Sonic Research ST-300 Turbo Tuner Mini

The LED ring on the Turbo Tuner is a true stroboscope. The LEDs are driven directly by the analog input signal and electronically strobed, showing the actual stroboscopic effect between the input signal and internally generated frequency reference. This gives instant response and extreme accuracy. 

A True Strobe Tuner in a Mini Stompbox Format
Super bright LED display readable in direct sunlight
Pop-Free True Bypass
Muted output with quiet relay switching
Chromatic and guitar/bass modes
Fully programmable for alternate tunings and temperaments
USB port for ease of customizing
Extreme accuracy: ±.02 cents guaranteed
Rugged die-cast aluminum case
Made in USA