Peterson AutoStrobe 490-ST

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Peterson AutoStrobe 490-ST

The AutoStrobe 490-ST is specifically made for the tuning of piano, marimba, steel pan, and other instruments requiring “stretched” interval tuning.

Capable of handling “stretched” interval tuning, this is the instrument technician’s most valuable tool. The Peterson AutoStrobe 490-ST offers a vast array of selectable “stretched” tuning options, including pianos of all types. Enjoy the instantaneous response times that only a Peterson can deliver and the relative tuning display of any audio source to 0.1 of a cent (1/1000 of a semitone) accuracy!

With the Model 490-ST, students, technicians, and musicians of all levels can utilize automatic (hands-free) note selection for absolutely the most accurate tuning of any instrument. Key features including real-time display of intonation to improve performance and listening skills while playing as well as mutable throughputs for in-line (yet silent) tuning during performances round out the package!


"Stretch" refers to specific adjustments in the frequencies (pitches) of notes to enhance the overall quality of tuning within an instrument. The AutoStrobe 490-ST comes with 9 factory preset tables that range from concert grand piano to spinet pianos. Users can program up to 31 stretch tunings of their own.


All Peterson products provide guaranteed tuning results to within +/-0.1 cent. That is 1/1000th of a semitone! This level of accuracy is the highest in the industry and what has made Peterson the choice of tuning professionals around the globe for over 65 years.


  • Wide Selection Of Pre-Programmed Stretch Files - Tables With Optimized Tunings For All Piano Types And Sizes. Up To 31 Additional Files May Be Programmed By The User.
  • Automatic Note Selection
  • Automatic Image Clarity And Contrast Control - Internal Compensation For Optimal Viewing Over A Wide Range Of Source Pitch And Volume.
  • Enhanced Clarity For Upper And Lower Register Notes - +2/-1 Display Feature Shifts The Strobe Patterns Into More Visible Middle Ranges - Bass Note Patterns Can Be Displayed Two Octaves Higher And Treble Note Patterns Can Be Displayed One Octave Lower In Strobe Display.
  • External Input And Through Output With Mute - For In-Line, Silent Tuning During Performances.


Automatic Image Clarity helps identify extremely high or low notes with the push of a button. The DISPLAY +2 / -1 push button changes the strobe motor speeds to allow the audio input to be displayed on the higher or lower bands on the strobe disc. Altering the speed of the motor permits viewing the extreme upper and lower registers much more easily.


Designed for user-friendly operation with little need for interaction once the initial desired settings have been entered. Hands-free tuning can be accomplished via the built-in mic or plug in a microphone for additional control of the sound source. Automatic Note Detection continually adjusts motor speed for viewing of the input sound relative to the nearest standard pitch.


  • Power Supply: Built-In (IEC)
  • Stretch Tuning Tables: 9 Preset Stretches
  • Note Range: C1 to B8
  • Note Selection: Automatic Or Manual
  • Foot Pedal Control: +/- Octave, Note Increment
  • Peterson Connect Compatible: No
  • Form Factor: Desktop/Bench
  • Accuracy: 0.1 Cents
  • Display Type: Single Analog Strobe Disc
  • Display Resolution: Infinite (Analog)
  • Construction: Metal Casing
  • Product Dimensions LxWxH: 13.4" x 6.375" x 3.5"
  • Product Weight: 7lbs. (3.18kg)
  • USB Port: No
  • Power: AC 100V to 240V
  • Built-In Microphone: Yes 
  • Built-In Speaker: No
  • Metronome: No 
  • Inputs: 1/4" Jack
  • Outputs: 1/4" Thru
  • Mute-able Output: Footswitch Controlled 
  • Tone Generator: No
  • Concert A Range: 350Hz to 550Hz
  • Global Cent Offset Range: +/- 50 Cents
  • Transposition Range: Keys of C, Bb, F, Eb 
  • Frequency Response Range: 32.70Hz to 7902.13Hz
  • Warranty: 1 Year
  • User Presets: 255 User Presets
  • Historic Temperaments: Yes