[hfsig] Performance of 24/192 soundcards?

[Thomas Sailer]

On Sat, 2004-09-18 at 00:23, Tom McDermott wrote:
> There was some discussion at the ARRL/TAPR DCC of 24-bit, 192 ks/s
> soundcards. Doing a google search on the subject leads to a few cards that
> actually have 192 ks/s for both the ADC and DAC (and allow sampling at
> 192k). Unfortunately none of the sites list the frequency response of these
> cards at the maximum sample rate (or any rate, for that matter).

I wouldn't expect the frequency response to be much of a problem. All
cards use Delta Sigma Converters, which do not require much anti
aliasing filter. So there is typically almost no filtering before the
ADC, so frequency response is determined mostly by the ADC.

If you look at the datasheets of those converters, (eg. BurrBrown/TI
PCM1804), converter noise increases significantly (30dB or so) towards
the upper band edge, in the PCM1804 case it starts to rise sharply above
48kHz. So you're limited to the range roughly from 1kHz to 48kHz.

> as current sound cards (about 20 KHz.) On the other, they could have
> something approaching 80KHz. Can't seem to find which by looking over the
> various PCI and USB cards.

I do have a Creative Soundblaster NX (USB), and it seems to work ok. I
used 96kHz/24Bit stereo capture.

Tom