Ali to sto ti je dato nije dato da sabiras i oduzimas, vec su to vrednosti za razlicite velicine. +9 je dbm iliti ono sto meri peakmetar iliti snaga izrazena u vatima, tj. koliko je puta veca data vrednost od referentne (1mW), a dBu je napon tj. VU metar i ovo sto su ti dali u decibelima je koliko je veca data vrednost od referentne koja je 0.775 volta.
Sabiranje te dve vrednosti decibela bi bilo nesto sto se zove sabiranje baba i zaba i cini mi se da nije moguce. Jesu i jedn i drugo decibeli, ali decibeli zavise od referentne vrednosti, ako referentna vrednost nije ista ne mozes ih sabirati niti raditi ista sa njima jer odma upadaju u kategoriju baba i zaba.
Oni su na wikipediji dali neke standarde i ima ih dosta -18 dbfs, pa i manje:
Quote:
dBFS is not to be used for analog levels, according to AES-6id-2006. There is no single standard for converting between digital and analog levels, mostly due to the differing capabilities of different equipment. The conversion level is chosen as the best compromise for the typical headroom and signal-to-noise levels of the equipment in question. Examples:[16][17][18]
EBU R68 is used in most European countries, specifying +18 dBu at 0 dBFS
In Europe, the EBU recommend that -18 dBFS equates to the Alignment Level
European & UK calibration for Post & Film is −18 dBFS = 0 VU
UK broadcasters, Alignment Level is taken as 0 dBu (PPM4 or -4VU)
US installations use +24 dBu for 0 dBFS
American Post: −20 dBFS = 0 VU = +4 dBu
The American SMPTE standard defines -20 dBFS as the Alignment Level
In Japan, France and some other countries, converters may be calibrated for +22 dBu at 0 dBFS.
BBC spec: −18 dBFS = PPM "4" = 0 dBu
German ARD & studio PPM +6 dBu = −10 (−9) dBFS. +16 (+15)dBu = 0 dBFS. No VU.
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http://en.wikipedia.org/wiki/DBFS
Opet ti kazem, sve ovo proveri jer ja nisam siguran u ovo, a mozda je najbolje da ih pitas koliko dbfs zele da ne bi gledao u pasulj.