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dB-dBu-dBV comparison table

dBu = 20 log V/0.775 where voltage is irrespective of impedance
dBm = 20 log V/0.775 where voltage is measured across 600 ohms
dBV = 20 log V/1

Multiplier (voltage ratio relative
to specified reference)
dB Voltage reference for PPM
UK scale
PPM
EBU scale
VU
UK scale
dBu dBV
10 20 7.75V 10.0V
4 12 3.08V 3.98V 7 12
8 1.95V 2.51V 6 8 4
7 1.73V 2.24V
2 6 1.55V 2.00V 2
5 1.38V 1.78V
4 1.23V 1.59V 5 4 0
1.41 3 1.09V 1.41V
2 975mV 1.26V
1 869mV 1.12V
1 0 775mV 1.00V 4 0 –4
–1 690mV 891mV
–2 615mV 794mV
0.7 –3 548mV 708mV –7
–4 489mV 631mV 3 –4 –8
–5 436mV 562mV
0.5 –6 388mV 501mV –10
–8 308mV 398mV 2 –8
0.25 –12 195mV 251mV 1 –12
–18 97.5mV 126mV
–24 48.9mV 63.1mV
–30 25.4mV 31.6mV
0.01 –40 7.75mV 10.0mV
–50 2.45mV 3.16mV
0.001 –60 774µV 1.00mV
–70 245µV 316µV

Note

Wizened and greying broadcast engineers who remember valves the first time round will also be aware that the spacing between scale marks 1 and 2 on a PPM used to be 6dB. Proud possessors of ancient BBC MNA/3, ATM/1, TPM/3 and PPM/6's will still only accept this scaling. However, since the introduction of (modern?) transistorised PPM drive cards, the spacing between scale marks 1 and 2 is 4dB.

Source: BBC Designs Department Handbook No. 3.186 (1976).

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