Peterson AutoStrobe 490 - Manual (Page 5)

Page 3
The first line indicates that the tuner is set for instruments
referenced to the Key of C. Line two indicates that the standard
for A is 440 Hz, the current note setting is "C", and that the global
pitch offset is set at 0 cents

deviation. Line three shows that the
tuner is currently set to automatically detect the nearest standard
pitch present in the audio input and use it as the current note
reference for tuning. The items on line four always indicate the
current function, if any, of the four Function buttons (labeled 1
through 4) directly beneath the LCD display. This is explained in
greater detail later in this manual.
KEY= C
A=440 C 00 ¢
AUTO
SETUP MODE
1 2 3 4
The built-in microphone will pick up an instrument from across a relatively quiet room. However, if you are working in a
noisy environment it may be helpful to use an external microphone (inserted in the EXTERNAL INPUT jack on the front
panel) to be more selective and point the microphone directly at the instrument you wish to tune.
Your AutoStrobe 490 tuner can function in either of two ways: MANual mode or AUTOmatic mode. Unless you choose
to change the default, the tuner will power up in the AUTO mode. In this condition, any strong audio tone input to the built-
in microphone (or EXTERNAL INPUT jack) will be internally analyzed—usually in well under a second—and the standard-
pitched semitone nearest in frequency to that of the input sound will appear on the LCD screen. The motor for the strobe
disc will automatically adjust in speed so that you can view the tuning of this input sound relative to this nearest standard
pitch. Although it is rotating very rapidly, one or more circular bands on the disc will appear to be moving very slowly or
will appear to be standing still. The lowest band exhibiting this effect indicates which octave the audio input signal occupies.
If the rotation appears to be to the left (counter-clockwise), your input sound is flat compared to this nearest standard-pitched
semitone. If the rotation appears to be to the right (clockwise), the input sound is sharp compared to the standard. If the
image appears to be standing still, the input is perfectly in tune with the standard. Furthermore, the slower the disc appears
to be rotating, the closer the input sound is to the standard. This makes for a very simple and natural visual feedback when
bringing an input sound into tune.
To tune to a different note, simply cease the current audio input and sound a different pitch. If the new input is closer to a
different standard-pitched semitone, the tuner will re-analyze the input, indicate this new pitch on the LCD screen, and, once
again, automatically adjust the motor so that the disc will properly indicate the relative tuning of this new input to the nearest
standard-pitched semitone.
NOTE: It is expected that the automatic note selection may not respond well at either extreme of pitch. The unit’s circuitry
is less sensitive at these extremes, and sounds of short duration or with strong, non-harmonic overtones can interfere with
the note detection. Automated note selection at pitch extremes is best optimized by using an external microphone (at the
EXTERNAL INPUT jack on the front panel) and placing it near the sound source. Alternatively, of course, MANual mode
note selection may be chosen to avoid the difficulty entirely.
NOTE: The automatic note detection feature is based on reference tuning of A=440 Hz and Global Cent Offset (which
appears on the second line of the RUN screen) set to 0 cents. Any deviation from these tuning references will limit proper
note sensing to less than the usual ±50 cents range. For most applications, deviations in the range of A430 to A450 or,
separately, up to about ±40 cents Global Cent Offset will yield reasonable results for automatic note selection. Of course,
there are no limitations over the full range of offsets available in the tuner when using MANual note selection.
HINT: When tuning a stringed instrument like a guitar or bass, image clarity and automatic note selection are usually
improved by plucking away from the bridge with a fingertip (as opposed to a fingernail or pick) using medium force. This
minimizes the harmonic (overtone) content of the tone while maximizing the fundamental frequency that is to be tuned.