A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) - Page 12 - diyAudio
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Old 3rd January 2013, 10:24 AM   #111
IanS1 is offline IanS1  United Kingdom
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Have just ordered my complete kit with 1 DAC board, Wave I/O, SPDIF board and PSU's.

Looking forward to having a go at my first DAC build project but with my limited electronics knowledge I might need some advice on the switching for USB/SPDIF inputs. Any thoughts to get me started?
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Old 3rd January 2013, 02:54 PM   #112
dddac is offline dddac  Germany
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Actually the spdif board allows for this. it has an auxililary i2s input which can be selected. it is all the board and in the kit.... better download the schematics from the dddac1543. there you can see how it works. you can also send pm of course
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Old 3rd January 2013, 03:03 PM   #113
IanS1 is offline IanS1  United Kingdom
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OK, thanks I'll take a look.
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Old 3rd January 2013, 07:24 PM   #114
dddac is offline dddac  Germany
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Quote:
Originally Posted by dddac View Post
Actually the spdif board allows for this. it has an auxililary i2s input which can be selected. it is all the board and in the kit....
and here is a small sketch / drawing how to connect it as the spdif board has relays on board to switch between I2S from the spdif decoder or the aux I2S input
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Old 5th January 2013, 04:25 AM   #115
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The below linked thread will likely be of interest to some participating in this thread.

Testing the pcm1794
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Old 5th January 2013, 05:49 PM   #116
clivem is offline clivem  United Kingdom
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Doede, have you picked up on this?

Assuming you are only using a SE out from the DDAC, grounding the neg out while utilizing the positive, (rather than it being tied to earth by 133R but otherwise unused), results in a ~3db reduction in 2nd harmonic from the pos out.
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Old 5th January 2013, 06:17 PM   #117
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Default Oscillation at LF80 output

I had oscillation around 200 KHz. It needed more than 100 nF. 0.47F + 0,1 F (already there) was necessary at least on my board.
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Old 5th January 2013, 06:32 PM   #118
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Quote:
Originally Posted by dddac View Post
and here is a small sketch / drawing how to connect it as the spdif board has relays on board to switch between I2S from the spdif decoder or the aux I2S input
I have something similar and it works well. Just replaced some parts by something "better" (few Jamicon 100F by Nichicon organic caps for exemple). However, you have to forget the ribbon cable for signal wires.
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Old 6th January 2013, 06:29 AM   #119
dddac is offline dddac  Germany
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Quote:
Originally Posted by crazyfrog View Post
I had oscillation around 200 KHz. It needed more than 100 nF. 0.47F + 0,1 F (already there) was necessary at least on my board.
Thanks for this Input. I will check (measure) later on my own DAC if it is the same here. The filter which Comes after the Regulator (LC) filters -70dB at 200 kHz, probably hence it is not noticed on the analog side of things. But as said, let me check this. Better to have no oscillations left over on the Regulator of course. Will do some tests and chime in later today
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Old 6th January 2013, 07:09 AM   #120
dddac is offline dddac  Germany
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Quote:
Originally Posted by clivem View Post
grounding the neg out while utilizing the positive, (rather than it being tied to earth by 133R but otherwise unused), results in a ~3db reduction in 2nd harmonic from the pos out.
mmm, need to check (measure) this again. I believe I tried and this messed up the DC bias of the other DAC output.
so, if you ground the not used output, what DC voltage did you get on the used one? did you measure this? Will check myself as well

PS: I use the transformer output a lot, so no Option for me anyway
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