 Later, the filters were redesigned to use off-the-shelf LM13600 OTAs.A useful illustration of the Korg-35 filter in-circuit is shown here  and some photographs illustrating the later LM13600 filter daughterboard are shown here .The tonal difference between the two is that the original Korg-35 filter has a slight amount of hiss which overdrives into the sound at high resonant settings.