The "H" version has two really cool features...the first and most important, the output gain make up knob has 40 detents for ultimate accuracy and resetablility, the second really cool feature is that we have the ability to preset the Peak Threshold so there is no way on gods earth that you can hit digital clipping when going into the HEDD unit.

By inserting the D-sub connector (supplied with appropriate jumpers) to the side chain port of the unit, you can disable the Peak Threshold control and preset your maximum output level to the A/D converter in the HEDD unit...(or any other A/D you may be using). This allows you to pay attention to the music, rather than concentrating on your level into your A/D converter.