RPi B+ works with I2S DACs, if:

  • four jumper wires used (different GPIO pins now)
  • AND: a Rasbian Linux Kernel Patch done (changed pinmux)

I did the patch (change three bytes in a kernel module) - works:

Raspberry Pi B+ and RPi-DAC

 

If DAC needs I2C for control - then it needs more effort to modify kernel (or wait for updated release,

even the most recent release June 2014 does not support yet).
Without the Kernel Patch and trying to use I2S - RPi - the B+ will hang.