Try to build an old style DAC, PCM1702

[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

 

[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]

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]

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]

... 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]

... 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]

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]

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

 

[bbp]

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]

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.

 

[lgqliu]

洞洞板的八爪鱼，不错，照片质量太差，看不清楚。

 

[Nazar_lv]

similar to DF1706, DF1704 is almost the best DF for PCM1704

the worst, the best would be pmd100/SM5842/5847/5846

 

[tritosine]

the worst, the best would be pmd100/SM5842/5847/5846

Digital filters IC's with max 50khz input frequency are the worst ...

Only DF1704-06 and SM5847 counts. 5847 is overpriced.

If you care about sound quality , you can use the PC processor to perform 2x oversampling with 64bit precision, and user defined filter roll-offs, you can even use the "apodizing" filter, and no , there won't be any preringing added by the DF1704 then.

Use this 24/88.2 format , or dither to 16/88.2 , and write to DVD, these can be done in "batch".


I sent bbp drawings of secondary PLL, that should clean up spdif jitter to 50ps, thats sufficient for 20bit perfomance.

 

[tritosine]

bbp, you should use a simple 2 pole passive anti aliasing filter though, no ? Why active?

 

[bbp]

bbp, you should use a simple 2 pole passive anti aliasing filter though, no ? Why active?

Hi tritosine, I have not test simple passive filter in this DAC, but I will try later.
I think passive LPF is enough for there's a 8X/16X DF in the DAC

 

[Eric Juaneda]

Various digital filters

Hi tritosine,

..If you care about sound quality, you can use the PC processor to perform 2x oversampling with 64bit precision, and user defined filter roll-offs, you can even use the "apodizing" filter, and no, there won't be any preringing added by the DF1704 then.

Use this 24/88.2 format , or dither to 16/88.2 , and write to DVD, these can be done in "batch"...

What kind of software do you use to perform this conversion?

 

[Nazar_lv]

Digital filters IC's with max 50khz input frequency are the worst ...

Fact that DF can understand more than 50 kHz sampling rate means only that they have more speed, but does not mean that they have the best algorithms and precision, so do not...
The best sounding (and technically best) DF are SM5845/CXD1244S/CXD1144BP/CXD2567M/PMD100/SM5842, and all this are 48kHz max