PCM2272 needs a 'Zobel network' at the output?

[CopperTop]

(edit: I meant PCM2704 - don't know why I put 'PCM2272' in the title!")

I have looked through the <a href="http://www.ti.com/lit/gpn/pcm2704/">data sheet</a> for TI's PCM2704 DAC and there is something it seems to be a bit vague on.

It apparently has a built in reconstruction filter and is capable of driving headphones directly. Distortion figures are given for various loads, with heavier loading increasing distortion. I wish to use the DAC to drive a power amp via a 10k pot, so I would be hoping that I could achieve something approaching the 0.006% specified for a ">10k ohm load". Nowhere does the main data sheet imply that any extra components are needed for the low pass filter to work at the output.

However, all the example circuits show a 'Zobel network' at the output, even when driving an amplifier input. This network is 16R in series with 22nF, so is a not-negligible load at higher frequencies.

I have included the network, and I am seeing distortion levels much higher than those specified for a 10k load.

My questions are:

(a) whether the Zobel network is necessary at all when driving a high-ish impedance amplifier input.
(b) Does the specified distortion include the 'Zobel network', or not?
(c) Have I missed something in the data sheet that throws light on why the network is included in the reference circuits?

Many thanks for anyone's help on this.