Meter scales & dBFS alignment
Translate between dBu, dBV, dBFS, VU and PPM scales (DIN, EBU, BBC) for a chosen digital alignment.
dBu
dBV
V
dBFS
VU
dB
dB
mark
dBu
Common digital alignments: EBU R68 puts 0 dBFS at +18 dBu (so −18 dBFS = 0 dBu); SMPTE RP155 puts 0 dBFS at +24 dBu (−20 dBFS = +4 dBu). Check your converters: many interfaces use other values. BBC PPM marks are only defined from 1 to 7.
How it works
Analogue and digital level meters use different scales and reference points. A digital alignment defines which analogue level corresponds to full scale, and thereby how much headroom is left above the reference level.
VU meters show average level and read 0 at +4 dBu. Peak programme meters (PPM) react faster and use different scales in different countries.
Formulas
- dBFS = dBu − (dBu at 0 dBFS)
- VU = dBu − 4
- DIN PPM = dBu − 6
- BBC PPM mark = 4 + dBu / 4
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