Practical Devices XM4 Bedienungsanleitung
XM4
Headphone Amplifier
User’s Manual
©2007 Practical Devices Corporation. All rights reserved.
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
3
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
4
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.
5
6
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.
7
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.
8
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.
9
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
10
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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