Kramer 904 User Manual

Kramer Electronics, Ltd.

USER MANUAL

Model:

904

Power Amplifier

Contents

1

Introduction 1

2

Getting Started 1

3

Overview 2

4

Your 904 Power Amplifier 2

5

Installing the 904 on a Rack 5

6

Connecting your 904 Power Amplifier 6

7

Technical Specifications 8

Contents

Figures

Figure 1: 904 Power Amplifier – Front and Rear View 3
Figure 2: Connecting the 904 Power Amplifier 7

Tables

Table 1: Features and Functions of the 904 Power Amplifier 4
Table 2: Technical Specifications of the 904 Power Amplifier 8

i

Introduction

1 Introduction

Welcome to Kramer Electronics (since 1981): a world of unique, creative and
affordable solutions to the infinite range of problems that confront the video,
audio and presentation professional on a daily basis. In recent years, we have
redesigned and upgraded most of our line, making the best even better! Our
350-plus different models now appear in 8 Groups1, which are clearly defined
by function.

Congratulations on purchasing your Kramer 904 Power Amplifier. This
product is ideal for:

 Presentation rooms and multimedia applications for quick, local audio

amplification

 Public address systems

The package includes the following items:

 904 Power Amplifier

 Power cord

 This user manual2

2 Getting Started

We recommend that you:

 Unpack the equipment carefully and save the original box and packaging

materials for possible future shipment

 Review the contents of this user manual

 Use Kramer high performance high resolution cables3

1 GROUP 1: Distribution Amplifiers; GROUP 2: Video and Audio Switchers, Matrix Switchers and Controllers; GROUP 3:

Video, Audio, VGA/XGA Processors; GROUP 4: Interfaces and Sync Processors; GROUP 5: Twisted Pair Interfaces;

GROUP 6: Accessories and Rack Adapters; GROUP 7: Scan Converters and Scalers; and GROUP 8: Cables and Connectors

2 Download up-to-date Kramer user manuals from the Internet at this URL: http://www.kramerelectronics.com

3 The complete list of Kramer cables is on our Web site at http://www.kramerelectronics.com

1

Overview

3 Overview

The high performance 904 Power Amplifier is a power amplifier for stereo
audio balanced signals. It can output up to 75 Watts RMS per channel, as it
uses the latest Class “T” technology for highly efficient conversion1 to the
pair of loudspeakers with the absolute minimum power loss.

The 904 includes:

 An OUTPUT LEVEL control knob to adjust the output signal

 OUTPUT LEVEL multi-color LED2 indications for left and right speakers

 Outputs for a headphone set and for a pair of loudspeakers3

 Easy-to-connect detachable terminal block connectors

 A MUTE button to block out the sound

To achieve the best performance:

 Connect only good quality connection cables, thus avoiding interference,

deterioration in signal quality due to poor matching, and elevated noise­levels (often associated with low quality cables)

 Avoid interference from neighboring electrical appliances and position

your Kramer 904 away from moisture, excessive sunlight and dust

4 Your 904 Power Amplifier

Figure 1 and Table 1 define the 904 Power Amplifier.

1 Preventing the 904 from over-heating

2 Green, yellow and red

3 Plugging in the headphone set automatically disconnects the loudspeakers

2

KRAMER: SIMPLE CREATIVE TECHNOLOGY

Your 904 Power Amplifier

Figure 1: 904 Power Amplifier – Front and Rear View

3

Your 904 Power Amplifier

Table 1: Features and Functions of the 904 Power Amplifier

# Feature Function

1 POWER Switch Illuminated switch for turning the unit ON or OFF

LEVEL

3 MUTE ON LED Lights when the MUTE button2 is pressed

4 SPKR OFF LED Lights when the headphone set is inserted, or the MUTE

5 LEVEL Control Knob Adjusts the output signal level

6 MUTE Button Press to block out the sound
7 PHONES connector Connects to the headphone set

8 INPUT (L-L+GR-R+)

Terminal Block

9 SPKR OUT Terminal Block

Connector

10 Power Connector with Fuse AC connector enabling power supply to the unit

LEFT LED output-signal level indication for the LEFT speaker1 2 OUTPUT

RIGHT LED output–signal level indication for the RIGHT speaker1

LED is ON3

Connects the balanced stereo audio input to the audio
source

Connects to a pair of loudspeakers

1 Green for normal output level, yellow for medium output level and red for high output level

2 Lights also when connecting the headphones

3 Also indicates power failure

4

KRAMER: SIMPLE CREATIVE TECHNOLOGY

Installing the 904 on a Rack

5 Installing the 904 on a Rack

This section describes what to do before installing on a rack and how to rack
mount.

Before Installing on a Rack

Before installing on a rack, be sure that the environment is
within the recommended range:

Operating temperature range +5 to +45 Deg. Centigrade

Operating humidity range 5 to 65 % RHL, non-condensing

Storage temperature range -20 to +70 Deg. Centigrade

Storage humidity range 5 to 95% RHL, non-condensing

CAUTION!!

When installing on a 19" rack, avoid hazards by taking
care that:

1 It is located within the recommended environmental

conditions, as the operating ambient temperature of a
closed or multi unit rack assembly may exceed the room
ambient temperature.

2 Once rack mounted, enough air will still flow around the

machine.

3 The machine is placed straight in the correct horizontal

position.

4 You do not overload the circuit(s). When connecting the

machine to the supply circuit, overloading the circuits
might have a detrimental effect on overcurrent
protection and supply wiring. Refer to the appropriate
nameplate ratings for information. For example, for fuse
replacement, see the value printed on the product label.

5 The machine is earthed (grounded) in a reliable way

and is connected only to an electricity socket with
grounding. Pay particular attention to supply
connections other than direct connections to the branch
circuit (for example, the use of power strips), and that
you use only the power cord that is supplied with the
machine.

How to Rack Mount

To rack-mount the machine:

1 Attach both ear brackets to the

machine. To do so, remove the
screws from each side of the
machine (3 on each side), and
replace those screws through
the ear brackets.

2 Place the ears of the machine

against the rack rails, and insert
the proper screws (not
provided) through each of the

four holes in the rack ears.
Note that:

 In some models, the front panel
may feature built-in rack ears

 Detachable rack ears can be
removed for desktop use

 Always mount the machine in the
rack before you attach any cables or
connect the machine to the power

 If you are using a Kramer rack
adapter kit (for a machine that is not
19"), see the Rack Adapters user
manual for installation instructions
(you can download it at:
http://www.kramerelectronics.com)

5

Connecting your 904 Power Amplifier

6 Connecting your 904 Power Amplifier

Connect your 904, as the example in Figure 2 illustrates:

1. Connect a balanced stereo audio source (for example, a line level mixer) to
the Left and Right INPUT terminal block connectors.

2. Connect the SPKR OUT block connector to a pair of loudspeakers, by
connecting the left loudspeaker to the “L+” and the “L-” terminal block
connectors, and the right loudspeaker to the “R+” and the “R-” terminal
block connectors. Do not Ground the loudspeakers.

3. If required, connect the PHONES connector to a headphone set (plugging­in a headphone-set to the PHONES connector will disconnect the
loudspeakers).

4. Connect the power cord1 (not shown in this illustration).

1 We recommend that you use only the power cord that is supplied with this machine

6

KRAMER: SIMPLE CREATIVE TECHNOLOGY

Speakers

Line Level Mixer

Connecting your 904 Power Amplifier

Pair of

Figure 2: Connecting the 904 Power Amplifier

7

Technical Specifications

7 Technical Specifications

Table 2: Technical Specifications1 of the 904 Power Amplifier

INPUTS: 1 balanced stereo on a 5-pin detachable terminal block

OUTPUTS: 1 differential Stereo loudspeakers output on a terminal block;

MAX. OUTPUT LEVEL:

BANDWIDTH: >20 kHz

S/N RATIO: 60dB

CONTROLS: Speakers out: <0 to 30dB;

COUPLING: Input: AC; Speakers out: DC; Headphones out: AC

AUDIO THD + NOISE: Speakers: 0.06%; Headphones: 0.05%
AUDIO 2nd HARMONIC: Speakers: 0.04%; Headphones: 0.007%

OUTPUT POWER: Up to 75 Watts RMS per channel

POWER SOURCE: 253VA, 230VAC

DIMENSIONS: 19” (W ), 7” (D), 1U (H) rack mountable (with ear brackets)

WEIGHT: 2.8kg (6.2lbs.) approx.

ACCESSORIES: Power cord, removable ear brackets and screws for attaching

1 Headphone output

Speakers: 52Vpp on 4 loads
Headphones: 8.4Vpp

Headphones: <-26 to 12dB (level for both)
DC offset adjustment for speakers (internal trimmers)

1 Specifications are subject to change without notice

8

KRAMER: SIMPLE CREATIVE TECHNOLOGY

LIMITED WARRANTY

Kramer Electronics (hereafter Kramer) warrants this product free from defects in material and workmanship under the
following terms.

HOW LONG IS THE WARRANTY

Labor and parts are warranted for seven years from the date of the first customer purchase.

WHO IS PROTECTED?

Only the first purchase customer may enforce this warranty.

WHAT IS COVERED AND WHAT IS NOT COVERED

Except as below, this warranty covers all defe cts in material or workmanship in this product. The following are not covered
by the warranty:

1. Any product which is not distributed by Kramer, or which is not purchased from an aut horized Kra mer dealer. I f yo u are
uncertain as to whether a dealer is authorized, p lease co ntact Kramer at one of the agents listed in the Web s ite
www.kramerelectronics.com.

2. Any product, on which the serial number has been defaced, modified or removed.

3. Damage, deterioration or malfunction resulting from:
i) Accident, misuse, abuse, neglect, fire, water, lightning or other acts of nature
ii) Product modification, or failure to follow instructions supplied w ith the product
iii) Repair or attempted repair by anyone not authorized by Kramer
iv) Any shipment of the product (claims must be presented to the carrier)
v) Removal or installation of the product
vi) Any other cause, which does not relate to a product defect
vii) Cartons, equipment enclosures, cables or accessories used in conjunction with the product

WHAT WE WILL PAY FOR AND WHAT WE WILL NOT PAY FOR

We will pay labor and material expenses for covered items. We will not pay for the following:

1. Removal or installations charges.

2. Costs of initial technical adjustments (set-up), including adjustment of user controls or programming. These costs are the
responsibility of the Kramer dealer from whom the product was purchased.

3. Shipping charges.

HOW YOU CAN GET WARRANTY SERVICE

1. To obtain service on you product, you must take or ship it prepaid to any authorized Kramer service center.

2. Whenever warr anty service is requir ed, the o riginal dated invoice (or a copy) mu st be prese nted as pr oof of warrant y coverage,
and should be included in any shipment of the product. Please also include in any mailing a contact name, company, address, and
a description of the problem(s).

3. For the name of the nearest Kramer authorized service center, consult your authorized dealer.

LIMITATION OF IMPLIED WARRANTIES

All implied warranties, including warranties of merchantability and fitness for a particular purpose, are limited in duration to
the length of this warranty.

EXCLUSION OF DAMAGES

The liability of Kra mer for any effective products is li mited to the repair or replacement of the product at our option. Kramer
shall not be liable for:

1. Damage to other property caused by defects in this pr oduct, damages based upo n inconvenience, loss of use of the pro duct, loss
of time, commercial loss; or:

2. Any other damages, whether incidental, consequential o r otherwise. Some countries may not allow limitat ions on how long an
implied warranty lasts and/or do not allow the exclusion or limitat ion of incidental or consequential da mages, so the above
limitations and exclusions may not apply to you.

This warranty gives you specific legal rights, and you may also have other rights, which vary from place to place.
NOTE: All products returned to Kramer for service must have prior approval. This may be obtained from your dealer.
This equipment has been tested to determine compliance with the requirements of:
EN-50081: "Electromagnetic compatibility (EMC);

EN-50082: "Electromagnetic compatibility (EMC) generic immunity standard.

CFR-47: FCC Rules and Regulations:

CAUTION!

Servicing the machines can only be done by an authorized Kramer technician. Any user who makes changes or modifications to

the unit without the expressed approval of the manufacturer will void user authority to operate the equipment.

Use the supplied DC power supply to feed power to the machine.
Please use recommended interconnection cables to connect the machine to other components.

generic emission standard.
Part 1: Residential, commercial and light industry"

Part 1: Residential, commercial and light industry environment".

Part 15: “Radio frequency devices
Subpart B – Unintentional radiators”

9

For the latest information on our products and a list of Kramer

distributors, visit our Web site: www.kramerelectronics.com,

where updates to this user manual may be found.

We welcome your questions, comments and feedback.

Safety Warning:

Disconnect the unit from the power supply before
opening/servicing.

Caution

Kramer Electronics, Ltd.

Web site: www.kramerelectronics.com

E-mail: [e-mail]

P/N: 2900-000058 REV 1