Filter Ping¶
Overview¶
A filter ping is a well known technique where a short trigger or gate is used to excite the filter's resonance, producing a percussive tonal burst — the filter "rings" at its cutoff frequency. Swell supports this natively: the filter will ping with the resonance knob set around 2 o'clock. Higher resonance settings reduce dampening of the oscillation; at maximum resonance the filter enters self-oscillation.
Setup¶
Resonance¶
Set the Res. knob to approximately 2 o'clock as a starting point. From here:
- Lower settings: More dampened decay — the ping fades quickly
- Higher settings: Longer ring, less dampening
- Maximum: Self-oscillation — sustained tone with no decay
Triggering¶
Patch a gate or trigger signal into the audio input. Short triggers produce a sharp percussive attack; longer gates sustain the excitation before the filter rings out.
The 1V/Oct input tracks the ping frequency — use a sequencer or keyboard CV here to play the ping chromatically.
The frequency knob sets the fundamental pitch of the ping.
Valve Mode Interaction¶
The Valve switch (Pre/Post) and valve configuration significantly shape the ping character:
- PRE mode: Produces a mellow ping response, closer to a classic filter being excited. The valve colours the signal before it enters the filter.
- POST mode with Comp ON: Produces a more compressed, richer ping. The valve saturates the filter's ring output, adding harmonic density and sustain character.
Triode/Pentode and Bias settings generate different tonal characters in line with the waveform produced by the valve — refer to Valve Operating Modes for the harmonic character of each combination.
Gain and Drive¶
Gain and Drive settings directly influence the ping intensity:
- Higher Gain or Drive settings produce a stronger, richer ping signal
- The red LED will flash on pings when gain and/or resonance is sufficient to drive the grid into saturation — this is expected behaviour, not a fault
- The white LED will illuminate at most ping settings, unless gain is very low
FM Feedback Ping¶
Patching audio FM feedback (no cable in the fm jack, fm knob away from centre) delivers a squelchy ping character:
- Positive FM settings (CW from centre): Regenerative feedback — reinforces the ping and extends the ring
- Negative FM settings (CCW from centre): Inverted feedback — suppresses peaks as the ring decays, producing a folded, complex decay character
Quick Reference¶
| Parameter | Effect on Ping |
|---|---|
| Res. ~2 o'clock | Starting point for ping |
| Res. higher | Less dampening, longer ring |
| Res. maximum | Self-oscillation |
| Frequency knob | Sets ping fundamental pitch |
| 1V/Oct CV | Tracks ping pitch to CV (chromatic playing) |
| PRE mode | Mellow, classic ping |
| POST + Comp ON | Compressed, richer ping |
| Higher Gain/Drive | Stronger, richer signal; red LED flashes |
| FM feedback | Squelchy character; polarity changes decay shape |