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

promitheus said:
Thanks, this would be interested to see.
I think that the voltage level of the TOSLINK input is too low.
the schematic shows 1,4V only. How much should the Coax S/PDIF be? 5V?


Here is the info from the CS8416 DS:

Differential Input Sensitivity, RXP[7:0] to RXN VTH - 150 200 mVpp

So 1.4V is certainly plenty. 🙂

You should be able to use what you have just fine. 🙂

Cheers!
Russ
 
I found a solution.
I read about the Elektor magazine tos to coax SPDIF converter and I can buy the Pcbs.
take a look at the attachement.

I will connect the data that goes to the Toslink transmitter inside the CD player to the pin1 IC2a see schematic.

If anybody wants the pdf file in english I can´t post it here so please contact me with email.
 

Attachments

Here's the scan from my Sony manual...

L385 and L386 are 0mH ferrites.
C388 is 1uF 16V ceramic
C387 is 180pF 50V ceramic
 

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First Opus is playing music... 🙂

Just wanted to let you folks know that the Opus is alive and well. Some pictures of the stuffed DAC and Receiver PCBs. 🙂

Its been a long time coming, but I believe it was worth the wait. :yes:

USB PCB and BA;/SE converter coming very soon now.

BTW, DipTrace rocks! Glad I switched from Eagle.

:drink:
Cheers!
Russ
 

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Re: First Opus is playing music... 🙂

Russ White said:
Just wanted to let you folks know that the Opus is alive and well. Some pictures of the stuffed DAC and Receiver PCBs. 🙂

Its been a long time coming, but I believe it was worth the wait. :yes:

USB PCB and BA;/SE converter coming very soon now.

BTW, DipTrace rocks! Glad I switched from Eagle.

Very nice work indeed, Russ. I might have to get a set of the new boards despite alredady having the proto's.

I agree with your opinion of DipTrace. I bought the DIY'er licence and haven't looked back.
 
Re: Re: First Opus is playing music... 🙂

promitheus said:
Hey the look absolutely wonderful!
Nice job! 😉

metalman said:


Very nice work indeed, Russ. I might have to get a set of the new boards despite alredady having the proto's.


Thanks guys!

I learned a lot from the beta.

I owe a lot to many of the forum members who gave me good advice and showed me where to find answers when I needed them.

I will be testing with two DAC boards tonight in dual differential mode (mono). That is supposed to get us another -3db SNR. like -117db was not low enough. 🙂

Cheers!
Russ
 
A bit skeptic about being computer powered

If the USB spec has 2 of its wires just for power (is this true?)

then it might be a simple matter to fix?:

Don't connect the 2 USB power wires to the circuit board from the USB plug that goes to the computer. Then you could attach wires from a battery pack or your own power supply to these terminals on the board?

If this is true, the instructions should point out which wires not to connect, and voltage required from the power supply. Can one use the same power supply as used for the DAC?
 
USB Bus or Self Powered

Hey guys,

Sorry for the delay in writing this, but after discussing this with Brian and a few other friends I have decided that it would be rather easy to design the USB module so that it can be use self powered or bus powered on the same PCB.

Using the digital (I2S) output I don't think this will make much difference at all (if any), but for those who might want to use the analog outputs of the USB module this will raise the performance quite a lot. Self powered this USB DAC module will easily outperform any NOS TDA15xx based DAC in terms of SNR and distortion. So even standalone a self powered USB DAC module should be quite good if you use suitable drivers etc...

For even better performance you can just take the I2S out from the USB module and feed an Opus DAC. Then you also have the benefits of balanced outputs.

FWIW I am also working on an Ethernet based module, but that me be a while in coming.

Cheers!
Russ