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The GrubDAC - Page 9

post #121 of 1076
Just a short update - the second Grub is up and running. I still think the PCM chip was the main problem, but reflowing that, the regulator and a few other iffy joints seems to have cleared it up.

Test points would be good, yes. Maybe 5V/GND pads on the side opposite the USB jack could be useful when mating with a Carrie, but I somehow doubt the board has space for that.

Anyway, nice one cobalt
post #122 of 1076
Thread Starter 
Quote:
Originally Posted by blippster View Post
Just a short update - the second Grub is up and running. I still think the PCM chip was the main problem, but reflowing that, the regulator and a few other iffy joints seems to have cleared it up.

Test points would be good, yes. Maybe 5V/GND pads on the side opposite the USB jack could be useful when mating with a Carrie, but I somehow doubt the board has space for that.

Anyway, nice one cobalt
Great that it works.

In the next revision, there will be the USB breakout right next to the USB jack as well as 5V/GND on the opposite side (next to the Carrie).
post #123 of 1076
Got a box of parts today and got my grub dac up and working first try. The soldering was not to bad after doing a couple other surface mount projects but I still had a couple of resistors fly across the room. I haven't had a change to sit down and compare it yet to my bantam or opus dacs but I'll post impressions when I do. I did briefly run my k240 sextetts directly off of it. They have a 600ohm impedance but the max volume was about as loud as I'd ever listen.

Thanks for this cool little project.
post #124 of 1076
Thread Starter 
I was just checking the online BOM and some capacitors are listed as backordered. All of these have easy replacements.

The PCM2707 is out of stock again. I do have a small quantity (5) that I will let go at my cost. PM me if you need one.

I think I will order a bunch to have available with the next run of boards.
post #125 of 1076
Hi cobalt.

i ahve a question about yout PCB layout, What program did you use, i use Diptrace and Eagle but i cant find any matching ic for the pcm2707, do i have to make it myself or is there any in the application.

Great job, looks very nice
post #126 of 1076
Thread Starter 
Quote:
Originally Posted by Toez View Post
Hi cobalt.

i ahve a question about yout PCB layout, What program did you use, i use Diptrace and Eagle but i cant find any matching ic for the pcm2707, do i have to make it myself or is there any in the application.

Great job, looks very nice
I use National Instruments Electronic Workbench (Multisim for schematic capture and Ultiboard for PCB layout). I had to setup the part myself which didn't work right the first time.

As for Eagle, this might be useful. Google is your friend.

EDIT: I should note that I've only found that Eagle library (the URL was posted here on Head-Fi) - I've never used it.
post #127 of 1076
This thread hasn't moved in a while. I was just curious to know how development is going, and if there is any other news anyone would like to share.
post #128 of 1076
Quote:
Originally Posted by nullstring View Post
This thread hasn't moved in a while. I was just curious to know how development is going, and if there is any other news anyone would like to share.
Well, cobaltmute contacted me recently for hole dimensions on the BantamDAC so we'd have commonality between the two designs, so I know he's working on it.
post #129 of 1076
Thread Starter 
I've got the next revision of the board done. There is some changes in footprint on some of the parts (from 1206 to 0805) and a general re-layout of the board to do things like get the LED near the USB, output near the Bantam output and put a power header on the far side from the USB to make it easier to power a Carrie board.

What I've been waiting on is feedback from the builders to see if there is anything else that needs to be done. So far the design must be pretty stable as the comments have been minimal and mostly focused on re-locating the the LED.

I'm trying to decide when it will be worth doing the next run of boards. The other issue is who to have make the boards. I'd like to go with someone like Imagineering, but the number of boards I need to have produced to make it cost effective is high and I don't know how long I want to sit on a board inventory. Nevermind the fact that I still have half the boards from the first run still in my possession.

As for the Grub2 (which would add some SPDIF and I2S headers and other tiems), that has been on hold until now as I wanted to finalize the revisions to the first board. I know what I'd like to do, now it is just executing that idea.
post #130 of 1076
Thread Starter 
I've done some maintenance on the Mouser online BOM to ensure that as much is in stock as possible.

The stock part for J1 is on backorder again - J1 alt has been added to the online BOM at a small price increase. You need to remove J1 yourself (I list both in case one comes back into stock).

I also had to change a few capacitors to in-stock versions.

The WM8524 is out of stock now, but there is stock on the PCM2707, go figure.
post #131 of 1076
keep up the good work =)

Do you plan on making the Grub2 the same size of the Grub?
post #132 of 1076
Thread Starter 
Losing my mind - I thought I responded to this this morning.

If I get what is in my head on PCB the way that I want to, Grub2 will fit in the same volume as Grub1
post #133 of 1076
Hi all,

I "finished" my build the other night. It isn't working. When I plug it in the OS (XP) tells me something along the lines of...

USB device not recognized...malfunctioned...yada yada yada.

I have 3.3V at L3. I have ohmed out all the pins on U1, U2 for solder bridges. Re-flowed them and ohmed them out again. I've also verified that pins that should be connected are connected (on U2, will check U3 again). I've started tracing through the rest of it but it is kinda hard on a two sided board.

This is only the third or fourth time I've done any SMD work. It isn't pretty but I am reasonably sure that all of my connections are sound and that I don't have any bridges.

Can anyone recommend any further course of action? How likely is it that I cooked a chip?

Thanks,
Michael
post #134 of 1076
Thread Starter 
Is this attached to something else (i.e like a Carrie)?

I would re-check the resistors R1, R2 and R3. I've seen not recognized errors from R1 not being connected properly.

And a picture may help.

EDIT: Another question - is this a cable dac build or one using the mini-usb connector?
post #135 of 1076
Stand alone cable dac

picture? may get to that but then you'd all see just how badly I solder.

Resistance is correct through R1,2,3.

When powered:
VDD = 3.3V
VBus = 3.3V
VCCP = 3.3V
Vcom = stabilizes at 2.2mV
Vccl = 38.5mV
Vccr = 5.6mV
Voutl & Voutr = 2.2mV

Second measuring (trust more):
When powered:
VDD = 3.3V
VBus = 3.3V
VCCP = 3.3V
Vcom = 3.2mV
Vccl = 39.8mV
Vccr = 12.4mV
Voutl & Voutr = 3.2mV








Quote:
Originally Posted by cobaltmute View Post
Is this attached to something else (i.e like a Carrie)?

I would re-check the resistors R1, R2 and R3. I've seen not recognized errors from R1 not being connected properly.

And a picture may help.

EDIT: Another question - is this a cable dac build or one using the mini-usb connector?
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