This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM1792: no sound

Part Number: PCM1792
Other Parts Discussed in Thread: PGA4311

Hello,

I'm designing an audio hifi power amplifier with integrated DAC, a PCM1792.

I build first prototype and I can't made the PCM1792DB (I purchase PCM1792DB) working.

The I2S come from an XMOS MCU, data format is I2S 24bit.

Then, I look on SCK pin, 24.576Mhz is present, on BCK I have the right frequency (around 2.8Mhz for a 48khz datarate), on LRCK I found the 48Khz frequency and I see bitstream on DATA pin.

nRST is high level, but maybe the init sequence is wrong.

init sequence:

1- 3.3VDAC is up, SCK is feed with a clock (24.576Mhz) analog power is OFF (5VA feeding analog pins of PCM1792), nRST is low

2-5VA analog is ON when I press a button (before I press buton 5VA is OFF)

3-XMOS MCU start init sequence with nRST only (I2C pins stays high level, no communication)

I expected PCM1792 start with right config (default I2S 24b format) and then seeing some sound from PCM1792 but nothing, 0VDC even the I bias which should give me about 2.5VDC on the 390R resistor is not working.

I see a voltage around 2.45V on IREF pin connected to a 10KR resistor.

Attached my schematics and a screen shoot showing nRST pin (nRST pin stay low when device power up, then XMOS MCU apply reset and put nRST in high level)

Tripple check solders, change PCM1792 with a new one; nothing change.

Any ideas ?

brix.pdf

  • Hi Briquel,

    There could be many things effecting this.  First, you should ensure that the XMOS is actually providing a data signal, and that signal is known, like a sine wave.

    You also have a error in your schematic.  You have shorted the VCOM pins together and shorted them to VCC.  That is not correct.

    Please try correcting that first. 

    Thanks,

    Paul

  • Hi Paul,

    You point the right issue!

    After a iron solder and strap session my amp is playing music!

    First time I build a DAC, on scope FFT I see 80dB THD full power @ 10khz looks good ! At 1Khz only the noise floor.

    A big thank to you, you save me time!

    Here fews picture of the first prototype of my amp and the straps over dac :)

    Lot's of TI inside :) (all dc dc regulators, low noise ldo and charge pump, pga4311, opamps...)

  • Very cool project! It must put off some heat!

    Too bad I didn't catch the VCOM issue on the first review :)