Practical Devices XM4 Manuel utilisateur

XM4

Headphone Amplifier

User’s Manual

Thank ou, and congratulations on our purchase of the XM4 Portable

Headphone Amplifier!

We’ve worked ver hard to provide ou with what ma be one of

the most advanced, feature packed, and best sounding headphone

amplifiers on the market toda . The XM4 is designed to be durable, flexible,

eas to use, practical, and above all, sound great. Each unit is carefull

manufactured, and then rigorousl tested for performance, durabilit , and

sound qualit .

If ou have an questions that are not answered b this manual,

please feel free to send us an email. Enjo the amp!

Yours trul ,

James Forest

President & CEO

A Word About Protecting Your Hearing

The most

valuable piece of audio equipment ou own are our ears. Smart people protect

their hearing. When using the XM4, or an headphones, get in the habit of

removing the headphones from your ears whenever ou:

•

Turn the XM4 on;

•

Connect or disconnect an cables,

•

Do ANYTHING that ma cause a sudden burst of loud sound.

Your onl have one set of ears, and ou can’t replace them. Never listen at

excessive volume. Always listen to music at reasonable volume, and most

importantl , use good common sense.

PLEASE

READ!

XM4 Block Diagram ....................4

Connecting Your XM4 .................5

Power Button Functions ..............6

Crossfeed Controls......................7

Disassembling the Unit................8

Replacing the Batter ..................9

Gain Boost Jumpers ..................10

Lithium Batter Charger.............11

External Power Suppl ..............12

Testing the Batter ....................13

Frequentl -Asked Questions .....14

Troubleshooting.........................15

Warrant and Guarantee ...........17

Technical Specifications ............18

Table of Contents

Output

Connect to

Headphones

Po er Button

Press button:

1 time = Turn on power for 1 hour

3 times = Turn on power for 3 hours

6 times = Turn on power for 6 hours

7 times = Turn on power forever

2 times = Toggle flashlight mode

5 times = Toggle dimming of blue LED

Press and HOLD to turn unit off.

Press once to displa batter voltage. For

example, if batter is at 8.5 volts, the amber

LED will flash 8, then 5 times. Input

Connect to MP3 pla er

or other audio source.

Main Volume

Amber LED

Flashes batter voltage when Power Button

is pressed.

Flashes a one-flash warning when the batter

is low (below 6.5 volts). Flashes a two-flash

warning when the batter is ver low (below

5.2 volts).

Blue LED

Indicates

power is on

Crossfeed Enable S itch

IN position: Crossfeed enabled.

OUT position: Crossfeed disabled.

Crossfeed Adjuster

Turn this potentiometer to

adjust the amount of

Crossfeed, from near-stereo

to 100% mono.

This onl has an effect when

the Crossfeed Enable Switch

is in the IN position.

Po er Connector

“Barrel” connector with 1.3mm

center pin. Center pin must be

positive.

Used to power and recharge

the XM4.

Battery Charger

Jumpers

Change these onl if ou

want to use a NiMH

batter . See Users

Manual Pages 12 and 13

XM4 Block Diagram

Gold-Plated Amp Chip Socket

Allows for future amp chip

upgrades and modifications for

those who like to experiment.

Gain Boost Jumpers

Jumpers installed: = +10db extra boost

Jumpers not installed: = +0db extra boost

Bass +6dB

Connecting Your XM4

1. Connect a suitable source to the input jack, as

pictured. Sources ma be MP3 or CD pla ers, iPods,

or an line-level devices.

2. Connect our headphones to the output jack.

Your headphones can have an impedance of 24 to 600 ohms.

The power button functions are activated b pressing repeatedl

within a three second window:

1 press: Turn unit on. The XM4 turns off

automaticall after one hour.

3 presses: Turn unit on for three hours.

6 presses: Turn unit on for six hours.

7 presses: Turn unit on. The XM4 will not turn itself off.

Press and hold: Turn unit off.

The unit will respond to button presses by flashing the

blue LE once for each hour it will stay on.

Additional po er button functions:

2 presses: Toggle flashlight mode.

5 presses: Toggle LED dimming.

Power button

Po er Button Functions

CrossFeed Controls

The XM4’s Crossfeed circuit simulates the sound stage of

loudspeakers, through our headphones.

•

Press the Switch IN to activate Crossfeed.

•

Leave the button OUT for full stereo operation,

b passing the Crossfeed circuit entirel .

Use a small screwdriver (Philips or Straightblade) to adjust

the Crossfeed Potentiometer:

•

All the wa clockwise to produce a mono signal;

•

All the wa counter-clockwise to produce a near-

stereo image.

Crossfeed Adjuster Crossfeed Enable Switch

Wh would ou want Crossfeed?

Most music is mixed to be

listened to on loudspeakers. The studio technicians mixing the recording

assume there will be alot of crosstalk, since with speakers the listener's left ear

clearl hears the right speaker's output, and vice versa. Thus, most music is mixed

with a ver wide stereo soundstage.

With headphones, however, the left ear onl hears the left channel, and the right ear

onl hears the right channel, with nearl zero crosstalk. This can, for man recordings,

cause the soundstage to appear to be "in the center of our head". Further, some

recordings (earl Beatles recordings are infamous for this) have each instrument and

vocal track panned 100% to either left or right, which can almost immediatel cause

listener fatigue. Crossfeed corrects this b bleeding some of the left channel into the

right, and vice-versa.

To re-assemble the unit:

1. Slide the unit back together

(make sure the circuit board

slides smoothly on the case's

guide rails)

2. Re-install the two screws. Do

not overtighten.

3. Re-install the batter and rear

panel.

Disassembling the Unit

Remove

t o scre s,

and push

circuitboard

from rear.

Help! I think I stripped the scre s

hen I tightened them! No, ou

didn’t. You can gentl pinch the case’s

screw receptacles with a pair of pliers,

as shown, to tighten things up.

If you need to change the Gain Boost Jumpers or Battery

Charger Jumper, you ill need to disassemble the unit.

Here's ho :

Note: there is a

notch in the case.

Make sure the case

is oriented so the

notch lines up with

the pushbutton, as

shown.

1. Turn the unit off, and remove the external

power adapter if connected.

2. Remove the rear panel using a Phillips

screwdriver. Remove the batter .

3. Remove the two screws on the front panel

(use the included 5/64” allen ke ). Note: ou

do NOT need to remove the volume knob!

4. From the rear, push the circuitboard out the

front of the case.

Replacing the Battery

Replace the batter b removing the rear panel, using a Philips

screwdriver.

•

Connect the batter clip to the new batter

•

Insert the batter clip-first into the XM4

•

The batter should not protrude out of the rear of the unit (if it

does protrude, ou won’t be able to completel screw down the

rear panel. Check that the batter cable hasn’t prevented the

batter from being pushed in completel ).

If the batter cable has become entangled, ou ma need to

disassemble the unit as shown on page 8.

With the volume knob at full, our XM4 will

deliver +13dB of gain. Additionall , ou can

install the Gain Boost jumpers, which will give

ou an extra +10dB of gain, for a total of

+23dB.

In order to get the best possible noise floor,

ou should not install the Gain Boost jumpers

unless: a) the volume of our headphones is

too quiet, and, b) ou have alread tried turning up the volume of our

Gain Boost Jumpers

Usuall , the Gain Boost jumpers are onl needed when using

headphones which have an impedance greater than around 150

To install or remove the Gain Boost jumpers:

1. Disassemble the unit (see page 8)

2. To install the jumpers, place a jumper of each pair of riser pins.

(Hint: if ou are removing the jumpers, place each jumper over

one pin only, so ou don't lose them).

3. Re-assemble the unit.

Jumpers are installed.

Gain boost is +10dB

Jumpers are removed.

Gain boost is disabled.

Jumpers are removed, but

are placed over a single

pin so the don’t get lost.

Gain boost is disabled.

Gain Boost

Jumpers

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