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Old 13th November 2009, 05:24 AM   #1
bbp is offline bbp  China
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Default Try to build an old style DAC, PCM1702

Just finish the work hours ago
CS8414 as the DIR receiver
DF1704 standard DF
PCM1702U X 2 DAC satge
OPA627AU as the I/V converter
LT1037 mfb LPF

All PCB made by myself , that made my hands look so poor >_<

The sound is pretty goooood
For the test result, I test the low level signal below:

Source : CD PRO (VAU1254/11) transprot , SONY test cd provides 16bit signal
60 dB Gain amplifier for oscilloscope TDS1020B, so, 100mv/DIV means 100uV actually ^_^

The pics bellow shows :
-60dB sinewave and FFT
-80dB sinewave and FFT
-90dB sinewave and FFT
Attached Images
File Type: jpg -60SINE.jpg (69.7 KB, 507 views)
File Type: jpg -60FFT.jpg (70.9 KB, 478 views)
File Type: jpg -80SINE.jpg (73.0 KB, 460 views)
File Type: jpg -80FFT.jpg (69.0 KB, 451 views)
File Type: jpg -90SINE.jpg (77.7 KB, 447 views)
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Old 13th November 2009, 05:29 AM   #2
bbp is offline bbp  China
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Quote:
Originally Posted by bbp View Post
Just finish the work hours ago
CS8414 as the DIR receiver
DF1704 standard DF
PCM1702U X 2 DAC satge
OPA627AU as the I/V converter
LT1037 mfb LPF

All PCB made by myself , that made my hands look so poor >_<

The sound is pretty goooood
For the test result, I test the low level signal below:

Source : CD PRO (VAU1254/11) transprot , SONY test cd provides 16bit signal
60 dB Gain amplifier for oscilloscope TDS1020B, so, 100mv/DIV means 100uV actually ^_^

The pics bellow shows :
-60dB sinewave and FFT
-80dB sinewave and FFT
-90dB sinewave and FFT
and the PCB ^_^
Attached Images
File Type: jpg 1704PCB.jpg (46.0 KB, 174 views)
File Type: jpg 1704pp.jpg (99.4 KB, 238 views)
File Type: jpg -90FFT.jpg (69.1 KB, 217 views)
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Old 13th November 2009, 05:58 AM   #3
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Nice project! I agree with the choices you made . Good job.

I dont see a single shortcoming on the digital part, when compared to newer designs. Not a single one. But you have to make the spdif receiver circuit as good as possible. (No toslink!)

I think I send you some datasheets, when I find it, that can clean up the spdif somewhat.

Last edited by tritosine; 13th November 2009 at 06:09 AM.
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Old 13th November 2009, 07:02 AM   #4
bbp is offline bbp  China
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Quote:
Originally Posted by tritosine View Post
Nice project! I agree with the choices you made . Good job.

I dont see a single shortcoming on the digital part, when compared to newer designs. Not a single one. But you have to make the spdif receiver circuit as good as possible. (No toslink!)

I think I send you some datasheets, when I find it, that can clean up the spdif somewhat.


thanks for the documents you provide, tritosine ^_^

this is the female-board under the PCM1702
Attached Images
File Type: jpg dir.jpg (121.7 KB, 197 views)
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Old 13th November 2009, 07:32 AM   #5
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... and dont forget you can basically "bypass" the df1704 if you "pre-oversample" the data inside a PC to 88.2khz , and burn those tracks to DVD , or use the PC source . Then the sonic signature of DF1704 becomes insignificant.
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Old 13th November 2009, 08:01 AM   #6
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Quote:
Originally Posted by tritosine View Post
... and dont forget you can basically "bypass" the df1704 if you "pre-oversample" the data inside a PC to 88.2khz , and burn those tracks to DVD , or use the PC source . Then the sonic signature of DF1704 becomes insignificant.

I got only USB to SPDIF converter based on PCM2707 and a CD transport of CD PRO ^_^
So the sample rate only runs in 16/44.1/48

I made a mistake on #1, the gain of the amplifier is 40dB
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Old 13th November 2009, 10:20 AM   #7
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pcm2707 is not good at all and might be obsolete soon, better make a good spdif receiver circuit optimised for 44.1 and multiples.
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Old 18th November 2009, 12:06 PM   #8
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DF1704 is not the best DF( OPA627 too far from the best option, distortions greatly increase with frequency
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Old 21st November 2009, 07:24 AM   #9
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Originally Posted by Nazar_lv View Post
DF1704 is not the best DF( OPA627 too far from the best option, distortions greatly increase with frequency

similar to DF1706, DF1704 is almost the best DF for PCM1704
or you may programme a FPGA to a ultra-high performance DF module ^_^
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Old 21st November 2009, 08:39 AM   #10
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DF1704 is 2*2*2 . Think of initial 2* oversampling as breaking up 2 sample points into 4. So if you precede df1704 with computer 2* oversampling , the DF going to process the already "broke" 4 sampling points, and insert new ones between those. Therefore , it CAN't be any significant anymore, especially with "slow roll off" mode on.
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