Lpc2000

I am trying to use the LPC2138 part as a simple voice device (play 16
khz voice).  Currently I am using a Keil MCB2130 eval board and
running a simple example program that plays 16 bit 8khz wav files via
the D/A port through a LM386 to the on board speaker (the wav file has
no hiss on my PC).  

The process works but there is a low level hiss or static in the
audio.  I have take the Aout and filtered it with a RLC filter to get
rid of the tinness from the audio but still has the hiss.  I also
tried using an off board amp and speaker but still have the
hiss/static in the audio.  

If the D/A is not changing then the hiss/static goes away so it does
not seem to be noise coupling over. 

I tried looking at the signal on the scope but can not see anything
above the scope noise. 

I am weak on audio stuff and am hoping to get some pointers. 

1. Is this hiss just from the D/A S/N ratio and I am stuck with it?? 

2. Is caused by the Vref and V3A being tied with the Digital Vcc?  (If
this I would assume it would still get the noise when the D/A is not
changing) 

3. Do I need to filter the Aout better? 

4. Any other test I should try??

Thanks 
Tom