I've been trying to draw, with asymptotic approximation, the Bode diagram of the following transfer function
$$G(s) = \frac{\frac{1}{80} - s}{s^2 (s + 4) (s + 5)}$$
The thing is, I don't why the amplitude plot start a little before $100$ dB.. I have two poles in the origin, therefore the line should start at $120$ dB (correct me if I'm wrong) with a pendency of $-40$ dB/decade. I calculated the Bode gain, which is equals to 1/1600; by converting the amount in dB, it returns $-64.08$ dB, so the amplitude plot should be vertically translated of -$64.08$ dB, thus the amplitude diagram should start at $120$ - $64.04$ = $55.96$ dB, but the result doesn't match with the several diagrams I draw in Maple and Matlab.
