Part Number: PCM1793
Hi, I need a DAC with AES/EBU input, so I used DIR9001 and PCM1793. The problem is that left signal from PCM1793 is not correct (is not a sine) . Could you please check the schematic below? Thanks in advance.
In reply to Claudio Fiorentini:
This is very interesting. I think we are at the point where we must confirm the actual data on the bus. Now I am pretty confident the DIR and PCM are configured correctly (both 24-bit standard I2S).
Can you set you SPDIF input to be a square wave at fS/2? As the output seems to have some kind of rectification, I am concerned the MSB of the DIN line is being incorrectly sampled or ignored.
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
Can you show LRCLK and the data on the same trace? And then LRCLK and BCLK?
Is LRCLK truly 64 bit clocks wide, with 32 for left and 32 for right?
If you had a four-channel 'scope you could monitor BCLK, LRCLK and data at the same time, that would help.
In reply to Paul_Frost:
Hi Paul,I set the AES-EBU input to generate a square wave at f=32 Khz(fS=48 Khz,but my generator can't sample below 32 Khz and accepts loaded signals only with fs = 48 Khz), so this is VOUTL-/VOUTL+:
and this is VOUTR-/VOUTR+:
In reply to Andy Peters:
these are LRCLK and DATA:
and these are LRCK and BCK:
so it seems correct.
Have you been able to change your digital source? For example, use a different source for the DIR9001. I would like to rule out the digital source being an issue. I would be worthwhile to verify if the data is actually correct. A square wave would make that easier.
The VOUTR trace looks like what happens when you feed the DAC an impulse (delta function) -- one sample at full scale with all other samples zero. You can see the sinc from the reconstruction filter. (BTW, you should have a sinc function sample/wave file for testing DACs.)
So that is a clue.
I can't count how many BCLKs you have in LRCLK high and low time.
Maybe the DAC chip is bad? I'm not a fan of shotgunning parts. Do you have another board built up that you can test?
Yes Paul, as I wrote you yesterday I used a square wave at fs=32 Khz, I post again the results:
Moreover, I've tried all the other sources available in my generator(sweep, chirp, delay,pnoise,wnoise,polarity,dolby,dts) and the right output wave on the dac is always cutted, so I think that it is damaged. Anyway, before mounting another one, is the schematic correct in your opinion? My major doubt is about the connection between the AES/EBU input and DIR9001.
There are 32 BCLKs in LRCK high and 32 in low time, I've also checked the analogical and the digital feed of the dac and they are correct, so I think that the dac chip is damaged and I've ordered other 2 chips.
Sorry for the confusion, when I saw that square wave I thought it was the LRCK, not the output. This looks as expected, where two channels are not latching the MSB correctly.
I think at this point replacing the device is the best option.
The AES input looks okay to me, but I am not 100% on your source. I do not think that would cause this issue.
I'll replace it and I'll keep you updated.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.