Didier Juges wrote:
I am not sure how to translate the IMD specs into integral or
differential non-linearity, but from what I have seen, IMD specs are
not significantly better for 24 bit sound cards than for the older
high-end 16 bit models, when high-end 16 bit models were available.
Noise specs are better, and that's about it.
In sound cards as in many other consumer products, customers equate
more bits to higher quality and today you cannot buy anything but 24
bit cards, regardless of the actual improvement obtained. I am not
sure the actual specs reflect the higher number of bits. I believe
Bruce has quite a bit of data on that.
Some of the high end ADC parts (not necessarily cards, which could
greatly compromise the performance) are quite good... they're sold into
applications for professional recording as well as the consumer gear.
The (amateur) software defined radio folks have looked into this, in
connection with direct conversion type receivers, because it affects the
performance on things like instantantaneous dynamic range: being able to
demodulate a small signal next to a big one, for instance.
So, over the, say, 100 Hz and up range, they're probably pretty good.
What I know is that the standalone A/D converters like the AD parts
referenced in the other emails have outstanding linearity specs (at
low bandwidth of course) at a price well below that of a "high
quality" sound card, so even if the specs were the same, it would
still make more sense to use the external device to measure a slow
moving DC voltage.
I agree there..
Didier
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