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The GrubDAC - Page 7

post #91 of 1072
Thread Starter 
Quote:
Originally Posted by keyid View Post
The build went pretty smooth. I tried kwame 100ohm resistors for R7/6, after listening to the default and couldn't hear much of a difference. Led should be placed near the usb, also it would be nice to have the G,OR,OL in a line sequence instead of 2x2 block.
For the next revision of the board, I've moved everything about. One of the key things was to get the LED next to the jack.

I'll look into the output block. It was easier to go 2x2 rather that 1x4. I did two OGs as I saw a comment in the BantamDAC info that people had asked for that and I was trying to be as compatible as possible.

Quote:
I connect 5v on the carrie to the V+ and 0v on the carrie to GND, which I think is correct.
That would be correct.
post #92 of 1072
Thread Starter 
Quote:
Originally Posted by joneeboi View Post
I got my boards the other day, and now I'm not sure what to do in regards to ordering parts. I'll have to wait on it a while. Good to hear it's getting a good reception. I can't wait to build mine.
Farnell in Singapore has 48 PCM2707 in stock. ~$25 shipping to Canada though.
Almost worth it to get a couple...
post #93 of 1072
having two OG behind each other is fine. Having OG, OR, OL in a line would be great and match the carries sequence so there are no wires looping each other.
post #94 of 1072
Just a suggestion, If the SSPND output drove the LED (through a transistor - only 2 ma output :-() then you could see when the pc has disabled the output for some reason.
post #95 of 1072
Thread Starter 
Quote:
Originally Posted by stwspoon View Post
Just a suggestion, If the SSPND output drove the LED (through a transistor - only 2 ma output :-() then you could see when the pc has disabled the output for some reason.
I like the idea, but it is not foolproof. The PCM goes into suspend after 5ms of no music as well (datasheet, pg 27), so as an "active" indicator it is not useful.

Now using a bi-color LED with red as power and green as music might be cool. I'd have to kill something (likely C9) to get the parts I needed in the right spot and it still would be a pain to route the SSPND to that spot.
post #96 of 1072
Just wanted to let you guys know, seems the PCM2707 is back in stock a mouser.

BTW, did someone try mouser 546-1551JTBU as a case? It looks quite nice (available in other colors as well), and looking at the PDF, it seems the screw holes are the exact right size for the PCB. Only question is, is there enough space between the two plastic parts for the PCB to fit in while allowing the case to be closed.
post #97 of 1072
Thread Starter 
Quote:
Originally Posted by KT88 View Post
Just wanted to let you guys know, seems the PCM2707 is back in stock a mouser.
Good to know.
Quote:
BTW, did someone try mouser 546-1551JTBU as a case? It looks quite nice (available in other colors as well), and looking at the PDF, it seems the screw holes are the exact right size for the PCB. Only question is, is there enough space between the two plastic parts for the PCB to fit in while allowing the case to be closed.
There is only 15mm total height for that case so it may be a bit small.

Now, once I get some PCM2707s, I have the parts to build it in a 1551HTBU. I think the extra 5mm in height should make it workable. I did order lower height caps for C9/C10 so we will have to see. The board does have to be modified with a Dremel to fit into the case and I may have to modify the case as well.
post #98 of 1072
Thread Starter 
Quote:
Originally Posted by KT88 View Post
BTW, did someone try mouser 546-1551JTBU as a case? It looks quite nice (available in other colors as well), and looking at the PDF, it seems the screw holes are the exact right size for the PCB. Only question is, is there enough space between the two plastic parts for the PCB to fit in while allowing the case to be closed.
Thought about this some more on the way to work.

C9/C10 are the caps that are the big height offenders. You could use SMT ceramics across the pads, but you get to $$$ for the quality chips in high capacitance.
post #99 of 1072
I think I'm gonna put one of them in the plastic box, and the other inside an aluminum box with a pimeta (v1) amplifier (and the third in the usual hammond case like the one for the mini^3/Carrie/y1 ).

I want to be able to switch between RCA input and the DAC, but there's just too many options at mouser. Can someone please help me find a nice switch/toggle for this?
post #100 of 1072
Thread Starter 
Quote:
Originally Posted by KT88 View Post
I think I'm gonna put one of them in the plastic box, and the other inside an aluminum box with a pimeta (v1) amplifier (and the third in the usual hammond case like the one for the mini^3/Carrie/y1 ).

I want to be able to switch between RCA input and the DAC, but there's just too many options at mouser. Can someone please help me find a nice switch/toggle for this?
http://www.head-fi.org/forums/f6/sim...8/#post6016813

I've been thinking about the same thing, switch RCA and DAC in an amp, only for me I think it is going to be a CTH or CK2III.
post #101 of 1072
Hi Erik,

Do you happen to know the mouser PN for a suitable item? I got lost in the tens of thousands of item's they have in that category
post #102 of 1072
Thread Starter 
Honestly, I haven't gotten that far in my planning yet. You may want to make a thread of it and someone else may see it and be able to help.
post #103 of 1072
Thread Starter 
GrubDAC as a cable dac in the aforementioned 1551HTBU.


General Pic:


Detail:


Stupidly Bright White LED shining through the case:


To do this you need to:
  • Cut two corners off the board.
  • Choose short caps for C9 and C10
  • Depending upon how short of caps you chose for C9 and C10, you may need to remove the 2 circuit board "bosses" in the case to get the board closer to the bottom. In my case I actually used a drill to remove them
  • If you had to remove the bosses, there is some "supports" for the board on the two pillers that the lid screws into that need to be removed. An Xacto worked well on these.
  • Drill holes for the two screws (1/8)" and the end grommets (1/4")
  • Use 4/40 nylon screws to avoid scratching anything the DAC sits on and use washers on the inside to ensure the DAC doesn't sit on the bottom of the case.
  • The other item of note is the USB drain wire. It will not fit in the Ground Holes. What I did was take the drain and the ground from the USB cable and put them in one of the holes of the USB connecter and then jumpered that to the GND positions (as the USB mounting holes are not connected to anything)

For this one, I used United Chemi-con polymer caps (PS-A and PS-E). They have quite large capacitance for the size

The big pain about this is trying to get the DAC into the case after you've soldered the wires on. It is a PITA, but it can happen. I like have the translucent case with the LED shining through as an effect.

I suspect that you should be able to do fit a Bantam in this same Hammond case. I did a search, but didn't find anybody doing it (but I might have searched wrong).
post #104 of 1072
i am strongly recommending you to add a headphone amp ic part using max9722,it's also powered by a charge-pump ,it has powerful output and low thd+n.comparing with any other charge pump based headphone amp ic ,its price is reasonable while its proformance is not bad(only not as good as Ti's tpa6130,but note that tda6130 is QFN package and not easy to purchase),max9722 must be a good addtion to this project
post #105 of 1072
Thread Starter 
If I do anything for headphones it will be optional.

And when choosing a white LED be wary of its Luminous Intensity. The one I chose lights up a dark room on 3mA. Must have chosen a flashlight LED.
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