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Thank you, and congratulations on your choice of the BOSS TU-15 Chromatic Tuner.
Before using this unit, carefully read the sections entitled: “USING THE UNIT SAFELY” and
“IMPORTANT NOTES” (separate sheet). 
These sections provide important information concerning the proper operation of the unit.
Additionally, in order to feel assured that you have gained a good grasp of every feature provided
by your new unit, this manual should be read in its entirety. The manual should be saved and kept
on hand as a convenient reference. 

 

As shipped, the TU-15’s batteries are not yet installed. Be sure to read “Changing the
Batteries” and then follow the instructions to install the batteries.

Copyright © 2002 BOSS CORPORATION
All rights reserved. No part of this publication may be reproduced in any form without the
written permission of BOSS CORPORATION.

 

 

Features

 

 

Backlit meter

 

 allows tuning even in dark environments.

• Also features an “

 

AUTO mode

 

,” which automatically determines the note name or string

number, and a “

 

MANUAL mode

 

,” where you can specify note names and string numbers

(which comes in handy after you’ve restrung your instrument).

• Includes “

 

CHROMATIC mode

 

,” which permits tuning to any of the twelve semitone steps by

note name over the entire chromatic scale, and a “

 

GUITAR/BASS mode

 

” for tuning to guitar

and bass string numbers.

• Compatible with seven-string guitars and six-string basses.
• Includes a 

 

Flat Tuning

 

 function, which lowers all pitches from one semitone to five semitones

(two and a half steps).

 

Open Tuning

 

  function makes it easy to achieve DROP D, OPEN D/E/G/A, and DADGAD

tunings.

 

OCTAVE ADJUST mode

 

 makes the octave adjustments required to maintain the correct pitch

when playing the frets.

 

SOUND mode

 

 plays the reference tone.

 

Accu-Pitch

 

 function produces a beeping tone to signal that the tuning is correct.

• AC adaptor jack for use with AC adaptor.

 

Auto Power Off

 

 function helps prevent battery drain (only when batteries are used).

 

 

Panel Descriptions

 

 

Display

 

 

Note About AUTO and MANUAL Modes

 

Normally, you will be using “

 

AUTO mode

 

,” in which note names and string numbers are

indicated automatically.
However, after restringing an instrument, or when using the 

 

Open Tuning

 

  function, it is more

convenient to use “

 

MANUAL mode

 

,” in which you specify the note names and string numbers

using the 

 

[NOTE] button

 

 in advance.

Pressing the 

 

[AUTO/MANUAL] button

 

  toggles the mode between “

 

AUTO

 

” and “

 

MANU

 

.” The

current mode is indicated in the display. 

 

 

Regarding CHROMATIC and GUITAR/BASS Modes

 

 

How to Use the Tuner

 

1.

 

Connect the instrument to be tuned to the INPUT jack.
The built-in mic is used for tuning acoustic instruments. When using the mic, make sure that
nothing is connected to the INPUT or OUTPUT jacks, and place the TU-15 near the instrument.

 

*

To prevent malfunction and/or damage to speakers or other devices, always turn down the volume, and
turn off the power on all devices before making any connections.

 

2.

 

Slide the POWER switch to [ON]. 
The reference pitch is indicated in the display.
To change the reference pitch, press the 

 

[PITCH] button

 

 one or more times until the pitch you

want to set as the reference pitch appears in the display (the factory default setting is 440 Hz).
If the power has been turned off by the 

 

Auto Power Off

 

 function, slide the POWER switch to

[OFF], then to [ON] again.

 

3.

 

Switch to 

 

AUTO mode

 

.

Normally, “

 

AUTO mode

 

” is used. In this mode, note names and string numbers are indicated

automatically.
If “

 

MANU

 

” appears in the display, press the 

 

[AUTO/MANUAL] button

 

  so that “

 

AUTO

 

” is

shown.

 

4.

 

Play a single note on the instrument.
The note name/string number for the note that is playing appears in the display. 
The meter and Tuning Guide show how far the note is from the correct pitch.

 

5.

 

Tune the instrument.
With the intended note name/string number appearing in the display, tune the instrument so
that both “ ” and “ ” of the Tuning Guide are lit, and the meter needle points to 0 (center
position).
When a stable pitch is achieved, the tuner makes a beeping sound, informing you that the
tuning is completed (with the 

 

Accu-Pitch

 

 function).

 

 

Flat Tuning

 

This lowers the actual pitch of all notes below the regular tuning (from one to five semitones, or
two and a half steps), and can be accomplished simply without changing the regular display.
Press the 

 

[FLAT] button

 

  and select the number of semitones the actual pitch is to be lowered

relative to the note appearing in the display.
No flat symbols appear when regular tuning is selected; “ ” indicates the pitch is lower by one
semitone, “

” a whole tone, and so on, with “

” marks indicating a drop of five semitones.

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CENT

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0

Meter & Display

[GUITAR/BASS] Button

[CHROMATIC] Button

[SOUND] 
Button

Power Switch [POWER]

Switches the power on and off.
Whenever the TU-15 has remained totally idle for 
approximately thirty minutes, while running on battery 
power, the power is automatically switched off.
To turn the power back on, first slide the POWER switch to 
[OFF], then to [ON] again.

Backlight Switch [LIGHT]

Switches the backlighting on 
and off.

Speaker

AC Adaptor Jack

Connect the AC adaptor (the optional 
BOSS PSA series) here.

OUTPUT Jack

The signal of the instrument connected to the INPUT jack is output 
from this jack. The tuner’s circuitry is completely bypassed once you 
place the POWER switch at the OFF position, so your instrument’s 
signal is output without any change in the tone quality.

INPUT Jack

Connect the guitar, bass guitar, or other 
instrument to be tuned here.

[PITCH] Button
[AUTO/MANUAL] Button
[NOTE] Button

[FLAT] Button
[OPEN TUNING] Button
[OCT ADJ] Button

MIC

Use this when tuning acoustic instruments.
Position the mic as closely as possible to the instrument.
Do not connect anything to the INPUT or OUTPUT jacks when 
using the mic.

 

Mode

Description

Operation

Displayed

CHROMATIC

 

Allows tuning any of the twelve
pitches in the chromatic scale.

Press the

 

 [CHROMATIC] button

 

.

The tone name and octave
are displayed.

 

GUITAR

 

Allows tuning by guitar string
number.

Press the

 

 [GUITAR/BASS] 

button

 

 one or more times until 

 

GUITAR

 

” is lit.

 

GUITAR

 

” lights up, and

the string number and
tone name are displayed.

 

BASS

 

Allows tuning by bass guitar
string number.

Press the

 

 [GUITAR/BASS] 

button

 

 one or more times until 

 

BASS

 

” is lit.

 

BASS

 

” lights up, and

the string number and
tone name are displayed.

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CENT

CENT

-50

0

Tuning Guide

The tuning indicator lights to show how close 
you are to the target pitch.
When “  ” lights: pitch is flat (low)
When “  ” lights: pitch is sharp (high)
When “  ” and “  ” light: in tune (

±

3 cents)

Meter

This shows the 

difference in pitch from 

the indicated note 

name or string number.

Backlight Indicator

“   ” lights when the 
backlight is on.

Batteries Low Warning 
Indicator

“   ” is normally off, but 
flashes when the batteries 
begins to run low. Replace 
batteries promptly when 
you see this indicator 
flashing.

Note Name/String Number 
Indicator

In CHROMATIC mode, this 
indicates the “note name” and 
“octave”; in GUITAR/BASS 
mode, it indicates the “string 
number” and “note name.”

OCTAVE ADJUST 
Mode Indicator

OCT ADJ

” lights up 

when the OCTAVE 
ADJUST mode is on.

FLAT TUNING Indicator

 REFERENCE PITCH

Indicator

AUTO/MANUAL Mode Indicator

OPEN TUNING Indicator

GUITAR/BASS Mode Indicator

 

 

Open Tuning

 

You can tune by string number not only with normal OPEN D/E/G/A, but with six kinds of open
tuning, from the often-used DROP D to DADGAD.
After switching to

 

 GUITAR/BASS mode

 

, press the 

 

[OPEN TUNING] button

 

 to select the type of

tuning you want to set.

 

In GUITAR Mode

In BASS Mode

 

 

Tuning While Listening to the Reference Tone 
(SOUND Mode)

 

The built-in speaker plays the reference tone.
In 

 

CHROMATIC mode

 

, you can play any of the twelve notes in the chromatic scale.

In 

 

GUITAR/BASS mode

 

, pitches corresponding to the open strings are played.

 

1.

 

First select the type of tuning you want to use (e.g., Chromatic, Guitar, Bass, Flat, or Open
Tuning).

 

2.

 

Press the 

 

[SOUND] button

 

.

 

3.

 

Press the 

 

[NOTE] button

 

 to display the note name or string number you want to tune.

 

4.

 

Tune the instrument to the reference tone.

 

5.

 

Press the 

 

[SOUND] button

 

 to stop playing the reference sound.

 

 

OCTAVE ADJUST Mode

 

To ensure that the correct pitch is played when you press the strings against the guitar frets,
Octave Adjust is required.
The TU-15 features an 

 

OCTAVE ADJUST mode

 

, which indicates whether you need to shift the

bridge up or down when the sound of the open string and the sound with the string pressed at the
twelfth fret are played. 
This function allows you to make octave adjustments quickly and easily.

 

1.

 

First tune the instrument in 

 

GUITAR/BASS mode

 

.

 

2.

 

Press the 

 

[OCT ADJ] button

 

.

The “

 

OCT ADJ

 

” in the display lights up, and the tuner switches to 

 

GUITAR

 

 or 

 

BASS mode

 

.

In 

 

MANUAL mode

 

, you can select the string to adjust by pressing the 

 

[NOTE] button

 

.

 

3.

 

Play an open string.
When the pitch stabilizes, “

 

OF

 

” lights up.

 

4.

 

Next, play the same string while holding it down at the twelfth fret.
When a stable pitch is obtained, “

 

12 F

 

” lights up, and the meter indicates the direction in

which the bridge should be shifted.
If the needle moves to the left side (the   side), shift the bridge toward the neck; if the needle
moves to the right side (the   side), shift the bridge away from the neck.

 

*

For instructions on moving the bridge, refer to the owner’s manual that came with your guitar.

 

5.

 

After shifting the bridge, repeat Steps 3 and 4.
This adjustment is complete when the meter is at 0 (center) while “

 

12 F

 

” is lit.

 

6.

 

When you have finished adjusting all of the strings, press the 

 

[OCT ADJ] button

 

  to exit

 

OCTAVE ADJUST mode

 

.

 

 

Changing the Reference Pitch

 

The frequency for A4 (Middle A on the piano) for an instrument (such as the piano) whose pitch
other instruments are tuned to is called the “reference pitch.”

The current reference pitch is indicated when you turn on the TU-15.
The reference pitch changes by 1 Hz each time you press the 

 

[PITCH] button

 

.

You can adjust the reference pitch to any value from A=430 Hz to A=449 HZ.

 

*

The factory default setting is A=440 Hz.

 

 

Preventing Battery Drain When Running on Batteries 
(Auto Power Off Function)

 

The TU-15 features an 

 

Auto Power Off

 

 function that helps prevent the batteries from going dead if

you forget to switch off the unit when using battery power.
After the TU-15 is turned on, if approximately thirty minutes passes without any button being
pushed or a tuning sound being input, the power is then turned off automatically.
To turn on the power after it has been turned off by the 

 

Auto Power Off

 

 function, first slide the

POWER switch to OFF, then slide it to ON once more.

 

*

The 

 

Auto Power Off

 

 function is turned on at the factory.

 

You can turn the 

 

Auto Power Off

 

 function on and off. Use the following procedure to switch the

setting to the opposite of the current setting.

 

1.

 

Turn the POWER switch to OFF.

 

2.

 

Hold down the 

 

[PITCH] button

 

, the 

 

[AUTO/MANUAL] button

 

, and the 

 

[NOTE] button

 

  and

slide the POWER switch to ON.
The 

 

Auto Power Off

 

  setting is switched, and the current ON/OFF status is indicated in the

display for approximately five seconds.

Afterwards, the indicators and operations work as usual, and you can then proceed to use the
tuner.

 

*

The 

 

Auto Power Off

 

 setting remains stored even after the power is turned off.

 

 

Using a Tone to Indicate Tuning is Completed 
(Accu-Pitch Function)

 

The TU-15 includes a “

 

Accu-Pitch

 

” function. This function plays a beeping sound when the pitch

stabilizes within a range of three cents above or below the correct pitch. The beeping sound that
tells you that a string is precisely in tune will have the pitch of a note from C6 to B6, depending on
the string being tuned. 

 

*

The Accu-Pitch function is turned on at the factory.

 

You can turn the 

 

Accu-Pitch

 

 function on and off. Use the following procedure to switch the setting

to the opposite of the current setting.

 

1.

 

Turn the POWER switch to OFF.

 

2.

 

Hold down the 

 

[SOUND] button

 

 and slide the POWER switch to ON.

The 

 

Accu-Pitch

 

 setting is switched, and the current ON/OFF status is indicated in the display

for approximately five seconds.

Afterwards, the indicators and operations work as usual, and you can then proceed to use the
tuner.

 

*

The 

 

Accu-Pitch

 

 setting remains stored even after the power is turned off.

 

 

Memory Functions

 

Once batteries are installed in the TU-15, a number of different settings can be stored in memory,
where they’ll be preserved even while the power is turned off. 
The settings stored in memory are listed below.
• Reference Pitch
• AUTO/MANUAL Mode
• Note Names/String Numbers in MANUAL Mode and SOUND Mode
• CHROMATIC/GUITAR/BASS Mode
• Flat Tuning Settings
• Open Tuning Settings
• Auto Sound Off Setting
• Accu-Pitch Setting

 

 

Changing the Batteries

 

A “batteries low” warning flashes in the display when the batteries begin to go dead. 
Replace the batteries as soon as possible. 

 

*

The settings stored by the memory function are reset to the default factory settings if the batteries are
removed from the tuner, or if the batteries get completely depleted. (However, the stored settings are
preserved if the TU-15 remains connected to an electrical outlet with the AC adaptor.)

 

1.

 

Press down and slide off the lid of the batteries
compartment (located on the bottom of the
unit).

 

2.

 

Remove the old batteries from the 
compartment.

 

3.

 

Insert two of the same type of fresh AA 
batteries.

 

*

Make sure the “+” and “-” ends of the batteries are
oriented correctly.

 

4.

 

Slide the lid back into place.

 

*

Do not mix fresh batteries with used ones, or mix batteries of different types. Doing so can result in fluid
leakage.

 

 

Calibrating the Meter’s Needle

 

Over time, or as the result of being knocked around, the meter needle may drift away from the 0
position. If this occurs, you can recalibrate the needle using the following procedure.

 

*

Normally, the needle almost never goes off center. Adjust the needle only in the event that it has shifted
from the 0 position.

 

1.

 

Hold down the 

 

[PITCH] button

 

 and turn the power on.

Confirm whether or not the needle is pointing at the 0 position.

 

2.

 

If the needle is not pointing to 0, then while holding down the 

 

[PITCH] button

 

, turn the

adjustment screw with a small, precision, flathead screwdriver (approx. 1.2 mm) until the
needle points to 0.

 

3.

 

Release the 

 

[PITCH] button

 

 to return the tuner to normal operation. 

 

*

Do not use any other tool than a small flathead screwdriver to make this adjustment, and do not use
undue force. Failure to observe these precautions may result in damage to the unit.

 

 

Main Specifications

 

Reference Pitch:

A4=430 Hz–449 Hz (1 Hz step)

Tuning Range:

E0 (20.6 Hz)–C8 (4186.0 Hz)

Tuning Accuracy:

± 1 cent

Input Impedance:

10 M

 

 

Indicator:

Meter, LCD Display

Speaker: 

36 mm x 1 dynamic type

Connectors:

Input Jack, Output Jack, AC Adaptor Jack

Power Supply

Dry Battery (R6/LR6 (AA) Type) x 2; DC 3 V, AC Adaptor DC 9 V (PSA
series; optional)

Power Consumption

15 mA (backlit off and SOUND mode off), 
55 mA (backlit on and SOUND mode on)

Expected battery life under continuous use (Carbon):

Approximately 45 hours (backlit off, SOUND mode off and A4
continuous input), 
Approximately 15 hours (backlit on and SOUND mode on)
* These figures will vary depending on the actual conditions of use.

Dimensions:

149 (W) x 58 (D) x 40 (H) mm /
5-7/8 (W) x 2-5/16 (D) x 1-5/8 (H) inches

Weight

190 g (including batteries) / 7 oz

Accessories

Dry Battery (R6 (AA) Type) x 2, Owner’s Manual, 
Leaflet (“USING THE UNIT SAFELY” and “IMPORTANT NOTES” ),
Information (sepalate sheet)

Option: 

AC Adaptor (PSA series)

 

*

In the interest of product improvement, the specifications and/or appearance of this unit are subject to
change without prior notice.

 

Type

Open Tuning Indicator

Regular

 

Not Displayed

 

OPEN D

OPEN E

OPEN G

OPEN A

DROP D

DADGAD

Type

Open Tuning Indicator

Regular

 

Not Displayed

 

DROP D

+50

-50

0

+50

-50

0

Auto Power Off Function ON

Auto Power Off Function OFF

+50

-50

0

+50

-50

0

Accu-Pitch Function ON

Accu-Pitch Function OFF

+ -

Meter Adjustment
Control

Owner’s Manual

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