Ugliest DAC.. but tiny!

[pixpop]

Just finished this silly project. It's a PCM2902, bus powered with no analog buffer. The wiring is straight from the 2902 datasheet.

It's about the size of a matchbox.

Surprised the heck out of me when I plugged it in, and it worked. No noise or hum problems, but the sound is so so. Quite poor bass for some reason, though the highs are fine. The output coupling caps are 10uF.

I wonder how much better it could sound if the power was done right.

An externally hosted image should be here but it was not working when we last tested it.

 

[tool49]

Interesting!

I made a bigger (about the size of two business cards side by side) version of the PCM2902. It outputs in a OPA2134 and the sound is quite good. I noticed a tremendous improvement when I added the REG103 as suggested in the suggested schematic of page 27.

I also built a wall powered unit (kind of defeats the point of USB but...) and the sound quality is leaps and bound better. Actually it is my reference when I build new gear now. The improvement is all around but it is especially present when driving harder loads (i.e. headphones).

Congratulations on the tiny design (I wish I could pack as much punch per cubic inches in my designs!)
Sébastien

 

[gmarsh]

beautiful hack... especially the SMT tantalum output capacitors hanging in the air

 

[jleaman]

post schematic ? id like to make a usb dac for my laptop.. Please. post schematic..

J'

 

[tool49]

Jleaman:

The wiring is straight from the 2902 datasheet.

I don't mean to be rude, but the schematic is in the datasheet

Sébastien

 

[jleaman]

Sorry can you post a link to that pdf then please ?

 

[paologatto]

Just finished this silly project. It's a PCM2902, bus powered with no analog buffer. The wiring is straight from the 2902 datasheet.

It's about the size of a matchbox.

Surprised the heck out of me when I plugged it in, and it worked. No noise or hum problems, but the sound is so so. Quite poor bass for some reason, though the highs are fine. The output coupling caps are 10uF.

I wonder how much better it could sound if the power was done right.

An externally hosted image should be here but it was not working when we last tested it.

Very nice pixpop!

I made something similar:

An externally hosted image should be here but it was not working when we last tested it.

(click to enlarge)


Only PCB:

An externally hosted image should be here but it was not working when we last tested it.

(click to enlarge)

Using an output buffer the sound is very good, also on basses. I used for input and output buffers the Burr-Brown OPA2353, that work with the 5V from USB.
Output coupling with bipolar 47 uF.

@ jleaman: just go to www.ti.com and search for PCM2902

 

[jleaman]

Re: Re: Ugliest DAC.. but tiny!

Very nice pixpop!

I made something similar:

An externally hosted image should be here but it was not working when we last tested it.

(click to enlarge)


Only PCB:

An externally hosted image should be here but it was not working when we last tested it.

(click to enlarge)

Using an output buffer the sound is very good, also on basses. I used for input and output buffers the Burr-Brown OPA2353, that work with the 5V from USB.
Output coupling with bipolar 47 uF.

@ jleaman: just go to www.ti.com and search for PCM2902

ANy boards left ? id buy one..

 

[pixpop]

I have another 2902 chip. Perhaps I'll build a better one, now that I've seen how easy it is. If I build another one, I'll connect all the inputs and outputs, not just the analog out as I did in this one.

Still, an M-Audio Transit is only $99.00

 

[jleaman]

I have another 2902 chip. Perhaps I'll build a better one, now that I've seen how easy it is. If I build another one, I'll connect all the inputs and outputs, not just the analog out as I did in this one.

Still, an M-Audio Transit is only $99.00

My point DIY Do It Your Self that is why i asked for the board.. I wonder if i could buy one if not i should be able to find a schematic and design my own board..

 

[jleaman]

Ok so i just ordered samples I got 5 PCM2902's hope i can get this simple thing working.. now all i need is a usb plug..Or i could use a old usb cable...

 

[karma]

i have used old ones. you just need the pinout or colors of the wires

 

[jleaman]

i have used old ones. you just need the pinout or colors of the wires

Im looking for the PCB board mounted ones.. I have lots of usb cables with end a on it but not the B end. : O )

J'

( nice webpage )

 

[pixpop]

I bought mine from digikey. They are PCB mounting, and I soldered the metal case directly to my copper board. Also bought the crystals from digikey, and mounted the crystal by soldering its case to the copper board, which is my ground plane.

 

[jleaman]

I bought mine from digikey. They are PCB mounting, and I soldered the metal case directly to my copper board. Also bought the crystals from digikey, and mounted the crystal by soldering its case to the copper board, which is my ground plane.

Do you have part numbers for the usb plug and the 12mhz Crystal from digi-Key. ?

Plz

j'

 

[pixpop]

The crystal is digikey X227-ND. I used 22pF capacitors with it. I can't find the invoice for the connector, sorry.

 

[jleaman]

Thanks,, Im thinking ill build both dacs the usb bus powered one and the other witch is powered with a external psu.

Just a question did you put in any switches i see 3 of them used are they for any thing ?, did you just leave them out. ?

 

[pixpop]

I left the switches out, and the pullup resistors that connect to them. I have nothing connected to pins 5-7, 12-13, 24-25.

 

[jleaman]

I left the switches out, and the pullup resistors that connect to them. I have nothing connected to pins 5-7, 12-13, 24-25.

I'm making a board tonight. thanks for posting this.. : O )

 

[richeros]

Anyone of you guys have one or two pcm2902 to send me?
I will pay of course.
That would spare me alot of money....