Tuesday, 22 April 2008

Make a Sound Card with PCM2702

Make a sound card is no more a complex issue. If you use great IC PCM2702 from BURR BROWN / Texas Instruments you can create a fully functional USB sound card. This sound card can be powered from USB port and has one stereo output. You don’t need to install any driver for Windows XP and Vista, because they are already inside. This is really plug and play.

Few months ago I have seen USB sound card called Alien DAC. The construction on the project web page inspired me to build this thing also.

The core of this construction is 16-Bit Stereo Digital-To-Analog Convertor with USB interface PCM2702.


Schematic of sound card with PCM2702

PCM2702 needs only few additional parts to work. The schematic is not complex. Sound card can be powered directly from USB port (jumper W1) or from external power supply (jumper W3). PCM2702 needs two power supply 3.3V (3V-3.6V) and 5V (4.5V-5.5V). I used fixed output voltage LDO TPS76733Q for 3.3V (IO2) and adjustable output voltage LDO TPS76701Q for 5V (IO3). Both LDO are produced by TI, I used this because I had it in my drawer. Any similar LDO can be used. Output voltage of IO3 should be set to little bit lower than input voltage to allow LDO good stabilization, in my case output voltage is set to 4.8V. Output voltage can be set by adjustable resistor R33. In case of low power supply, IO3 can be shorted by jumper W3. LED D3 signalizes power on.

Small ferrite beads are placed before all power pins of PCM2702 and in Vbus and GND of USB. These small beads reduce high frequency hum. I had a problem find this small SMD ferrite beads in local stores but finally I acquire few of them from old hard drive. They are not absolutely necessary, you can use zero ohm resistors instead of them.

Low-pass filter is placed in output signal path to reduce sampling frequency. An OPA2353UA dual op amp is configured as a stereo 2nd-order low-pass filter.

Led diode D1 is illuminated when PCM2702 plays audio data received from the USB bus. Led diode D2 is illuminated when USB bus suspends audio data transmission to the PCM2702.


PCB Assembly diagram

Bottom side (single side PCB, made by standard etching method)

Assembled top side

Assembled bottom side

This circuit works very well. I only shorted crystal during soldering so the circuit didn’t work, but after removing the short the sound card started to work. I have tested in Windows 2000, XP and Vista. It works in all mentioned systems. Drivers are present in operation system so the sound card is ready in few seconds after you connect it.

During writing this article I have found that PCM2702 is now not recommended for new design, but TI offer even better solution. PCM2704, PCM2705 have same functionality as PCM2702, but they include output filter. They are able to drive directly headphones. Volume and Mute can be controlled through SPI bus in PCM2705 or with pushbuttons in case of PCM2704. PCM2704 and PCM2705 are in TSSOP28 package. PCM2706 is similar to PCM2704 and PCM2707 to PCM2705 but in addition they have I2S bus. PCM2706 and PCM2707 are in TQFP32 package. I recommend using these new chips for new design (look at the TI web page).

PCM2702 Texas Instrument

PCM2702 Evaluation Board

Alien DAC

Download project including schematic, assembly diagram and PCB.


aNhe said...

hai, your project same with I want to do in my final project in my college. but the different is I use microcontroller inside, but my problem is synchronize micro with other component. so can you help for this problem ?

Miroslav Batěk said...

Hi fawdfa, I'm not sure if I will be able to help you, but you can send me more details about you project and about your problems to mail diy4fun@gmail.com. I will look at that.

garry said...

hello sir, iam gaurav i am working on this project in my college. Sir it will be very kind of you if you please tell me the values of(L11,L12...so up to L15) of this project and what are they?
lz sir rply fast....

Unknown said...

Hi Gaurav, L11..L18 are ferrite beads. They suppress high frequency disturbance and noise. The resistance should be 600Ohm at 100MHz. But these components are not neccesery. You can put wire instead of them.

Vai_chidrewar said...

Hello sir,
as it is mentioned that pcm2702 is not recommended now for design instead pcm2704/5/6 are used .Have you the modified circuit built using these replacement ICs.If it is so will you please give its link.
Thank you!

Miroslav Batěk said...

Hello, no I didn't modified the circuit for newer ICs. But it is on my "TO DO" list. I would also like to make a similar circuit with PCM2902, which has also audio input.

Anonymous said...

hie i want to do your project for my final examination but the problem is of getting the pcm 2702 am located in zimbabwe and my project is due end of september dont you have an alternative component to use instead of the pcm 2702 something say which i can get locally or in south africa

Miroslav Batěk said...

Hi Tendai, please send me an email to diy4fun@gmail.com I will try to help you solve your problem.

DaNlluD said...
This comment has been removed by the author.
DaNlluD said...

why are you using SMD resistor will this schematic work with normal ones

Unknown said...

Works fine out of the box on Ubuntu and CentOS Linux. Not really surprising though, Linux supports everything ;-)

snowboy3k said...

sir i will like to get more information on this project base on the uses, where can we use the sound card on, advantage and disadvantage in using it.. Also i will like to ask if is possible to include a memory slot in it..

i will like to know the list and work of each component on the project because this is my 1st time of doing it and am really happy to have come across urs..

Litan said...

Bro. I want to know all the calculation of the components.
Can u help me?

Unknown said...