Sound Devices HX-3 User manual

©2001 Sound Devices, LLC
HX-3 Headphone
Distribution Amplifier
User Guide and Technical Information
™
SOUND DEVICES
Sound Devices, LLC
300 Wengel Drive
Reedsburg, WI 53959 USA
Voice 608.524.0625
Fax [phone]
www.sounddevices.com

HX-3 Headphone Distribution Amplifier
User Guide and Technical Documentation
2
General Description
The HX-3 from Sound Devices is a portable, stereo headphone amplifier
designed for critical audio monitoring. The audiophile-quality headphone
amp is ideal for adding headphone feeds for portable and studio appli-
cations.
The HX-3 provides three independent headphone feeds from balanced
or unbalanced, line sources. Each headphone output has its own level
control, peak LED, and ¼-inch output connector. With its extended
bandwidth and high drive capability the HX-3 can drive headphones of
various impedances to high levels with very low distortion, important for
monitoring in high SPL environments. It is powered from two-AA batter-
ies or external DC.
The HX-3 will provide years of superb audio performance under the
most punishing field conditions.
Features
High Performance Headphone Amplifier
 Three independent headphone outputs with individual gain controls.
 Dynamic range exceeding 120 dB.
 10 Hz to 50 kHz audio bandwidth.
 Capable of driving headphones to high levels with very low distortion.
 Peak indicators show overload of each headphone feed.
 Stereo / mono switch.
Flexible Inputs / Outputs
 Two balanced XLR line level inputs
 Unbalanced ¼-inch and 1/8-inch stereo inputs.
 Loop output to connect additional HX-3s in series for extra headphone outputs.
Flexible Powering
 Internal battery power (two-AA) for convenient, low cost power.
 Excellent battery life >10 hours (nominal drive level with alkaline batteries).
 External 5-17 VDC powering.
Durable Mechanical Construction
 High strength aluminum chassis withstands punishing field conditions.
 Strap loops on each side for easy mounting or wearing.
 Panel-mounted connectors for strength and reliability.
 Easy access battery compartment for quick battery changes.

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©2001 Sound Devices, LLC
www.sounddevices.com
Specifications
Frequency Response: 10 Hz - 50 kHz, +/- 1.0 dB, any input to any output, gain
controls set to 50%
Voltage Gain:
Output Clipping Level: +18 dBu minimum with 600 ohm load
+16 dB minimum with 300 ohm load
Headphone Output
Impedance:
200 ohms
Input Clipping Level: XLR : +24 dBu minimum
1/4-inch and 1/8-inch inputs : +22 dBu minimum
Dynamic Range
(balanced line inputs):
120 dB minimum
THD + Noise: 0.03% maximum
(from 10 Hz to 22 kHz @ +10 dBu input and output level, 300
ohm load, 10 Hz - 22 kHz filter bandwidth)
Inputs: XLR : electronically balanced, 22k ohm input impedance
1/4-inch unbalanced : 9.1k ohm impedance
1/8-inch unbalanced : 9.1k ohm impedance
Note: only one set of inputs (balanced or unbalanced) should
be connected at a time.
Loop Output: Unbalanced, 200 ohm output impedance
Internal Voltage Rails: +15 V and -15 V, regulated
Power:
Internal : 2 AA alkaline batteries, XX hours life typical with nomi-
nal
External: 5 - 17 VDC via threaded coaxial connector (5.5 mm
outer diameter, 2.1 mm inner diameter), pin positive, sleeve
negative. Voltages above 17 VDC cause no damage to unit, but
will open an internal poly fuse. Poly fuse will reset when voltage
is removed.
Power LED: Green indicates power and good battery. Red indicates power
with low batteries. LED turns red when approximately 4 hours of
battery life remain.
Operating
Temperature Range:
0 to 70 degrees C
32 to 160 degrees F
Dimensions: 43 mm x 94 mm x 140 mm (h x w x d)
(1.7" x 3.7" x 5.5")
Weight (unit only): 0.56 kg
1.24 lbs.
Included Accessories 1/4-inch to 1/8-inch Tip-Ring-Sleeve interconnect cable
Rubber feet (4)
Locking DC plug
Gain Loop Out Headphone Output (1,2,3)
Bal. Line -3 dB 34 dB
HP Input -1 dB 35 dB

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HX-3 Headphone Distribution Amplifier
User Guide and Technical Documentation
1. Stereo/Mono Switch
Sums stereo or two-channel inputs to mono for mono headphone
monitoring.
2. Headphone Gain
Controls Volume of each headphone output.
3. Headphone Peak LED
Illuminates 3 dB before clipping to indicate onset of headphone dis-
tortion.
4. POWER LED
Bi-color LED illuminates green when the unit is powered and
changes to red when approximately four hours of battery life
remain.
5. POWER Switch
Powers the unit from either Internal batteries or External DC.
Seamless switchover from each power source.
MONO
STEREO
PEAK PEAKPEAK PEAK POWER
INT EXT
HEADPHONE
AMPLIFIER
Front Panel Controls
234 5
1

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©2001 Sound Devices, LLC
www.sounddevices.com
6. XLR Line Inputs
Line level, electronically-balanced inputs.
7. Loop Output
Output connection enabling interconnection of multiple HX-3s.
Loop Out is Tip-Ring-Sleeve, unbalanced, stereo connection.
Connect to loop input to cascade units.
8. 1/4-inch and 1/8-inch Stereo Inputs
Unbalanced, stereo, Tip-Ring-Sleeve inputs. Connect to output of
another devices headphone output, tape deck output, etc.
9. HEADPHONE OUTPUTS
Panel mounted headphone jack for each output. Output #1
has an 1/8-inch jack in parallel with the 1/4-inch jack.
10. BATTERY Compartment
Requires two AA batteries for operation. Insert positive (+)
end of battery first.
11. DC Input
Locking coaxial DC input accepts voltages from 5 to 17 VDC.
Center pin is positive.
LR
LINE INPUTS
LOOP
OUT
STEREO/LOOP IN
TIP = L
RING = R
SLEEVE = GROUND
5-14 VDC
12
3
HEADPHONE OUTPUTS
Output Panel Connectors
Input Panel Connectors
678
910 11

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HX-3 Headphone Distribution Amplifier
User Guide and Technical Documentation
Operational Notes
Headphone Outputs
Because the HX-3 uses independent drive circuits for each of its three
headphone circuits, headphones of various impedances can be connect-
ed the the HX-3 without interaction. The HX-3 can drive high and low
impedance headphones to loud levels.
 The HX-3 is capable of driving headphones to dangerous
levels. Take precautions to prevent hearing damage.
Powering the HX-3
The HX-3 is designed to operate on two AA alkaline cells for approxi-
mately XX hours into 75 ohm headphones (at nominal levels). The audio
performance of the HX-3 does not vary throughout the life of the batter-
ies.
Several factors affect battery life including - battery chemistry, ambient
temperature of operation, headphone impedances, headphone drive lev-
els, and number of headphones in use. The chart below can be used as
a starting point to estimate battery life. Experimentation is recommended
to determine battery life for each individual setup. Note: Nickel-
Cadmium batteries are not recommended in the HX-3 since these batter-
ies have lower energy per cell than other types and will result in very
short service.
Battery Type Operational Characteristics Battery Life
Duracell AA MN
1500
Powered, idle XX hrs.
Duracell AA MN
1500
Driving single, 75 ohm head-
phones at nominal level
XX hrs.
Duracell AA MN
1500
Driving three, 75 ohm head-
phones at high levels
XX hrs.
(Test conditions: 70 degrees F)

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©2001 Sound Devices, LLC
www.sounddevices.com
Connection Diagrams
The HX-3 can be used in a variety of headphone applications. Below are
a few examples of interconnection setups using the HX-3.
One or more units can be added and “daisy-chained” for additional
headphone feeds from a mixing console. Loop additional HX-3 amplifiers
with the included Link cable.
The headphone outputs of portable audio electronics can be connected
to the the HX-3 for additional headphone feeds. The included 1/4-inch
to 1/8-inch can be used to connect the line-out or headphone output to
the HX-3.
Included 1/4-inch to 1/8-inch Link cable
LR
LINE INPUTS
LOOP
OUT
STEREO/LOOP IN
TIP = L
RING = R
SLEE VE = GROUN D
LR
LINE INPUTS
LOOP
OUT
STEREO/LOOP IN
TIP = L
RING = R
SLEE VE = GROUN D
LR
LINE INPUTS
LOOP
OUT
STEREO/LOOP IN
TIP = L
RING = R
SLEE VE = GROUN D
Mixing
Console
Monitor L
Monitor R
Included 1/4-inch
to 1/8-inch Link
cable

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HX-3 Headphone Distribution Amplifier
User Guide and Technical Documentation
FCC Statement
This device has been tested and found to comply with the limits for a
class B digital device, pursuant to part 15 of the FCC rules. These limits
are designed to provide reasonable protection against harmful interfer-
ence in a residential installation. This equipment generates, uses, and
can radiate radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful interference to
radio communications. However, there is no guarantee that interference
will not occur in a particular installation.
Warranty
Sound Devices, LLC warrants the HX-3 Headphone Distribution Amplifier
against defects in materials and workmanship for a period of ONE (1)
year from date of original retail purchase. This is a non-transferable
warranty that extends only to the original purchaser. Sound Devices,
LLC will repair or replace the product at its discretion at no charge.
Warranty claims due to severe service conditions will be addressed on
an individual basis. THE WARRANTY AND REMEDIES SET FORTH ABOVE
ARE EXCLUSIVE. SOUND DEVICES, LLC DISCLAIMS ALL OTHER WAR-
RANTIES, EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF MER-
CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. SOUND
DEVICES, LLC IS NOT RESPONSIBLE FOR SPECIAL, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES ARISING FROM ANY BREACH OF WARRAN-
TY OR UNDER ANY OTHER LEGAL THEORY. Because some jurisdictions
do not permit the exclusion or limitations set forth above, they may not
apply in all cases.
For all service, including warranty repair, please send the HX-3, along
with proof of purchase date to:
Sound Devices, LLC
Service Repair
300 Wengel Drive
Reedsburg, WI 53959 USA