversed in the circuit if they went on the top? 
	

	
	
		
		

		
		
	


	



   
  It's still early and I woke up to a lot of thunderstorms ... my brain is obviously not working yet.


----------



## cobaltmute

tomb said:


> Wouldn't they be reversed in the circuit if they went on the top? :blink:
> 
> It's still early and I woke up to a lot of thunderstorms ... my brain is obviously not working yet.




Grab a PCB, and put a resistor into its proper position. Now pull out the resistor and put it into the board, in the same holes, from the other side.

Is there a difference?

From a physical mounting perspective, not really.

From a trace perspective yes. In the pupDAC, the trace would be on the bottom of the board from the op-amp. If the resistor is on the top of the board, the signal leaves the op-amp, travels to the through-hole, through the distance of the board, up the lead and into the resistor. If the resistor is on the bottom of the board, it travels to the through hole pad, up the lead and into the resistor.


----------



## tomb

I know I left my brain in bed earlier, but where's your sense of humor this morning?
	

	
	
		
		

		
		
	


	




  Everyone knows when you turn a resistor around, the current goes the other way.
	

	
	
		
		

		
		
	


	



   
  Seriously, it looks good - let's do it.


----------



## cobaltmute

Well, I did forget to mention the difference in gravitational forces on the current..... 

For the truly geeky:
Total number of pins: 257
Pins in a net: 242
Not connected pins: 15
Total number of vias: 50
Total number of connections: 194
Unrouted connections: 0
Completion: 100%
Total number of parts: 88
Total number of nets: 48


----------



## c12mech

Quote: 





cobaltmute said:


> Well, I did forget to mention the difference in gravitational forces on the current.....
> 
> 
> 
> ...


 
  Thanks for that list of truly geeky information.  I'm one of those that likes as much "useless" information as possible. 
   
  I'm waiting for a couple of regulators that Mouser was out of to get here from Digikey.  Then I will start putting it all together.


----------



## tomb

Just an update, but cobaltmute and I are on track to build two new prototypes (changes as he recently posted) and then we're going to production.  The plans are to have full kits with custom Hammond 1455C801 or 1455C802 cases.


----------



## Misterrogers

Fantastic news Tom. Will be be able to grab just the case/plates?


----------



## tomb

Quote: 





misterrogers said:


> Fantastic news Tom. Will be be able to grab just the case/plates?


 
  Probably.  Most likely, it's purchasing a kit without the case that will be the problem.  My experience with custom cases is that they often end up being the most expensive item and requiring a huge investment in volume as well.  For the MiniMAX kits that I sell, for instance, a manufacturing run of those cases from Lansing is the largest single investment that Beezar makes.  I simply can't afford to offer the kits without the cases.
   
  Obviously, the little Hammond cases for the pupDAC won't be that much (I hope).  That may mean that custom machining/silkscreening is simply not practical, though - as was the situation for the plastic cases used with the grubDAC and SkeletonDAC.  We'll just have to see how the numbers shake out when I get the design finalized and start getting quotes.


----------



## Mullet

MrR~ FWIW the panels with custom engraving cost $38 shipped from Front Panels Express. A Hammond case is $12 plus $6 shipping at Mouser. That's $50+ for a full case.

I won't know if my measurements were 100% accurate until at least August 11th when I get back from my Scandinavian adventures. If all goes well you guys can use DXFs from my design.


----------



## tomb

Well, folks - the new prototype works great (latest layout from cobaltmute above).  I had no issue at all soldering the PCM chips with the longer traces.  Offset is 2mV left and 3mV right, measured fromt the "GND" pad.  It sounds exactly the same - just as good, in other words.
   
  I'm going to continue to fool around with it this weekend, but plans call for ordering production PCB's on Monday.  I'm also commissioning Hammond to do a manufacturing run of custom-machined cases (1455C801).  I'm shooting for blue anodizing with laser-etched graphics (that will be done locally).  The kits and cases should be reasonably priced on Beezar.
   
  It will take 4-6 weeks to get all this done, though, so please be patient. 
	

	
	
		
		

		
		
	


	



   
   
  P.S. It took me about 4 hrs to build, working steadily, another hour to clean, and then I let it sit out in the sun on top of my car.  That quickly took care of any residual alcohol and flux.
	

	
	
		
		

		
		
	


	




  It worked the first time out and continues to play seamlessly.


----------



## scootsit

I'm very excited! I just started searching craigslist for the right toaster oven....


----------



## KimLaroux

Quote: 





tomb said:


> Well, folks - the new prototype works great (latest layout from cobaltmute above).  I had no issue at all soldering the PCM chips with the longer traces.  Offset is 2mV left and 3mV right, measured fromt the "GND" pad.  It sounds exactly the same - just as good, in other words.
> 
> I'm going to continue to fool around with it this weekend, but plans call for ordering production PCB's on Monday.  I'm also commissioning Hammond to do a manufacturing run of custom-machined cases (1455C801).  I'm shooting for blue anodizing with laser-etched graphics (that will be done locally).  The kits and cases should be reasonably priced on Beezar.
> 
> ...


 
   
  That's one way to kill a circuit using static discharge. I admit never have thought about this method before. I might try it next time I need a fried MOSFET.
   
  On a more serious note, have you an idea for the price of the kits yet?


----------



## tomb

Quote: 





kimlaroux said:


> That's one way to kill a circuit using static discharge. I admit never have thought about this method before. I might try it next time I need a fried MOSFET.
> 
> On a more serious note, have you an idea for the price of the kits yet?


 
  So, you think sunlight and a bit of heat is the same as applying current to the circuit?
   
  I'm not sure I understand your logic - the dang thing was sitting on top of standoffs, maybe that's the point you're missing.
	

	
	
		
		

		
		
	


	




  That's OK, it's not the first time in this thread that my intelligence has been low-balled.
   
  How much are the kits?  Your right arm will do for starters ...  Seriously, that's yet to be determined.  We're working on it.  Just keep in mind that Mullet was talking $38 just for endplates.  In my experience, we should be able to do a complete anodized case with silkscreening from the mfr for a similar or just slightly more selling price than doing FPE endplates.  We're upgrading the expectations by attempting a different color (than black or clear) with Hammond cases and using laser-etching.  Can we still meet that price goal for the cases?  I hope so, anyway ...


----------



## scootsit

Quote: 





tomb said:


> So, you think sunlight and a bit of heat is the same as applying current to the circuit?
> 
> I'm not sure I understand your logic - the dang thing was sitting on top of standoffs, maybe that's the point you're missing.
> 
> ...


 

 Are you planning on selling full kits or could we get just the board and the case? Or am I jumping the gun by a month or so?


----------



## tomb

Quote: 





scootsit said:


> Are you planning on selling full kits or could we get just the board and the case? Or am I jumping the gun by a month or so?


 
  No, the primary thing to remember is that Beezar will only sell _complete_ kits, that means PCB and custom case included.
   
  However, the PCB and custom case will be available separately.  So, you could order both and then buy the parts from Mouser and DigiKey.  It's just that Beezar will not sell the parts without the case (PCB is understood).
   
  Keep in mind that if we price things correctly, there will be no advantage to ordering the PCB and case separately - unless you're overseas and have a completely different source of the electronic parts.


----------



## tomb

PICS - not much has changed.  There are longer pad traces for the PCM chips, the RCA jacks have cutouts in the PCB for the under-tabs, the Mica capacitors have much more clearance than before, and then on the bottom - no ground plane under the opamp.
   









 Click on these for a bigger pic:


----------



## scootsit

Quote: 





tomb said:


> No, the primary thing to remember is that Beezar will only sell _complete_ kits, that means PCB and custom case included.
> 
> However, the PCB and custom case will be available separately.  So, you could order both and then buy the parts from Mouser and DigiKey.  It's just that Beezar will not sell the parts without the case (PCB is understood).
> 
> Keep in mind that if we price things correctly, there will be no advantage to ordering the PCB and case separately - unless you're overseas and have a completely different source of the electronic parts.


 

 Excellent, that's what I wanted to know. I have a lot of the necessary components in my parts bin or in samples, that's why I was asking.
   
  Thanks, Tomb.


----------



## KimLaroux

Quote: 





tomb said:


> So, you think sunlight and a bit of heat is the same as applying current to the circuit?
> 
> I'm not sure I understand your logic - the dang thing was sitting on top of standoffs, maybe that's the point you're missing.
> 
> ...


 
   
  Nah, it's when you place it on, or take it off. Cars, with their rubber tires, are know to build up static charges. They discharge trough you when you touch the car. Don't tell me you've never had a shock when touching a car! 
   
  My point was, when the DAC is between you and the car when these discharges happen, things can go wrong. But then I might be overthinking this. As usual... Still would not do it, though.


----------



## Mullet

I've been completely done with my Pup for about a week now. My measurements were pretty spot on. The USB port is slightly off on the horizontal axis, but still fits fine. The RCA holes are pretty spot on and are larger than they need to be because variations on how you solder them in. Overall, I'm very happy with this build. For those who are wondering the build cost me ~$100 for parts, panels, etc. I'm sure TomB will come in around the same price or maybe a little cheaper.
   
  Here's a few pics...


----------



## tomb

$100 is going to be tough to hit.  I'm wondering whether in that estimate you counted for the fact that I supplied you with the PCB, DAC chip and a couple of other items for FREE.  I won't be able to do that with kits.


----------



## tomb

We're working toward blue-anodized cases with laser-etching.  The manufacturing order with Hammond has already been placed.  The production PCB's are on order, too.
   
  This is a glimpse at the case design that's been supplied to Hammond and the laser-etching service:




  About the post above, $100 may be hard to hit, but that's the neighborhood and the hope is that it won't be a lot more than that. (crossing my fingers)


----------



## MrDavis

Very nice case design.  I like it.


----------



## scootsit

Quote: 





tomb said:


> We're working toward blue-anodized cases with laser-etching.  The manufacturing order with Hammond has already been placed.  The production PCB's are on order, too.
> 
> This is a glimpse at the case design that's been supplied to Hammond and the laser-etching service:
> 
> ...


 
  Looks great, I seriously cannot wait!


----------



## Mullet

Quote: 





tomb said:


> $100 is going to be tough to hit.  I'm wondering whether in that estimate you counted for the fact that I supplied you with the PCB, DAC chip and a couple of other items for FREE.  I won't be able to do that with kits.


 

 I didn't have a few items in my figure. Keeping in mind the cost savings of prototyping... even at ~$130-$140 for a full kit, etc. it's well worth the cost for such a compact DAC that gets the job done. This DAC is the equivalent of the Cavalli Compact Tube Hybrid in the price, performance, size category. Thanks again cobaltmute and TomB.


----------



## tomb

The production PCBs are in:


----------



## scootsit

Quote: 





tomb said:


> The production PCBs are in:


 
  So excited, I cannot wait!


----------



## forsakenrider

Wow! I got buried in a cave and just stuck my head out to see all this! nice work guys!!
   
  i still havent built mine, I went away for holiday and when I came back I was supposed to move and get settled in. well things changed and now im without work bench, desk, iron, or anything for maybe another month!!! I do have my original pup1 with me though luckily!
   
  Nice work with the progress everyone!


----------



## tomb

Yep - we're checking the production submittals from Hammond on the custom case right now.  Hopefully, we'll have a prototype case in a 2-3 weeks, perhaps.  Then things get interesting as I get them anodized and laser-etched.  We'll keep in touch with the progress - this should be fun and I know dang well it's worth it.


----------



## Misterrogers

Hey gang - just chiming in. My Pup has been doing admirable duty day in and day out at work. I currently have it paired with my 'Wire' build which I've just cased up. Tom - when the cases are in, I hope you'll sell them separately. I like your design, and I'd rather use your case than make a custom front panel. Thanks again for your efforts to make this DAC/Kit available!


----------



## tomb

Yeah, I'm looking at that.  The problem is, nobody can run a business by simply becoming a Mouser custom-ordering/re-packaging service.  We'll see if the price I will have to sell at will be palatable for you customers vs. ordering the BOM by yourselves.  Otherwise, I will have to package everything together.  Anyway ... I'll get that all figured out once the case manufacturing is set.  Worst case, I'll sell the cases separately, but not the parts.
   
  BTW - the case prototype is in - I'm testing out the anodizing and laser-etching tomorrow.  Here's some pics, but keep in mind that the case is a rough, unfinished prototype from Hammond .  It's meant to check the machining, only:
   












   
  I'm working on what shade of blue anodizing will work best with the laser-etching.  As you can see, cobaltmute has designed the PCB so that you can use the Hammond case with or without the bezels.


----------



## dwatanabe

Looks really nice. How can I get my hands on a kit? Anyone working on a non-oversampling design?


----------



## tomb

Test for the anodizing and laser etch:


----------



## scootsit

Those look amazing!
  Any idea when the boards/cases will be available?


----------



## tomb

About 3, maybe 4 weeks at the most ...


----------



## scootsit

Quote: 





tomb said:


> About 3, maybe 4 weeks at the most ...


 

 Awesome! Are you going to sell short kits or complete kits? I'm most interested in just the boards and case, I have 2/3s of the parts laying around.


----------



## tomb

The boards and case would most likely always be sold separately.


----------



## scootsit

Quote: 





tomb said:


> The boards and case would most likely always be sold separately.


 

 Excellent, thanks! I really can't wait, it looks like an amazing product, which is no surprise, you and cobaltmute tend always impress.


----------



## tomb

Quote: 





scootsit said:


> Excellent, thanks! I really can't wait, it looks like an amazing product, which is no surprise, you and cobaltmute tend always impress.


 
  scootsit, you've been excited from the beginning.  I will make certain that you get an opportunity at a kit/case.  If for some unbelievable reason that doesn't happen, I'll send you one of my prototypes.


----------



## scootsit

tomb said:


> scootsit said:
> 
> 
> > Excellent, thanks! I really can't wait, it looks like an amazing product, which is no surprise, you and cobaltmute tend always impress.
> ...



wow. thanks tomb, I appreciate that.


----------



## scootsit

Is there a BOM available? I may have some free time this weekend, and I'd like to see what I have in my parts drawer and what I still need.


----------



## tomb

Quote: 





scootsit said:


> Is there a BOM available? I may have some free time this weekend, and I'd like to see what I have in my parts drawer and what I still need.


 
  See if this works -
http://www.diyforums.org/PupDAC/bom/pupDAC-prelim-BOM.xlsx
   
  Note that for the kits, there are equivalent RCA jacks at Mouser that I used, but the 3.5mm jack is only at DigiKey.  You may also need some help from cobaltmute on X1 - it's gone to 1000 part minimum orders at Mouser and DigiKey.
   
  I have the cases back from the anodizer today.  Laser-etching begins Monday.  Mouser has shipped me the kit parts, but I haven't received them yet.  In any event, the kits should be available soon.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 It works. cobaltmute, any ideas on X1?
  Regarding the RCAs, is there room to panel mount them?
   
  I assume your kit includes X1, maybe that is the best way to go...
   
  For PCM2707, you have it speced with PCM2707PJTRG4, is there any difference between that and PCM2707PJT or PCM2707PJTG4?


----------



## tomb

Quote: 





scootsit said:


> It works. cobaltmute, any ideas on X1?
> He will have to answer this one ... if nothing else, we may be purchasing them in qtys of 1000, because they're used on the grubDAC, too.
> 
> Regarding the RCAs, is there room to panel mount them?
> ...


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 Tomb, you're a gentleman and a scholar. Sample request sent to TI, going to go through my parts drawer tomorrow!


----------



## cobaltmute

scootsit said:


> It works. cobaltmute, any ideas on X1?




The C3391 in 12Mhz is an equivlant part from Crystek that is on order at Mouser.

It looks like the follow should also work from Mouser.
695-CSX750FBC-12 
815-ASV-12-EJ-T

As I type this, there is 4500 is stock between those two parts so you should be good.


----------



## scootsit

Quote: 





cobaltmute said:


> Quote:
> 
> 
> 
> ...


 

 Great, thanks!


----------



## tomb

Some shots of the cases prior to laser-etching next week:


----------



## HiGHFLYiN9

Looks great Tom!! Thanks as always for putting so much time and effort into projects for the DIY community.


----------



## scootsit

I agree, that looks sexy, particularly without the bezels. I'm not sure it even needs engraving, there's something so simple about it.
   
  Can the outputs of the DAC be hooked up to two different devices at the same time? I'm considering feeding this into two amps.
   
  Also, what are the dimensions on the speced RCAs and 3.5mm jacks, I want to try to find equivalents at Mouser.
   
  Thanks!


----------



## Mullet

Quote: 





scootsit said:


> Can the outputs of the DAC be hooked up to two different devices at the same time? I'm considering feeding this into two amps.


 
  Yes. I do this all the time. Love it.


----------



## tomb

Looks like Mouser had a change of heart on the oscillator -
http://www.mouser.com/ProductDetail/Crystek-Corporation/C3391-12000/?qs=sGAEpiMZZMsQtlBhqKq43bqBrGYLfENu
   
  986 of them are due in on Election Day (11/6/2012).
   
  Just an update, but the cases are being laser-etched as I'm typing this.  They should be finished by the middle of next week.  I'm working fast and furious on the website and hope to build one of the exact kits as a build thread this weekend - just to make sure everything's working.


----------



## scootsit

Quote: 





tomb said:


> Looks like Mouser had a change of heart on the oscillator -
> http://www.mouser.com/ProductDetail/Crystek-Corporation/C3391-12000/?qs=sGAEpiMZZMsQtlBhqKq43bqBrGYLfENu
> 
> 986 of them are due in on Election Day (11/6/2012).
> ...


 
  If worse comes to worse, they always have that other oscillator that is about 50 cents more and has better specs that cobaltmute posted (fewer ppm). I got a toaster oven yesterday, have all of the ICs, just need a few passive parts and I'm ready to go!
   
  Regarding connectors, Mouser appears to have exact drop in components, for the RCAs, try the Kycon KLPX-0848A-2
   
  If you search for that, you will find the entire product line, available in tin or gold plating. They do not stock white, with gold plating, but they do stock red and black with gold plating, also any color with tin.
   
   
  I'm thinking this 3.5mm will work:
 STX-3150-3N  It says that it is switched, but according to the catalog/data sheet, it isn't. It's a half mm off here and there, but I think it will work. Cobaltmute or tomb will have to chime in, I'm not sure.


----------



## tomb

The laser-etcher made a mistake, so I've ordered more endplates to have them done again.  Unfortunately, that will take another 2-3 weeks.


----------



## scootsit

Quote: 





tomb said:


> The laser-etcher made a mistake, so I've ordered more endplates to have them done again.  Unfortunately, that will take another 2-3 weeks.


 

 They look great! What's the mistake?


----------



## Goobley

I'm guessing it's the grave accent (`) over the p. Either way they look superb, a mistake like that certainly wouldn't bother me.


----------



## funch

Looks like collector-item status to me. I'd take one in a heartbeat.


----------



## tomb

Quote: 





goobley said:


> I'm guessing it's the grave accent (`) over the p. Either way they look superb, a mistake like that certainly wouldn't bother me.


 
  You get the cigar!  It was actually a note leader's arrowhead in my drawing (identifying the type of font).  I don't blame him at all, though.  I was disappointed, but stuff happens and it was an honest mistake.  *His work is simply outstanding.*  He's even paying for the mistake - one can't ask anymore than that.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 Nope, and I agree, collector's item! I actually thought it was some sort of embellishment to the font, that was intentional!


----------



## cobaltmute

I have to say that tomb has done some fantastic work on the case. I've had some input in the graphics and that, but he has done an outstanding job in putting the work together.


----------



## tcpoint

Ditto.


----------



## Misterrogers

Double ditto!


----------



## scootsit

Do you guys think this will fit as the 3.5mm?
  Some of the pins are off by as much as 1/2 mm, will that be a problem?
  http://www.mouser.com/ProductDetail/Kycon/STX-3150-3N/?qs=sGAEpiMZZMv0W4pxf2HiV3p8sCuGBLybHE9Af3%252bGhVk%3d
   
  And these for the RCAs?
  http://www.mouser.com/Search/Refine.aspx?Keyword=KLPX-0848A-2


----------



## tomb

Quote: 





cobaltmute said:


> I have to say that tomb has done some fantastic work on the case. I've had some input in the graphics and that, but he has done an outstanding job in putting the work together.


 
  Many thanks!!  And to the rest of you, too!
   
  'Course, a lot of the issue has been trying to get that _*cobalt-*_blue color for some reason. 
	

	
	
		
		

		
		
	


	









   
   
  P.S. Yes, cobalt-blue is actually a bit darker.  However, the color of the case is a shade or two darker than in the digital images.  It's very hard to get both the actual color shade and still show the aluminum sheen that's present to the naked eye.


----------



## funch

Quote: 





misterrogers said:


> Double ditto!


 
   
  Double dog ditto (get it; pup, dog? I'm so funny)! 
	

	
	
		
		

		
		
	


	




   
   
  Seriously, are you willing to sell a kit with the 'collectors edition' end plates?


----------



## tomb

Hmm ... already answered a PM about this.  I think I gave the wrong impression.
   
  A bad endplate does not ruin any of the rest of the case assembly.  When you buy these things in bulk, Hammond could care less which pieces you want - neither does the anodizer or the laser-etcher.  As far as they're concerned, their job was X pieces of metal - shaped, machined, and processed a certain way.  The replacement is simply to order and process more of the endplates.  The potential impact was really to me because the cost of the mistake is times 100 (how many cases I have invested).  Plus, it delays the date at which all of the kits will be ready - which is why I posted about it to let you all know what was going on.
   
  So, there will be no "bad case kit" to sell or recoup - only 100 extra endplates with a laser-etch mistake.  If you want one of the bad endplates as a collectors item - I'll send you one - but it's not going to be any use beyond that.


----------



## scootsit

Quote: 





tomb said:


> Hmm ... already answered a PM about this.  I think I gave the wrong impression.
> 
> A bad endplate does not ruin any of the rest of the case assembly.  When you buy these things in bulk, Hammond could care less which pieces you want - neither does the anodizer or the laser-etcher.  As far as they're concerned, their job was X pieces of metal - shaped, machined, and processed a certain way.  The replacement is simply to order and process more of the endplates.  The potential impact was really to me because the cost of the mistake is times 100 (how many cases I have invested).  Plus, it delays the date at which all of the kits will be ready - which is why I posted about it to let you all know what was going on.
> 
> So, there will be no "bad case kit" to sell or recoup - only 100 extra endplates with a laser-etch mistake.  If you want one of the bad endplates as a collectors item - I'll send you one - but it's not going to be any use beyond that.


 

 If we were okay with the bad end-plate, and everything else was already done, could we perhaps place orders before you get the replacements?


----------



## tomb

Quote: 





scootsit said:


> If we were okay with the bad end-plate, and everything else was already done, could we perhaps place orders before you get the replacements?


 
  What would I do with the perfectly good, correct endplates at that point?
   
  Sometimes I think I reveal too much of the business side of things ... sorry.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 I was thinking about that as I typed it. Well, I would love an extra end plate, I'm 100% sure I'll find a use for it... I already have some in mind...


----------



## tomb

Quote: 





scootsit said:


> I was thinking about that as I typed it. Well, I would love an extra end plate, I'm 100% sure I'll find a use for it... I already have some in mind...


 
  I will include the bad endplate as an extra in the first orders for as many that last.  The laser-etch guy has asked for several dozen that he's going to pass around as examples of his work - knowing that no one outside of this community is going to even realize the mistake, especially without the rest of the case.  That should still leave plenty to include in kits as extras for awhile, though.


----------



## funch

Fair enough, and thanks for all the info. Knowing more of the 'bidness' end of it helps us appreciate more what you go through to make all this great stuff available to us.


----------



## kchapdaily

hey guys just coming into this thread, ive searched but cant find any posts about when/where kits will be available. ill continue trying to find info in this thread. wanted to join the conversation as well


----------



## cobaltmute

tomb is dealing with the issue of the error on the one end plate. He has to get the new end-plates, get them anodized and laser etched. So a least a few more weeks until the kits will be ready for sale, as far as I know.


----------



## kchapdaily

ah gotcha. i built a grubdac a while ago. while i dont actually need to upgrade or anything, i think id just like to compare sound quality. and im hearing very good things about this, so i figured id get a kit while i can!


----------



## tomb

Quote: 





cobaltmute said:


> tomb is dealing with the issue of the error on the one end plate. He has to get the new end-plates, get them anodized and laser etched. So a least a few more weeks until the kits will be ready for sale, as far as I know.


 
  Yes, this is exactly correct.


----------



## geofftnz

Excellent... gives me time to move into the massive money-pit my new house and set up a decent workbench for electronics.


----------



## tomb

I built the production version of the PCB just to make sure everything works:


 

 


   
  Cobaltmute's extended pad-traces on the PCB for the PCM chips worked great!  I had no issues whatsoever and it worked the first time, every time.


----------



## scootsit

Quote: 





tomb said:


> I built the production version of the PCB just to make sure everything works:
> 
> 
> 
> ...


 

 Looks great!!!
  So...does that mean it's time?!


----------



## tomb

Not quite - I believe the new endplates have shipped, but I haven't received them yet.  When I do, it will still take a week to a week and a half to get them anodized and then laser-etched.


----------



## scootsit

Quote: 





tomb said:


> Not quite - I believe the new endplates have shipped, but I haven't received them yet.  When I do, it will still take a week to a week and a half to get them anodized and then laser-etched.


 

 Okay. This is shaping up perfectly! By the time that's done, and all, I will have completed my thesis and defended my MS, it'll be a little graduation present to myself!


----------



## Lefuneste

Well what can I say... My Credit Card is screaming!!
  The finished product looks awsome!! Can't wait to solder it to life!!
   
  By the way did you have to change something to the BOM? Any updates on that? Maybe We can already start ordering components...


----------



## DingoSmuggler

Quote: 





lefuneste said:


> Well what can I say... My Credit Card is screaming!!
> The finished product looks awsome!! Can't wait to solder it to life!!
> 
> By the way did you have to change something to the BOM? Any updates on that? Maybe We can already start ordering components...


 
  Patience my friend.
   
  They are being offered as complete kits, so you don't have to worry about sourcing the BOM yourself.


----------



## scootsit

Quote: 





dingosmuggler said:


> Quote:
> 
> 
> 
> ...


 

 They're also being offered as short-kits for those of us that have a parts bin full of nearly everything on the board.


----------



## Avro_Arrow

Looks good!
  The Pup is born
   
  Congratulations TomB and CobaltMute.


----------



## tomb

The pupDAC website is now complete and live:
*pupDAC*
   
   
  P.S. The replacement front plates are at the anodizers now.  Hopefully, I can get them to the laser-etchers next week and then we're off and running!


----------



## Lefuneste

Excellent documentation as usual. This is really the "creme de la creme" of a DAC dude!!
My God!! What a Beauty this DAC is!!

I am already so happy with my OsConized GrubDAC which has a unbelievable clarity and depth, I can't wait to check this marvel out.

Only the look of it makes me cry!! And the cobalt blue color... This is too good to be true!!

THANKS for the MASSIVE ACHIEVEMENT!!


----------



## Lefuneste

By the way I've just checked out the BOM to see if I was good from the previous preprod version.

The only missing Mouser part was the 3.5mm jack. As it's a pain in the bottom to order one item only from Digikey, I've checked references at Mouser for the same measurements and came up with this reference *806-STX-3150-3N*
I believe it should fit right on the PCB as it measures the same as the Digikey part. *Please someone correct me if I am mistaking!*

Also for such a beauty, I would like Gold plated RCA output. I got these *806-KLPX-0848A-2RG* (Red One) and *806-KLPX-0848A-2BG* (Black One as the White is non stocked... There's also a Yellow one 2YB).

Finally I wanted a more precise time base and came up with this *815-ASV-12-EJ-T* which is 20 ppm instead of 25 for the same price. Well this is really over the head...

For those interested I have the project ready to be shared on Mouser, but I am probably not the first one to have it in the starting blocks I guess...

Overall it's 73.98 USD including standard Hammond enclosure in Silver (13.08) and an extra Opamp OPA2836 (3.71 USD). Without these we're good to go for a mere 57.19 USD (!), once we get our custom case from Beezar. Overall it's 120 USD as shown in the BOM (45 USD for the custom Case, 10 USD for the PCB and 5 USD for the custom screws).

For such a price, I think this is going to be a HUGE success!!

I also may consider switching the red LED for a violet one just to keep the color in tunes... Ehehe...


----------



## tomb

Quote: 





lefuneste said:


> By the way I've just checked out the BOM to see if I was good from the previous preprod version.
> The only missing Mouser part was the 3.5mm jack. As it's a pain in the bottom to order one item only from Digikey, I've checked references at Mouser for the same measurements and came up with this reference *806-STX-3150-3N*
> I believe it should fit right on the PCB as it measures the same as the Digikey part. *Please someone correct me if I am mistaking!*
> Also for such a beauty, I would like Gold plated RCA output. I got these *806-KLPX-0848A-2RG* (Red One) and *806-KLPX-0848A-2BG* (Black One as the White is non stocked... There's also a Yellow one 2YB).
> ...


 
  It appears that you are correct about 806-STX-3150-3N.  It must be new, because even the Mouser salesman couldn't find it for me a month ago - only a 5-pin version.  If it checks out completely, I'll add it to the Mouser side of the BOM.
   
  Gold RCA's look really ugly with a blue case and white-silver laser-etching.  Silver jacks were selected on purpose.  Keep in mind the silver RCA jacks are plated nickel, not tin.
   
  Cobaltmute will have to confirm on the oscillator, but we knew there were substitutes.
   
  Remember those blue-anodized aluminum screws include my tapping the case for 6-32 threads.  Being aluminum, those screws will strip if the case is not tapped.  The normal screws that come with the case are regular 'ol silver phillips self-tapping screws.
   
  The total price of the kit will be $125 - you're forgetting to add in the 806-STX-3150-3N on the Mouser side of the BOM.  Just so everyone understands, the price of the case will be $50 without the kit.  There has to be some advantage to ordering it all together, after all.  Plus, just to kick things off, I'm inluding _both_ the OPA2835 and LMH6643 opamps in the first 100 kits. 
	

	
	
		
		

		
			




   
  Thanks for the kind comments on the website.  It may be the most thoroughly detailed website I've made, yet.  About the only thing it doesn't have is movies - maybe I'll add that eventually.


----------



## tomb

Weird.  The pins are slightly off in the drawing for 806-STX-3150-3N, but when measuring the DigiKey jacks that I have, the pins measure closest to the Mouser drawing, not DigiKey's.  I'm almost certain it will work - cobaltmute left ample pad hole clearances, but I'll order one to make sure and let you know.


----------



## cobaltmute

For that oscillator, don't confuse PPM accuracy with low jitter. 

The crystek unit is reported by others to be low jitter, which is more important than absolute accuracy. 

But the bottom line is any 12Mhz oscillator that fits the pads with the right pinout will work.


----------



## Lefuneste

Hey guys thanks for the update. Yeah I agree, after reading you Tom, maybe the gold is less good looking than nickel plating after all.
  And for your comment CobaltMute, I take it as granted, you have a much better knowledge than me on electronics. Thanks for taking time to give us this info.


----------



## funch

I'll be checking here http://beezar.com/catalog/index.php daily until they are available.


----------



## WhiteFireDragon

Hi guys, my first post here. Been lurking for a while, but finally decided to make an account to thank all the guys with contribution to this project, especially *tomb*. Can't wait to get one of these.
   
  Just for clarification though, would it be "cheaper" to buy only the case and PCB and order the same exact parts from the material list from mouser/digikey, or would it just be more worthwhile to get the full kit for $125?


----------



## tomb

Quote: 





whitefiredragon said:


> Hi guys, my first post here. Been lurking for a while, but finally decided to make an account to thank all the guys with contribution to this project, especially *tomb*. Can't wait to get one of these.
> 
> Just for clarification though, would it be "cheaper" to buy only the case and PCB and order the same exact parts from the material list from mouser/digikey, or would it just be more worthwhile to get the full kit for $125?


 
  Thanks for the compliment, but I couldn't do anything if cobaltmute hadn't created it, first.
   
  As for ordering separately, you would eat up the difference in shipping, at least.  Plus, the case will be more expensive outside of the kit.


----------



## WhiteFireDragon

Will you guys offer any kind of fully assembled units? If not, can I offer to assemble it for people?


----------



## tomb

Quote: 





whitefiredragon said:


> Will you guys offer any kind of fully assembled units? If not, can I offer to assemble it for people?


 
_No offense, but I believe posting those type of questions in the DIY section are outside the bounds of Head-Fi policy - or at least answering them is. _


----------



## WhiteFireDragon

Oh sorry, I didn't realize that. I just thought maybe someone would want this DAC but not have the equipment or dexterity to make one, so was just curious if you guys also build for people.
   
  I think I'm too new on this forum so I can't go back to delete that post


----------



## tomb

That's OK - I just don't want to see this thread deleted. We probably have stretched the rules already a couple of times, but when you start talking about selling ready-built products, it turns into a commercial activity almost immediately.  Deleting a thread has happened before (not to this thread, but similar ones).


----------



## DingoSmuggler

Quote: 





tomb said:


> The pupDAC website is now complete and live:
> *pupDAC*


 
   
  WOOF!


----------



## Lefuneste

Hey Tom, just a quick update for the BOM.

Line 21 you specified the *C0805C225K9RACTU* as a Ceramic 2.2uf 10V X7R 10%. I believe you meant *C0805C225K8RACTU* which has the good values.

C0805C225K9RACTU is rated 6.3V. Not that it matters that much I know... But I just try to help in my way... 

The funny thing is that the 6.3V costs twice the price of the 10V... :rolleyes:


----------



## scootsit

Quote: 





lefuneste said:


> Hey Tom, just a quick update for the BOM.
> 
> Line 21 you specified the *C0805C225K9RACTU* as a Ceramic 2.2uf 10V X7R 10%. I believe you meant *C0805C225K8RACTU* which has the good values.
> 
> ...


 

 Will it make a difference? Otherwise, it's time to go scrounging through the part drawer again. Am I right in thinking the only difference is the voltage rating?


----------



## scootsit

Quote: 





tomb said:


> The pupDAC website is now complete and live:
> *pupDAC*
> 
> 
> P.S. The replacement front plates are at the anodizers now.  Hopefully, I can get them to the laser-etchers next week and then we're off and running!


 

 w00t!


----------



## cobaltmute

scootsit said:


> Will it make a difference? Otherwise, it's time to go scrounging through the part drawer again. Am I right in thinking the only difference is the voltage rating?




It won't make a difference. 

As for the price difference between the parts, I usually choose the cheapest variant that meets the need and by preferred manufacturer. As time progresses, places like Mouser may changes prices based upon various things (like the prices when they purchased the stock). I suspect the prices on those parts have changed since I spec'ed the BOM originally, as I would have chosen the cheapest based upon size, value and rating (X7R), not counting voltage.


----------



## pontius

Greetings everyone. New here.  I just built a couple grubdacs and am pretty happy with the experience and results.  Can anyone who's heard both the pupdac and grubdac describe the difference in sound quality?  This looks like a neat kit.


----------



## cobaltmute

pontius said:


> Greetings everyone. New here.  I just built a couple grubdacs and am pretty happy with the experience and results.  Can anyone who's heard both the pupdac and grubdac describe the difference in sound quality?  This looks like a neat kit.




tomb always seems to put together excellent kits.

As for the sound compared to my other designs, neither tomb or I will tend to comment as we have both interest in the design. Hopefully someone else will make comments for you.


----------



## clarkdale661

Hi guys, I'm new here so excuse the newb question: what is the advantage of this low-powered (USB) amp compared to an amp that gets plugged straight into the wall? No need for a dedicated PSU? I would think AC powered amps get more juice to run the amps.


----------



## scootsit

Quote: 





clarkdale661 said:


> Hi guys, I'm new here so excuse the newb question: what is the advantage of this low-powered (USB) amp compared to an amp that gets plugged straight into the wall? No need for a dedicated PSU? I would think AC powered amps get more juice to run the amps.


 

 This is a DAC, not an amp. There aren't many low amps that run off of USB that I can think of, most are battery for portable use, or have a power supply plugged into the wall for desktop use.


----------



## Avro_Arrow

Quote: 





clarkdale661 said:


> Hi guys, I'm new here so excuse the newb question: what is the advantage of this low-powered (USB) amp compared to an amp that gets plugged straight into the wall? No need for a dedicated PSU? I would think AC powered amps get more juice to run the amps.


 

 If you are referring to the PupDAC, it's not an amp at all and not designed to drive headphones directly.


----------



## tomb

Anodizing looks real good on the replacement front plates.  I'm carrying them to the laser-etcher tomorrow.  Hopefully, we'll be ready to go by mid-week next week.


----------



## scootsit

Quote: 





tomb said:


> Anodizing looks real good on the replacement front plates.  I'm carrying them to the laser-etcher tomorrow.  Hopefully, we'll be ready to go by mid-week next week.


 

 PERFECT! I defend my thesis on Monday!


----------



## tomb




----------



## WhiteFireDragon

So that means all the new faceplates just finished?


----------



## Forte

There on the Beezar website.


----------



## scootsit

FINALLY I WILL BE ORDERING TONIGHT!


----------



## randytsuch

Just ordered a full kit, looking forward to how this sounds


----------



## scootsit

I gotta say, I priced the entire BOM on Mouser, and the whole kit is a great deal!!
  Again, I have nearly all of it in my parts drawer, so I'm getting just board and the case, but still!


----------



## tomb

Well, as usual - I under-estimated how long it would take me to hand tap the cases, bag up the screws, DigiKey 3.5mm jack, and the extra LMH opamp.  All the rest is/was ready to go, but that's slowing me down.
   
  I hope to have the first few orders shipped out tomorrow and then maybe I'll catch up with everything in the next day or two. Please be patient.


----------



## randytsuch

Quote: 





tomb said:


> Well, as usual - I under-estimated how long it would take me to hand tap the cases, bag up the screws, DigiKey 3.5mm jack, and the extra LMH opamp.  All the rest is/was ready to go, but that's slowing me down.
> 
> I hope to have the first few orders shipped out tomorrow and then maybe I'll catch up with everything in the next day or two. Please be patient.


 
  Thanks for the update, I was wondering what was going on. 
   
  Speaking for myself, an extra couple of days is no big deal, but I am hoping I am high on your list anyway .
  I was kind of figuring this as a Christmas vacation project, although it would be nice if I could build it before.
   
  Randy


----------



## tomb

Quote: 





randytsuch said:


> Thanks for the update, I was wondering what was going on.
> 
> Speaking for myself, an extra couple of days is no big deal, but I am hoping I am high on your list anyway .
> I was kind of figuring this as a Christmas vacation project, although it would be nice if I could build it before.
> ...


 
  If I don't catch up by Friday at the most, I'll eat a pupDAC.  Seriously, a few days ... I don't think you have any concern, especially in the US.


----------



## cobaltmute

tomb said:


> If I don't catch up by Friday at the most, I'll eat a pupDAC.




I almost want to see that happen, just to see it. 

I think you'd want to get Blendtec to see if it will blend first.


----------



## scootsit

Quote: 





cobaltmute said:


> Quote:
> 
> 
> 
> ...


 

 "Don't breathe this"


----------



## randytsuch

Quote: 





tomb said:


> If I don't catch up by Friday at the most, I'll eat a pupDAC.  Seriously, a few days ... I don't think you have any concern, especially in the US.


 
  Just got shipping notice, I guess Tom didn't want to find out what a pupDAC tastes like.


----------



## tomb

Yeah, well ... everybody's pupDAC orders that I've received have shipped.


----------



## tcpoint

Great.  Thanks for the time and effort.


----------



## scootsit

Received today, looks spectacular! Thanks Tomb


----------



## randytsuch

It's alive!  
	

	
	
		
		

		
			




   
  This has to be a record for me, package came in the mail yesterday, started it and stayed up late last night, got all the SM parts on front before I went to bed.
  This morning, did the SM on the back side and all the TH parts.
   
  Did have a few problems, all my fault.
  I had a solder bridge on the dac chip, found it because I decided to ohm out between each pin to make sure things were OK  Could see it, even under magnification, but a couple pins ohmed to 0, so I used some wick to remove and then it was fine.  FYI, if you ohm out some pins end up getting tied together that are not obvious so you need to check against the schematic.
   
  When I plugged it in, USB device was not recognized.  I had a few of the voltage regs that I didn't solder correctly (it was late last night).  Once I fixed those, it was recognized, device installed, and it made music 
	

	
	
		
		

		
		
	


	



   
  I did hear some "static" at first.  I dried it out a little with a heat gun at low, carefull not to heat too hot, and put it in the case, then static went away.
 1mv offset on left, 0mv offset on right.  Used the "default" opamp.
   
  It has plenty of drive for an iem, and for no breakin with cheap buds it sounds really good. 
   
  Will let it run for a while, and then try with better iems.
   
  I did make a few changes, just because .  I used some different caps around the dac, and replaced some of the lytics with other ones I had, silmics and an organic polymer.
  I also lost one cap in my carpet , so it was replaced with the closest I had to it.  That was a 2.2uf, it is now a 4.7uf.  Had to improvise that one becaue it was a bigger package.
  Of course mine does not look nice like tomb's example, but it works.
   
  Kit was very nicely put together, made it easy to build, everything was well labeled and packaged.  Really worth it to buy the kit instead of trying to buy the stuff yourself from Mouser.
  My one suggestion would be to add reference designations to the labels, especially for the IC's, where you can.  I know that is one IC used in multiple places, but all the rest are unique so they could be labeled like this, if you don't use the same IC's for other kits.  Would make it easier.
   
  Randy


----------



## tomb

Glad to hear it, Randy!!
   
  About the parts labels - it was one of those things that happen when working remotely with people on a project.  I had many conversations with the salesperson at Mouser and we were both emphasizing that each series of parts would be individually-bagged and labeled with "part numbers."  It wasn't until I received the entire volume of kits that I realized their "part numbers" were different than my idea of "part numbers."  That's why I emphasized referencing the BOM and include one in every kit.
   
  This was the very first time I ever had Mouser completely make up the parts kits.  I think they did a great job.  We just blew it on communication about the part numbers.  It'll be fixed on the next round. 
   
   
  P.S. Told you guys about that moisture thing.  It's gratifying to hear that you didn't lose your cool and got out the heat gun.


----------



## randytsuch

So when I listened right after I built them I was a little disappointed with the sound, but after letting it run in a little, I think it sounds really nice.
   
  I mostly connected it to my O2, driving some IEM's.  I can drive IEM's straight out of this, but it has too much gain, so I have to be at a low volume in windows.
   
  I looked at the artwork, and it looks easy to cut the traces to the headphone jack, and connect a small resistor to the jack instead.  I'll probably start with 50ohms, and see how that goes.
   
  Randy


----------



## cobaltmute

randytsuch said:


> So when I listened right after I built them I was a little disappointed with the sound, but after letting it run in a little, I think it sounds really nice.




I'm glad you like it. I would agree that the clean sound of it is something that can take a little while to appreciate.


----------



## tomb

I've been told by another person besides Randy that a few of the capacitors' part #'s are different than on the BOM.  When in doubt, please check the part number's rating at Mouser and reference that with the rating on the BOM.
   
  I will have this documented later tonight, will post it, and include corrections on the BOM since I'm including a printout in the kits.


----------



## randytsuch

So I cut the traces to the headphone jack tonight and added a 50 ohm resistor in series to the jack.
   
  First resistor was too big (a resista) so it didn't fit 
  The board wouldn't slide back into the case.
   
  Found a smaller dale which is the same type in the kit I think, and it just fits 
   
  It helps, before when I plugged directly into the jack before I was almost at min volume, now I am maybe at a 1/3.
   
  But I am worried if I make the resister bigger it may degrade the sound, so I might try lowering the opamp gain now.
   
  I will probably try using a 1k for the feedback resistor, and see how that works.
   
  Randy


----------



## tomb

No offense, but that seems like a lot of cutting on a DAC that was primarily designed as a source.
	

	
	
		
		

		
		
	


	




  I mean, we've said it should power efficient IEM's  or the like, but when I've tried it - I just used the volume control on Foobar.  I know that's heresy, but it's not like it was a permanent scenario - just something fun to try outside of the primary purpose as a source.


----------



## tomb

OK - here is the story on the kit parts vs. the BOM.  I am sorry for the confusion, but there are only two parts bags that have different part #'s than the BOM and *that are not totally obvious:*
   
  C1, C23, C30, C37 - the kit part # is GCM2195C1H103JA16D
  C7, C31 - the kit part # is GRM2185C1H153JA01D
   
  Even so, the parts counts of the two items match exactly and there is no other possibility of confusing these parts with others.  Plus, one could always look the parts # up on Mouser to be certain.  Nevertheless, the intent was to make it simpler than that. 
	

	
	
		
		

		
		
	


	



   
  BTW, I've made this BOM different than all the other BOM's I made in that if you actually click on the link for a part, you should get a multi-part search result on Mouser that lists *all* of the parts available with the required ratings.  The part #'s in question, along with the part #'s that were on the original BOM, are all in that list when you click the link.  The reason the mixup happened is that while negotiating with Mouser over making up the kits, several of the parts lines went temporarily out of stock.  To simplify things and get the kits going, I told Mouser to use the most inexpensive, available part that had the qualifying ratings.  So, while I standardized the small 805 caps on the BOM with Kemet "C0805" part numbers, Mouser substituted Murata caps for the two items above.  _They were still in the list if you clicked on the link in the BOM_.
   
  Regardless, I have changed those two part items to match the bags in the kit.  I've also reduced the part # text string for the other 805 caps, even though 75% of the string matched the kit parts bags exactly - only some qualifying suffix characters are different (such as "ACTU" or "ACAUTO").  These really have no bearing on the ratings of the part, which comes in all the numbers/characters before that.  That may not have been totally obvious, but hopefully reducing those parts' text strings will remove confusion.  Just as a for instance, clicking on the BOM Mouser link for "C6, C8, C11, C12, C17" results in 9(!) pages of parts, all of which meet the required ratings.  The important part of the text string is simply, "C0805C104K."  Even then, one of the other mfrs with totally different part #'s can be used - if it's in the list for that rating.
   
  The following are also different part #'s on the kit bags than on the BOM, but surely these are totally obvious:
  X1 - the clock oscillator (the kit uses a series C3392 instead of C3391)
  LED1 - the LED (it's 3mm and it's red ...)
  C3, C18 - the Mica caps (there's nothing else that remotely looks like purple hearts with leads sticking out) 
	

	
	
		
		

		
		
	


	



  I'm not going to worry about changing the part numbers on these items.
   
  All the other changes have been made and uploaded to the pupDAC website.  Future kits will include printouts of the revised BOM.


----------



## scootsit

So is the old BOM wrong? Or is this just in the kits?


----------



## cobaltmute

My understanding is nothing is "wrong" per se.

The issue, again to my understanding, is that some of the part numbers in the kits do not match the part numbers on "the BOM". This will mean that you as builder may need to take a step or two more to ensure that you put the right part in the right place.

The issue is that there are many, many parts that could fit a position on the board. For example, a 1uF SMT 0805 X7R capacitor. You could also use X5R or X8R. For stocked parts, Mouser has 137 different parts that fit that bill. All of them will work, but based on past history/bias/phase of the moon, we choose a part for a position. And then when tomb makes a kit, for some reason, another part may be put in the kit instead due to stocking issues. An example of this is X1 - Mouser changed the minimum qty on the part we were using, so the part had to be changed. 

As a result the BOM is a living thing, that changes depending upon what is in stock when parts are ordered.

So, to my understanding, there is nothing wrong with the BOM or the kit - the issue is that some parts are not labelled in a way that is immediately clear where that part goes on the PCB. You may have to check the part value, to the BOM value to be clear where it goes.


----------



## randytsuch

Quote: 





tomb said:


> No offense, but that seems like a lot of cutting on a DAC that was primarily designed as a source.
> 
> 
> 
> ...


 
   
  [size=medium]Hi[/size]
   
  [size=medium]First, let me say this is not intended to be argumentative, just want to present my point of view on my “cuts”.[/size]
   
  [size=medium]It is “interesting” that the PupDAC was intended to be a source, but I think that is selling it short.  I started out using it as a source, with my laptop and an O2 as the amp.  But since the PutDAC has an opamp, it seems to be quite capable of driving IEM’s.[/size]
   
  [size=medium]It makes a nice, easy to use, portable setup, using my laptop, PupDAC and a set of IEM’s.[/size]
   
  [size=medium]My only “complaint” is that the PupDAC has too much gain for my IEM’s, using mostly TDK BA200, RE-262 and Sony MH1-C at this time.  The Sony is the hardest to drive, but still with a stock PupDAC, I am very low on the Windows volume scale for my listening levels.[/size]
   
  [size=medium]So I am making some mods to my PupDAC to make try to get the windows volume at least above 50% for my use.  I am also worried about data loss using digital volume control so I like to be high up on the scale when I do use it.[/size]
   
  [size=medium]As for the cuts, there are two required, and they are easy.  I made the cuts on either side of the headphone connector, top side of board.  The traces go from the RCA jacks output to the headphone out jack, one coming from each side.  These traces are all by themselves, with NOTHING around them, so it really would be hard to mess it up.  When cutting, I make sure the trace ohms out before cutting, then cut and make sure that it no longer ohms out.[/size]
  [size=medium]Before I added the 50 ohm resistor, I did notice some hiss on my IEM’s when I would pause the music.  That hiss is no longer audible after this mod.[/size]
  [size=medium]I am also considering other “mods” to my PupDAC, just because I’m an engineer and I can’t leave well enough alone.[/size]
   
  [size=medium]As for the parts “substitutions”, I wanted to add that I don’t consider the parts to be mistakes.  My company does it all the time, depending on what is available for purchase.  When you use a standard size and value surface mount cap, there are probably at 5 different companies at Mouser that make basically the same part.  If the size, value, voltage rating and dielectric are the same, we would consider them to be equivalent and use them interchangeably.[/size]
  [size=medium]It just may be a little confusing if you don’t understand how capacitors are numbered.[/size]
   
  [size=medium]Randy[/size]


----------



## tomb

I guess if you're already at the low point on the Windows volume scale, then all that makes sense.

And yes, there is nothing "wrong" with the BOM.

Thanks cobaltmute and good post, Randy!


----------



## cobaltmute

randytsuch said:


> It is “interesting” that the PupDAC was intended to be a source, but I think that is selling it short.  I started out using it as a source, with my laptop and an O2 as the amp.  But since the PutDAC has an opamp, it seems to be quite capable of driving IEM’s.




I agree with your point, but one thing to be aware of is that the negative rail generator can only create 60mA before it limits.

So, yes it can drive headphones. But at loud volumes or larger current requirements, the negative rail to the opamp could collapse in all sorts of interesting ways.


----------



## randytsuch

So I played a little with gain, and it is better (for me) now.
   
  You need to change R6, 8, 17 and 19.  What matters is the ratio between R5, 7, 16 and 18 and these other resistors, ratio is 15 to 1 using the default values.
  I actually changed all of these resistors, and changed the ratio to 7 to 1, and am around 1/2 on the volume scale now.
   
  I may drop it a little more, to around 5 to 1, and will probably settle with that.
   
  Randy


----------



## DingoSmuggler

Got a box with a picture of a puppy on it today.
  Checked all the items off the BOM during my lunch break and everything is accounted for. The packaging for the OPA was a bit ridiculous, a silica gel pack and moisture indicator card, it took up more space than the rest of the parts combined. 
	

	
	
		
		

		
		
	


	



  Hopefully i can find some time to construct it tonight.


----------



## DingoSmuggler

just putting the last few components in and should have this going. 

curious as to what the corner frequency of the analog lowpass filter is, as the 220pf seems like a fairly small value, and my calculations had up rather high (hoping i was wrong)


----------



## rededge

i have soldered up my dac but it is  not getting recognized. all the voltage is fine except the 4.5v is 4.7v.
   
  any assistance?


----------



## jERiCOh

I had the same problem. I used a better quality usb cable and luckily it started to work... As for the 4V5 reading 4.7V, mine is at 4.75V and works perfectly. I hope changing the cable works for you too.


----------



## tomb

Quote: 





rededge said:


> i have soldered up my dac but it is  not getting recognized. all the voltage is fine except the 4.5v is 4.7v.
> 
> any assistance?


 
  If it's not the cable and all your voltages are OK, then take a closer look at U1, the PCM2707.  That chip controls all of the USB and connection to the PC.  If you have some bridges or pins that may not be cleanly soldered, that would prevent the PC from recognizing the pupDAC as a legitimate USB device.  I hesitate to suggest re-flowing, but if it all else fails ...
   
  You might try posting a pic, too - maybe we'll spot something.


----------



## rededge

i re-soldered re-cleaned and did manage to get it working. so i decide to give it one more clean and when i reconnected it now windows simply does not detect the dac, no sound to indicate a usb device.
   
  3v3 next to pcm2707 is less than 0.5v and the +2.5v is less than 0.5v.
   
  so what have i blow up.


----------



## randytsuch

Quote: 





rededge said:


> i re-soldered re-cleaned and did manage to get it working. so i decide to give it one more clean and when i reconnected it now windows simply does not detect the dac, no sound to indicate a usb device.
> 
> 3v3 next to pcm2707 is less than 0.5v and the +2.5v is less than 0.5v.
> 
> so what have i blow up.


 
   
  On the schematic, U2 is in the upper right of sheet 1, this is the regulator that generates 3.3V for U1.
   
  I would check to make sure all pins of U2 are soldered correctly.  You could also check L3 because 3.3V has to pass through L3, but that is a relatively easy part to solder.
   
  U10 generates the 2.5v which is used for the opamp for the output, and won't affect the USB device detection.  You still need to fix, and I would look at U10.  I had my share of problems soldering those little regs down too.
   
  When you cleaned the board, you probably pushed pins around.  If the pins are not well soldered, then they could lose contact, I would guess that is what happened.  Better to find and fix now than to have it stop working in a month and have you scratching your head.
   
   
   
  Another general comment.
  The schematic could be more helpful.  For example is says "TP1" on the schematic, but it says "3V3" on the board, so you need to figure out how to relate these.  You also need to cross reference the schematic against the parts list for all of the parts values.
   
  I have marked up my schematic to add in parts values, some notes, and part numbers so I don't have to refer to the PL all the time.
   
  Randy


----------



## christsay

Just finished up the build and everything is working great.  Thanks for the great design and kit guys!
   
  Also, just want to say that customer services at beezar is awesome!  Mouser miscounted and only put five of the ferrites in the bag instead of 6, Tom shipped out two ferrites the day before Christmas and I received them today.
   
  -chris


----------



## tomb

Quote: 





christsay said:


> Just finished up the build and everything is working great.  Thanks for the great design and kit guys!
> 
> Also, just want to say that customer services at beezar is awesome!  Mouser miscounted and only put five of the ferrites in the bag instead of 6, Tom shipped out two ferrites the day before Christmas and I received them today.
> 
> -chris


 
  Great!  Glad to hear it and thank you for the kind comments.


----------



## tomb

I've updated the BOM on the website to contain two changes:
   
  1. Added the option for using the OPA2836 opamp for U9
  2. Included the Mouser version of the 3.5mm jack: STX-3150-3N
   
  Both the opamp and the 3.5mm jack have been fully vetted and they work well.
  (I built 4 more pupDACs over the holidays using these parts.):
http://www.diyforums.org/PupDAC/PupDAC-bom.php


----------



## tomb

Any thoughts, results, or comments from some of you that have built a production version?


----------



## Lefuneste

Hi guys.
  Just finished mine today!! I have had great time working on it! Spent about 6 hours taking PLENTY of time soldering it all perfectly. It just came to life at once, as usual with all your kits Tom! I may be the first French Puppy breeder as well!! Yeahhh!!
   
*I have to say that this thing sounds outrageously good!! *I used to have a GrubDAC customized to my needs (caps and clock), but I wasn't suspecting such a big difference in sound with the Puppy.
  The sound is definitely more transparent. I started with an opening track of ambient music, where there is a water noise. I know this track very well having heard this record again and again (flac file with Foobar exclusive output mode). The record is called "Voices from the lake" and is from a collective of minimal DJ from Italy. It is really amazing if you're into ambient and minimal stuff. Anyway, this water sounds on the Pup incredibly real compared to the already excellent rendering of the Grub that I knew so well. I also tried it with Anthony Rother's "The Machine Room" album. Synth modulations are freakingly real you can feel the texture of the sound. Overall, the highs are much more detailed and airy. Really amazing how they detach and take room. The low frequencies go really LOW. They are abyssal!!. On my gear they are lacking a very tiny bit of definition, but this is definitely due to my setup or to the tweaks I conducted (see below). I have a tube headphone preamp (Project Sunrise with Amperex Buggle Boy ECC88 from Holland) and I only tried my headphones so far (Beyer DT990Pro 250 Ohms). *The sound is incredibly spacious and vast. Almost out of this world!!* I have difficulties stopping listening to this DAC. I've been stucked to it for the last 12 hours!! I will try it tomorrow on my Adam monitors.
   
  On the list of remarks
   
  -I have implemented the improved 2836 Opamp as suggested, not many hesitations about it. Too bad I can't find a simple way to roll the opamps. I haven't found any SMD to DIP8 adapter. If someone knows where to get this please let me know. Maybe a future version will include this. It would be great, but less useful than let's say on a CD player due to the limited number of possible opamp choices for such a low voltage.
   
  -Silkscreen may have a little numbering issue for R5 on the back of the PCB, it should read R6 (I thought my eyes were dead but no...). Really not much of an issue if you know what you're talking about when handling the iron, but maybe for the beginners it may lead to confusion. Probably already noticed by someone or it really my eyes that are dying...
   
  -For the soldering of the PCM1794 chip, it is quite difficult I have to say as the pins are really close and the chip is high as a cliff. The secret is to have a good flux pen. I accidentally soldered 3 pins well together (Dohh...) with a BIG UGLY drop of solder. I almost thought I had Murphy's law striking... I wicked as much as I could (be careful not to pull the wick on a hard solder or you'll pull the pins out!!), but I couldn't get the bridge to leave because of thick solder texture. Then I grabbed my pen, and Voila!! It just melted the solder perfectly and had it climb up the pins by capillarity just like magic. I touched up all pins afterwards to have a perfect finish. I fluxed every single solder afterwards (Voltage regulator, USB chip even some ceramics). It's just mandatory to have one of these for SMD work. Because after you mess with solder too long it tends to loose it's flux, and behaves like a paste. If you add flux again it goes back to liquid. VERY USEFUL!
   
  -I confirm, the reference I found for the mini-jack connector goes perfectly. I had spent a couple of hours reading data sheets to find this one... I am not completely useless Yeah!! 
   
  -I couldn't help but to change the supplied electrolytics by some Oscons (that's the way I do things sorry, don't blame me!!) I just find the oscons to sound unbelievable and I believe I can hear the difference!! Arf...
   
  But Tom, where can I find detailed explanations for the electrolytics choices of values. I would be very interested!!
  There are 4 types, One (C22) is the main PSU buffer (upgraded to Rubycon MBZ 1500 uF at 10V), 2 are for output decoupling (C26, C27 upgraded to oscons SEPC 470uF 6.3V), one is not yet understood (C10 upgraded to Nichicon KA 225uf 25V) but seems to have an important role in filtering (I need to read more of the manual and of the blog sorry!), and the last 4 Voltage decoupling for the DAC chip (C2 C9 C16 C19 upgraded to Elna SILMIC II 22uf 25V, but I acknowledge the FM panasonics are really good too).
*But Tom, why on Earth did you specify 63V value on these? *I mean there must be a reason, but when I look at the diagrams I only see 5V class voltage there. I really scratched my head for good on this... Does 63V value bring something to this decoupling function such as higher ripple tolerance? DAC technical note only states 10uF value there but doesn't recommend higher voltage value so I am puzzled. I am planning to replace these 4 by oscons too by 47uF at 16V or maybe large Tantalums they may be adequate there. Is there a problem going to 16V? I can't see any it works fine at 25V with my ELNAs, but you're the master!
   
  Anyway, the PupDAC is a really wonderful piece of equipment I have to say probably sounding like multi KUSD DAC!! I will keep you updated for more tweaks in the future.
   
  All the Best!!
   

  Close match on all caps
   

  That's a close one, perfect fit with Rubycon MBZ 1500uF 10V
   

  It's ALIVE...


----------



## tomb

Quote: 





lefuneste said:


> Hi guys.
> Just finished mine today!! I have had great time working on it! Spent about 6 hours taking PLENTY of time soldering it all perfectly. It just came to life at once, as usual with all your kits Tom! I may be the first French Puppy breeder as well!! Yeahhh!!
> 
> *I have to say that this thing sounds outrageously good!! *I used to have a GrubDAC customized to my needs (caps and clock), but I wasn't suspecting such a big difference in sound with the Puppy.
> The sound is definitely more transparent. I started with an opening track of ambient music, where there is a water noise. I know this track very well having heard this record again and again (flac file with Foobar exclusive output mode). The record is called "Voices from the lake" and is from a collective of minimal DJ from Italy. It is really amazing if you're into ambient and minimal stuff. Anyway, this water sounds on the Pup incredibly real compared to the already excellent rendering of the Grub that I knew so well. I also tried it with Anthony Rother's "The Machine Room" album. Synth modulations are freakingly real you can feel the texture of the sound. Overall, the highs are much more detailed and airy. Really amazing how they detach and take room. The low frequencies go really LOW. They are abyssal!!. On my gear they are lacking a very tiny bit of definition, but this is definitely due to my setup or to the tweaks I conducted (see below). I have a tube headphone preamp (Project Sunrise with Amperex Buggle Boy ECC88 from Holland) and I only tried my headphones so far (Beyer DT990Pro 250 Ohms). *The sound is incredibly spacious and vast. Almost out of this world!!* I have difficulties stopping listening to this DAC. I've been stucked to it for the last 12 hours!! I will try it tomorrow on my Adam monitors.


 
   
  Many, many thanks for relaying your opinions.  Cobaltmute and I have known this for some time, but it's nice to hear it all confirmed by someone not connected.  Things have been kind've slow for the pup, actually.  It doesn't have the razz-ma-tazz 24-bit USB to attract all the unwashed masses, but I don't think it needs it.  Some people say the 24-bit thing is over-rated, too, compared to a good-quality DAC that's been implemented well, and this is definitely one! 
	

	
	
		
		

		
		
	


	






   


> On the list of remarks
> 
> -I have implemented the improved 2836 Opamp as suggested, not many hesitations about it. Too bad I can't find a simple way to roll the opamps. I haven't found any SMD to DIP8 adapter. If someone knows where to get this please let me know. Maybe a future version will include this. It would be great, but less useful than let's say on a CD player due to the limited number of possible opamp choices for such a low voltage.


 
   
  I hear you - but it's going to be a bit difficult with the faster opamps that we've listed and vetted.  As you noticed below, cobaltmute even put some of the resistors on the back side to cut down on the trace and lead length.  The potential for instability is definitely there, as some of us experienced during the prototyping stage.  There are such adapters, I think, but I doubt that they would be a good idea.
   


> -Silkscreen may have a little numbering issue for R5 on the back of the PCB, it should read R6 (I thought my eyes were dead but no...). Really not much of an issue if you know what you're talking about when handling the iron, but maybe for the beginners it may lead to confusion. Probably already noticed by someone or it really my eyes that are dying...


 
   
  Dang!  I've built 5 of the new PCBs and never noticed this.  It's not exactly a "5", but it's for sure a piss-poor "6."  I will highlight that this weekend on the website to make certain that no one makes this mistake.  Thanks for pointing it out!!
   


> -For the soldering of the PCM1794 chip, it is quite difficult I have to say as the pins are really close and the chip is high as a cliff. The secret is to have a good flux pen. I accidentally soldered 3 pins well together (Dohh...) with a BIG UGLY drop of solder. I almost thought I had Murphy's law striking... I wicked as much as I could (be careful not to pull the wick on a hard solder or you'll pull the pins out!!), but I couldn't get the bridge to leave because of thick solder texture. Then I grabbed my pen, and Voila!! It just melted the solder perfectly and had it climb up the pins by capillarity just like magic. I touched up all pins afterwards to have a perfect finish. I fluxed every single solder afterwards (Voltage regulator, USB chip even some ceramics). It's just mandatory to have one of these for SMD work. Because after you mess with solder too long it tends to loose it's flux, and behaves like a paste. If you add flux again it goes back to liquid. VERY USEFUL!
> 
> -I confirm, the reference I found for the mini-jack connector goes perfectly. I had spent a couple of hours reading data sheets to find this one... I am not completely useless Yeah!!


 
   
  Yeah, it's really no different than the old PCM2702 on the AlienDAC and the BantamDAC - or the PCM2704/5 used on the SkeletonDAC, but yes - it's probably an order of magnitude more difficult than the square PCM2706/7.  A flux pen was talked about and recommended all the way back during the AlienDAC.  I bought one and have used it ever since - it's still half-full.  So, the investment is really cheap considering how long it lasts.  I've never done any SMD without it.
   
*EDIT: Oops - forgot that it was scootsit that found the Mouser mini-jack!*  It worked out well on the last 4 I built and Mouser will probably be the primary source after this first run of kits.  The ones supplied in the kits came from DigiKey, though.  I had purchased 100 of them well before I ordered the rest of the kit parts from Mouser.
	

	
	
		
		

		
		
	


	



   


> -I couldn't help but to change the supplied electrolytics by some Oscons (that's the way I do things sorry, don't blame me!!) I just find the oscons to sound unbelievable and I believe I can hear the difference!! Arf...
> 
> But Tom, where can I find detailed explanations for the electrolytics choices of values. I would be very interested!!
> There are 4 types, One (C22) is the main PSU buffer (upgraded to Rubycon MBZ 1500 uF at 10V), 2 are for output decoupling (C26, C27 upgraded to oscons SEPC 470uF 6.3V), one is not yet understood (C10 upgraded to Nichicon KA 225uf 25V) but seems to have an important role in filtering (I need to read more of the manual and of the blog sorry!), and the last 4 Voltage decoupling for the DAC chip (C2 C9 C16 C19 upgraded to Elna SILMIC II 22uf 25V, but I acknowledge the FM panasonics are really good too).
> *But Tom, why on Earth did you specify 63V value on these? *I mean there must be a reason, but when I look at the diagrams I only see 5V class voltage there. I really scratched my head for good on this... Does 63V value bring something to this decoupling function such as higher ripple tolerance? DAC technical note only states 10uF value there but doesn't recommend higher voltage value so I am puzzled. I am planning to replace these 4 by oscons too by 47uF at 16V or maybe large Tantalums they may be adequate there. Is there a problem going to 16V? I can't see any it works fine at 25V with my ELNAs, but you're the master!


 
   
  OK - You scared the you-know-what out of me with that pic of the giant power cap.  I wasn't reading too closely at first and thought maybe Mouser had messed up and supplied a 63V cap instead of a 6.3V cap, there.  C22 is definitely a 6.3V cap and that's what's packaged in the kits. (whew!)  I assume what you photographed is your Rubycon upgrade and that's fine if it fit for you.  As for the others, it's simply impossible to find smaller uf-rated electrolytics in very low voltages.  The caps are not very big as they are and they are what cobaltmute wanted.  That said, I can't imagine that your Oscons would ever be a downgrade.
	

	
	
		
		

		
		
	


	



   
   


> Anyway, the PupDAC is a really wonderful piece of equipment I have to say probably sounding like multi KUSD DAC!! I will keep you updated for more tweaks in the future.


 
   
  Many, many thanks!!  Cobaltmute and I have toiled over this DAC for a few _years_, now.  *You have no idea how gratifying it is to hear this.* 
	

	
	
		
		

		
		
	


	









   


> All the Best!!
> 
> 
> Close match on all caps
> ...


 
   
  YAY!!!


----------



## Lefuneste

Hi Tom and thanks for your long reply.
   
  -On the PCB print, I agree with you, it is not a real 5 nor a real 6, something in between. It's not really that important, but I believe you should correct it for begginners out there as R5 and R6 have different values.
   
  -For the 63V value, I expected that this was the reason. It doesn't hurt actually to have thicker foils in life!!  As decoupling of other DAC chips often relies on 63V values for MKS caps, I had to ask.
*But you didn't answer my question about the 120 uF cap, is its value of some importance in filtering something or can I upscale it without problem? I believe it's not really a problem but I prefer to make sure.*
   
  -For the 24 bit stuff Ahaha don't make me laugh, you should visit France someday, I'll make you listen to my TDA1541 pushed to the limits on a 25 year old Sony CD player... CD specification only talks about 16 bit, the rest is BS as it relies on data manipulation except if you produce music in 24 bits which some people do, but usually they think their gear is the best out there and only realy on latest solid state technology, not taking seriously DIYers and tube afficionandos.I thought the same before starting to build a Project Sunrise preamp... Leave the extra bits to others (for the moment)... There are countless reports of gizmo-bits not being even statiscaly noticeable (check SACD listening tests on Wikipedia). Furthermore one extremely important aspect of your DACs (Grub & Pup) is the fact that they don't need a driver AT ALL. I've used them on Linux, Windows, Mac without ever wondering what ASIO horrible driver I had to install. I LOVE it this way. I have no words to describe this simple pleasure of plugging this killer of a DAC straight away from my pocket and killing everybody out there, wether at a party or in anyones place. I've got a huge collection of useless soundcards that I've used thoughout my long DJ life all of them eating 24 bits. I was possibly the first in France to mix MP3 in 1998 and at that time, you had to rely on terrible equipement, that got even worse in my opinion. You still mix 16bits 44.1kHz tracks you know!! Pfff... You DAC is the best price/performance/convenience out there, no doubt about it! And you have ferrites all over, not the case of many DIY DACS out there. This kit looks and sounds like a real achievement for the community. Not even talking about the uber-coolesque case design!! I actually start to thing to implement it in my car system...
   
  -For the opamp, I'll leave it like this as I actually really love the sound of this 2836, not too harsh, quite analog. Perfect match, I haven't tried BOM caps, but with caps upgrades I did, the DAC sound plenty analog and detailed. Not harsh AT ALL (oscon effect possibly). Again trebles are airy, bass is really deep to the cave. Response seems linear, but not boring at all. You really rediscover your tracks and can tell difference between bad and good MP3 encoding at once. A good sign certainly. I can't stop listening this Pup!!
   
  Thanks Tom!!
   
  BTW did you notice that Right and Left are reversed when looking at the DAC to plug a cable? Lol... I just realised that building a passive input switch todayusing same Hammod case and a DPDT Russian military switch!! SWEET!!


----------



## cobaltmute

lefuneste said:


> BTW did you notice that Right and Left are reversed when looking at the DAC to plug a cable? Lol... I just realised that building a passive input switch todayusing same Hammod case and a DPDT Russian military switch!! SWEET!!




This was by design to keep the straightest path from the PCM1974 to the outputs. They follow on the same side as they are on the chip. Otherwise I would have had to cross traces on the board, and I didn't want to do that for various reasons.

As for the values of the caps, so long as they are above what will be seen by the cap, you can choose any value you want.


----------



## scootsit

I used a toaster oven and did the top side reflow-style, it came out AWESOME!
  I have a bridge or two, but everything is centered and straight (except U10, but it's not too bad).
   
  I'm going to touch it up tomorrow and then get started on the bottom.
   
  Using solder paste and the oven, the top took under 1hr to fully populate.


----------



## tomb

Quote: 





scootsit said:


> I used a toaster oven and did the top side reflow-style, it came out AWESOME!
> I have a bridge or two, but everything is centered and straight (except U10, but it's not too bad).
> 
> I'm going to touch it up tomorrow and then get started on the bottom.
> ...


 
  That's great!
   
  Heh - the bottom is a piece of cake after the top.  Just go slowly and carefully.  The SMD caps are not hard to solder, but there are a heck of a lot of 'em on that back side and you wouldn't want to get them mixed up. 
	

	
	
		
		

		
			





  Soldering the opamp will seem like soldering through-hole after the PCM and TPS chips.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 I really love the solder paste, I may actually use it with the iron. It flows really nicely. We'll see, I'm going to experiment a bit. I guess I can do the back by hand, but I'd prefer to bake it - I just don't think that will work.


----------



## Lefuneste

Another interesting use of toasting ovens!! I already used it to heat treat knife blades after quenching!!
  Believe it or not, it can ALSO be used to toast bread!!  What an invention this is!!


----------



## KimLaroux

Quote: 





scootsit said:


> I really love the solder paste, I may actually use it with the iron. It flows really nicely. We'll see, I'm going to experiment a bit. I guess I can do the back by hand, but I'd prefer to bake it - I just don't think that will work.


 
   
  Would the components on the top side (flipped over) not just fall off once the solder melts?
   
  Unless of course you own a close-field anti-gravity generator.


----------



## tomb

Quote: 





kimlaroux said:


> Would the components on the top side (flipped over) not just fall off once the solder melts?
> 
> Unless of course you own a close-field anti-gravity generator.


 
  According to scootsit, the re-melt temp is much higher, so it may not be as silly as it sounds.


----------



## scootsit

Quote: 





kimlaroux said:


> Quote:
> 
> 
> 
> ...


 

 Virgin solder melts about 200F cooler than does already melted solder. I'm thinking it's because of the flux. If you hit the reflow temp, then it probably would, though the surface tension may actually keep it in place.


----------



## KimLaroux

Now that's interesting... I didn't know melting temperatures changed like that. Or that flux affected it. I thought the only thing flux did was clean surfaces to help solder flow on it.
   
  I'll have to remember this one. Thanks for the tips.


----------



## scootsit

Quote: 





kimlaroux said:


> Now that's interesting... I didn't know melting temperatures changed like that. Or that flux affected it. I thought the only thing flux did was clean surfaces to help solder flow on it.
> 
> I'll have to remember this one. Thanks for the tips.


 

 It doesn't really make sense, and someone more in the know than I may have to clear that up. But, I'm assuming it's about surface area. Little metal filings will melt before solid globs will. So, I'm sort of assuming the melting point is more or less the same, but by suspending it in a fluid with a boiling point exactly at the melting point of the metal, you create a homogenized high-surface-area fluid ready to melt at the drop of a hat. A big glob needs to get much hotter to maintain a consistent temperature near the melting point, especially since there is no flow.


----------



## scootsit

Alternatively, and now that I think of it, more likely - the melting point of each metal (which is ground into a dust) could be one thing (low), but the melting point of the homogenized alloy could be a bit higher.


----------



## scootsit

My OPA2835 doesn't have a dot on the top, instead it has a line across one end. Is the line on the pin 1/pin 8 end?


----------



## tomb

This is mentioned in the Build Thread and in the construction pages on the pupDAC website.  The line is on the same side as if there was a dot.  If you think about it, the dot is no different than a line, unless you're talking a four-cornered chip like the PCM2706/7.


----------



## scootsit

Quote: 





tomb said:


> This is mentioned in the Build Thread and in the construction pages on the pupDAC website.  The line is on the same side as if there was a dot.  If you think about it, the dot is no different than a line, unless you're talking a four-cornered chip like the PCM2706/7.


 

 Great, thanks! I figured as much and just built it anyway. All the SMT stuff is done, just scrubbed the hell out of it with alcohol. It's weird that the OPA2835 can't even be in humid environments before being soldered, but after it can be submerged. I guess something would crack with the heat. Anyway, I used the solder paste and basically stuck each piece in it, then used the iron to heat it. The result is that you can have the iron in one hand and the tweezers in the other, no need to hold any solder, so you can make sure each piece lines up perfectly.


----------



## Lefuneste

Hi guys, just a quick update photo as I've received the oscons for the decoupling of the DAC chip (47uF, 16V). Here's the result once mounted in place of the ELNA SILMIC II 22uF 25V I had put in place of the already excellent Panasonic FM (original kit capacitor). BTW unsoldering was quite tedious in order to fully respect the vias. This really requires a little experience, so be carefull if you ever have to unsolder through-holes components on this delicate PCB. I also had to clean each hole of solder before putting new caps with a vaccum pump.
   
  Sounding with Oscons appears improved on clarity and depth. Rendering seems to have slightly increased in purity. The most interesting effect is the staging and space sensation. Of course at this level of native quality, it is all very subjective!! Anyway, good luck with your projects!!


----------



## tomb

Quote: 





scootsit said:


> Great, thanks! I figured as much and just built it anyway. All the SMT stuff is done, just scrubbed the hell out of it with alcohol. It's weird that the OPA2835 can't even be in humid environments before being soldered, but after it can be submerged. I guess something would crack with the heat. Anyway, I used the solder paste and basically stuck each piece in it, then used the iron to heat it. *The result is that you can have the iron in one hand and the tweezers in the other, no need to hold any solder, so you can make sure each piece lines up perfectly.*


 
  Actually, this has been the recommended method since day 1 - without solder paste.  You apply the solder to a single pad, first.  The you re-melt it with the iron in one hand and place the part with tweezers in the other hand.  That's fundamental with manual SMD soldering.


----------



## tomb

Quote: 





lefuneste said:


> Hi guys, just a quick update photo as I've received the oscons for the decoupling of the DAC chip (47uF, 16V). Here's the result once mounted in place of the ELNA SILMIC II 22uF 25V I had put in place of the already excellent Panasonic FM (original kit capacitor). BTW unsoldering was quite tedious in order to fully respect the vias. This really requires a little experience, so be carefull if you ever have to unsolder through-holes components on this delicate PCB. I also had to clean each hole of solder before putting new caps with a vaccum pump.
> 
> Sounding with Oscons appears improved on clarity and depth. Rendering seems to have slightly increased in purity. The most interesting effect is the staging and space sensation. Of course at this level of native quality, it is all very subjective!! Anyway, good luck with your projects!!


 
  Great!  As with any DIY project, it's the tweaking that often makes it fun!!


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 I know, and that's how I've always done it, but I've found it a little hard to line up and get it to stay in place. Anyway, the paste just really flowed easily and allowed for repositioning while I soldered. Also, the paste holds the piece in place. Imagine sort of pushing each component into a soft clay or something. While the flux is, in and of itself, sticky this is a little different.


----------



## tomb

Quote: 





scootsit said:


> I know, and that's how I've always done it, but I've found it a little hard to line up and get it to stay in place. Anyway, the paste just really flowed easily and allowed for repositioning while I soldered. Also, the paste holds the piece in place. Imagine sort of pushing each component into a soft clay or something. While the flux is, in and of itself, sticky this is a little different.


 
  There's nothing that stops you from re-positioning a part without solder paste.  That was just my point.  You apply solder to one pad - whether it's a PCM chip or just an 805/1206 cap or resistor.  Then you can walk away, have a coke or a beer, watch a movie, wake up the next day, whatever.
   
  All you need to do the next time you work on it is hold the prospective part with tweezers in one hand while melting the solder on that pad with the soldering iron in your other.  There's no limit to how many times you can re-heat the one pad and then re-position the part.  In fact, what causes grief is thinking that once placed and the solder cooled, you can't do anything about it.  That's not true, at least with regular solder wire and a flux pen or flux paste.  Anyway, it's better to go ahead and re-melt the solder again and re-position the part for however many times it takes - until you get it right.  Once anchored, you can then solder the other pads (or pins if it's an IC chip) without much worry.  No extra solder involved.
   
  I just didn't want anyone misled and let them think they had to have three hands to solder SMD.  That's not the case. 
	

	
	
		
		

		
		
	


	



   
  P.S. A good flux pen almost does the same thing as you describe - the stuff is a lot like glue if you let it sit for awhile.


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 Yes. Everything you just said is correct. In fact, I think my problem is that I always solder both sides too quickly. Also, I finally got the flux pen you recommended, it's great. The one that mouser ships via USPS, the 952, I think, it's the no clean, low solids one. Anyway, that one doesn't really work well, it's not sticky. The one you recommend is awesome.
   
  No, you don't need 3 hands at all, I'm just incompetent! I don't know why I am so bad at this, but I am.


----------



## Lefuneste

Following your discussion about repositioning, I've just found out about this great book on Dave's EEV blog. Everything you need to know about SMDs. It seems quite complete on every aspects you have to know!!
   
  http://www.amazon.com/gp/product/1907920129/ref=oh_details_o00_s00_i00
   
  Just ordered it from Amazon.com second hand. It's just been released and covers all techniques and concepts. You can get it with 4 SMD projects kit. It seems quite nice. Check out the review on Daves' blog. I think it's his January mailbag review. If you don't know this blog yet, then you are up for a night streaming...


----------



## tomb

Quote: 





scootsit said:


> Yes. Everything you just said is correct. In fact, I think my problem is that I always solder both sides too quickly. Also, I finally got the flux pen you recommended, it's great. The one that mouser ships via USPS, the 952, I think, it's the no clean, low solids one. Anyway, that one doesn't really work well, it's not sticky. The one you recommend is awesome.
> 
> No, you don't need 3 hands at all, I'm just incompetent! I don't know why I am so bad at this, but I am.


 
  You are not bad at this ... when you get it fixed, it'll be as good anyone's.
   
  Quote: 





lefuneste said:


> Following your discussion about repositioning, I've just found out about this great book on Dave's EEV blog. Everything you need to know about SMDs. It seems quite complete on every aspects you have to know!!
> 
> http://www.amazon.com/gp/product/1907920129/ref=oh_details_o00_s00_i00
> 
> Just ordered it from Amazon.com second hand. It's just been released and covers all techniques and concepts. You can get it with 4 SMD projects kit. It seems quite nice. Check out the review on Daves' blog. I think it's his January mailbag review. If you don't know this blog yet, then you are up for a night streaming...


 
   
  That almost looks like a pupDAC PCB on the cover!


----------



## Ikarios

Honestly I found SMD soldering to be the easiest soldering I've ever done as long as you have a good iron, small tweezers, and steady hands. With the one-pad method Tomb mentioned there's no positioning to really be done, no leads to cut, no solder to juggle, nothing. Just solder a pad, flux it up to make the joint look pretty, heat up the solder, and slide the part into place. Helping hands are really nice to have, but not really necessary for SMD IMO.


----------



## tomb

Quote: 





ikarios said:


> Honestly I found SMD soldering to be the easiest soldering I've ever done as long as you have a good iron, small tweezers, and steady hands. With the one-pad method Tomb mentioned there's no positioning to really be done, no leads to cut, no solder to juggle, nothing. Just solder a pad, flux it up to make the joint look pretty, heat up the solder, and slide the part into place. Helping hands are really nice to have, but not really necessary for SMD IMO.


 
  This is the way I feel.  The PCM chips can still be a b*tch, but SMD resistors and capacitors are easier in the long run than through-hole.  I'd almost go so far as to say the SOIC opamps are easier than DIP-8 and plugging in the opamp.  At least with SOIC-8, you know you have a good connection and don't have to worry about bending the pins or having the contacts wear out.


----------



## randytsuch

Quote: 





tomb said:


> This is the way I feel.  The PCM chips can still be a b*tch, but SMD resistors and capacitors are easier in the long run than through-hole.  I'd almost go so far as to say the SOIC opamps are easier than DIP-8 and plugging in the opamp.  At least with SOIC-8, you know you have a good connection and don't have to worry about bending the pins or having the contacts wear out.


 
  My only problem with SM resistors and caps is that they are easier to lose.  I have pushed too hard on them, while trying to hold them down to solder, and they go flying, and then tried to find them on a carpeted floor, or in a messy garage.  PITA.
  I was better with the pupdac though, didn't lose any parts 
   
   
  Randy


----------



## Misterrogers

yep, you get better by repetition and tweaking your approach. I used to try and hold parts down, but now I use the 'lots of rosin, tin a pad, rely of surface tension' technique. Some fine tweezers can then aid in fine adjustments to alignment before removing heat. Still - I always order a few extra smd caps or resistors.


----------



## scootsit

Just a bit of an update. I have a friend that is an electrical engineer, and he could not figure out what was wrong with it either, it just kept acting as if there was a short somewhere. He took it to work where he has all kinds of fancy equipment and lifted half of the PCM off of the board, to his surprise, everything was immediately fixed. I have a short inside of the PCM chip. I probably baked it a little too hot. In short, I feel a little better about my abilities (or lack there of!).


----------



## tomb

Quote: 





scootsit said:


> Just a bit of an update. I have a friend that is an electrical engineer, and he could not figure out what was wrong with it either, it just kept acting as if there was a short somewhere. He took it to work where he has all kinds of fancy equipment and lifted half of the PCM off of the board, to his surprise, everything was immediately fixed. I have a short inside of the PCM chip. I probably baked it a little too hot. In short, I feel a little better about my abilities (or lack there of!).


 
  Well, it's good to know what the problem was.  Good luck on fixing it!


----------



## scootsit

Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


 

 Yep! I think that it happened while baking or trouble shooting, I may have shorted U2 and gotten 5V going to it, which would have been too much. I just ordered a few new chips, he's going to replace it for me, because he has way, way nicer tools. Evidently the pad going to U6 lifted on it, so we'll replace that trace with a bit of copper wire, it is really short anyway. Thanks for all the help. I'll report back when I get it fixed!


----------



## Mikael109

Would I run into any issues extending the USB lines to something like this mounted to a Hammond case?
   
  I'm looking to put a PupDAC in the same case as a Pimeta V2 so I can save some space using only one enclosure and forego the RCA cables, but I've read that using wire to increase lead lengths on certain Amps/DACs is a bad idea..


----------



## tomb

Quote: 





mikael109 said:


> Would I run into any issues extending the USB lines to something like this mounted to a Hammond case?
> 
> I'm looking to put a PupDAC in the same case as a Pimeta V2 so I can save some space using only one enclosure and forego the RCA cables, but I've read that using wire to increase lead lengths on certain Amps/DACs is a bad idea..


 
  Can't predict everything, but you might want to slice up a USB pigtail cable or buy some USB shielded cable.  Depending on the proximity of the PIMETA, there might be some interference issues.  Shielded USB cable should do the trick.  The small exposed leads used to solder the cable into the pupDAC PCB shouldn't matter.


----------



## KimLaroux

The proper way would be to use a short length of USB cable between the board and panel mounted socket. Don't forget to earth the shield, or it'll be useless.
   
  I was gonna say you could probably use any shielded cable with 4 wires, but it may be problematic if the wrong wires are twisted together inside the cable.
   
  Though when you consider that people created USB cables from nothing more than braided wires, you'll probably be fine using whatever you have on hand. If you have issues, then maybe try something better, but otherwise... Meh. Just give it a try and see.


----------



## tomb

Just an FYI, but I updated the RMAA testing on the pupDAC website:
http://www.diyforums.org/PupDAC/PupDACrmaa.php
  I had never tested a fully cased version with the OPA836.  I sitll have a crapty testing environment - I think the pup would easily do 10-15% better on all measurements if done by someone else. 
	

	
	
		
		

		
			





  However, it's superiority to the grubDAC in a direct comparison is quite apparent.


----------



## tomb

Another FYI - all PupDAC kits (full and short) will be supplied with the OPA2836 from now on. 
	

	
	
		
		

		
		
	


	



   
  With a bandwidth of 205MHz, a slew rate of 560V/us, and current drive of 50ma, it's simply superior in every way.  Even though I have the other opamps already, it seems to me that everyone deserves the best we can do if they order a kit.


----------



## UKToecutter

Nice one Tom.
   
  Must put my order in soon !!!


----------



## bada bing

Another PuP DAC lives
	

	
	
		
		

		
		
	


	




. I finally got a few hours of free time and a little ambition and assembled the kit I bought several months ago. It went together in a couple hours without a hitch. I only dropped one of the 805 caps on the floor and amazingly enough it was right at my feet with no cussing and searching, That's about my best, minimum-clutz SMD project yet. The PuP passed voltage and offset tests without a problem on the first try and is playing music now.
   
  I'm using it with an O2 amp driving HD800's for a "break in". The O2 is my only cap coupled amp and I'll give it few hours before it gets full trust with a DC coupled amp. Early impressions are it's sounding pretty nice with a "detailed and revealing" signature. Definitely has lots of "air" and extension on top. I'll try to post some detailed impressions after I get some hours on it.
   
  Thanks to Cobaltmute and Tomb for another fun project.


----------



## tomb

Quote: 





bada bing said:


> Another PuP DAC lives
> 
> 
> 
> ...


 
  Cool!  Glad it turned out well and you're enjoying it.  You should be able to simply measure the offset between the PCB ground pad and one of the output connectors to satisfy your concern with an amp that doesn't have filtering caps.


----------



## akgfan

If only it had volume pot.


----------



## tomb

Quote: 





akgfan said:


> If only it had volume pot.


 
  It's not intended to amplify, where a volume pot would be appropriate.  Just an FYI, but the ODAC has no volume control, the Gamma 1 has no volume control, neither does the Gamma 2.  The AlienDAC, BantamDAC, GrubDAC, SkeletonDAC, EasyDAC, OPUS DAC, Monica DAC ... none have a volume control.  I could go on, but maybe you get the idea.


----------



## Misterrogers

So... you're saying that you're gonna add a volume control?


----------



## tomb

Quote: 





misterrogers said:


> So... you're saying that you're gonna add a volume control?


 
  Ha.


----------



## akgfan

Yeah, I know. But that's the problem. I would need usb powered combo DAC/amp with volume pot for using it with notebook. You know how bad the volume control on notebook can be...


----------



## Blanko

A nother Pup DAC is alive. 
  It took me about 6h to build. Since I had zero experience I was postponing the constuction as far as possible in order to get decent equipment.
  It's hard to believe but here in germany it is close to impossible for a starving student like me to buy german made tools for a decent price.
  I ended up ebaying used stuff and ordered the most from the US. Even Weller tips and Felder flux I had to get from overseas.
  The first batch wasn't supplied with the OPA2836. It was a pain to get a sample from TI.
  I'm very glad that my first smd project worked out all fine. 
  On the first startup there was a strange popping sound on the left channel and a few scratching noises like a needle on vinyl.
  I blame the moist in the opa, I will give it a few days to dry and burn in.
  All the measurements where fine exept for the 4.5V which is a stable 4.75V. I hope this wont kill my puppy.
  I replaced some caps with FR-type Panasonics with higher capacitance or a lower voltage rating for lower ESR.
  I could have gone for a larger Nichicon C22. But I love the Panas, so I stayed with the provided one.
  With my Ultimate Ears triple.fi I couldn't test really the SQ properly because my stepped ladder attenuator isn't finished yet.
  IEMs are far too sensitve furthermore I don't like software volume control.
  From what I could hear the puppy is at least on par with my rockboxed Sandisk clip zip playing FLACs.
  Many thanks to cobalmute and tomb for this great kit. I can't attach any pictures atm. Maybe later.
   
  Cheers!


----------



## tomb

Quote: 





blanko said:


> A nother Pup DAC is alive.
> It took me about 6h to build. Since I had zero experience I was postponing the constuction as far as possible in order to get decent equipment.
> It's hard to believe but here in germany it is close to impossible for a starving student like me to buy german made tools for a decent price.
> I ended up ebaying used stuff and ordered the most from the US. Even Weller tips and Felder flux I had to get from overseas.
> ...


 
  Sounds great!
   
  A few comments:
  1.  Yes, the OPA2836 is so superior, there's no question it should be the standard for the pupDAC.  That's why I decided to include it in the kits later than yours - despite all expenses at my cost.  To be honest, I had already invested in the LM6643 at high volume, when we discovered that the OPA2835 was essentially superior.  That's why the first kits inclued the LMH chip for free in addition to the OPA2835. 
	

	
	
		
		

		
		
	


	




  As time went on, I discovered that the OPA2836 was stable in the pupDAC - probably because cobaltmute re-designed the PCB and put the critical resistors on the bottom of the PCB.  Also, I think TI used the OPA2835 as a prototype and when they were satisfied with the design, they went all out with the next chip - the OPA2836.
   
  2. There's nothing wrong in experimenting with upgrades of through-hole electrolytic caps.  Just make sure that they are truly superior to the excellent selections that cobaltmute has already provided.  I've built 4 using a Nichicon UHN 1500uf 6.3V cap as C22 and upgrading the C26/C27 caps to Panasonic FM's instead of FC's.  Keep in mind that these changes are really just in the margins, but the results are at least equivalent, if not slightly better.  The kit still offers an almost optimum selection of parts, but the thing to take from this is that the design is flexible and can be upgraded, if desired.
   
  3. The 4.75V is what I register on my pupDACs, too.
   
  4. If you used the OPA2836, put it out in the hot sun to ensure that any moisture has been cooked out of the chip.


----------



## Blanko

As promised a picture. To be honest I'm quite proud of my first smd hand soldering job.
   
  http://imageshack.us/photo/my-images/560/p1000190jx.jpg/


----------



## tomb

Quote: 





blanko said:


> As promised a picture. To be honest I'm quite proud of my first smd hand soldering job.
> 
> http://imageshack.us/photo/my-images/560/p1000190jx.jpg/


 
  If that's your first, you should be very proud!  It looks like excellent work!


----------



## Blanko

Thanks for the compliment tomb. I use a Weller WTCPS with a 60° 3mm wide bevel tip. I solder at 310° C.
  The flux I used in large amounts is a FSW-32 "solderoil" from Felder. Solder wire is a 0.5 mm Sn60Pb38Cu2.
  I really took all the time I needed for construction. In my oppinion preparation is the most important thing.
  I read a lot about soldering techniques. watched videos and talked with professionals. I guess I learned quite a lot from the mistakes others made.
  Luckily they shared their issues on the forums so their strugle wasn't in vain, because others can avoid those mistakes.
   
  The PCB and chips are clean and dry now. I had them in the oven for one hour at 50° C.
  When no music is playing the pup is dead silent. 
  Since I have a real crappy DMM I couldn't measure the output DC offset. But everything is working superb so I dont have concerns about this.
   
  The sound the pup delivers is stunning with my AKG K420. I don't own better head phones. The only comparison I have are my UE triple.fi 10 for portable use.
  Ofcourse the K420 are no match for them but I have never heared them perform better. 
   
  Later the pup's purpose is to feed a battery powered TA2021b amp hooked up to a raspberry Pi running xbmc in order to play some FLAC files from the network. 
  Still need to build some high efficiency fullrange speakers. Everything is meant to be a very low power consumption system, which is small and portable. 
   
  Cheers!


----------



## Blanko

Unfortunately I'm experiencing the same issue as Mullet. When Volume is low or no music is playing
  I sometimes hear a pulsing noise lasting one or two seonds.
  There also is a frequent crackling sound. Those sounds aren't very loud but quite anoying. Only the left channel is affected.
  I double checked every chip for bridges though my magnification isn't sufficient. I held the PCB against a bright LED lamp.
  There was nothing suspicious.
  I used 99.5% isopropyl alcohol for cleaning. As Mullet indicated his problem was solved after he had replaced U9 with LMH6643
  and swapped U5 plus U7.
  Could this help in my case too? It's hard for me to get replacement parts. A Mouser shipment to Germany costs me 30$.
   
  Somehow I managed to measure DC offset. It reads -1.5 mV on the left and 1.2 mV on the right channel.
  This is really frustrating since I put so much effort in it but I got excited to early.
  I have no experience with desoldering so I fear I end up with a bricked pup in the end.
  Any suggestions?


----------



## Misterrogers

Hey Blanko - I'm sure tomb or cobolmute will provide 'next steps', just wanted to encourage you to hang in there. DIY is a journey that teaches some of its very best lessons the hard way. Push through the troubleshooting, learn as much as you can about the 'why' the change/fix addresses the issue, and work carefully. 
   
  As to desoldering, you'll need a couple of things in your kit. Firstly, good quality solder braid. There's a world of difference between the effectiveness of the good vs. the cheap stuff. If you're going to continue doing SMD work, you'll need to at least pick up a reasonable second Iron. Early on, I removed 2 pad components with two irons, then cleaned up with braid. A cheap solder sucker can also help, though more so with through hole work.
   
  I've since picked up some SMD Tweezers, power suction, hot air pencil, reflow oven... yeesh, I've spent some money. And while I have, it's all seriously lowered the frustration level and increased the enjoyment. It's no big deal to lift parts (without lifting pads .
   
  Bottom line - hand in there!


----------



## Avro_Arrow

I noticed I get some noise when running the Pup from my laptop but it's perfectly quiet when used with my desktop.
  Can you try a different source?
   
   
  Quote: 





blanko said:


> Unfortunately I'm experiencing the same issue as Mullet. When Volume is low or no music is playing I sometimes hear a pulsing noise lasting one or two seonds.
> There also is a frequent crackling sound. Those sounds aren't very loud but quite anoying. Only the left channel is affected.
> I double checked every chip for bridges thoug my magnification isn't sufficient. I held the PCB against a bright LED lamp. There was nothing suspicious.
> I used 99.5% isopropyl alcohol for cleaning. As Mullet indicated his problem was solved after he had replaced U9 with LMH6643 and swapped U5 plus U7.
> ...


----------



## Mullet

It could be the same issue. I'm still not sure whether my issue was with U5 and U7 or if it had more to do with U9. I still haven't gone back to a different U9 and I probably won't because it's not worth the time.
   
  I'd advise to buy something like chipquik, which will help remove the chip(s). Either way, you're going to have to spend more money to get this working. Overall, you should be able to get this working properly like I did.


----------



## tomb

Sorry to hear this, Blanko.  The good thing is that from your description, it sounds like the opamp, U9.
   
  Here are some questions/suggestions:

 I can't tell from the single photo you posted, but did you solder the R6, R9, R17, and R21 resistors on the back side of the PCB?  If on the top of the PCB, it's possible the extra lead length is causing the opamp to become unstable.
 It's possible the mica capacitors may be contributing to this, also.  Can you squeeze them further down into the PCB?  I've built over 10 now and the OPA2836 is absolutely stable on my builds.  However, I squish those mica's down so far into the PCB that some of the leads and hole-plating come off in strips.  You certainly don't want to break anything by forcing it too hard, but I'd try to get the cap body as close to the surface of the PCB as possible.  You can heat one of the holes/leads up, then try to pull it through with pliers from the other side.  It depends on much you have to grip on the bottom after trimming the leads, though.
 In the whold scheme of things, removing the opamp is pretty simple.  Add enough solder to one side of the opamp - try to cover all four pins on one side.  The soldering iron should be able to keep the whole solder blob melted.  At the same time, use a small knife/dental pick or similar to carefully pry the chip up from the PCB on that side.  Add a solder blob to the other side and remove the chip.  Clean up the PCB with de-soldering braid.  It works an awful lot simpler than it sounds. 
	

	
	
		
		

		
			



   
  If none of that works, then maybe Mullett is correct that the problem could be the charge pump or one of the regulators.   Let us know what you can about the questions/suggestions.


----------



## Blanko

First of all thanks for encouraging me.
  What I have done so far:
   
  1. Tried a different source. I plugged it in the USB hub of my raspberry pi. Same problem.
   
  2. Desoldered the mica cap and got it one mm deeper into the PCB but the lead space on this one is simply too big to get it flush.
      I could push a few resistors deeper into the PCB. Yes, R6, R9, R17, and R21 are mounted on the backside.
   So far no change. all measurements where as before.
   
3. Desoldered U9 with two irons, wicked all excess solder up, cleaned pads and put LMH down.
   The 5V are both lower than before. ca 4.8V. DC offset is very high. R: 3.5mV L: -4.5mV.
   Still recognized by the PC, still playing audio. Pulsing and crackle are gone but I have a much higher noise floor than before.
      Before right channel was silent. Now both sound like a small waterfall.
   
  I guess I have still the same problem as before only the two OPA's behave different in this matter.
  At least I could compare both OPA's and I have to say that the 2836 is the better one not only in measurements.
  There are some audible differences especially in the heights and upper voices. The 2836 has more headroom and crisper heights than the LMH.
  The LMH sounds a bit richer and warmer in the mids. It also has a more punch in the lows but the bass of the 2836 goes a bit deeper and is more defined
   
  Depending on whether I get spares for U5 and U7 or not I'm going to replace them. But for now I don't know what to do else.
  Could I have added to much Capacitance? C2 and its brothers are 68uF, C10 is 220uF and C26/27 are 470uF.


----------



## Mullet

I have a few extra 2835s and wanted to give the 2836 a shot. Anyone want to trade?

I think I already know the answer to this... being that the PCM2707 is only capable of 16/48 does that mean that is what is coming out of the PCM1794? Or does the 1794 upsample or oversample to 24/192?


----------



## Avro_Arrow

You only get what the PCM2707 gives you...
   
   
  Quote: 





mullet said:


> I have a few extra 2835s and wanted to give the 2836 a shot. Anyone want to trade?
> 
> I think I already know the answer to this... being that the PCM2707 is only capable of 16/48 does that mean that is what is coming out of the PCM1794? Or does the 1794 upsample or oversample to 24/192?


----------



## tomb

Quote: 





blanko said:


> First of all thanks for encouraging me.
> What I have done so far:
> 
> 1. Tried a different source. I plugged it in the USB hub of my raspberry pi. Same problem.
> ...


 
  I'm guessing now that it's somewhere in the regulators or the charge pump, as Mullett also suggested (U5 and U7).  However, keep in mind that's only a guess.  It's very strange that things were fine at first, but then deteriorated to this extent.
   
  I doubt the capacitance could be any issue.  I've built several with higher value capacitors - so have other people.  My latest builds use 1500uf at C22 and Panasonic FM's at C26/C27 - same 330uf, but the impedance and ripple are much, much higher.  There's no issue.


----------



## Mullet

I'd think its the charge pump that is generating the pulsing noise. Once I changed that out things seemed to work out.
   
  What's the benefit of using higher capacitance C22 and higher impedance/ripple for C26/27?


----------



## tomb

Quote: 





mullet said:


> I'd think its the charge pump that is generating the pulsing noise. Once I changed that out things seemed to work out.
> 
> What's the benefit of using higher capacitance C22 and higher impedance/ripple for C26/27?


 
  I hope that's good advice and thank you for it - you have more experience getting a problem pup to work than me. 
	

	
	
		
		

		
		
	


	



   
  C22 is the primary power cap.  My experience with the Bantam and Alien seem to indicate that the higher capacitance you can manage at the power level, the more stable the DAC USB connection is - plus, more bass may result because power is more stabilized throughout the board. A similar thing is true with C26/C27.  Those are the "power caps" for the opamp output.  So, the more capacitance - or higher quality capacitance - you can put there, the better the bass.  Bass usually needs more power or cleaner power to really come through.  Think putting two 470uf caps in a CMoy circuit instead of two 220uf as originally conceived.
   
  'Course, the above is all un-proven empirical opinion.  It seems pretty likely that it's not going to hurt, though, unless the capacitance is so high that the DAC draws enough start-up current to get knocked off the USB circuit.


----------



## geofftnz

I put together my pupdac today, but it hasn't gone particularly smoothly... It recognises in Windows, all voltage test points pass, but I'm getting a very large offset of -0.5V on the left channel and -2.4V on the right. Hooking up the scope shows some audio signal, but at a very low level. I'm not sure where to start debugging - I've reflowed half the connections on the board, concentrating around the resistors surrounding the opamp, but not joy.
  
 Any ideas?


----------



## tomb

geofftnz said:


> I put together my pupdac today, but it hasn't gone particularly smoothly... It recognises in Windows, all voltage test points pass, but I'm getting a very large offset of -0.5V on the left channel and -2.4V on the right. Hooking up the scope shows some audio signal, but at a very low level. I'm not sure where to start debugging - I've reflowed half the connections on the board, concentrating around the resistors surrounding the opamp, but not joy.
> 
> Any ideas?


 
  
 The opamp controls offset.  Ensure that you have the resistors soldered on the bottom of the PCB (R6, R9, R17, R21)*, that all resistors are correct, and that they're flush to the surface of the PCB (minimizes parasitic effects from leads longer than they should be).
  
 If none of that works, the kit still comes with the OPA2835 in addition to the OPA2836 that I manually add to the kit.  De-solder the OPA2836 and install the OPA2835 - see if that makes a difference.  I'll send you another OPA2836 it that turns out to be the case.
  
  
 * For that matter, ensure that you haven't mixed up R6 with R5.  The silkscreen for R6 on the bottom of the PCB is defective and it looks like "R5."


----------



## geofftnz

tomb said:


> The opamp controls offset.  Ensure that you have the resistors soldered on the bottom of the PCB (R6, R9, R17, R21)*, that all resistors are correct, and that they're flush to the surface of the PCB (minimizes parasitic effects from leads longer than they should be).
> 
> If none of that works, the kit still comes with the OPA2835 in addition to the OPA2836 that I manually add to the kit.  De-solder the OPA2836 and install the OPA2835 - see if that makes a difference.  I'll send you another OPA2836 it that turns out to be the case.
> 
> ...


 
  
 hmmm... I was wondering if it was maybe a resistor mix-up. Both signals out of the opamp are very stable non-rail voltages. I'll check that when I get home. FWIW I installed the OPA2835 first - I'll swap with the OPA2836 if the resistors don't show up anything.
  
 This project hasn't been my best soldering effort either, so I can't rule out bad workmanship.


----------



## geofftnz

tomb said:


> The opamp controls offset.  Ensure that you have the resistors soldered on the bottom of the PCB (R6, R9, R17, R21)*, that all resistors are correct, and that they're flush to the surface of the PCB (minimizes parasitic effects from leads longer than they should be).
> 
> If none of that works, the kit still comes with the OPA2835 in addition to the OPA2836 that I manually add to the kit.  De-solder the OPA2836 and install the OPA2835 - see if that makes a difference.  I'll send you another OPA2836 it that turns out to be the case.
> 
> ...


 
  
 I checked the resistors and they were all in the right place. (I was being super meticulous, so it was a bit worrying to think that I'd maybe messed that up). I measured a bunch of point to point resistances around the opamp and they all summed to expected values. In the end I cut out the 2835 and replaced with the 2836. It's now showing +130mV offset on both channels - not ideal, but better than the whole volts I was seeing before. On my ****ty scope with no audio playing I'm seeing a 50Hz at around 3mV, plus what looks like a ringing pulse up in the MHz range at a similar amplitude. Audio looks good on the scope when I play something, so I'm going to be brave and hook it up to my (AC-coupled) amp.
  
 Edit: audio sounds good to my untrained ear. I'm a much happier lad compared to last night - didn't really want to have killed 2 out of 3 cobaltmute/tomb kits


----------



## tomb

geofftnz said:


> I checked the resistors and they were all in the right place. (I was being super meticulous, so it was a bit worrying to think that I'd maybe messed that up). I measured a bunch of point to point resistances around the opamp and they all summed to expected values. In the end I cut out the 2835 and replaced with the 2836. It's now showing +130mV offset on both channels - not ideal, but better than the whole volts I was seeing before. On my ****ty scope with no audio playing I'm seeing a 50Hz at around 3mV, plus what looks like a ringing pulse up in the MHz range at a similar amplitude. Audio looks good on the scope when I play something, so I'm going to be brave and hook it up to my (AC-coupled) amp.
> 
> Edit: audio sounds good to my untrained ear. I'm a much happier lad compared to last night - didn't really want to have killed 2 out of 3 cobaltmute/tomb kits


 
  
 0.13V offset is perfectly acceptable for the pupDAC ...  it may be that the OPA2835 got damaged somehow.  Sorry you had to go this route, but you'll be happier with the OPA2836 anyway - it's a far superior opamp.  JMHO, but the 2835 was just a silicon prototype for the 2836.  When TI/Burr-Brown felt the design was vetted, then they really turned up the performance on it for the 2836.
  
 The ringing pulse could be caused by anything, but if it's in the MHz range, it's not audible.  The only other thing I would suggest checking is the lead length on the mica capacitors.  Once again, it's the parasitic effects of the lead lengths, but it takes some effort to really get those micas down low to the PCB (like pliers pulling the leads through - _carefully_).  As for the 50Hz, that's probably just a USB-power artifact.


----------



## geofftnz

tomb said:


> 0.13V offset is perfectly acceptable for the pupDAC ...  it may be that the OPA2835 got damaged somehow.  Sorry you had to go this route, but you'll be happier with the OPA2836 anyway - it's a far superior opamp.  JMHO, but the 2835 was just a silicon prototype for the 2836.  When TI/Burr-Brown felt the design was vetted, then they really turned up the performance on it for the 2836.
> 
> The ringing pulse could be caused by anything, but if it's in the MHz range, it's not audible.  The only other thing I would suggest checking is the lead length on the mica capacitors.  Once again, it's the parasitic effects of the lead lengths, but it takes some effort to really get those micas down low to the PCB (like pliers pulling the leads through - _carefully_).  As for the 50Hz, that's probably just a USB-power artifact.


 
  
 I stood at my workbench last night for two hours going through all the tracks that I gravitate towards when testing audio - it was hard to turn everything off and go to bed... I'm not unhappy at all for having to swap out the opamp - thank you for including both in the kit! As for power & noise, I'm throwing some pretty nasty stuff at it: My laptop on AC has rubbish power (visible on USB power and very audible on the on-board sound) and I have CFL lighting very close to where I'm working, which likes to inject noise into anything and everything. Most of the power for my house flows through the wall behind my workbench, so that's another 50Hz source.
  
 I had to put a couple of 90° bends in the mica leads to get them to fit - you were right about the quality control on these. They're as flush as I can get them though - probably added 0.5-1.0mm of lead length. Would SMT mica caps be an option here? http://nz.mouser.com/ProductDetail/Cornell-Dubilier/MC12FA221J-F/?qs=sGAEpiMZZMtLiKaZgV7flf17yrFrEpwIzcWZX3sn33I%3d


----------



## tomb

geofftnz said:


> I stood at my workbench last night for two hours going through all the tracks that I gravitate towards when testing audio - it was hard to turn everything off and go to bed... I'm not unhappy at all for having to swap out the opamp - thank you for including both in the kit! As for power & noise, I'm throwing some pretty nasty stuff at it: My laptop on AC has rubbish power (visible on USB power and very audible on the on-board sound) and I have CFL lighting very close to where I'm working, which likes to inject noise into anything and everything. Most of the power for my house flows through the wall behind my workbench, so that's another 50Hz source.
> 
> I had to put a couple of 90° bends in the mica leads to get them to fit - you were right about the quality control on these. They're as flush as I can get them though - probably added 0.5-1.0mm of lead length. *Would SMT mica caps be an option here? http://nz.mouser.com/ProductDetail/Cornell-Dubilier/MC12FA221J-F/?qs=sGAEpiMZZMtLiKaZgV7flf17yrFrEpwIzcWZX3sn33I%3d*


 
 Hmm ... that's a cobaltmute question.  Seems like at one point he said we could replace them with film caps, but I'm not sure.  During prototyping, he seemed to think offset issues were focused on the opamp resistors.  That's why he made the change to put four of them on the bottom of the PCB.  However, if I'm interpreting things correctly, the mica capacitors are essentially the decouplers for the power supply to the opamp.  That's why I suspect that perhaps long lead lengths with the micas could cause an issue.
  
 Hopefully, he will see this and reply.


----------



## geofftnz

tomb said:


> Hmm ... that's a cobaltmute question.  Seems like at one point he said we could replace them with film caps, but I'm not sure.  During prototyping, he seemed to think offset issues were focused on the opamp resistors.  That's why he made the change to put four of them on the bottom of the PCB.  However, if I'm interpreting things correctly, the mica capacitors are essentially the decouplers for the power supply to the opamp.  That's why I suspect that perhaps long lead lengths with the micas could cause an issue.
> 
> Hopefully, he will see this and reply.


 
  
 My interpretation was that the micas were part of a low-pass filter on the differential pair coming from the DAC, since the opamp has bandwidth well above audio frequencies... I'll defer to the actual designer though


----------



## tomb

geofftnz said:


> My interpretation was that the micas were part of a low-pass filter on the differential pair coming from the DAC, since the opamp has bandwidth well above audio frequencies... I'll defer to the actual designer though


 
  
 You're right.  Looking again at the schematic, they're applied to the signal outputs of the DAC.  Further, "The analog filtering is minimal, only using one high quality silver mica capacitor in the signal path."  That's a quote from the EZDac technical info, which was some of the basis for the differential-to-single-ended-gain-stage on the pupDAC.
  
 So as far as what I had been saying ... never mind.


----------



## scootsit

Hey gents, I've been away for a while, it's been a crazy couple of months, two moves, new jobs, etc, etc. Anyway, a year or so ago, I was working on building an effects pedal for a friend, then well, things got busy and it didn't happen. Now that I've settled, I want to get back to work on it. I recall someone posted somewhere on head-fi (I'm pretty sure it was this thread) a link to a company that custom engraved and silk-screened electronics boxes. I think it's the company used for the Pup. Anyone have any ideas?
  
 Thanks!


----------



## geofftnz

scootsit said:


> Hey gents, I've been away for a while, it's been a crazy couple of months, two moves, new jobs, etc, etc. Anyway, a year or so ago, I was working on building an effects pedal for a friend, then well, things got busy and it didn't happen. Now that I've settled, I want to get back to work on it. I recall someone posted somewhere on head-fi (I'm pretty sure it was this thread) a link to a company that custom engraved and silk-screened electronics boxes. I think it's the company used for the Pup. Anyone have any ideas?
> 
> Thanks!


 
  
 Might be wrong, but I think it's Hammond.


----------



## scootsit

geofftnz said:


> scootsit said:
> 
> 
> > Hey gents, I've been away for a while, it's been a crazy couple of months, two moves, new jobs, etc, etc. Anyway, a year or so ago, I was working on building an effects pedal for a friend, then well, things got busy and it didn't happen. Now that I've settled, I want to get back to work on it. I recall someone posted somewhere on head-fi (I'm pretty sure it was this thread) a link to a company that custom engraved and silk-screened electronics boxes. I think it's the company used for the Pup. Anyone have any ideas?
> ...


 
 Cool, thanks. I checked with them, I remembered seeing a service with an online interface that also used CAD, so you could edit it and upload it and get an immediate quote. I'll check with Hammond tomorrow and see if they're not too outrageous for just one or two.


----------



## Avro_Arrow

scootsit said:


> I remembered seeing a service with an online interface that also used CAD, so you could edit it and upload it and get an immediate quote.


 

Front Panel Express


----------



## scootsit

avro_arrow said:


> scootsit said:
> 
> 
> > I remembered seeing a service with an online interface that also used CAD, so you could edit it and upload it and get an immediate quote.
> ...


 
 That's the one, thanks a ton!


----------



## tomb

scootsit said:


> geofftnz said:
> 
> 
> > scootsit said:
> ...


 
 Hammond certainly makes the pupDAC cases, but the anodizing and laser-etching was done locally in Atlanta:
http://www.newhouseproducts.com/
http://www.lasertechatlanta.com/
  
 Hammond is now making those cases in the same blue, so I'd order them directly from them if you are interested.  Their quality, quite frankly, is not that good if you order them in RAW aluminum.  I get the feeling they dump them all in a giant dumpster to get scratched up, first.


----------



## geofftnz

tomb said:


> I get the feeling they dump them all in a giant dumpster to get scratched up, first.


 
  
 It's called "Vintage", so your DAC goes with your threadbare tshirt and $250 ripped jeans.


----------



## scootsit

tomb said:


> scootsit said:
> 
> 
> > geofftnz said:
> ...


 
 I'm not building the same thing. If possible, the effects pedal would actually work better with the Bud cases, anyway. I appreciate the tip, though. I'm going to try Front Panel Express.


----------



## tomb

geofftnz said:


> tomb said:
> 
> 
> > I get the feeling they dump them all in a giant dumpster to get scratched up, first.
> ...


 
 Yep.


----------



## funch

I thought I'd pull this thread up out of the dead pool. I finished mine a couple of days ago, and am quite impressed. For no more than this DAC costs to build, it's a great performer. I was looking for a
small DAC to go with my 'Wintergreen Handwarmer' tin amp, which itself is a great performer as well. Fabulous match. Of course, I'm feeding mine with a Beezar Doodlebug USB de-crappifier.

Even through my Eddie Current BA, it sounds excellent. Bang-for-the-buck ratio is high. Definitely recommended if you're looking for a cheap, small DAC.


----------

