[cobaltmute]

Billyk is right - you have to be prepared to do SMD. Do not rush, do not hurry and do not panic. If you feel rushed or frustrated, you need to step away.

It takes me about 2 hours to do a grubDAC. I'm slow and methodical. And they work right the first time, every time.

 

[Billyk]

Quote:

Originally Posted by cobaltmute It takes me about 2 hours to do a grubDAC. I'm slow and methodical. And they work right the first time, every time.

Well I will admit that the 30 minute time was for the actual soldering, I had spent prolly more than 30 minutes setting it all up, laying out the parts, etc. So come time to solder, I just had to pickup the part and go! And of course I did not count the 20 minutes it takes to find the 0805 chip that I shot across the room by squeezing it too hard with the tweezer

Slow and careful is the right way to do it, my biggest problem is the packaging, so if I lay it all out before hand, labeled on a sheet or two of paper, with the BOM and schematic it makes it easier.

 

[ziplock]

Going to give this one a go.

Boards and parts ordered. I'm looking forward to the build.

I think I'll put a few pieces on at a time while I wait for the 2707s to become available. No reason to rush.

Anybody else building one?

 

[Billyk]

I will be as soon as I finish the four proto versions. Just need those 2707s!

 

[tomb]

Remember to check on the PCM2706's. Those work, too, and are arriving sooner at most places, I believe.

 

[cobaltmute]

Quote:

Originally Posted by ziplock /img/forum/go_quote.gif I think I'll put a few pieces on at a time while I wait for the 2707s to become available. No reason to rush.

If you're going to do that be very careful - you want to make sure that you do things in an order that you don't make it difficult to solder down the PCM2707. I would do the bottom chips only if I were to do that.

 

[tomb]

Quote:

Originally Posted by cobaltmute /img/forum/go_quote.gif If you're going to do that be very careful - you want to make sure that you do things in an order that you don't make it difficult to solder down the PCM2707. I would do the bottom chips only if I were to do that.

Agreed! When I put my two together for the first time, I chose the PCM2706/7 as the very first item to solder - even before the WM chip. It seemed to work best that way.

 

[ziplock]

Quote:

Originally Posted by cobaltmute /img/forum/go_quote.gif If you're going to do that be very careful - you want to make sure that you do things in an order that you don't make it difficult to solder down the PCM2707. I would do the bottom chips only if I were to do that.

Right. I'll probably save most of the through hole for last. Possibly L2 as well.

It just depends on how it looks when I get the board.

The DAC chips look like a piece of cake to solder down. Rather large pitch, no? .65 and .8mm

 

[cobaltmute]

The PCM2707 being TQFP-32 seems to be about the same as putting down a SOIC chip. Bit more work in alignment due to the pins on the four sides. the WM8524 I find not too bad as well.

I would definitely leave the through hole for last. Putting that in before the SMT stuff can lead to issues.

My basic plan for doing a grubDAC:
PCM2707
WM8524
XO
Then top side SMT R and C
Bottom side TPS regulator
Bottom side SMT R and C
Through hole R
Through hole C

When doing R and C parts, I do the blob of solder and then slide the part in method. I always do the non-ground plane side of the part first as the ground plane sucks heat and makes it hard to align the part. I also look at the board and plan what order will make sure I don't "bury" an end of a part making it hard to solder afterwards

 

[netsky3]

I have a little question: between the grubdac and the bantam wich is the better one?
Where i can find the specs of them?

 

[cobaltmute]

There is this for specs on the BantamDAC. To my knowledge no-one has done a RMAA on the grubDAC. I would do it but I do not have a good input source that I can test with.

They sound different as the BantamDAC is AC-coupled (capacitor in-line). I'll let others comment on the difference in sound. Both are in-expensive though and if you build both you can have a good idea for yourself.

 

[netsky3]

Quote:

Originally Posted by cobaltmute /img/forum/go_quote.gif There is this for specs on the BantamDAC. To my knowledge no-one has done a RMAA on the grubDAC. I would do it but I do not have a good input source that I can test with. They sound different as the BantamDAC is AC-coupled (capacitor in-line). I'll let others comment on the difference in sound. Both are in-expensive though and if you build both you can have a good idea for yourself.

Thank you.
I'd like to know more opinions about the sound differences

 

[antonyfirst]

Which is the smoother one between the two?
What does the fact of having inline capacitors imply (against not having them)? Warmer/less trebly sound? Or the other way around?

 

[cobaltmute]

Quote:

Originally Posted by antonyfirst /img/forum/go_quote.gif Which is the smoother one between the two? What does the fact of having inline capacitors imply (against not having them)? Warmer/less trebly sound? Or the other way around?

The point of having the capacitors inline on the BantamDAC is that the PCM2702 output mid-rail (~2.5V) DC and the capacitor blocks that.

As for the sound of the capacitor? That is a religious debate. Black Gates, Vitaman Q, Wima, Silmic, Cerafine, Muse, Solen, Vishay Roederstein, etc all have been said to have different sounds. It comes down to personal preference to determine which one you like.

The grubDAC doesn't need a DC blocking cap. The WM8524 uses a charge pump to generate a negative rail and outputs a low offset signal. So you are trading the capacitor for a technology to create the negative rail.

So the grubDAC and the BantamDAC are different beasts in the output stage and they sound different. Some people have commented already in this and the Carrie thread, so you can get some opinions here and there. A few more vocal builders would help out a bit in this regard

 

[Juaquin]

Well no capacitors means you don't have bass roll-off. That's not a problem with the Bantam anyways, though. And of course, if you believe capacitors audibly color sound there's that too.