For now, we deal only with 'voltage' amplification (gain) and damping (loss).
V2 >V 1 = amplification, dB value is positive and V 2< V 1 = damping, dB value is negative.
V2 / V1 means the ratio. The amplification or the damping in dB is:
L = 20 × log (voltage ratio V 2 / V 1) V 1 is the reference.
Using voltage we get: Level in dB: L = 20 × log (voltage ratio)
+6 dB = two fold the voltage
+12 dB = four fold the voltage
+20 dB = ten fold the voltage
+40 dB = hundred fold the voltage
Using power we get: Level in dB: L = 10 × log (power ratio)
+3 dB = two fold the power
+6 dB = four fold the power
+10 dB = ten fold the power
+20 dB = hundred fold the power