What about the other side of audio-phoolery: audio FFT? I'm thinking more along the lines of an ARRL FMT.
>________________________________ > From: Tom Van Baak <t...@leapsecond.com> >To: Discussion of precise time and frequency measurement <time-nuts@febo.com> >Sent: Thursday, March 27, 2014 6:10 PM >Subject: Re: [time-nuts] FEI-5660 Rubidium Oscillator > > >> Recently I happened across an eBay listing for an Antelope Audio Isochrome, >> a device that apparently packages an SRI-PRS10 rubidium oscillator and >> distribution amplifier in a box and sells to audiophiles for a price in the > >Bruce, > >There have been threads about this on time-nuts every few years. The consensus >is that audio companies that use atomic clocks are naive. It makes good >marketing, though. > >Then again, speaking from experience, many of us make the same mistake: first >thinking that precise time is the goal, then thinking that precise frequency >is what counts, and later thinking that stability is what really matters, and >only eventually realizing that all of these metrics are functions of tau, and >that tau ranges from MHz/microseconds to years. Phase noise plots along with >log-log ADEV plots start to tell the whole story. > >In the case of digital music, as far as I know, L(f) phase noise in the audio >band and ADEV(tau) frequency stability from microseconds to seconds is far >more important to the fidelity of digital recording and playback than absolute >SI-accurate frequency or long-term timekeeping. Consequently, most atomic >frequency standards are actually a poor choice as a sampling reference clock >-- because their jitter (short-term noise) is no where near as good as a >free-running, undisciplined, high-end OCXO. > >True, the PRS10 is a better choice than other cheap telecom rubidium's but >none of these comes close to the performance of a premium OCXO. For the >ultimate audio reference clock you want to avoid Rb, or GPSDO, or Cs for that >matter. Instead pick a 1e-12 or 1e-13 stable OCXO, strap it to a 100 pound >block of granite, and leave it alone. > >/tvb > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
