Bueno, buscando un poco más por Internet, he encontrado esto por si a alguien le interesa:

This particular receiver (Onkyo 501) only uses the absolute scale. If you read the manuals for the higher models like the 801, it says that a value of 82/100 (82%) on the absolute scale is equivalent to 0dB on the relative scale, so I initially chose 82% (65) of the 501's 0-79 scale. I could not get my target 75dB at that volume setting because the channel trims only go down to -12.
Para mas informacion:
http://www.hometheaterhifi.com/forum....php/t-61.html