[Beftus]

Thanks! It's clear acrylic, the led is embedded in the center.

Just so you know, if this "puppy" ends up available in kit form @ Beezar I'm gonna steal your idea!
"Imitation is the sincerest form of flattery"
Thanks for sharing.

 

[Gotez]

Nice build!! Good idea to use the acrylic to 'break' the led light.

 

[c12mech]

I asked earlier about about running wires directly from c24 and c26.  Cobaltmute pointed out about the fact of DC offset  unless I were to go balanced.  I started looking at the data sheet for the PCM1794a and it shows a balanced ciruit but it looks like it only goes to one xlr plug.  If I wanted to make this a balanced output dac can I just go straight off c24 and c26 with their respective grounds to two xlr plugs?  I'm still getting myself a little confused as to how to implement the balanced part.  I'm working on a balanced amp right now and would like to see how far I can take this dac design.

 

[cobaltmute]

The circuit you may be thinking of in the datasheet is for mono-mode using  PCM per channel (Figure 26).
 
Look at page 24 - The first two op-amp (the ones above each other) perform the current to voltage conversion and created the balanced signal.  The third op-amp performs balanced to single ended conversion.
 
In the pupDAC, I to V conversion is done via resistors to ground.  C24/C26 acts like a filter by making the high-frequency common and then the op-amp does balanced to single ended conversion, along with gain.

 

[MrDavis]

Any news on when a production board might be coming out? 

 

 

[cobaltmute]

I've started laying out the next version, but have been a little distracted lately with the r1 so it will be a couple of weeks for me to finish off the lay of the revised PCB. 

 

[c12mech]

I finally got all my parts in and finished this project tonight.  I've been listening to random songs that I know very well and I can honestly say that this is the best I've heard any one of these songs sound.  This is by far the best thing I've built yet for improved sound quality.  
 
Cobaltmute, first of all thanks for this design.  I am now wandering if there is any way to make a direct SPDIF in for this dac?  I imagine it would take a dedicated power supply also but would it be possible?  I've seen the 1794 used in an SPDIF only version somewhere else  but can't seem to find it now.  If it's not possible that's fine I'm just curious since I'm working on another project that is SPDIF out only.

 

[cobaltmute]

To make it SPDIF, you could hack something onto the I2S lines, bypassing the USB input and putting your own SPDIF input.  I'd suspect that it would be quite challenging.
 
I've run through a lot of ideas about what to do with the revision of the board, but I have settled for updating the existing layout.  The beauty of the board is that it is relatively simple for very good sound.  Down the road I'll do something that has SPDIF input.

 

[c12mech]

I think I'm going to give it a try just to satisfy my curiosity.  After looking at the datasheet for a while it looks as though I could just tap into pins 5 and 8 for the data in and data ground.  I will be wiring it directly to the data out and ground from the board of my cd transport.  This is just an experiment to see if I can get it to work.  I'll let you know how it goes.
 
I've got a couple of different TI dac chips that I am working on right now in regards to an SPDIF dac.  I'm still trying to get a handle on using eagle to put the circuit together.  I can do it a whole lot faster on paper but that makes it a little harder to get the pcb layout done.  As I get farther along I'll start my own thread about it and ask for input from the group here.

 

[Avro_Arrow]

I can help you with that.
 
Quote:

I think I'm going to give it a try just to satisfy my curiosity.  After looking at the datasheet for a while it looks as though I could just tap into pins 5 and 8 for the data in and data ground.  I will be wiring it directly to the data out and ground from the board of my cd transport.  This is just an experiment to see if I can get it to work.  I'll let you know how it goes.
 
I've got a couple of different TI dac chips that I am working on right now in regards to an SPDIF dac.  I'm still trying to get a handle on using eagle to put the circuit together.  I can do it a whole lot faster on paper but that makes it a little harder to get the pcb layout done.  As I get farther along I'll start my own thread about it and ask for input from the group here.

 

 

[c12mech]

Thanks Avro_Arrow.  As I get a little farther along I will be in touch with you.  My ultimate goal is SPDIF input and balanced output using as few parts as possible.  This will be to compliment the cd transport project I'm working on.  
 
Back on topic, the more I listened to this dac last night the more I liked it.  There seems to be more separation between instruments and there placement in the sound stage.  On the live recordings I listen to it actually sounded "live" which I had to get used to at first.  I'm really enjoying this thing. 

 

[forsakenrider]

My stopped working today! D'oh! what happened? when I turned on the computer this morning the dac wasn't recognized. U1 is getting hot again and theres 2.2ohm to ground on the 3.3tp. Darn, how could a short come the far in?

 

[cobaltmute]

That is really strange.  Never seen an issue where I board that has been running for a while goes bad. 
 
The electrolytic is the right way around? 
 
Not sure what else to check other than looking at everything attached to that power trace.

 

[forsakenrider]

All the capacitors are correct. When I remove L3 everything goes back to normal voltages. so I just theres a short somewhere after that. Its not the i2s lines this time, its not C13, so I Maybe U3 or some pins on U2. Either way, after another 2 hours of searching and frustrated! the board is getting in bad shape from all the playing.
 
Whens V2 coming

 

[MrDavis]

Any updates on the production version?