lør, 14 08 2010 kl. 18:15 +0000, skrev g4ilo: > Well, that isn't my experience. Regardless of the chip set used, it's the > entire product including the drivers that will determine the performance. > > My suspicion is that these devices run at a fixed sampling rate, and that > resampling to the rate requested by the software is carried out by the > drivers. Resampling can be done accurately, at high CPU cost, or less > accurately but more quickly. Any resampling is undesirable, but its effect > may not be very noticeable with the slower digital modes because if a weak > signal doesn't decode you may think that's just because it is weak. > > Personally I don't think it is worth economizing in this area. And no, I > don't have shares in SignalLink. > > Julian, G4ILO
The Signalink USB (which I recommend myself with the caveats on my homepage), uses one of the same Cheap chips used by the low cost general purpose adapters, in this case the "USB Audio Codec". As a class of devices you are certainly correct in your assumption about the drivers, but again, as a class of devices, they support all std. sampling rates from 48000 and down, with one notable exception: 11025 (this became a de facto std many years ago when it was the fastest rate these newfangled devices (i think the first was a SoundBlaster 8-bit adapter) would do), many many applications default to this, and for compatibility reasons its being fudged in the Windows driver SW rather than aborting the requesting application. Funny enough (or not as things may be) Linux drivers don't do this and abort any application requesting 11.025 from one of these devices! (this is the only case I know of where resampling comes into play). Anyway, if your purpose isn't high quality HiFi or ultra high sampling rate for SDR radios, i can recommend the cheaps sound cards - get real, they have more than sufficient dynamic range, and you only need a frequency response of some 500-2500 Hz anyway! Vy 73 de OZ1PIF/5Q2M, Peter ***************************************** ** Genius is one per cent inspiration, ** ** and ninety-nine per cent ** ** perspiration. ** ** -- Thomas A. Edison ** ***************************************** email: peter(no-spam filler)@frenning.dk http://www.frenning.dk/oz1pif.htm Ph. +45 4619 3239 Snailmail: Peter Frenning Ternevej 23 DK-4130 Viby Sj. Denmark *****************************************
