Calibrate 0dB to 0dB
How do i calibrate 0dB everywhere in Ardour 2.6.1 with an sblive 5.1 card under Debian Lenny.
Capture line in shows about -18dB. This is regardless if it is sent -30dB or +4dB from an extern mixer. -30dBu output on the extern mixer shows peaks about -20dB on the meters in Ardour. +4dBu on the extern mixer shows -18dB in Ardour.
The mixers headroom is +10dB. A still clean signal +9dB on the extern mixers vu-meter and line out boosted +4dB (resulting on a crunchy sound on the sound card) shows in Ardour with peaks about -17dB.
Capture a cd show peaks about -5dBu in ardour. It might depend on the cd.
The reference voltage for the decibel unloaded (0 dBu) is the voltage required to produce 1 mW of power across a 600 Ω load (approximately 0.7746 Vrms)
It would be nice to know if it is possible to calibrate the levels. Perhaps it is an ALSA issue?
If someone is interested...
A sine wave at -10dBu is about 0.1 volt rms
A sine wave at +4dBu is about 1.228 volt rms
A sine wave at +6dBu is about 1.55 volt rms
-10dBu is consumer audio standard
+4dBu is American profesional audio standard
+6dBu is some German standard