posted 01 April 2003 23:08            

exciters.kym

Both are included in the attached sound. The Bass Boost has been described in detail in another topic thread. The HF Exciter included here gives just a tinge of that almost metallic feeling when you bite on a piece of aluminum foil. It's teasingly delicious sounding.

The "diode" used for a half-wave rectifier comes from subtracting 1.0 from the signal. That forces the signal to one edge of the DSP saturation limit. These fixed-point DSP's can't normally load and store values beyond the range [-1.0,1.0). So whenever a signal might overflow, instead of wrapping the way an integer processor would, they use something called "saturating arithmetic".

Values that would overflow are pinned to one limit or the other. Hence, subtracting 1.0 from a signal causes all the negative portions to clamp to -1.0, while the positive going portions exhibit normal behavior with the added DC offset. Hence we form a half-wave rectifier with DC offset from the simple subtraction of 1.0 from the signal.

As far as I can tell, this design is unique in that we encourage the nonlinear production of harmonics. Double up the input signal amplitude and the harmonics grow four times greater. That is apparently pleasing to the mind, since our ears sort of work that way too....

Enjoy!

- DM

[ Lots of exciters use a "diode" characteristic. That much isn't new. That simply generates harmonics. But the breakthrough in these two Sounds is the subseqent multiplication of the rectified signal with the input signal itself. That's what makes the amplitudes a nonlinear function of input signal level. The diode creates the harmonics; the multiplier makes them psychoacoustically pleasing...]