Pre-Emphasis with IIR Filter

You can increase dc gain by rescaling the coeffs.

The following scaling may be useful:

h =[16 -15.5].

this should give you some 20dB more near dc.

To implement that you need to multiply inpyt by 16, use shift by 4 bits instead of multiplication and thats why I chose this value. The other coeff will be -15.5 = 155/10.

You can also avoid division by scaling 155/10 to ?/16 then just truncate 4 bits.

But be warned that this gain could be too much for high frequencies and lead to clipping/overflow, in that case keep coming down.