A decent "home studio" soundcard would have easily 60+ dB of separation across it range and probably much higher. For the outrageous sum of around $150 you can get the ESI Juli@ from eBay (and real dealers) with better than 60 dB of separation, below 5 Hz to 100 KHz response, differential inputs and good Windows, Mac and Linux support. It seems any other approach would probably value time at below minimum wage or less for the effort. Here is a review showing 100+ dB separation http://ixbtlabs.com/articles2/esi-julia/ The card uses local crystals for its oscillators so it has lower jitter than the cheap solutions. If it helped the measurement you could drive the crystal input with an external oscillator etc. For more extended low frequency response you could bypass the input caps but the dc offsets would need attention.
Demian Martin Product Design Services Date: Fri, 21 Aug 2009 22:51:40 +0200 From: Christian Vogel <[email protected]> Subject: Re: [time-nuts] Using cheap sound cards for measurements To: Discussion of precise time and frequency measurement <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hi Lux, > Syncing inexpensive cards is a real chore (and the only reason to be > thinking about using this in the first place is to keep the cost to a > minimum, otherwise, you might as well build a special purpose little > box with counters & A/Ds, and an interface) I've had too many problems with cheap (onboard) soundcards in the past, even when using them for their intended purpose, so I would not advice to use them for anything quantitative. But if you *really* want to syncronize inexpensive soundcards, it's rather trivial, see for example http://quicktoots.linuxaudio.org/toots/el-cheapo/ . Just buy a few dozens for a EUR/$ each and hunt down the ones with identical oscillator frequencies ;-). But don't expect miracles, you end up with a few synchronized cards that only happen to not skip samples with respect to each other. Compared to decent signal input they are still cheap cards, and hog the CPU for their individual servicing. Chris _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
