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PHDA

02 

– REFERENCE CLASS HEADPHONE AMPLIFIER  

1-CHANNEL

SAFETY INFORMATION

1.  Please read these instructions carefully. 
2.  Keep all information and instructions in a safe place. 
3.  Follow the instructions. 
4.  Observe all safety warnings. Never remove safety warnings or other information from the equipment. 
5.  Use the equipment only in the intended manner and for the intended purpose. 
6.  Use only sufficiently stable and compatible stands and/or mounts (for fixed installations). Make cer-

tain that wall mounts are properly installed and secured. Make certain that the equipment is installed 
securely and cannot fall down. 

7.  During installation, observe the applicable safety regulations for your country. 
8.  Never install and operate the equipment near radiators, heat registers, ovens or other sources of heat. 

Make certain that the equipment is always installed so that is cooled sufficiently and cannot overheat. 

9.  Never place sources of ignition, e.g., burning candles, on the equipment. 
10.  Ventilation slits must not be blocked. 
11.  Do not use this equipment in the immediate vicinity of water (does not apply to special outdoor 

equipment - in this case, observe the special instructions noted below. Do not expose this equipment 
to flammable materials, fluids or gases. 

12.  Make certain that dripping or splashed water cannot enter the equipment. Do not place containers 

filled with liquids, such as vases or drinking vessels, on the equipment. 

13.  Make certain that objects cannot fall into the device. 
14.  Use this equipment only with the accessories recommended and intended by the manufacturer. 
15.  Open the device for changing the battery, do not modify this equipment. 
16.  After connecting the equipment, check all cables in order to prevent damage or accidents, e.g., due 

to tripping hazards. 

17.  During transport, make certain that the equipment cannot fall down and possibly cause property 

damage and personal injuries.

18.  If your equipment is no longer functioning properly, if fluids or objects have gotten inside the equip-

ment or if it has been damaged in another way, switch it off immediately and unplug it from the 
mains outlet (if it is a powered device). This equipment may only be repaired by authorized, qualified 
personnel. 

19.  Clean the equipment using a dry cloth. 
20.  Comply with all applicable disposal laws in your country. During disposal of packaging, please sep-

arate plastic and paper/cardboard. 

21.  Plastic bags must be kept out of reach of children.
22.  If the equipment has been exposed to strong fluctuations in temperature (for example, after trans-

port), do not switch it on immediately. Moisture and condensation could damage the equipment. Do 
not switch on the equipment until it has reached room temperature. 

23.  Do not step on the power cord. Make certain that the power cable does not become kinked, especially 

at the mains outlet and/or power adapter and the equipment connector. 

24.  When connecting the equipment, make certain that the power cord or power adapter is always freely 

accessible. Always disconnect the equipment from the power supply if the equipment is not in use 
or if you want to clean the equipment. Always unplug the power cord and power adapter from the 
power outlet at the plug or adapter and not by pulling on the cord. Never touch the power cord and 
power adapter with wet hands. 

25.  To disconnect the equipment from the power mains completely, unplug the power cord or power 

adapter from the power outlet. 

26.  Unplug the power cord and power adapter from the power outlet if there is a risk of a lightning strike 

or before extended periods of disuse.

CAUTION: 

  

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

There are no user serviceable parts inside. Have repairs carried out only by qualified service personnel. 

CAUTION – HIGH VOLUME LEVELS WITH AUDIO PRODUCTS!
This equipment is intended for professional use. Therefore, commercial use of this equipment is subject 
to the respectively applicable national accident prevention rules and regulations. As a manufacturer, Adam 
Hall is obligated to notify you formally about the existence of potential health risks. Hearing damage due to 
high volume and prolonged exposure: When in use, this product is capable of producing high sound-pres-
sure levels (SPL) that can lead to irreversible hearing damage in performers, employees, and audience 
members. For this reason, avoid prolonged exposure to volumes in excess of 90 dB. 

MANUFACTURER’S WARRANTY & LIMITATION OF LIABILITY 

You can find our current warranty conditions and limitation of liability at: http://www.adamhall.com/media/
shop/downloads/documents/manufacturersdeclarations.pdf

To request warranty service for a product, please contact Adam Hall GmbH, Daimler Straße 9, 61267 Neu 
Anspach / Email [email protected] / 49 (0) 6081 / 9419-0

        PROPER DISPOSAL OF THIS PRODUCT 

(WASTE ELECTRICAL AND ELECTRONIC EQUIPMENT) 

(Valid in the European Union and other European countries with waste separation) 
This symbol on the product, or the documents accompanying the product, indicates that this appliance 
may not be treated as household waste. This is to avoid environmental damage or personal injury due 
to uncontrolled waste disposal. Please dispose of this product separately from other waste and have it 
recycled to promote sustainable economic activity.

SCOPE OF APPLICATION

The PHDA02 is a reference class headphones amplifier providing three modes of operation - stereo, 
mono, und dual mono. In Stereo mode, the L/R input signals are fed to the left and right earspeakers while 
the volume level is set by the Stereo/Left control. The front panel inputs allow for simultaneous connection 
of two headphones in parallel. In Mono mode, the left and right channels are summed, and the resulting 
mono signal is fed to both the left and right earspeakers. Again, volume is governed by the Stereo/
Left control. In Dual Mono mode, the left and right channels can be used independently with individual 
level controls for the left and right earspeakers. The PHDA02 is designed for standard headphones with 
impedances from 8 to 600 Ohms. Impedance matching is achieved by a specially designed switchable 
transformer. Uncommon and costly, this solution provides superior performance, dynamic range, and sig-
nal-to-noise ratio at all loads. Combo input sockets provide balanced XLR and unbalanced TS connection 
while parallel XLR outputs enable daisy chaining of multiple units. The PHDA02 features an integrated 
power supply operating with mains from 100VAC to 240VAC, low-noise op amps, and the output amplifi-
ers’ discrete power transistors are mounted on heatsinks. Dimensions are 1U 9.5“.

SETUP AND OPERATION

The standard rules for placement and operating environment apply, i.e. do not use the PHDA02 near 
water or moisture. Protect all cables from being walked on to prevent pinching and tripping. Although the 
PHDA02 does not generate significant amounts of heat it should not be operated close to heat producing 
equipment. Use the included IEC power cord for mains connection. Keep the unit switched off while mak-
ing all connections to prevent noise (the mains indicator LED next to the power switch does not illuminate).
Combo sockets allow for balanced and unbalanced input. For connecting balanced outputs to INPUT-L and 
INPUT-R use microphone cable, for unbalanced connection use instrument cable. To connect consumer
equipment with RCA (cinch) outputs to the PHDA02 use RCA cable with RCA-to-6.3mm TS adapters. High
quality shielded cable should be used in all applications. Input sensitivity ranges from instrument to pro-
fessional studio levels with plenty of headroom. Use the LINK OUT sockets to insert the PHDA02 between 
two devices for monitoring, or daisy chaining multiple units. NOTE: unbalanced input results in unbalanced 
LINK output, i.e. if a TS jack is connected to the combo input PINS 3 and 1 of the corresponding XLR LINK 
output are bridged. The ground lift switch between the link sockets has been provided to eliminate ground 
loops. In the UP position PIN 1 is ungrounded, engaging the switch (DOWN position) connects PIN 1 to 
ground. Let yout ears be the judge and keep the switch in the position that causes the least interference..
The PHDA02 features front panel TRS connectors for simultaneous connection of two (stereo) head-
phones. For best results the headphones should have similar impedances and sensitivity. Common im-
pedances range from 8 Ohms to 600 Ohms. The PHDA02’s output is switchable for optimum matching 
and dynamic range. Select the 8 Ohm position (UP) for headphones with impedances from 8 to 60 Ohms, 
for headphones with higher impedances select the 200 Ohm setting (DOWN). The PHDA02’s standard 
mode of operation is stereo with the amplified LEFT/RIGHT input signals present at the headphone outputs 
while the STEREO/LEFT control governs playback volume. To verify the mono compatibility of a stereo 
signal or listen to a mono input signal engage the STEREO MONO switch. In DUALMONO mode, the 
headphone outputs are switched to mono (tip and ring of the 6.3mm connector are bridged). Also, the left 
input is assigned to the left headphone output while the right input is assigned to the headphone output 
on the right to enable independent, simultaneous listening to the mono signals with two headphones. 
The left and right side volumes are governed by the STEREO/LEFT and RIGHT controls. Engaging the 
STEREO/MONO switch (DOWN position) mixes both mono input signals while the mix is present at both 
headphone outputs.

TECHNICAL SPECIFICATIONS

Product type:

Headphone Amp:

Type:

1-channel

Inputs:

2

Input connectors:

6.3 mm Jack, XLR

Input impedance:

(balanced) 20 k, (unbalanced) 10 k Ohm(s)

Outputs:

2

Output connectors:

XLR, 6.3 mm Jack

Power output:

2 x 400 mW

Minimum connected impedance:

2 x 8 Ohm(s)

Frequency response:

20 - 20000 Hz

Controls:

volume

Indicators:

on

Operating voltage:

integrated (115 / 230 V)

Operating voltage:

240 V AC / 50 - 60 Hz

Cabinet material:

sheet steel/aluminium

Cabinet surface:

powder coated/anodized

Width:

222 mm

Height:

44 mm

Depth:

175 mm

Weight:

1.58 kg

© Palmer Musical Instruments, Adam Hall GmbH, D-61267 Neu-Anspach, Daimlerstr. 9, Germany TEL: ++49 (0)6081 94190

FAX: ++49 (0)6081 43280 WEB: www.adamhall.com, www.palmer-germany.com EMAIL: [email protected]

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