Rogs, thanks for the correction.
According to dB dBu dBFS dBV to volts audio conversion digital - calculator volt to dBu and dBV dB mW SPL dB decibels 0 dBFS - convert dB volt normal decibels relatioship relation explanation analog audio absolute level true rms convertor converter decibel to dbfs converter calculation online attenuation loss gain ratio reference audio engineering sound recording dBFS dBVU 0 dB audio logarithm level converter peak to peak p-p impedance voltage pro consumer audio digital analog recording level - sengpielaudio Sengpiel Berlin
We don't use the dBm in audio engineering. That belongs to power, we don't need here.
So dBu & dBm have the same reference level, 0.775V. But 1 dBm refers to when this voltage is applied to a 600 ohm load impedance, hence the power dissipation of 1mW. Whereas 1dBu refers to when this voltage goes into amuch higher impedance load, the typical situation in a modem electronic input circuit. So we're not interested in the power dissipation aspect at all.
Therefore the standard meter zero-level for pro audio is4dBu, not4dBm.I'll amend my previous message.
Dan.
I always tend to think of dBu as dBm'Unloaded' .....probably not technically correct, but it works for me data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
THISchart gives values for them all.... and just goes to show how the audio (and telephone) 'gurus' from back in the day managed to make the already difficult concept of the Decibel even more awkward !