It's an ASI6514 that says Input Level -10 to +24dBu in 0.5dBu steps. Is that what you're referring to?
— Patrick patr...@scnv.net > On Apr 11, 2017, at 7:08 PM, Fred Gleason <fr...@paravelsystems.com> wrote: > > On Apr 11, 2017, at 20:56, Patrick <patr...@scnv.net > <mailto:patr...@scnv.net>> wrote: > >> I've always been confused about dB, dBu, dBm, dBFS and possibly others. > > ‘dB’ is short for decibel. It’s merely a ratio between two different power > (or sometimes voltage) levels, expressed logarithmically. For the long > explanation, see: > > https://en.wikipedia.org/wiki/Decibel > <https://en.wikipedia.org/wiki/Decibel> > > Since ‘dB’ all by itself is merely a ratio, to be meaningful it has to be > expressed in terms of some sort of standard signal. A couple of the common > ones used in audio engineering are: > > dBm - Ratio against a 1 milliwatt signal into a 600 ohm load. > dBFS - “Full Scale” —e.g. the maximum level that a particular PCM > digital encoding can represent —e.g. +32768 / -32767 for PCM16. > > The first has meaning only in analog contexts, while the second is meaningful > only in the digital realm. If you play Rivendell's standard reference tone, > it will show a ‘zero’ level on the meters, which corresponds to -16 dBFS, or > approximately 15.8 % of the full-scale amplitude of the digital signal (about > +/-5177 at the peaks). Likewise, on a properly operating analog ASI card > with the trim controls set to ‘zero’, that same tone should give you an > analog output level of +4 dBm (a common analog ‘reference’ level used by > pro/broadcast audio gear), while putting a signal of that amplitude into an > analog input should give a ‘zero’ indication on Rivendell’s meters. > >> >> When I go to RDAdmin->ManageHost->AudioPorts I get options to set the Input >> and >> Output reference levels, which are all currently at 0 dB. >> >> Is that the trim you're talking about? If so, would increasing the input >> reference level make >> the input more or less sensitive? > > Yes. Increasing the reference level will have the affect of making inputs > less sensitive while increasing the average level of outputs. Bear in mind > that these trims controls are not supported on all ASI cards, and where they > are they often have a very limited range. The spec sheet for the particular > card (most of them available at http://www.audioscience.com > <http://www.audioscience.com/>) should have the details. > > Cheers! > > > |----------------------------------------------------------------------| > | Frederick F. Gleason, Jr. | Chief Developer | > | | Paravel Systems | > |----------------------------------------------------------------------| > | A room without books is like a body without a soul. | > | -- Cicero | > |----------------------------------------------------------------------| > > > _______________________________________________ > Rivendell-dev mailing list > Rivendell-dev@lists.rivendellaudio.org > http://caspian.paravelsystems.com/mailman/listinfo/rivendell-dev
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