Nady Audio HE-1 Hum Eliminator

Technically 10/10
Cosmetically 7.5/10
Nady's HE-1 is a compact noise canceller that eliminates 60Hz or 120Hz AC noise from your audio signal by up to 20dB. The device features a fully passive design that safely breaks ground loops while leaving the signal ground intact. It features a dual-channel I/O interface with 1/4" TRS connectors and can automatically convert the signal between balanced and unbalanced lines. The result is high-quality sound with minimal noise and distortion.
Compact and durable metal housing
Eliminates 60Hz or 120Hz AC noise from the audio signal by up to 20dB
Fully passive design safely breaks ground loops, leaving the signal ground intact
Dual-channel I/O interface with 1/4" TRS connectors can automatically convert the signal between balanced and unbalanced lines
The compact Nady HE-1 is a win-win option for quickly and easily removing 60/120 cycle AC noise from your signal path. This two-channel mini-box is designed to eliminate ground-fault noise and also functions as a direct box, capable of converting unbalanced signals to truly balanced for long cable runs without interference. Its passive design makes it easily portable, as it does not require an AC outlet. A few of these units are indispensable in every musician's or touring gig's kit bag.
Features
Easily eliminates AC hum (60Hz/120Hz) with up to 20dB of attenuation
Automatically converts signals between balanced and unbalanced lines at either end, can also be used as a direct box that converts signals from unbalanced to truly balanced
Securely breaks ground loops, leaving all signal grounds intact
Dual-channel input/output with 1/4-inch TRS "smart" connectors
Fully passive design with audiophile-grade components delivers the best possible sound quality without noise or distortion