Lpc2000

I  have dropped into this discussion 1/2 through but felt like contributing

Don't forget that the 6dB/bit applies to the A/D or D/A REGARDLESS of 
sample rate. This factor can be used to improve accuarcy in both 
conversions by increasing the sample rate.

If you sample a 10 bit A/D at 400Kz, then down sample to 44Khz (probably 
using a linear phase  finite impulse reponse filter{ FIR }) then you get 
a noise reduction because you filter off the higher sample noise 
frequencies. You will achieve an extra 3 bits - i.e equivalent to a 13 
Bit A/D.

The same applies to D/A - take the digital samples at 44Kz increase 
frequency to 400Kz - apply an FIR in the digital domain then send to 
your D/Q. The advantage of this is that the analoge filter on the output 
is very simple as it operates at 400Kz.

Some of the early CD players worked on this principal. They had a high 
freq 14 bit D/A. The advantage of this is the improved phase response of 
the system. Jo public couldn't understand how a 14 bit D/A was giving 16 
bit performance so I think they stopped doing it.

I can give FIR details if anyone is interested.

DSP rules ! Yay !  I havent done this stuff since the 80's

Owen Mooney