USB based DAC project

[bluetech]

Since I' not using the I2S (FSEL=1), I'm gonna connect them all to ground.

What about the Dout pin (17) that i'n not using either? Shall i connect it to ground??

 

[astouffer]

What about the Dout pin (17) that i'n not using either? Shall i connect it to ground??

Ah I should have explained that a little better. Outputs are usually fine to leave floating. Logic inputs should never float.

 

[jaydeecee]

ANYBODY

I want to use my existing NOS DAC but it doesn't have a USB input. I have seen USB to SPDIF units, has anyone any experience with these in their system.
Would it be better to get a new USB DAC? This is for a high end audio system but I want to use my laptop with iTunes.

Any advice welcome!

 

[bluetech]

Thank you for your comments.

New schematic attached.

All Function and HID inputs grounded.

 

[bluetech]

Hello,

I'm still struggling with the PCM2706.

I have build on a stripboard the attached schematic.

Any idea what went wrong.

The message i get is that the device has malfuctioned and cannot be recognised by windows.

Any suggestions welcome, I'm desperate.

Thank you

 

[SoNic_real_one]

I don't know why you connect all the inputs to the ground. In the TI application there are NOT all connected, especially pin 11.

I am attaching the pic from data sheet, but a good implementation you can find here (credit to Russ White):
http://www.twistedpearaudio.com/docs/digital/usb_sch_1.0.pdf

 

[rt123]

Hi,

I have just been assigned a similar project to work on. Did you manage to complete yours??

 

[bluetech]

No unfortunatelly I'm still having problems with the implementation.

I cannot make the PCM2706 to work.

However if you have any question, I could try to answer them

good luck

 

[error401]

If it's helpful to you, you can find my PCM2707 implementation schematic and PCB here. PCM2707 is pin-compatible with PCM2706 so I guess this might be useful. It is confirmed working.

FSEL should have a pull up/down so it can't inadvertently be floating (and then it only needs a 2-pin jumper). U2 is a 74LVC1G08, a 1 gate 2-input AND with 5-volt tolerant inputs as a level switcher, run with Vcc at 3.3V. It's not strictly required, just makes sure the device won't start up without local power (voltage divider on Vbus works too), but don't put 5V here.

Pretty straightforward.

 

[rt123]

Thanks guys!

@error401: Thanks for the schematic! I'll try it out and get back to you if I have any doubts.