On 18-1-2011 10:16, Invisible wrote:
> On 17/01/2011 05:50 PM, Darren New wrote:
>> scott wrote:
>>> In general more power means you have more possibilities to do stuff to
>>> increase the quality.
>>
>> Or, more bitrate means more switching means more power. Running a DAC at
>> 22KHz is going to take lots more power than running it at 8KHz.
>
> For decent speech transmission, you apparently need a spectrum that goes
> up to about 4 KHz. That means at least 8,000 samples per second.
>
> A CD-quality digital signal is 44,100 samples per second. That's only
> about 5x higher. Are you seriously telling me it takes 5x the power to
> do that?

It depends a bit on the type of DAC. In general power consumption in 
CMOS is almost linear with clock frequency. It does take almost no 
energy to keep a switch in one position, only to flip it to the other 
state. For more than 8 bits resolution often low-pass filtering of 
oversampled data is used, which increases frequency and thus the power 
consumption.

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