function [B,A] = boost2(fs, fc, bw, gain);
%BOOST - Design a boost filter at given gain, center
%        frequency fc, bandwidth bw, and sampling rate fs
%        (default = 1).
%
%        Cookbook formulae for audio EQ biquad filter coefficients
%        by Robert Bristow-Johnson  <rbj@audioimagination.com>

Q = fs/bw;
w0 = 2*pi*fc/fs;

A=sqrt(gain);
alpha = sin(w0)/(2*Q) 

b0 =   1 + alpha*A
b1 =  -2*cos(w0)
b2 =   1 - alpha*A
a0 =   1 + alpha/A
a1 =  -2*cos(w0)
a2 =   1 - alpha/A

A = [a0 a1 a2] / a0;
B = [b0 b1 b2] / a0;

if nargout==0
  freqz(B,A);
  title('Boost Frequency Response')
end