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Comments for my PCM2702 DAC layout?

#1
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8/10/06 at 5:23am
  • Joined: November 2004
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When I missed the 1st round of Alien DAC boards, I decided to do my own board layout to best suit what I wanted. The following is what I came up with. It measures 50x26mm, and for the most part, I just copied the schematic used by the Alien DAC, dropping the BUF634 section, as I only plan to have this bus powered, replaced the regulators with the SOT23-5 versions, which allows the use of TPS79333 and TPS793475 3.3v and 4.75v fixed regulators, which are less expensive than REG101, and pin compatible. I also went to 6.4x13.3 mm film coupling caps for the output, instead of 6.3mm electrolytics. Anyways, I am looking for comments on the DAC and layout, especially ones relating to how to improve it.

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#2
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8/10/06 at 11:24am
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looks pretty good imo.
one question: are the beads for the analog supplies directly under the bypassing caps on top?

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#3
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8/10/06 at 12:17pm
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Quote:
Originally Posted by t52
looks pretty good imo.
one question: are the beads for the analog supplies directly under the bypassing caps on top?
Yes.
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#4
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8/10/06 at 4:10pm
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Would low value film caps cause a bass roll of? I remember from the Alien dac thread that one should use at least 4.7uf do that you have a low frequency filter.
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#5
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8/10/06 at 6:16pm
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depends on the input impedance of the following stage. for an amp the value is far from critical, e.g. (@ -3dB)
10k 2uF -> 8Hz
15k 2uF -> 5Hz

I can hear the silence ...

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#6
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8/3/08 at 10:50pm
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I finally got around to having some boards made up by BatchPCB. It will be definitely easier to get the necessary vregs in SOT23-5.

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#7
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8/3/08 at 11:37pm
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These things are very cool! They're only 1" x 2" - about the size of a couple of postage stamps (the little ones)!

TomB

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#8
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8/4/08 at 9:59am
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That is very nice. How about squeezing one of those on the miniMax?

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#9
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8/4/08 at 10:10am
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Quote:
Originally Posted by rds View Post
That is very nice. How about squeezing one of those on the miniMax?
Nope - the fit is too tight. The regular MAX is a different matter, however.

TomB

GrubDAC Step-by-Step Build Thread!!
Starving Student Millett Hybrid PCB Build Thread!!

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#10
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8/6/08 at 1:50pm
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The prototype boards shown above are on their way to several people right now. Things have been a madhouse at work this week, but I hope to have a preliminary BOM posted tomorrow evening. Except for the SOT-23 regs, commonality with Alien DAC parts should only be limited by the pad sizes.

TomB

GrubDAC Step-by-Step Build Thread!!
Starving Student Millett Hybrid PCB Build Thread!!

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#11
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8/6/08 at 6:22pm
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Nice work tomb, maybe a replacement for the AlienDAC project with its pesky, difficult to find SO-8 REG101s. The silk could use a bit of cleanup I guess, but other than that it looks great.

PS. You "stole" my DAC project name! http://www.head-fi.org/forums/f6/min...ve-i-v-292673/
http://audio.gotroot.ca/
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#12
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8/6/08 at 6:45pm
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Quote:
Originally Posted by error401 View Post
Nice work tomb, maybe a replacement for the AlienDAC project with its pesky, difficult to find SO-8 REG101s. The silk could use a bit of cleanup I guess, but other than that it looks great.

PS. You "stole" my DAC project name! http://www.head-fi.org/forums/f6/min...ve-i-v-292673/
I'm not tomb, but that is basically what this project was intended to be, when I missed the Alien DAC group buy, I redid the layout for my own preferences, and when I saw they were going to make more, I bought some of those, and put this on the back burner until now where the regs are getting extremely difficult to source. There is definitely a few things that need to be cleaned up, and that will happen before any more are made.

Sorry about the name issue, I didnt even think about it. Tom an I have just been calling it the mini DAC in our emails since we started looking at actually getting boards made for it, and just stuck with it as a name. That is the problem with generic names like miniDAC, they have already been used. Guess I could go back to the name of the folder the layout files are kept in on my PC, "PCM2702 DAC".
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#13
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8/6/08 at 7:45pm
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Quote:
Originally Posted by cetoole View Post
I'm not tomb, but that is basically what this project was intended to be, when I missed the Alien DAC group buy, I redid the layout for my own preferences, and when I saw they were going to make more, I bought some of those, and put this on the back burner until now where the regs are getting extremely difficult to source. There is definitely a few things that need to be cleaned up, and that will happen before any more are made.
Sorry cetoole, I saw tomb's response and assumed he did it all! Silly me.

Quote:
Sorry about the name issue, I didnt even think about it.
Totally kidding, go ahead and use whatever name you want, I don't plan on my project going anywhere, and even if it did, it's such a generic name...
http://audio.gotroot.ca/
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#14
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8/6/08 at 7:51pm
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Well, I am tomb. Colin and I make a great team and I feel privileged to work with him. However, I am not the acomplished board designer. My job is documentation and support.

EDIT: Not a very good documenter at that, I guess this is another instance where I sat on the post too long before submitting it. Sorry for being redundant.

TomB

GrubDAC Step-by-Step Build Thread!!
Starving Student Millett Hybrid PCB Build Thread!!

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#15
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8/6/08 at 9:14pm
  • Joined: March 2008
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Would this board be easier to work on than the original Alien DAC? And if so... anyway some more people can get a hold of them?
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