Searching for a simple DAC schematics - DIR9001+PCM1794

[Alexium]

Greetings.
I'm pretty sure I've seen several such DACs, but now I just can't find them. Could someone please throw a link at me?
Thanks in advance.

[Alexium]

No suggestions? Datasheet schematics it is, then.

[theAnonymous1]

Hi Alexium,

Attached is my schematic of a basic DIR9001 + PCM1794A. I've built it so I know it works. I later added a SRC4192 for upsampling and an external clock.

You need to come up with your own solution for an I/V stage.

[ktta]

Hello. Try this:
DIR9001 DIR9001 SPDIF decoder
PCM1794 PCM1794A audio DAC

[theAnonymous1]

I forgot there is an error in my schematic. The filter pin is on the wrong node of the passives. It's easy to see where it should go.

[Alexium]

Thank you both very much!
theAnonymous1, how's the sound? My impression was passive I/U is not a good choice for PCM179x. What are the requirements to the subsequent amplifier?
Oh, and how can I adjust for twice a lower output current (I have a prototype board with PCM1798)? Should I double the 420 Ohm resistors? I'm quite a noob in electronics...

[theAnonymous1]

Sound is excellent IMO, but I used an I/V stage similar to the one in the link ktta posted. When I made the schematic I was still undecided on what to do for I/V.

I'm sure there are lots of optimisations that can be done to my circuit, but where do they end once you start? You eventually end up with a cutting board size PCB with hundreds of components. I like to keep things simple.

[Alexium]

Originally Posted by theAnonymous1

I'm sure there are lots of optimisations that can be done to my circuit, but where do they end once you start?

Well, since I'm not a fanatic, for me they end once they stop sound better

Originally Posted by theAnonymous1

I like to keep things simple.

Me too, thanks again for the design!

P.S. So, should I double the I/U ohms for twice a lower current? Or am I understanding its operation wrong?

P.P.S. Don't you, by any chance, have a PCB layout for this? I've tried to make a layout for just a bit bigger scheme, and the process make me feel like the dumbest person in the world. I guess topological cretinism is my diagnosis.

[theAnonymous1]

The higher the R value the higher the output voltage (and noise) will be, and the lower the current draw on the DAC outputs.

If you base your design around my schematic, I would patch in the I/V LPF stage from the second link ktta posted.

Sorry, I'm horrible at math so you will need to figure out what R value is best for the 4mA p-p of the PCM1798.

[Alexium]

Originally Posted by theAnonymous1

The higher the R value the higher the output voltage (and noise) will be, and the lower the current draw on the DAC outputs.

So I actually understood it correctly, for once!
As far as I already have a half-assempled prototype board, I guess I'll experiment with I/U.