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CLAP - TR-808 Style Hand Clap

TR-808 inspired digital hand clap synthesizer with band-pass filtered noise and adjustable decay.

Controls

Potentiometers / CV Inputs

Control Function Range Description
POT1 / A0 Filter Q 0.5-4.0 Band-pass filter resonance (left=wide, right=narrow)
POT2 / A1 Decay Time 20-200 ms Envelope decay duration
POT3 / CV3 Filter Frequency 50 Hz - 8 kHz Band-pass filter center frequency

Jacks / Pins

Jack Function Type Description
OUT (GPIO1) Audio Output PWM Output 10-bit PWM audio at ~36.6 kHz
IN1 (GPIO7) Trigger Input Digital Input Rising edge trigger for clap sound
IN2 (GPIO0) Accent Input Digital Input HIGH = half volume (-6dB attenuation)
LED (GPIO5) Envelope LED PWM Output LED brightness follows amplitude envelope
BUTTON (GPIO6) Manual Trigger Button Triggers clap sound manually

Button Function

  • Press: Manually trigger clap sound

Features

  • Three-Burst Structure:

    • Two 4ms noise bursts at start (15ms spacing)
    • Exponential decay tail for realistic clap sound
    • Total ~60ms-215ms duration depending on decay setting

  • Filtered Noise Synthesis:

    • White noise generation
    • 2-pole band-pass filter (cookbook formula)
    • Adjustable center frequency (50 Hz - 8 kHz)
    • Variable Q factor (0.5-4.0)

  • Real-Time Control:

    • All parameters adjustable during playback
    • Smooth parameter interpolation
    • 22,000 sample buffer (~0.60 seconds maximum)

  • Audio Quality:

    • ~36.6 kHz sample rate
    • 2ms fade-in, 1ms fade-out for click-free operation
    • Exponential decay envelope with curvature control

  • Visual Feedback:

    • LED envelope follower (PWM brightness)
    • Shows amplitude envelope in real-time

Patch Recommendations

Classic 808 Clap

  • POT1 (Filter Q): 60% (moderate resonance)
  • POT2 (Decay): 40% (~90ms decay)
  • POT3 (Frequency): 50% (~2 kHz center)
  • Use: Drum patterns, on backbeat

Tight Clap

  • POT1 (Filter Q): 70% (higher resonance)
  • POT2 (Decay): 20% (short, ~50ms)
  • POT3 (Frequency): 60% (~3 kHz, bright)
  • Use: Fast patterns, rhythmic fills

Reverb Clap

  • POT1 (Filter Q): 40% (wide filter)
  • POT2 (Decay): 80% (long, ~180ms)
  • POT3 (Frequency): 45% (~1.5 kHz)
  • Use: Ambient, large spaces, send to reverb

Snappy Clap

  • POT1 (Filter Q): 80% (narrow, ringing)
  • POT2 (Decay): 15% (very short)
  • POT3 (Frequency): 75% (~5 kHz, very bright)
  • Use: Electronic percussion, hi-energy tracks

Deep Clap

  • POT1 (Filter Q): 30% (wide)
  • POT2 (Decay): 60% (~140ms)
  • POT3 (Frequency): 20% (~500 Hz, dark)
  • Use: Techno, industrial sounds

Version History

v1.0 (2025-01-17)

  • Initial release
  • TR-808 inspired clap synthesis
  • Three-burst noise structure with exponential tail
  • 2-pole band-pass filter with adjustable Q and frequency
  • Real-time parameter control
  • Accent input for velocity sensitivity
  • LED envelope follower
  • Click-free fade-in/fade-out
  • ~36.6 kHz sample rate

Technical Specifications

  • Platform: Raspberry Pi RP2040/RP2350 (Pico 2)
  • Sample Rate: ~36.6 kHz (150 MHz / 4096)
  • Audio Resolution: 10-bit PWM (0-1023)
  • Buffer Size: 22,000 samples (~0.60 seconds)
  • Filter Type: 2-pole band-pass (Cookbook formula)
  • Envelope: Exponential decay

Notes

  • Accent input provides -6dB attenuation when HIGH (useful for velocity sensitivity)
  • Three-burst structure is fixed timing (15ms spacing between bursts)
  • Parameters can be adjusted in real-time while sound is rendering
  • LED output can drive external LED for visual envelope indication
  • Fade-in/fade-out prevents clicking at start/end of sound