Silvertune Pedal

Hard autotune in a stompbox. Same DSP brain as the Silvertune CLAP plugin, running bare metal on a Daisy Seed.

Foot on = robot. Foot off = raw. Mid-song. Mid-word.

Hardware

Enclosure

• 125B aluminum enclosure (~$5)

On the PCB

• Daisy Seed microcontroller (~$30) — electro-smith.com
• ElectroCookie breadboard-style PCB, 52.1×88.9mm (~$8)

Mounted to enclosure, wired to board

• 4× B10K vertical potentiometer (RK097 or equivalent)
• 2× 1/4" mono jack
• 1× DC power jack (5.5/2.1mm, center positive)
• 1× SPDT momentary footswitch
• 1× 5mm LED + 470Ω resistor
• 1× SSD1306 OLED display, 0.96", 128×64, I2C

Total: ~$55-65. All through-hole. No SMD. Soldering iron and patience.

Knobs

Control	Function	Range
KEY	Root key	C through B
SCALE	Scale	Chromatic → Major → Minor
WIDE	Doubler blend	0% = off, 100% = full doubler
TUNE	Tune Strength	0% = no correction, 100% = full robot
Footswitch	Bypass	Toggle on/off
LED	Status	On when engaged

Display

The OLED shows the current state at a glance:

• Default (key set): large key name on top, scale name below — e.g. C# / MAJOR
• Default (chromatic): just CHROMATIC centered
• While adjusting a knob: shows that parameter's value for 2 seconds, then returns — e.g. WIDE: 75%, KEY: C#, TUNE: 100%, SCALE: MAJOR

The display mirrors the Silvertune plugin interface in a DAW.

Wiring

See WIRING.md for full connection reference and board-layout.png for the PCB layout.

The Daisy Seed sits on the ElectroCookie PCB straddling the center gap (rows 6–25). All other components — pots, jacks, footswitch, LED, OLED — mount to the enclosure and connect back to the board via hookup wire.

Signal	Daisy Seed pin
OLED SDA	D12 (pin 13)
OLED SCL	D11 (pin 12)
LED anode	D22 (pin 29) via 470Ω
Footswitch	D25 (pin 32)
KEY knob	A0 (pin 22)
SCALE knob	A1 (pin 23)
MIX knob	A2 (pin 24)
TUNE knob	A3 (pin 25)
Audio IN	AUDIO IN L (pin 16)
Audio OUT	AUDIO OUT L (pin 18)

Build

1. Install the ARM toolchain

# Arch / CachyOS
sudo pacman -S arm-none-eabi-gcc arm-none-eabi-newlib

# Ubuntu / Debian
sudo apt install gcc-arm-none-eabi libnewlib-arm-none-eabi

2. Build the Daisy libraries

cd lib/libDaisy
make
cd ../DaisySP
make

3. Build the firmware

# From the project root
make

This produces build/silvertune_pedal.bin.

4. Flash to the Daisy Seed

Put the Daisy into DFU mode (hold BOOT, press RESET, release BOOT), then:

make program-dfu

Live vocal setup

Mic → Inline Impedance Matching Transformer → Silvertune Pedal → Amp

An inline impedance matching transformer (XLR female → 1/4" male, e.g. Shure A85F or similar) brings a dynamic mic signal up to instrument level and matches impedance — no interface, no mixer, no phantom power needed. Plug straight into the pedal's input jack.

How it works

1. Audio comes in mono from the input jack
2. A bare YIN pitch detector (~80 lines, no dependencies) finds the fundamental frequency
3. The detected pitch is quantized to the nearest note in the selected key/scale
4. A two-tap grain shifter with Hann window crossfade shifts the pitch to the target note
5. WIDE knob blends in a second pitch-shifted voice detuned +8 cents for a doubler effect
6. Zero latency. No FFT. No buffering. Sample by sample.

License

GPL-3.0 — same as the plugin.