[Lf] [Fwd: LF: WOLF test results, soundcard trouble]

[Andre' Kesteloot]

Rik Strobbe wrote:

> >The true sample rates of the soundcard were then measured by other means,
> >they were:
> >
> >8002.87 samples / second for the DAC (used to transmit)
> >7938.09 samples / second for the ADC (used to receive)
>
> One shouldn't expect too much accuracy from the soundcard ADC's. Errors up
> to 1% in the sampling rate won't effect their use for games etc... so why
> should the manufacturer make them more accurate (and expensive). I wonder
> if someone ever tested the linearity, the error will be likely in the same
> range.
>
> If we want to go more accurate we either have to calibrate each soundcard
> individualy (and hope that there isn't too much drifting) or go to another
> device.
> A good 16 bit ADC with 'no missing code' and a max. sample rate of 10kHz
> and up costs no more than a few $, even high quality 18 or 20 bit ADC's are
> available for 10$ or less. So the hardware isn't a real problem. Question
> is how to get the data from this ADC into the computer ?
> One way would be to make a plug-in card, but that would :
> - require us to open the PC and plug in a card
> - require to convince windows that the card is there
> - rule out most portable PC's
> Another way is tranfer the data via a port into the PC. Most suitable are
> either the serial port or the USB port.
> Advantage of the serial port is that also the older PC's have it,
> disadvantage is the maximum baudrate of 115kB/s (would mean a max. sample
> rate of +/-5.5kHz).
> The USB port can transfer many MB/s, but isn't available in older PC's.
>
> A well designed external ADC board could solve many of the problems that
> occur with the soundcard and shouldn't be too expensive.
> The first question is : is there a 'market' for such a device
> A second question : if there is a 'market', are the software developers
> willing to adapt their software for such a device.
>
> 73, Rik  ON7YD