Technical specifications

The current QRNix hardware and DSP path.

These facts describe firmware 0.3.5 and the v0.2.0 board design.

Audio and operation

At a glance.

Application	Standalone DSP noise reduction between a radio audio source and a speaker or amplifier.
Modes	Bypass, Spectral with manual one-second noise capture, and Adaptive with a continuously updated per-bin estimate.
Input behavior	Two audio input channels are monitored. QRNix selects the stronger sustained channel and processes the selected signal as mono.
Output behavior	The selected, processed mono signal feeds both audio outputs.
Source recommendation	Line output preferred. Controlled headphone output supported. Speaker-level output requires external attenuation before the current line input.
Controls	Reduction 0 to 30 dB, Smoothing 0 to 100%, Whitening 0 to 100%, and Aggression 0.00 to 2.00; three-position mode switch; one button.
Extra features	Tone-kill in all modes, Post-filter in Spectral and Adaptive, CLIP input-overload indication, and automatic input selection.
Display	Optional 0.96 inch SSD1306 OLED, 128 by 64 pixels, I²C address 0x3C. Audio processing continues without it.
Power	USB.

DSP engine

SGTL5000 ADC → STFT → selected noise-reduction core → inverse STFT → SGTL5000 DAC.

25 ms frames, rounded to a 2048-point CMSIS-DSP FFT in both noise-reduction modes.

Spectral and Adaptive processors are never allocated together. A mode change frees the old processor before creating the next one.

Board

Processor	Teensy 4.0, NXP i.MX RT1062 ARM Cortex-M7 at 600 MHz, 1 MB RAM, 2 MB flash.
Audio hardware	Teensy Audio Shield Rev D or D2 with SGTL5000 codec.
Board size	51.3 by 66.8 mm.
Stack	Two layers, 1.6 mm nominal thickness.
Front panel hardware	Four 10 kΩ trim pots, three-position mode switch, button, and OLED provision.
Audio jacks	Line In and Line Out.
Firmware	0.3.5, LGPL 2.1-or-later.

Current input limit