ScottW wrote:

"Arny Krueger" wrote in message
...
"R" wrote in message

Stewart Pinkerton wrote in
:

On Wed, 15 Dec 2004 22:45:20 GMT, "Rich.Andrews"
wrote:

What I mean by parallel is that the data stream for one channel
feeds 2 dacs at once and the resultant output of the dacs are tied
together. Many of the high end CD players and D-A units use that
circuit topology as it lowers the distortion levels.

Thinking back for a while, I remember the days when doubling up DAC chips
was sorta popular.

There was even a tweak that stacked two DAC chips on top of each other.
This kinda worked because many DAC chhips of the era had high impedance
outputs, so that their outputs were summed at the input to the following
stage.

The net effect was that the output voltage was doubled (6 dB), while any
internally generated uncorrelated noise increased by only 3 dB.

Care to explain this voltage doubling claim of yours Arny? I smell more
snake oil than hi-rez in PC/ABX.

Just stepping in here.....

Those old converter chips were current output. 2 chips = twice the current =
double the voltage for the same output stage following it.

The noise only rises by 3dB since noise isn't a coherent signal ( it's random
). Each converter produces its own random noise so there is an overall
improvement in S/N of 3dB. You need to understand how signals sum to properly
follow this bit.

Standard output voltage can be obtained by halving the feedback resistor value
in the op-amp following the DAC. This helps reduce noise a tiny bit too since
lower value resistors have less thermal noise.

Graham