Acid Filter Explorer
Sweep a TB‑303‑style resonant low‑pass in real time — drag the cutoff, crank the resonance toward self‑oscillation, and hear the squelch through a live acid engine. Then copy the settings straight into your own synth.
Acid filter FAQ
What makes the TB‑303 filter sound like “acid”?
Two things: a resonant low‑pass filter whose peak climbs sharply as you raise resonance, and an envelope that sweeps the cutoff on every note. High resonance plus a short, punchy decay and note slides gives the squelchy, vocal “acid” character. This tool lets you hear each of those move independently.
What filter slope does the 303 use?
The 303 uses a diode‑ladder low‑pass. Its nominal slope is often quoted at 24 dB/oct, but because of the ladder topology the effective slope near the cutoff behaves closer to 18 dB/oct — which is the character modelled in this tool's response curve.
How do I recreate this in my own synth?
Use a sawtooth oscillator into a resonant low‑pass filter. Set the cutoff, resonance and amp decay to the values shown in the copy chips, add a touch of drive, and slide between notes for the classic glide. Any synth with a resonant filter and an envelope will get close.
Is the audio a real 303?
No — it's a Web Audio recreation running live in your browser, built to behave like a 303‑style resonant filter for learning and sound‑design. The response curve is illustrative (the shape, not a lab measurement), but the passband, resonant peak and rolloff all track a real ladder low‑pass.