Try to build an old style DAC, PCM1702

bbp · 13th November 2009, 06:24 AM

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

bbp · 13th November 2009, 06:29 AM

Quote:

Originally Posted by bbp

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 ^_^

tritosine · 07:09 AM

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.

bbp · 13th November 2009, 08:02 AM

Quote:

Originally Posted by tritosine

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

tritosine · 13th November 2009, 08:32 AM

... 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.

bbp · 13th November 2009, 09:01 AM

Quote:

Originally Posted by tritosine

... 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

tritosine · 13th November 2009, 11:20 AM

pcm2707 is not good at all and might be obsolete soon, better make a good spdif receiver circuit optimised for 44.1 and multiples.

Nazar_lv · 18th November 2009, 01:06 PM

DF1704 is not the best DF( OPA627 too far from the best option, distortions greatly increase with frequency

bbp · 21st November 2009, 08:24 AM

Quote:

Originally Posted by Nazar_lv

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 ^_^

tritosine · 21st November 2009, 09:39 AM

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.

13th November 2009, 06:58 AM	#3
tritosine diyAudio Member Join Date: Aug 2008	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 07:09 AM.

18th November 2009, 01:06 PM	#8
Nazar_lv diyAudio Member Join Date: Oct 2009 Location: Banderstadt Blog Entries: 8	DF1704 is not the best DF( OPA627 too far from the best option, distortions greatly increase with frequency __________________ "In developing audio devices we can always find creative non standart solutions that will ensure the best sound" (с) www.overture.org.ua

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13th November 2009, 08:32 AM	#5
tritosine diyAudio Member Join Date: Aug 2008	... 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.

13th November 2009, 11:20 AM	#7
tritosine diyAudio Member Join Date: Aug 2008	pcm2707 is not good at all and might be obsolete soon, better make a good spdif receiver circuit optimised for 44.1 and multiples.

21st November 2009, 09:39 AM	#10
tritosine diyAudio Member Join Date: Aug 2008	DF1704 is 222 . 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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