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Old 17th March 2013, 02:49 PM   #371
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I believe your question has already been answered earlier in this thread, read here for more background - Grounding of Mixes Signal Systems
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Old 17th March 2013, 03:13 PM   #372
qusp is offline qusp  Australia
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I gave you a reply, short explanation and a brief pointer as to a way around it, but it seems you didnt understand it.

both are still connected to and in the dac chip and if the 2 are separate and at slightly different potentials, it will create circulating loop currents/noise inside the chip, both directly and parasitically.

its a bandaid solution that doesnt even work, use proper grounding and decoupling, use slots in the ground plane to shield delicate parts if you like, but it should be one plane. section it if you like but all should be connected, otherwise it will seek out its own connections and the loops may not be where you think/hope

how exactly are you going to define analogue and digital parts anyway?

aside from it also being the suggested modern practices with much more delicate devices than this to avoid it, the ESS app notes make a specific point of recommending to NOT do it.

and yes Chris, it is a bit De Ja Vu all over again

Quote:
Originally Posted by diy mekkern View Post
IMHO I would believe that a complete separation of analog/digital ground with be a very positive mod. Due to the high frequencies working on the digital busses. And a separation from USB ground from computer. Which in total should reduce noise ??

Or is there better ways around this ?
Or isnt it an issue ? Then I would like a short explanation if anyone got it.

Thanks for reply :-)

Last edited by qusp; 17th March 2013 at 03:22 PM.
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Old 17th March 2013, 03:35 PM   #373
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OOps ;-)

Thanks for your patience anyway. I certainly do understand Im walking far away on thin ice here.

My reason for thinking this, was that in ESS´s papers everything is noted as AGND and GND. I didnt know they both were connected in the chip. which I do understand that makes a serious issue. We dont want the main ground connection in the middle of the chip.....

Thanks again
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Old 18th March 2013, 01:32 AM   #374
qusp is offline qusp  Australia
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No problem, yeah well it depends exactly how you define analogue and digital supplies whether they are joined in the chip. having each supply separate but with all joined under the chip is also fine. The idea is to provide each signal with a low impedance return and shortest loop possible, so that fast slewing digital signals dont have anywhere they would rather be. with bad layout you could still have benefit I guess.

check the ES9008 app note, actually I remembered incorrectly, they dont specifically say its bad, but they mention doing extensive testing and finding no benefit.

Quote:
ESS has experimented with DAC evaluation PCBs ground planes to determine any benefit of split plane grounds for analog and digital ground. It is our finding and recommendation to use only one ground plane for both digital and analog grounds as it simplifies layout and provides no performance degradation
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Old 19th March 2013, 04:23 AM   #375
rade95 is offline rade95  United States
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I am still puzzled and confused with some of the postings: glt you are talking about a need for 1.2V supply, in addition to 3.3V AVCC and 3.3V DVCC. However I don't see a need for a 1.2V regulator for a v2 board. I just got my v2 board and it has AVCC, DVCC and additional 3 pins marked +12, GND and -12V. I don't get it why does this board require +-12V PS? I am yet to figure out where to source AVCC power supply. For +-12V (if really needed) I will use a TP Placid bipolar PS and for DVCC 3.3V I will use ADP7104 eval board. Any recommendations for AVCC 3.3V regulator?
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Old 19th March 2013, 06:32 AM   #376
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The 1.2V reg is usually already soldered to the board.

+/- 12v is for the op amps.
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Old 19th March 2013, 01:08 PM   #377
rade95 is offline rade95  United States
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Quote:
Originally Posted by KlipschKid View Post
The 1.2V reg is usually already soldered to the board.

+/- 12v is for the op amps.
Thanks KlipschKid, that explains it. Since I will try direct output, I will skip using +-12V supply, unless I decide to install the OPAMPs.
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Old 26th March 2013, 04:59 AM   #378
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Thanks guys for an excellent thread so far.
You have convinced me to purchase a board, and give myself the goal of my first DIY digital project. (see below for my parts so far.....)
I am currently plowing through the 300+ posts in this thread.

Before I ask something already mentioned/answered....I'm gonna ask something probably already mentioned/answered.
As a digital newbie, I wonder about some digital interface basics. So bear with me for a moment whilst I reveal my inner binary child.....
.......
1) I'm not sure I need USB input, but surely I want toslink and coaxial.
If I put USB in...(i2s board)....are there rules for it's clock, and the DAC board's clock ?....as in proper sync ?
(I plan on using a good on-board clock, so using the i2s clock may be a step down...if I understand correctly)
Links for a good i2s ?

2) I see that balanced analog output is available on this board, however I want Balanced and unBalanced outs. Is this an "off the board" solution?....or can both be pulled from the board ? (loading one or the other only) I suppose a front or back panel switch could accomplish this too.

3) can the 680 ohm's become 1k ?...ultra precision resistors are easier to source at this value. I already have some 100 ohm Vishay 0.2ppm....It would be nice if these paired resistors had the same tempco.


Thanks...I'll keep reading/researching to answer my other questions !!

=Randy=

-ebay DIYINHK’s ES9018 board
-one "Kubota low noise regulator full blown version kit !! "
-two TPS7A47 Eval Boards
possible clocks:
-ASV-50.000MHZ-E-J-T
-CCHD-950-25-100 mHz
-FXO-HC736R-50 mHz


p.s.....just thinking here....doesn't the quality in the audio chain also depend on the digital source before the DAC ?...or are 1's and zero's >>> just 1's and zero's ?

Last edited by redrabbit; 26th March 2013 at 05:11 AM.
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Old 27th March 2013, 06:32 AM   #379
smms73 is offline smms73  Portugal
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what you guys think of this oscillator ? less than 2 euros in mouser, very good jitter values.

http://www.vectron.com/products/appn...CC1_Series.pdf

http://www.vectron.com/products/xo/VCC1.pdf
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Old 27th March 2013, 05:06 PM   #380
qusp is offline qusp  Australia
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good for the money I guess, but there is nothing outstanding there
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