Source Audio SA144 Source Audio Soundblox Pro Poly-Mod Filter 23 Filter Sounds including 2-Pole Low Pass, 4-Pole Low Pass, Single Peak, Triple Peak, Peak & Notch, and Phasers. Positive and Negative filter sweep with variable range and sensitivity. Wet/Dry Mix knob featuring our signature low-end preserving algorithm Lo-Retain. 4 modulation sources including envelope, LFO, expression pedal and Hot Hand. Tap tempo speed control for LFO and State-of-the-art DSPOur proprietary 56-bit Digital Signal Processor, the SA601, with crystal clear 24-bit converters.