[t52]

Quote:

Originally Posted by ezkcdude That's great. I'm hoping everything works. What chips are you using, and what is your power supply?

hope so too... chips are pcm1794 and ad1896 (btw. you sent them to me

)
power supply is nonexistant up to now, probably will use the +/-15V lm317 supply i already have for my active crossover for testing...
...and i need a coax spdif source - all my sources only have toslink (optical) outs :/
if i had a tssop/dip adapter i'd breadboard a pcm2902 usb -> spdif converter soon - lots of work ahead...

 

[ezkcdude]

Quote:

Originally Posted by t52 hope so too... chips are pcm1794 and ad1896 (btw. you sent them to me ) power supply is nonexistant up to now, probably will use the +/-15V lm317 supply i already have for my active crossover for testing... ...and i need a coax spdif source - all my sources only have toslink (optical) outs :/ if i had a tssop/dip adapter i'd breadboard a pcm2902 usb -> spdif converter soon - lots of work ahead...

Maybe you can find or borrow a sound card with a coax output?

And...what about the op amps. What are you planning there?

 

[t52]

Quote:

Originally Posted by ezkcdude Maybe you can find or borrow a sound card with a coax output? And...what about the op amps. What are you planning there?

the problem is: i dont have a pc anymore, just a laptop for daily work (and it's not quite easy to stuff a pci card in there, hehe) and a htpc which has it's pci slot occupied by the sat receiver card...
but i'll get the dac built first and then find a source for it

opamps: still the opa132pa on breadboard, possibly with opa2132 double opamps as noninverting buffers before the summing amp.
schematics here:

 

[ezkcdude]

Well, first the bad news. I tried to build another board today using upgraded parts (AD1896, PCM1794, etc). For whatever reason, it doesn't work. In trying to fix it, I actually toasted one of the op amps, so now it's useless.

O.k. the good news. I built another (beefier) power supply for my original board, and realized that the reason the negative regulator hadn't been working was there was an adjustment resistor missing on the negative side of the original PSU! I had been operating the DAC with two separate supplies, as I mentioned earlier. So, at least, now I can confirm that the previous "prototype" design definitely works with a single dual supply, as it should. This is good news. I will roll back most of the changes back to the prototype, so I know I have something that definitely works. Here's a pic:

 

[t52]

time to reopen this thread...
had some real pain soldering my ezdac yesterday, i had to remove almost every 0805 component after soldering it because i had a short with the groundplane somewhere... also had to remove the two ssop28 chips before that - had misaligned them slightly, hope they survived that procedure...
now i doublechecked all caps and resistors, no more shorts with the gp. i'm missing the two 100r resistors (0805, in series with the clock lines), will have to get them today. must have made a mistake on the lm317 divider values also, because i read 2.1 and 3.9v on the outputs of the regs, but not much current going in there, only a few mA...
will report back someday this evening, hope this thing will fire up soon!

 

[ezkcdude]

Good luck. I hope the chips are o.k., and everything works. I'll check back in tonight after I get back from "The Shins" concert I'm going to

.

 

[multibit16]

Just waiting for the crystal to arrive and mine will be ready for test

I did measure the voltages without the crystal, all supplys seems to measure nice.
Only thing I noticed was that one output gives 0.2mv DC and the other is 300 odd mV DC, I'm not sure whats may be causing this yet but will measure again once the crystal is fitted.
The 24R and 200R resistors came in packs of 50 so I matched them up.

Good luck with yours jürgen , I'll look forward to your results

 

[t52]

very nice soldering job! my pcb looks completely ugly since i have removed the 2 chips and resoldered almost every damn component

hope it will work though... didn't have time to buy the missing resistors today and i'm busy for the rest of the week, so next possibility to work on it will probably be next weekend... good luck for your dac multibit16!

 

[ezkcdude]

Leo, I sent the crystals on Friday. Hopefully, they will arrive soon. Looks like a nice soldering job. Also I like the beefy heatsinks. I promise it is overkill, but it can't hurt to run them cool.

 

[multibit16]

Quote:

Originally Posted by t52 /img/forum/go_quote.gif very nice soldering job! my pcb looks completely ugly since i have removed the 2 chips and resoldered almost every damn component hope it will work though... didn't have time to buy the missing resistors today and i'm busy for the rest of the week, so next possibility to work on it will probably be next weekend... good luck for your dac multibit16!

Thank you

I wouldn't worry about the neatness as long as it works ok

If your struggling for 100R 0805 smd resistors I have a few minimelf 0102 100R's spare

 

[multibit16]

Quote:

Originally Posted by ezkcdude /img/forum/go_quote.gif Leo, I sent the crystals on Friday. Hopefully, they will arrive soon. Looks like a nice soldering job. Also I like the beefy heatsinks. I promise it is overkill, but it can't hurt to run them cool.

Thats great thank you, I promise as soon as they arrive I'll stick one in and post the results

Should I be concerned about the offset on one side? my amp uses an input coupling cap so hopefully it should be ok

 

[ezkcdude]

Quote:

Originally Posted by multibit16 /img/forum/go_quote.gif Thats great thank you, I promise as soon as they arrive I'll stick one in and post the results Should I be concerned about the offset on one side? my amp uses an input coupling cap so hopefully it should be ok

I have no idea about the offset, and why they would be different. I guess we'll just have to wait and see.

 

[22906]

Is it possible to build this DAC with balanced outputs by omitting the opamps/using dual channel opamps?

 

[ezkcdude]

Quote:

Originally Posted by m3_arun /img/forum/go_quote.gif Is it possible to build this DAC with balanced outputs by omitting the opamps/using dual channel opamps?

Theoretically, you could just take the outputs after the passive I/V stage, but you'd probably want to up the R values by quite a bit, perhaps 5- to 10-fold.

Oh, FYI, here's some clips from The Shins' concert last night:
http://www.youtube.com/watch?v=N7qqXTnbDIQ

 

[multibit16]

Crystal arrived this morning

Its now fitted, as soon as BNC plug is connected for the spdif that offset is gone, both channels now measure 0.1/0.2mV DC.
Dac is currently running in, so far the sound is quite good.

BTW I built the PCM1794 version