Hi Paul,
Thank you for your answers. Comments below.
PStamler writes:
On Nov 18, 8:39Â*pm, Randy Yates wrote:
Â* 1. If you backtrack to 0 dB from this wikipedia article
Â* Â*http://en.wikipedia.org/wiki/Line_level
Â* the reference levels for dBu and dBV are 0.775 VRMS and 1 VRMS,
Â* respectively. Is this correct? Are the reference levels I've given
Â* here exact?
No and yes, respectively. The reference level for dBu is actually
0.77459666924148337703585307995648V, according to my calculator --
that's the voltage equivalent of 1mW into a 600 ohm load.
Ah, that's right - it's the voltage level that corresponds to 0 dBm (1
mW) when delivering to a 600 ohm load.
The reference level for dBV is exactly 1V.
Got it.
Â* 2. Is there a standard for converting from dBFS to dBu? If so, Â* what is it?
No. There's an informal standard used in the film industry and in many
broadcast applications of +4dBu = -20dBFS, but it's never been
codified as an official standard. The informal standard, though, is (I
believe) based on an rms scale -- in other words, a tone that would
read 0 VU on a VU meter calibrated to +4dBu would be -20dBFS. Correct
me if I'm wrong on that last bit, but that's what I think is the case.
There seems to be no universal agreement, but you are close to what this
guy says (under "Here come the numbers..."):
+22dBu = 0dBFS == +4dBu = -18dBFS.
I'm still not sure if that's FS sine or FS square.
--
Randy Yates % "Remember the good old 1980's, when
Digital Signal Labs % things were so uncomplicated?"
% 'Ticket To The Moon'
http://www.digitalsignallabs.com % *Time*, Electric Light Orchestra