Phase Vocoder Time Stretcher Kit with Arduino Due + LED
Phase Vocoder Time Stretcher Kit — Slow Any Song to Half Speed Without Pitch Change (Arduino Due)
Every part needed, pre-tested for compatibility, with an AI build companion trained on this exact project. Shipped from Bengaluru in 3-5 days.
Musicians know the frustration: slow down a fast solo and the pitch drops, making it useless for learning. This kit solves that — you’ll build a real-time audio time stretcher that halves the speed while preserving the original pitch, powered by Arduino Due’s processing muscle and a precise overlap-add STFT algorithm. Plug in a microphone or line input, hear the slowed audio through a high-quality speaker, and watch the time-domain waveform live on the OLED — a dedicated practice companion for your music stand.
What You'll Build
You’ll assemble a fully functional, standalone audio processor that captures live sound, processes it in real time using a 512-point FFT-based phase vocoder, and outputs the stretched audio at half speed with intact pitch. The finished unit includes a MAX9814 microphone preamp, MCP4725 DAC, and PAM8403 amplifier, all calibrated to work together inside a custom enclosure. The 0.96-inch OLED displays the waveform and processing status, and a single 9V supply makes it portable enough for any practice session.
What You'll Learn
- Implementing overlap-add short-time Fourier transform (STFT) on a 32-bit microcontroller
- Configuring dual-buffered DMA on Arduino Due for true real-time audio capture and playback
- Designing a low-noise analog front-end with a MEMS mic and 12-bit I²C DAC
- Calibrating the entire chain from microphone to speaker for minimal latency and phase coherence
Kit Contents
| Component | Quantity |
|---|---|
| Arduino Due | 1 |
| MAX9814 Electret Microphone Amplifier | 1 |
| MCP4725 12-bit I²C DAC Module | 1 |
| PAM8403 3W Class-D Audio Amplifier | 1 |
| 3W 8Ω Speaker | 1 |
| 0.96-inch OLED Display (I²C) | 1 |
| 100nF Ceramic Capacitors | 15 |
| PCB Prototype Board | 2 |
| Enclosure Box | 1 |
| 9V 1A DC Power Supply | 1 |
| Soldering Iron (30W) | 1 |
| Lead‑Free Solder Wire (50g, 0.8mm) | 1 |
Why Buy This Kit Instead of Sourcing Parts Separately
| Factor | Sourcing Separately | Compoden Kit |
|---|---|---|
| Compatibility checks | You verify every part | Pre-tested as a system |
| Build support | Forums and scattered tutorials | AI companion trained on this exact project |
| Time to first working build | Days of debugging | Hours, with step-by-step guidance |
| Shipping coordination | Multiple sellers, multiple delays | One shipment from Bengaluru in 3-5 days |
Who This Kit Is For
This advanced kit is built for serious musicians and audio engineers who want a dedicated hardware practice tool, final-year B.Tech ECE/EEE students tackling real-time DSP as a capstone project, and instructors at IITs, NITs, and VIT teaching embedded signal processing. It also fits Smart India Hackathon teams prototyping assistive music technology, where preserving pitch while modifying tempo is critical.
Built and Backed by Compoden
Every Compoden kit ships with an AI build companion trained on this exact project — accessible via a QR code on the box, with WhatsApp and email backup. We've spent 10 years building projects for makers, schools, and institutions across India. If a part fails because of a manufacturing defect, replace it free within 7 days.
What if I get stuck during the build?
Open the AI companion on your phone, describe the symptom, and get debugging steps specific to this circuit. You can also message us on WhatsApp — our team reads every message and often responds within a few hours.
Can I use this kit with an electric guitar or line-level input?
Yes. The MAX9814 includes automatic gain control and can handle instrument-level signals. For line-level sources, simply adjust the onboard trimmer or use a resistive attenuator (values provided in the build guide).
How does the phase vocoder preserve pitch while slowing down audio?
The algorithm separates magnitude and phase information in the frequency domain. Time-stretching is done by resynthesizing frames with phase adjustments that maintain harmonic relationships; the STFT overlap-add method ensures smooth, artefact-free output at half speed.
Can I modify the stretching factor beyond 0.5×?
Absolutely. The firmware is open and well-commented — you can change the stretch ratio from 0.3× to 1.0× in the code. Our AI companion explains exactly which constant to modify and how to recompile for the Arduino Due.
Arduino Due implements overlap-add STFT to stretch audio to half speed without pitch change for slow practice.
What's in this kit
Choose your assembly option:
- Soldering Kit — 25W soldering iron, 60/40 solder wire, flux, and small perfboard for permanent assembly.
- Breadboard Combo — 800-point full-size breadboard with 65-piece jumper wire pack for solderless prototyping.
Other projects you can build
Shipping Information
- Prepaid Orders: ₹75 for orders up to ₹999, FREE shipping above ₹999
- COD Orders: ₹125 shipping + ₹50 COD fee = ₹175 total
- Delivery Timeline: Dispatch in 1-2 days, delivery in 2-7 days depending on location
Returns & Warranty
- 7-Day Return: Manufacturing defects only (approval required)
- Warranty: 7 days from delivery
- Non-Returnable: Batteries, consumables, cut wires, clearance items