PreSonus Blog

The Filter Shape Shifter

Ah yes…the good old days. When tape cost a week’s salary, you had to clean your recorder’s tape heads and capstan every day, and worst of all, there was no undo. And I had to make fun effects by laboriously breadboarding parts, soldering, and deciding what tradeoffs to make because an effect with 26 controls and 12 switches wasn’t really viable.


But now we have Studio One so we don’t have to mess with tape, and FX Chains, so we can make our own crazeee multieffects without having to solder anything! Which brings us to this week’s tip.


Back in the 70s, sample-and-hold effects from synthesizers were a big deal. This effect synched to tempo, and stepped through a resonant filter. Its cutoff frequency changed on the beat, and held until the next beat, at which point it changed to a different random cutoff frequency. I always liked that effect with guitar, and thought it would make a good Friday Tip, along with a companion, downloadable FX Chain. But I got carried away…check out the audio example, with guitar, bass, and drums.


Fig. 1 shows the FX Chain basics. The chain splits the stereo input by channel, into two Autofilters. These are modulated by their LFO step sequencers, which sync to the beat. The filters are before Ampire, so they alter the distortion character in a more subtle way than they would if they followed Ampire. 


Figure 1: The Filter Shape Shifter “block diagram.”

Here’s the story on the Macro Controls (Fig. 2).


Figure 2: Macro controls for the Filter Shape Shifter FX Chain.

Cutoff and Resonance are “master” controls for both filters. The Filter Modes choose the filter types for the left and right Autofilters, while the two LFO Beats controls choose the rhythmic sync for the left and right LFOs.


R Step Offset is a bit unusual. It changes the values for all of the right LFO’s steps except for 1, 4, 8, and 12. Automating this parameter and varying it can add a considerable amount of variety to the sound, but keeping a constant, relatively high filter frequency on steps 1, 4, 8, and 12 maintains the beat.


Mix changes the wet/dry mix for both filters, and Widen enables a Binaural Pan when you want a wider stereo spread. And you know you want it.


Do check it out, and have fun warping your guitar-meets-Ampire sound!