22 Dec
2005
22 Dec
'05
10 p.m.
James Courtier-Dutton <James(a)superbug.co.uk> writes:
Hi,
I have a question for some audio professionals out there.
What is the smallest sensible gain control step in dB.
Is it 0.5dB ?
I am asking, because if one is using a digital gain control in a 24bit
fixed point DSP, once could use almost any step size, so I am looking
for the smallest sensible size to use.
Well, the minimum possible difference for 24bit is between -2^23+1 and
-2^23, and that would be about 0.000001dB.
Some people mentioned earlier on a previous thread
that there was
something called soft gain control, where the user moves the gain up a
step, but the mixer gradually(fairly quickly) adjusts the volume to
the new level, so no clicks are heard on the speakers. How does these
soft gain controls prevent the clicking? Do they wait for the zero
crossing point to adjust the gain?
No, why should they? You just ramp up the volume linearly. If you
want to be even nicer, you use a shape that is even smoother.
Basically, you put the step pulse from the jump gain through a low
pass filter, preferably one that does not overswing.
--
David Kastrup, Kriemhildstr. 15, 44793 Bochum