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

[hayenc]

Russ,

Nice to see some support for trying the Wolfson chip. Not sure it was a suggestion to use as much as a question. Glad it is going forward. I am still trying to find time to power up the eval board.

On the digital interface circuit, I will be interested to test out the circuit you are showing (same as eval board). For some alternatives, might go from the Cirrus AN134 to the AES papers at http://www.scientificonversion.com/ to see some transformer alternatives for isolation. Adding a transformer might break the KISS approach, but could be worth leaving an alternative, especially if looking at the higher rates.

I have been using Peter Daniel's NOS DAC's quite happily for some time, but they are single-ended out, so I look forward to this option. They use a SN75179 on the digital input, but I don't know the legacy or restrictions on using this circuit.

My leaning would be the CS8416 to handle 192kHz, with the added complexity of some 3.3 volt regs. CS8414's are heading the way of CS8412's on availability.

On the reset circuit, the eval board has a simple one that only ties to the Wolfson, nothing going to the CS8414. Worth looking at. Eval board manual can be downloaded from their site, but I suspect you already have.

My four or five cents worth. Looking forward to see how this project works out.

Craig

[Luke]

Hi Russ,

nice work, nice approach,just one question, how readily available are these wolfson dacs for diyers?

[hayenc]

http://www.profusionplc.com/

Been very responsive in shipping to US.

[awpagan]

sounds like an interesting project.
i2s dac v-out
havn't heard the wolfson dac.

but with V-out there are possiblities as in the cd63/67 thread.
passive filter then simple buffer.

allan

[Ed LaFontaine]

The new Rega Apollo CD player uses the Wolfson WM8740. Their effort is said to "reinvent" the $1000 CD player.


More can be seen here: http://www.rega.co.uk/

[awpagan]

Originally posted by Ed Lafontaine
The new Rega Apollo CD player uses the Wolfson WM8740. Their effort is said to "reinvent" the $1000 CD player.


More can be seen here: http://www.rega.co.uk/

Tackey red led display

but otherwise the proof is in the sound.

lets see how the wolfson goes, should have possibilties

allan

[jleaman]

Originally posted by Russ White
Terry,

Thanks for the input. It really helps to know that I am not in this alone. I am sure there will be a lot to learn along the road.

The K.I.S.S rule is certainly in full effect for me here. Having guys like you around helps keep me motivated. BTW I nearly have a couple of SuSy Channels ready to be fed from my XBOSOZ which I hope will soon be fed by this DAC.

Cheers!
Russ

ANOTHER good project Are you building one of these just for your self ? I have a dac that i love but would like to replace. Expecially if it is a Dac you'r designing.

[Russ White]

Hey guys,

Progress report:

I have had some time to create an initial layout. After thinking about the S/PDIF inputs I decided that for the first version of this design I will use the basic scheme which Wolfson used in their demo board.

I am sure there are better ways to do S/PDIF input, and here is the good news, you still can. Because I allow for I2S input you could easily create a reciever module and just send I2S to the DAC. I already have designed a PCM2707 module which I will use for input into the DAC.

The optical TORX reciever stays but its use is optional. You can easily omit it.

I will post some layout ideas here shortly.

One thing to remeber is that the PCB will be small. 4" x 1.5" and all of the modules (USB reciever, analog filter, etc...) will be designed to stack. So you can pick and choose what goes on the stack.


I had already worked out design details for the CS8414 and I can see quite a few suppliers with lots of them, but I also see the merits of the CS8416 and am 90% sure I will switch to that receiver. I just need to do some research on what would be required as far as rest on power up and on loss and regaining of digital signal.

Any pointers there. I am searching but if someone has a good link now would be agreat time to share it.

Thanks for all the support. I am very confident about the WM8740. I think it is my design skills which will be the weak point, no the chip.

Cheers!
Russ

[jleaman]

Originally posted by Russ White
Hey guys,

Progress report:

I have had some time to create an initial layout. After thinking about the S/PDIF inputs I decided that for the first version of this design I will use the basic scheme which Wolfson used in their demo board.

I am sure there are better ways to do S/PDIF input, and here is the good news, you still can. Because I allow for I2S input you could easily create a reciever module and just send I2S to the DAC. I already have designed a PCM2707 module which I will use for input into the DAC.

The optical TORX reciever stays but its use is optional. You can easily omit it.

I will post some layout ideas here shortly.

One thing to remeber is that the PCB will be small. 4" x 1.5" and all of the modules (USB reciever, analog filter, etc...) will be designed to stack. So you can pick and choose what goes on the stack.


I had already worked out design details for the CS8414 and I can see quite a few suppliers with lots of them, but I also see the merits of the CS8416 and am 90% sure I will switch to that receiver. I just need to do some research on what would be required as far as rest on power up and on loss and regaining of digital signal.

Any pointers there. I am searching but if someone has a good link now would be agreat time to share it.

Thanks for all the support. I am very confident about the WM8740. I think it is my design skills which will be the weak point, no the chip.

Cheers!
Russ

Well said.. I always been told keep your head up and think positive and it will all work. If not the first time you try again and again. It just get's better.

[hifimaker]

hi Russ,

I seriously rethink the SPDIF input section. There are a lot of threads in this section where this part of the design has been hashed out. A small transformer is a good idea to isolate the DAC from the source. There are other considerations as well.

-David