My first DAC!

MWP · 2003-09-12 12:36 pm

Hi guys...

I had to show off my first DAC project success.

In the chain of parts: PCM2902 -> DIR1703 -> PCM1730 -> OPA627BPs.

The PCM2902 is doing a good job of interfacing with the PC... looks like it doesnt do any resampling, much better than a cheap SPDIF out soundcard.

All ive got it to compare to is my Turtlebeach SantaCruz soundcard, so i cant really say how it sounds as yet.

A few photos of the PCB finished and working:
http://www.overclockers.com.au/~mwp/pics/dac

The schematic:
http://www.overclockers.com.au/~mwp/temp/MWP-USB-DAC.pdf

Yay! :bigeyes:

kiwi_abroad · 2003-09-13 1:04 am

Good looking work.
Did you design and etch the board yourself, if so, How did you do the image transfer?
Also, how did solder the SMD chip? What pitch are they?

Adrian.

MWP · 2003-09-13 3:14 am

Did you design and etch the board yourself, if so, How did you do the image transfer?

Yeh, i designed & made the board here at home.
The transfer was done onto the presensitised double sided board (kinsten brand) using bubble jet printer transparency sheets and a bubble jet pronter (Canon S400).
One sheet for each side, both sides exposed seperatly under a fluro for 16mins.

Sounds low-tech i know, but it works brilliantly... there are lots of 14mil tracks on that board for the surface mount ICs.
Ive also made lots of other boards this way.

Nice and cheap too.

Also, how did solder the SMD chip? What pitch are they?

Soldered by hand by first tinning the pads on the PCB very lightly, then placing the IC and quickly running a clean soldering iron tip accross the leads.
With the help of good flux, it works every time.

The pads on the ICs are 14mil wide with a 11mil gap.

demeter · 2003-09-16 8:13 pm

usb DAC

Could you give to project PCB in any normal format??? (pdf, tiff, bmp)
(((Thank you!)))

MWP · 2003-09-17 5:40 am

Ok, im building a web page for it here:

http://www.overclockers.com.au/~mwp/dac3/

Should be finished shortly, with schematic, top, bottom and overlay pdf's.

analog_sa · 2003-09-17 9:41 am

And how does it sound compared to the Santa Cruz? Did you also compare it to the PCM2902 alone?

demeter · 2003-09-17 7:13 pm

please name IC11,IC12 ???Best Regards

MWP · 2003-09-18 3:50 am

And how does it sound compared to the Santa Cruz? Did you also compare it to the PCM2902 alone?

Its hard to compare them since i really dont listen to music that makes picking up details easily possible.
Also, my speakers are not the best... they get upgraded next.

But i can say that the DAC is a lot quieter than the SantaCruz (no PC induced noise), and sounds much much clearer.
The mid-lows are much more defined.

I didnt compare the PCM1730s output to the PCM2902's since i didnt put any way of getting the PCM2902s signal off the board.

Please name IC11,IC12 ???Best Regards

Ooops, thats an old schematic... ill put up a new one.
IC11 = REG103-5
IC12 = 78LM33

The new schematic:
http://www.overclockers.com.au/~mwp/dac3/mwp-dac3-sch.pdf

Matttcattt · 2003-09-18 7:49 am

If you didnt get my E-mail, may i use your schematic and PDB layouts make a copy of your DAC?

MWP · 2003-09-18 12:21 pm

Matttcattt said:
If you didnt get my E-mail, may i use your schematic and PDB layouts make a copy of your DAC?

I didnt...
And, yeh, thats fine.
All the info (beisdes parts list) is on page:
http://www.overclockers.com.au/~mwp/dac3/

Matttcattt · 2003-09-18 1:59 pm

MWP said:
I didnt...
And, yeh, thats fine.
All the info (beisdes parts list) is on page:
http://www.overclockers.com.au/~mwp/dac3/

Thanks a lot! ill start ordering parts soon. ill post my results.

MWP · 2003-09-19 4:21 am

Originally posted by Matttcattt Thanks a lot! ill start ordering parts soon. ill post my results.

Cool... itll be great to see what other people think of it.

5th element · 2003-09-20 1:16 am

Im going to post here rather then my other post. Anyway, I've looked over and over various datasheets and as far as I can tell the PCM1794 uses no microcontroller whatsoever, and I think I know exactly how to use it, with a little help from your DAC for a steep learning curve. Anyway I am going to build a similar thing to you with the USB gizmo with the DIR1701 and then two 1794's in mono mode. I hope you dont mind that im going to use your basic wiring diagrams and then implement my own DAC, as it would be a great help.

I've already made the PCB for the USB controller, its taking quite a while getting used to Utilboards sizes ect, but im getting there.

I hope ill be able to report a success in the near future, however I start uni on monday, my first day

, so there might be a delay getting all that sorted.

MWP · 2003-09-20 4:28 am

5th element said:
Im going to post here rather then my other post. Anyway, I've looked over and over various datasheets and as far as I can tell the PCM1794 uses no microcontroller whatsoever, and I think I know exactly how to use it, with a little help from your DAC for a steep learning curve. Anyway I am going to build a similar thing to you with the USB gizmo with the DIR1701 and then two 1794's in mono mode. I hope you dont mind that im going to use your basic wiring diagrams and then implement my own DAC, as it would be a great help.

I've already made the PCB for the USB controller, its taking quite a while getting used to Utilboards sizes ect, but im getting there.

I hope ill be able to report a success in the near future, however I start uni on monday, my first day , so there might be a delay getting all that sorted.

Hey, your right... i just assumed it would need a micro becuase it has the different modes... but they are just high/low control lines.
Cool

Its just a pitty this part isnt offered in the samples program

If it was i would take a shot also at building a dual PM1794 DAC.

BTW... i put the schematics and stuff up on the web page for other people to use, so go nuts

5th element · 2003-09-20 1:06 pm

cheers!

5th element · 2003-09-20 1:32 pm

One last thing, regarding the DIR1703 and setting the default sample frequency. Does the chip sense the sample frequency it receives and change accordingly, so the default set by the set pin brsel doesnt really matter. So leaving it open is the simplest option. The data sheet says it does sense the sample frequency so im assuming I dont need to bother with setting anything.

MWP · 2003-09-21 1:27 pm

5th element said:
One last thing, regarding the DIR1703 and setting the default sample frequency. Does the chip sense the sample frequency it receives and change accordingly...

It does.

5th element · 2003-09-21 2:02 pm

ok thats it i know everything I need to now, unless I build it and it fails

. OK well ive done half the PCB all that left to do is the i/v and to set the dac chips.

Once again cheers Matt

Micky_mike · 2003-09-21 5:05 pm

Well first of all nice DAC. It looks great.
I also like to build one but...
I've never build something like this and I need a lottttt of help.
So I hope you can support me here otherwise I'm not able to build it because even the schematic is a problem for me.

I don't know how the power supply has to be connected and how all the different parts are connected. I'm sorry for being such a newbie I hope you can help me here.

Michael

MWP · 2003-09-22 3:36 am

Micky_mike said:
Well first of all nice DAC. It looks great.
I also like to build one but...
I've never build something like this and I need a lottttt of help.
So I hope you can support me here otherwise I'm not able to build it because even the schematic is a problem for me.

I don't know how the power supply has to be connected and how all the different parts are connected. I'm sorry for being such a newbie I hope you can help me here.

Errr... well dont try this then

Its not a project for a beginner.

Go build a GainClone amp or somthing like that first to get you aquainted with power supplies, etc.

My first DAC!

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