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Old 7th May 2005, 07:53 AM   #1
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Location: Victoria - Aus
Default troubleshooting my new dac

Iíve been working on a dac and finally got the circuit board for it and Iíve now soldered it altogether

board
schematic

Being a bit new to all this I donít really know what to do now that it doesnít exactly work

There were a few things that troubled me with something shorting the 5v digital line to ground and I was removing parts trying to track that down, and ended up finding it at C65 on the board (in the pic linked above)

Next after that, the reg102's use for regulating the digital side voltage werenít playing nice
The 5v one was outputting 4.75v with 5.6v feeding into it
As well as the 3.3v ones outputting 4.1v and 4.25v with them being fed from the 5v (that was at 4.75v)

Playing with some of the space chips of these I still couldnít get them to output the voltage that they should have been even under no or little load out of circuit

Just using an lm7805 and an lm317t bypassing the reg102's onboard, it is now being fed the correct 5v and 3.3v now

With that going now, I plug in an optical signal from a cd player in it and all I am getting is white noise and static out of it, pausing or removing the signal stops the sound so something is getting through

I'm thinking that the df1704 and pcm1704 wants a 24bit wordlength and its only getting 16bit, in setting up the pins on the chips I wasnít exactly sure what ones I was meant to set them to so I chose the ones that seemed to be the standard values

I am sort of stumped and where to go now, I donít have an oscilloscope or fancy test equipment to play with, so if anyone could look over what I have done and point out anything I have missed I would be very grateful

Thanks,
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Old 7th May 2005, 09:52 AM   #2
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Both pictures are from the board, NO schematic!
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Old 7th May 2005, 09:54 AM   #3
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Hi DaKi][er,
I have in my hands the PCM1704 EVM Board (and must say that it sounds really good, I use it as reference DAC..), and I see that it uses more or less the same components than your project.

On the EVM there are 26 jumpers/switches in the digital section, to try all possible settings. I made a picture, if this can help you, of the right settings for receiving normal SPDIF signals from CD players and soundcards:

Click the image to open in full size.

You can find the settings meaning in the PCM1794 EVM manual.

Bye,
Paolo

PS: in your post both the links go to the PCB image..
This is the schematic link: http://www.mypage.tsn.cc/dakiller/dac1/dacs.png
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Old 7th May 2005, 10:11 AM   #4
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Ahh yes, the schematic is here - http://www.mypage.tsn.cc/dakiller/dac1/dacs.png (i just copied the board hyperlink and didnít change the url )

Thankyou very much for that pic of the evaluation board paologatto, I did look through the documentation on it but it didnít explain it any better than the datasheets

Iíll have a look over it in detail, not looking forward to changing pins on the df1704; soldering (as well as unnecessarily de-soldering) was fun enough
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Old 7th May 2005, 12:43 PM   #5
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Quote:
Originally posted by paologatto
You can find the settings meaning in the PCM1794 EVM manual.
[/B]
I meant PCM1704 EVM..

Just tell me also if you want that I try some settings change according with your schematic. I have not deeply examined all the settings changes in the EVM, but I remember that with some combinations the effect was similar to what you describe as digital "crackling" noise.

Since I have the EVM board now mounted and working, it's not a problem for me to make some experiments..

bye


PS: and.. YES! it accepts the SPDIF out of the PCM2902!
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Old 7th May 2005, 01:02 PM   #6
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The only thing I can see that I got was the IW0 pin I had set high for 24bit input and it should be low for 16bit, I probably set it to that thinking I would get a 24bit dac overall and it would have just worked with 16 bit as well

So I managed to lift that pin on the df1704 and pulled it low but now i am getting nothing at all, itís getting late here so Iíve left it till tomorrow

The original sound I wouldnít call it 'crackling', it was a white noise like sound but you could hear changes in it that might have been quiet parts in the music or such
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Old 7th May 2005, 02:08 PM   #7
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Quote:
Originally posted by DaKi][er
The only thing I can see that I got was the IW0 pin I had set high for 24bit input and it should be low for 16bit, I probably set it to that thinking I would get a 24bit dac overall and it would have just worked with 16 bit as well

So I managed to lift that pin on the df1704 and pulled it low but now i am getting nothing at all, itís getting late here so Iíve left it till tomorrow

The original sound I wouldnít call it 'crackling', it was a white noise like sound but you could hear changes in it that might have been quiet parts in the music or such
I have not checked in your schematic how you configured the in/out formats of the DF1704 and of the PCM1704, but hope that the following info can be useful.

Here are some very experimental results of settings changes.. try to understand what is more near to your case:

- Receiving 16 bit PCM data from a CD player, listening to Alexander OST by Vangelis

Modifiying the following bits:

---------------------------------
[1]

IIS = H
IW0 = L
IW1 = L
OW0 = H
OW1 = H

Sounds perfect
---------------------------------
[2]

IIS = L
IW0 = L
IW1 = L
OW0 = H
OW1 = H

hear like white digital noise. Silence if I stop the CD
---------------------------------
[3]

IIS = H
IW0 = H
IW1 = L
OW0 = H
OW1 = H

Sounds perfect, like case [1]
---------------------------------
[4]

IIS = H
IW0 = L
IW1 = H
OW0 = H
OW1 = H

Digital noise like case [2]
---------------------------------
[5]

IIS = H
IW0 = L
IW1 = L
OW0 = L
OW1 = H

or

OW0 = H
OW1 = L

or

OW0 = L
OW1 = L


Sounds very bad and/or very attenuated, like you were playing with a 2 bit DAC
---------------------------------

I tried also changing the SW101 that chenges the PCM1704 20/24 bit data interface. When on 20 bit (and configuration [1] above) the output is very distorted. On H (24 bit) works fine.

So, I suggest you to investigate IIS, IW1, IW0, OW1 and OW2.

Let me know..

Bye,
Paolo
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Old 7th May 2005, 02:19 PM   #8
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it was originaly configured for your case [3] at the start and i was getting noise and changing the IW0 to then be your case [1] then just gave me silence

i cant really play with jumpers, it is just directly soldered to the board and changeing the IW0 was hard enough
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Old 7th May 2005, 02:34 PM   #9
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Quote:
Originally posted by DaKi][er
it was originaly configured for your case [3] at the start and i was getting noise and changing the IW0 to then be your case [1] then just gave me silence

i cant really play with jumpers, it is just directly soldered to the board and changeing the IW0 was hard enough

uhm... have you checked that the CS8416 is configured for I2S format? Actually in the EVM there is a CS8414 but the behavior should be quite similar..
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Old 7th May 2005, 06:58 PM   #10
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Quote:
Originally posted by paologatto



uhm... have you checked that the CS8416 is configured for I2S format? Actually in the EVM there is a CS8414 but the behavior should be quite similar..

Dude, they is chalk and cheese. This may be of more use.
http://www.cirrus.com/en/pubs/rdData...cs8416eb-2.pdf
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