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

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#41
awpagan said:

Russ
any updates on your project?

allan
Click to expand...


Getting prototype PCBs made next week after the holiday. Just had to finish off some other projects first. This one is up next. 🙂

There will definitely be a USB to I2S converter too. Will probably get that made at the same time. I may contact a few of you to see if you are interested in beta testing the DAC and/or USB PCBs.

The DAC board on its own should be able to go directly into a 10-100K load with no problem (most preamps) , but it would not be filtered at all. I have a third line stage module based on the THS4131 which I will use to filter the output a bit. Balanced input and output.

I will post circuit details here soon. Along with pics of the layout for those who are interested.

One question to anyone who knows, can anyone shoot me a link to a good small input trafo to use for SPDIF that is easy to obtain in the U.S.? I am thinking of including one, but I need to find a good simple example of an SPDIF input circuit using a trafo and identify the trafo I could use.

Cheers!
Russ
 
#42
Russ White said:
One question to anyone who knows, can anyone shoot me a link to a good small input trafo to use for SPDIF that is easy to obtain in the U.S.? I am thinking of including one, but I need to find a good simple example of an SPDIF input circuit using a trafo and identify the trafo I could use.
Click to expand...

What, this kind of thing?
 
#44
Russ White said:



Getting prototype PCBs made next week after the holiday. Just had to finish off some other projects first. This one is up next. 🙂

There will definitely be a USB to I2S converter too. Will probably get that made at the same time. I may contact a few of you to see if you are interested in beta testing the DAC and/or USB PCBs.

The DAC board on its own should be able to go directly into a 10-100K load with no problem (most preamps) , but it would not be filtered at all. I have a third line stage module based on the THS4131 which I will use to filter the output a bit. Balanced input and output.

I will post circuit details here soon. Along with pics of the layout for those who are interested.

One question to anyone who knows, can anyone shoot me a link to a good small input trafo to use for SPDIF that is easy to obtain in the U.S.? I am thinking of including one, but I need to find a good simple example of an SPDIF input circuit using a trafo and identify the trafo I could use.

Cheers!
Russ
Click to expand...

I have ordered the eval pcb with some dac's to try.
the reason i like the voltage out is so i can try something like this
http://www.diyaudio.com/forums/showthread.php?s=&threadid=54009&perpage=10&highlight=&pagenumber=193
post 1924


allan
ps also would like to try the software version
 
#51
Found this on Epanorama:

The transformer must have good coupling factor, so the transformer core must be a toroidal core made of high permiability material. The prototype described in the magazine uses Philips Type TN13/7.5/5-3E25 core which has permiability rating (yt) of 4500. THe primary and secondary windongs consisted of 6 turns of 0.5 mm diameter enamelled copper wire laid on opposite sides of toroid. The transformer used in this prototype was described to have a bandwidth raged from 50 kHz to 17 MHz, which is more than adequate for an S/PDIF link
Click to expand...
 
#58
Russ White said:
My hope is to order a few prototype PCBs next week. 🙂 It won't be long now.

Would anyone be upset if I omitted the TORX input?

Thanks for the ijnterest.

Cheers!
Russ
Click to expand...


An optical connection would be great, since my PCMCIA sound card has only an optical output, others many be in the same situation. Also the optical connection eliminates any chances of computer PSU noise getting into the DAC.

-David
 
#60
OK guys, about to get some made

Here is the current circuit.

Some notes:

1) I am not sure if I need R9 or not, and if I do if I have the correct value.

2) I have set the WM8740 to reset with the CS8416, which aoocurs on power up after the digital voltage reach 3.3V.

3) Both the digital side of the WM8740 and the CS8516 are running on a singal 3.3V digital supply. The analog side of the WM8740 should be 5V.

4) I will add a legend for al the jumpers and what they do.

Cheers!
Russ
 

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