Live will display -inf at -70 dB which is not sound off at all... With common 24-bit interfaces, your are at -132 dB on the theoretical safe side. But then you get a pretty big range on your dial which displays -inf. At 16-bit its -96 dB which is probably silent enough. But I would really set the lower end to -70 dB and split -132. -70. and force it to -inf. I set the exponent to 0.33333....

Stefan