International dBFS Levels -
On a technical note, 0dBm (an old telephone and early broadcast system of
reference) is the voltage required to dissipate 1mW into 00 ohms = 0.775v
ac. 0dBu (also 0.775v ac) just means that the impedance of the circuit is not
specified. These, set in granite actual voltage levels, rather go out of the
window when referred to dBFS figures associated with digital converters!
(dBFS = deciBels Relative to Full Scale... i.e the clipping point of the
system)
There is no single standard for setting where the 0dBFS point is...!!!
For example...
1. EBU R 8 is used in most European countries, specifying +18 dBu at 0
dBFS
2. In Europe, the EBU recommend that -18 dBFS equates to the
Alignment Level
3. European & UK calibration for Post & Film is −18 dBFS = 0 VU
4. UK broadcasters, Alignment Level is taken as 0 dBu (PPM4 or -4VU)
5. US installations use +24 dBu for 0 dBFS
. The American SMPTE standard defines -20 dBFS as the Alignment
Level
7. In Japan, France and some other countries, converters may be
calibrated for +22 dBu at 0 dBFS.
8. BBC spec: −18 dBFS = PPM "4" = 0 dBu
9. German ARD & studio PPM + dBu = −10 (−9) dBFS. +1 (+15)dBu
= 0 dBFS. No VU.
10. Belgium VRT: 0dB (VRT Ref.) = + dBu ; -9dBFS = 0dB (VRT
Ref.) ; 0dBFS = +15dBu.
0VU on the Aurora Stinger VU meter (the yellow LED) is +4dBu (1.228v ac)
and normally -18dBFS on the meters of most digital converters. Any other
digital reference could be used but the higher above -18dBFS you go, the
headroom, both analogue and digital, drops by the same amount! Not good!
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