On Tuesday 11 December 2012 08:47:51 pm VE4PER/ Andy wrote: > RMS is 0.775 and average is closer to 0.5 so be sure to compare > apples to apples and oranges to oranges
That one is telephone standard. Actually .7745966692... volts RMS, and that is in 600 ohms, so that is the original zero dbm. The apples to apples thing is SO important in this regard. Most professional audio gear these days has an output impedance that is very low, on the order of 45 ohms, and most pro gear has an input that is greater than 10K ohms, and while there is good reason for that, it also immediately means that our arbitrary db reference needs to be defined. Is it an apple, or is it an orange ? ( the actual output Z of the amps is closer to zero ohms, and the build-out resistors are there to avoid blowing amps ) (( and if you wire it wrong, that output Z can actually go negative !! )) .775V RMS in 600 ohms is exactly the same voltage as .775V RMS in 45 ohms, or 10K ohms, but the power is substantially different, and quite possibly the characteristics of the audio through it. 0db is not the same in 45 ohms as in 10K ohms. Or, is it ? This has little to do with program automation, but can have quite a bit to do with how it sounds. Of course, it's irrelevant when you play MP3's. -- Cowboy http://cowboy.cwf1.com _______________________________________________ Rivendell-dev mailing list [email protected] http://lists.rivendellaudio.org/mailman/listinfo/rivendell-dev
