Mr White's "Opus", designing a simple balanced DAC

[Russ White]

I think I understand #4 much better now. Reread that part of data sheet on page 23.

[Russ White]

OK, perusing through both data sheets I feel pretty good about #1 now too.

[jean-paul]

Originally posted by Russ White
I adjusted some package sizes for the parts Brian has actually specked out. Thanks a ton for that hard work Brian.

Also adjusted a few cap values.

That is a nice pcb.

Please do not directly AC couple RXN to GND. AFAIK the reset circuit you have doubts about will do its work as it should.

Please reconsider the thought of the 3.3V and 5V regs on the pcb....

[Ulas]

Originally posted by Russ White
Please, please, please take the opportunity to review things over the weekend.

Methinks you don’t understand the function of some of the DAC pins. Why would you want a pull-up/pull-down on an output? And why so many jumper options? If you consider how the circuit will be used 100% of the time you could delete most of them. Along those lines, you received some good suggestions from rfbrw, which you ignored, and you ignored the recommended layout in the datasheet. I guess you and the diyAudio Experts know more about PCB layout and component selection then the engineers who designed the chips.

[Russ White]

Originally posted by Ulas


Methinks you don�t understand the function of some of the DAC pins. Why would you want a pull-up/pull-down on an output? And why so many jumper options? If you consider how the circuit will be used 100% of the time you could delete most of them. Along those lines, you received some good suggestions from rfbrw, which you ignored, and you ignored the recommended layout in the datasheet. I guess you and the diyAudio Experts know more about PCB layout and component selection then the engineers who designed the chips.

Your statement about the output pin makes me wonder if you have read the data sheet yourself, though I am quite willing to concede I may have a mistake here or there... Which pin exactly are you referring to? If I have a mistake I would love for you to show me exactly how little I know, and then point me in the right direction.

The jumper options are there for flexibility.

How can I say how the circuit will be used 100% of the time? It is not just for me.... or for one purpose...

I read rfbrw suggestion very carefully. And I could not find anywhere is the CS8416 data sheet where it describes an output in regard to deemphasis .

Which part of the layout did I ignore on the data sheet? keep in mind every PCB design has some compromises. This PCB leans toward a minimum of SMT parts. So some layout considerations were necessary. Still I think I have things laid out pretty close to what is recommended.

Your last couple sentences just make you sound like you have some axe to grind. I have always plead ignorance, so you must not be talking about me.

Please be more specific if you are trying to be helpful.

Cheers!
Russ

[Ulas]

Originally posted by Russ White
Your statement about the output pin makes me wonder if you have read the data sheet yourself.

Of course I read the datasheet: I am one of the few here who bothers with such details.

Originally posted by Russ White
How can I say how the circuit will be used 100% of the time? It is not just for me.... or for one purpose...

I see. So this is a commercial venture. Why do first-time DAC designers try to design a DAC for everybody else?

Originally posted by Russ White
I read rfbrw suggestion very carefully. And I could not find anywhere is the CS8416 data sheet where it describes an output in regard to deemphasis.

That wasn’t his only suggestion.

Originally posted by Russ White
Your last couple sentences just make you sound like you have some axe to grind. I have always plead ignorance, so you must not be talking about me.

Actually, I am. You are eager to copy circuit fragments from the all-knowing diyAudio Experts but you ignore the recommendations of the chip designers. I wonder why.

Originally posted by Russ White
Please be more specific if you are trying to be helpful.

It’s your design, or should I say, it’s the diyAudio Expert’s design. I am not one to tell you what to do and how to do it; there are plenty of diyAudio Experts here who think they know far more than I do and will tell you what to do and how to do it. You started this thread saying you looked at this project as a learning experience. Well, here’s your chance. Read…Think…Study…Learn. Or not.

[Russ White]

Ulas,

I have no idea what on earth you are are after.

But I surely hope you find it...

I take suggestions from every place. I implement those things I can understand. I read the data sheets, and I act on them in a way that fits my project.

rfbrw made a point about possible problem if a I2S source was connected to the PCB at the same time as the receiver. I have made it clear the PCB was not designed for that (if you use external I2S you either omit the DAC or the Receiver). What other input from that person are you referring to?

I have nothing but respect for those in the forum as well as those who wrote the data sheet.

And I wish you the best friend.

:EDIT: I myself plan to use this DAC a half dozen ways... Thus the jumpers. :/EDIT:

Cheers!
Russ

[maxlorenz]

Hi Russ,
I had a quick look at DAC's specs sheet and I saw a couple of points that could be useful.
*Wolfson recommends R of 51ohm in series for BCKIN and SCLKIN.
*output R load (R11-13-14-15) only as part of suggested external filter circuit.
Sorry if this is already known

Regards
M

[jean-paul]

Originally posted by maxlorenz

*Wolfson recommends R of 51ohm in series for BCKIN and SCLKIN.
*output R load (R11-13-14-15) only as part of suggested external filter circuit.

True, these series resistors are required. Output Rload resistors won't harm and can be of use with the choice of output stage. It's just good design practice to reference outputs to ground.

After the helpful comments of expert Ulas I think pins 26 and 27 of the Wolfson chip can be tied to GND continuously so no need for jumpers. The NV/ERR pin 14 can be tied low to GND by a 47K resistor. Also a LED + resistor can be connected from the pin to GND for indication of a receiver/datastream error. The same pin can be connected via an inverter/transistor to MUTEB pin 25 on the Wolfson chip as suggested by rfbrw. The MUTEB pin 25 needs to be pulled down for slow mute when an error occurs. A useful addition.

[maxlorenz]

Thanks Jean-Paul
You see, even the dumb can learn...

Output Rload resistors won't harm and can be of use with the choice of output stage.

Two questions:
*How big this R must be? 1M, 100K?
*IF I omit the output coupling cap, do I still need the R?

About output section, I understand that the Opus DAC is intended to be used "as is", wich maybe needs an active balanced preamp (DAC + Pre: one box solution?). In my case (with TVC) I will put a R in series to stay higher than 600R.
I have tried direct DAC chip outs before (AK4393) and, while being very transparent, it lacked bass omph...

Regards
M