2 layers21 × 51 mm
2 layers99.1 × 79.4 mm
Missing Fundamental
ice458/Missing_Fundamental- Size
- 99.1 × 79.4 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 60
- Nets
- 64
- Pads
- 202
- Tracks, vias
- 227, 176
- Pours
- 9
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 7 Aug 2026
- Updated
- 11 Aug 2026
Overview
Missing Fundamental is an open-source printed circuit board by ice458, from the ice458/Missing_Fundamental repository on GitHub, published under the MIT licence. It is a 2-layer board of 99.1 × 79.4 mm with 60 parts on 64 nets, routed with 227 tracks and 176 vias.
It is built around the NJU77552G-TE2, PAM8403DR and PT8211-S, with the NJM2866F33-TE1 among its other parts. Its parts include 23 capacitors, 14 resistors, 6 ICs, 4 switches and 2 connectors. It belongs with the RP2040 boards of this library.
Main components
4
NJU77552G-TE2
SOP-8-55℃~+125℃ -900mV~2.75V 1.7MHz 1.8V~5.5V 1pA 1pA 1uV/℃ 24nV/√Hz@1kHz 4 40mA 50uA 5mV 70dB 800V/ms Built-in compensation、EMI filtering/RF suppression Rail-to-Rail Input, Rail-to-Rail Output SOP-8 Operational Amplifier ROHSNisshinbo Micro Devices Inc.Operational Amplifier
PAM8403DR
SOIC-16-40℃~+85℃ -59dB 0.15% 2 Single-Ended Inputs 2-Channel 2.8V~5.5V 3Wx2@4Ω 80dB 87% 8mA Class D Filterless architecture SOIC-16 Audio Amplifiers ROHSDiodes IncorporatedAudio Amplifiers
PT8211-S
SOP-8-150mil16 2 3.3V Serial SOP-8-150mil Digital to Analog Converters (DAC) ROHSPTCDigital To Analog Converters (DAC)
NJM2866F33-TE1
SOT-23-5-40℃~+85℃ 1 100mA 14V 180mV@(60mA) 180uA 3.3V 75dB@(1kHz) Fixed Over Current Protection、Over Temperature Protection Positive SOT-23-5 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSNisshinbo Micro Devices Inc.Voltage Regulators - Linear, Low Drop Out (LDO) Regulators
README
README.mdMissing Fundamental
小型スピーカーの低音再生能力を、DSP処理によって物理的な限界を超えて向上させる基板です。
コンセプト
ミッシングファンダメンタル現象(基音が実際には存在しなくても、倍音列の間隔から脳が元のピッチを補完して知覚する現象)を利用しています。低域信号から意図的に倍音を生成し、小型スピーカーが再生しやすい帯域に載せることで、実際には出ていない低音を知覚上再現します。
詳細は こちら。
主な処理
- ランブルカット(60Hzハイパス)+ 倍音生成
- スピーカー周波数特性補正EQ(6段直列)
- ステレオエンハンサー / クロストークキャンセル
- ソフトクリップ、ラウドネス補正
- スイッチによるDSP ON/OFF切り替え
すべて48kHz・float演算でリアルタイム処理しています。
ハードウェア
- マイコン: Raspberry Pi Pico2 (RP2350)
- DAC: PT8211
- アンプIC: PAM8403
基板データは hardware/ です。
ビルド
Raspberry Pi Pico SDKでビルドします。
ライセンス
Parts
60| Qty | Value | Footprint | References |
|---|---|---|---|
| 12 | 10k | Resistor_SMD:R_0603_1608Metric | R2, R3, R4, R5, R8, R9, R10, R11, R12, R13, R14, R15 |
| 10 | 1u | Capacitor_SMD:C_0603_1608Metric | C6, C12, C13, C15, C16, C17, C19, C21, C22, C23 |
| 8 | MountingHole_3.2mm_M3 | MountingHole:MountingHole_3.2mm_M3 | REF1, REF1, REF2, REF2, REF3, REF3, REF4, REF4 |
| 6 | 0.1u | Capacitor_SMD:C_0603_1608Metric | C2, C4, C5, C7, C8, C11 |
| 4 | SW_Push | Button_Switch_THT:SW_PUSH_6mm | SW1, SW2, SW3, SW4 |
| 3 | NJU77552G | Package_SO:SO-8_3.9x4.9mm_P1.27mm | U2, U4, U6 |
| 2 | 100k | Resistor_SMD:R_0603_1608Metric | R6, R7 |
| 2 | 1n | Capacitor_SMD:C_0603_1608Metric | C3, C10 |
| 2 | 470p | Capacitor_SMD:C_0603_1608Metric | C1, C9 |
| 2 | 680p | Capacitor_SMD:C_0603_1608Metric | C18, C20 |
| 2 | Speaker | Connector_JST:JST_XH_B2B-XH-A_1x02_P2.50mm_Vertical | LS1, LS2 |
| 1 | 100u | Capacitor_THT:CP_Radial_D6.3mm_P2.50mm | C14 |
| 1 | AudioJack3 | My_Connector:MJ-8435 | J1 |
| 1 | Barrel_Jack_Switch | Connector_BarrelJack:BarrelJack_CUI_PJ-102AH_Horizontal | J3 |
| 1 | NJM2866F33 | Package_TO_SOT_SMD:SOT-23-5 | U1 |
| 1 | PAM8403D | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U5 |
| 1 | PT8211 | Package_SO:SO-8_3.9x4.9mm_P1.27mm | U3 |
| 1 | RaspberryPi_Pico | Module:RaspberryPi_Pico_Common_THT | A1 |
Questions
How big is the Missing Fundamental PCB?
It measures 99.1 × 79.4 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Missing Fundamental use?
60 parts, built around the NJU77552G-TE2, PAM8403DR, PT8211-S and NJM2866F33-TE1. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Missing Fundamental KiCad files?
From the ice458/Missing_Fundamental repository on GitHub, at the commit this page was made from: the board is hardware/Missing Fundamental.kicad_pcb and its schematic hardware/Missing Fundamental.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Missing Fundamental design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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