AutoStrobe 490-ST






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Capable of handling “stretched” interval tuning, this is the instrument technician’s most valuable tool. The Peterson AutoStrobe 490ST 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.


Standard tuning temperament suitable for regular or alternate tuning, 100 cent intervals - no Sweetening.

Guitar & Bass

Tempered for clean 5ths when playing electric guitar with distortion.
A unique tuning adjustment for standard-tuned guitars (or, additionally, for “1/2-step down” tuning: E=, A=, D=, G=, B=, E= as well as simple open chord tunings) in which “power-chord” 4ths and 5ths are optimized. This is very useful in situation where distortion is to be used as part of the guitar tone. (This “stretch” avoids a compromise of the P5TH temperament under the Temperament presets through the ability of stretch files to have independent adjustments for each “E” string.)

Historic Temperaments

Kirnberger III Temperament
Werckmeister III Temperament
Young Temperament
Pythagorean Temperament
Just Major Intonation
Quarter Comma Meantone Temperament
Just Minor Intonation

Stretch Tunings

Useful for all concert style grand pianos of approximately 8 feet in length or greater. This minimal stretch profile may also be of use on smaller pianos strung with thin piano wire or in situations where the user wishes a greater coherence of fundamental pitch throughout the instrument.
Optimal for a 6’ to 7’11 range of grand piano.
Taken from optimal settings for vertical and grand pianos of many makes and sizes, this profile will produce a reasonable tuning for non-critical applications. It also provides a good starting point for creating your own stretch profiles.
Useful for grand pianos that are 5’10” or smaller in scale.
Suitable for vertical pianos equal or exceeding 51 inch.
Taken from optimal settings for many makes and sizes of vertical pianos, this profile will produce good results for any vertical-style piano in typical playing environments for such pianos.
Designed for vertical pianos in 39 inch to 51 inch range.
Designed for vertical pianos smaller than 39 inch, this profile is the most extreme (farthest bass and treble note stretching) of these piano preset stretches.

Compare to Sweetened Tunings offered in other products.


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.


Proudly designed, manufactured, and tested in Alsip, IL U.S.A.

Since 1948, Peterson Strobe Tuners is deeply committed to innovation as well as excellence in design, manufacturing, and customer service.

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

Is the accuracy the same for all Peterson tuners?

Yes, the accuracy is within 0.1 cents (1/1000 of one semitone) as with all Peterson Strobe Tuners. An important thing to note is that Peterson Strobe Tuners have ultra high definition displays, so not only are they highly accurate in detecting a note but they have the ability to display that accuracy. Other products claim accuracy but do not have the high definition screen to display the level of accuracy in which they claim. If you cannot see the accuracy, it is of little value. Only Peterson provides High Definition Strobe Tuning.

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How do I read a strobe display?

Basically, the strobe image appears to travel to the left if your instrument is flat of the desired pitch and to the right if it is sharp. On earlier models such as the StroboStomp 1, StroboStomp 2, VS-1, VS-II and V-SAM, the strobe image travels upward if your instrument is sharp and downward if your instrument is flat of the desired pitch.

Adjust your instrument until the pattern is as close to still as possible. Strobe displays are 'real-time' and extremely high definition. They require very precise tuning adjustments to stop the display because the frequency/pitch of any instrument is never totally stable.

You'll quickly learn to read the display, make the most precise adjustments and appreciate the high resolution that only a Peterson provides.

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What should I do if my new Peterson product doesn't seem to work properly?

If you've first tried all of the solutions offered here, please contact Peterson directly. It is important that you do NOT return the product to the store in which you purchased it without Peterson instructing you to do so. If your unit is problematic, we would like to limit the chances of another customer purchasing the returned unit. Always arrange for product service or replacement directly with Peterson.

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How do I manually update Peterson Connect for Google Chrome?

Google Chrome will automatically update your extensions every couple of hours. However, if you'd like to force an update:

  • Click on the three horizontal lines in the upper right corner of the Chrome browser.
  • Choose More Tools, then Extensions.
  • Check the box for 'Developer Mode'
  • Click the button labeled 'Update Extensions Now'

If this doesn’t work, you can delete the extension from the same page and re-install Peterson Connect for Google Chrome.

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Is there a carrying case available?

We have carrying cases available that are very useful if you will be frequently traveling with your Peterson tuner. You may purchase your case directly from us at Peterson or from your local dealer. Cases are available for the AutoStrobe™ line and the VS-1, VS-2, and V-SAM tuners. The StroboClip and StroboPLUS come with packaging that has been designed to protect your tuner.

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490ST Instruction Manual English Rev2

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Dual Footswitch

Dual Footswitch


For remote Octave +/- selection (490-ST and StroboRack only).



AutoStrobe Soft Case

AutoStrobe Soft Case


Soft but durable, with double zippered flap top, space for additional accessories, and an adjustable/removable shoulder strap.




AutoStrobe Rack Kit


Converts any AutoStrobe™ model to a 19" rack format. AutoStrobe™ 490 not included.




AutoStrobe 590

$969.00 - $989.00

The AutoStrobe 590 is THE preeminent mechanical strobe tuner for tone generation and metronome facilities. It combines both input instrument tone and audio standard reference tone at the output for simultaneous visual and audible tuning along with exceptional intonation training! The 590’s key features (automatic note tracking and audio tone generation capabilities) make it a favorite in the classroom, at the factory, or backstage. And as usual, only a Peterson can respond at the speed of light to display relative tuning information extracted from any audio source down to 0.1 of a cent (1/1000 of a semitone) accuracy! Finally, utilize automatic (hands-free) note selection for fast tune ups of instruments. Proudly made in the USA.




AutoStrobe 490

$729.00 - $749.00

The Peterson AutoStrobe 490 is agreed by music students, technicians, and professionals to be the standard by which all tuners are measured. Only Peterson could bring you the kind of real- time intonation critical enough for ear training use. Enjoy hands-free note selection for fast, accurate tuning of instruments. Other companies may boast of their strobe tuner capabilities, but buyer beware! The AutoStrobe 490 is a truly stroboscopic mechanical tuner capable of fundamental and overtone display. Key features include mutable throughputs for in-line (yet silent) tuning during performances, automatic image clarity and contrast control which internally compensate for optimal viewing over a wide range of source pitch and volume, improved clarity for upper and lower register notes (our +2/-1 display feature shifts the strobe patterns into more visible middle ranges so that bass note patterns can be displayed two octaves higher and treble note patterns can be displayed one octave lower in strobe display), and easy transposition (strobe patterns appear at the correct note for Bb, F, and Eb instruments).



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