B&K 7250 User Manual

600.39 Kb

Reference 7250/7260

series II

Five/Six Channel Amplifier


B & K Components Ltd.

P/N 13007 Rev.0004

B&K Components, Ltd 2100 Old Union Road Buffalo, New York 14227

P/N 13007 Rev.0004

Table of contents

Safety Precautions

page 2

Purpose and function

page 3

Design and construction

page 3


page 3

Rear panel view

page 4

Rear panel description

page 4 - 6

Level controls

page 5


page 5 - 6


page 6

Control Muting

page 8 - 9

System installation

page 7

Making the connection

page 7 - 8


page 10

Care and cleaning

page 10


page 11


page 12

Accessories included: Manual and Power cord


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The lightning flash with arrowhead, within an equilateral triangle, is intended to alert the user of the presence of uninsulated “dangerous voltage” within the product’s enclosure that may be sufficient magnitude to constitute a risk of electric shock to you.

The exclamation point within an equilateral triangle is intended to alert the user of the presence of important operating and maintenance (servicing) instructions in the literature accompanying the unit.

ŸObservance of polarity is essential. Double-checkconnections before turning the amplifier on. The amplifier can be damaged if polarities are incorrect.

ŸDamage can occur to your speakers if the power rating* of each individual driver is exceeded by the amplifier. Make sure that all the drivers in your speaker system are capable of handling not only the power being delivered by the amplifier, but the energy that is likely to be generated during strong passages.

ŸTurn amplifier ‘off’ before plugging in or unplugging input and speaker cables!!!

ŸThe Reference 7250/7260 series II is equipped with raised feet so that continuous ventilation can be maintained. They help to keep acoustic feedback into the amplifier at a minimum. They also provide a measure of protection against scratching any surface the unit might be resting on. Do not alter or remove them.

ŸDo not stack anything on top of the amplifier (preamplifier, processor, source...etc.).

ŸLeave at least 2-3inches clearance from the top of the amplifier to the next shelf, component, etc., to insure proper ventilation.

*If you are at all unsure of what the speaker ‘ratings’ are, contact your dealer.

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The Reference 7250/7260 series II purpose and function

The Reference 7250/7260 series II is a high current, five/six channel power amplifier. It is designed to be used in all types of audio or audio/video systems.

Design and construction

The Reference 7250/7260 series II utilizes high quality electronic circuitry to achieve an environment wherein a detailed, transparent, and highly musical sound can be realized. The high quality parts complement includes state-of-the-artsolid state devices, 1% metal film resistors, computer grade electrolytic power supply capacitors, and a high capacity toroidal transformer.

The Reference 7250/7260 series II operates class A predriver and AB high current

MOSFET power output stages. It is capable of reproducing the most demanding audio signals at rated power levels.



Toroidal Transformers -

Efficient, high current, shielded transformer.

Discrete Circuitry -

More accurate and three dimensional reproduction of


source material.

Class A Predriver -

Improves low level detail for smoother, more musical



AB MOSFET Output Stage - For efficient linear power delivery and protection from


thermal overload

Gold Plated Connectors -

Improved connections for better sound and minimized


signal loss and degradation.

1% Metal Film Resistors -

Low noise resistors for better sound and a greater


degree of repeatability.

High Current -

Ability to reproduce demanding recordings.

Computer Grade Capacitors - Large capacity computer grade electrolytic capacitors for extended low frequency control and improved dynamics.

Fused Outputs -

Provides protection from accidental shorting of amplifier



Heavy Duty Binding Posts - Improved current carrying capacity and ease of use.

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Rear Panel View
































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































AC fuse holder


Amplifier control muting input/output


AC Input receptacle


Level controls


Speaker outputs

































Speaker fuses

Rear panel description

1. AC fuse holder - Holds the AC Line fuse. This fuse is a 15 Amp / 250 Volt

Slow Blow fuse. Replace with same type and value fuse only.

2.AC Input receptacle - For attaching the supplied AC power cord to the amplifier.

3.Speaker outputs - For connecting the speakers to the amplifier. Explained further

on page 6.

4. Amplifier control muting input/output -

To provide remote switching of mute on/off of the amplifier.

Explained further on pages (8 - 9).

5. Level controls -

For adjusting the input level of each channel into the amplifier.


There are five/six level controls on the back of the amplifier.


One level control for each channel.

6. Inputs -

For connecting signal patch cables (interconnects) from the


preamplifier to the amplifier to pass signal. Pages (5 - 6).

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7. Speaker Fuses - Protection against amplifier damage in the case of shorted speaker wires. Replace fuse with same value 6 AMP SLOW BLOW only!


Level controls

When using the level controls, first start with them turned all the way up (clockwise). Then adjust them according to your system requirements to match the sound level coming from each speaker. This is a rough adjustment for matching different driver impedances. Any fine tuning should be done by the preamplifier

Example: When using 4 ohm and 8 ohm speakers together, the 4 ohm may sound louder than the 8 ohm at a given volume level. The level controls on the amplifier are used to match the speakers volume levels. Clockwise will increase the output. Counter Clockwise will decrease the output.


RCA type connectors accept line inputs from the preamplifier’s output connectors. There are five/six input connectors, one for each channel, that may be used to connect the amplifier to the preamplifier.

RCA cable connector

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Here is a typical preamplifier to amplifier setup:


Five way binding posts are provided. One pair for each channel. They are designed to accept a banana-typeplug or spade lug connector (shown below) and are color coded for easy identification. The positive (+) post should always be connected to the speakers (+) jack. The negative(-)post should always be connected to the speakers(-)jack.

Spade connector Banana jack

Here is a typical amplifier output setup:











































































































































































































































































































































































































































































































































































































































































































































































































































































































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System Installation

There will most likely be a number of cables involved in the installation of your home entertainment system. Preplanning is essential in order to maximize system efficiency.

We recommend the following as a means of helping you reach that goal:

§Make a diagram of your proposed system by laying out the relative location of each component in the system. Then lay out the proposed cable runs between them. Number each cable and record its length on the diagram for future reference.

§Cable runs are critical in that they must be kept away from sources of power radiation (amplifiers, power cords, heaters, etc...). For safety reasons, they should also be kept out of traffic areas.

§The process of optimizing the system will include the type of cable, the length of the run, and the obstructions it must deal with along its run. Your dealer can advise you on the products available and their relative merits. If building custom length audio cables is not your strength, your dealer should be able to help you with that as well.

§When possible, use a separate AC power line for the amplifier, one that is not shared by any other household component. Important!

Tip: Take a piece of string (longer than the longest cable run) and mark it at each foot of length. Then do a mock cable run using the string, dressing it neatly along the way. Count the divisions to the next full foot, and add one foot to allow for some movement of the components. This will provide you with the ideal cable length.

Making the connection

§Before doing anything, insure that the power switch on the amplifier’s front panel is in the ‘off’ position.

§Again, it is recommended that you locate a separate AC power outlet for the amplifier, one that is not shared by any other audio component in the system or any other house hold component. This will eliminate the possibility of the amplifier ‘modulating’ the power being supplied to the component and compromising the signal originating from that component.

§Locate the AC power cord provided with the amplifier and plug it into the power input receptacle in the rear panel. Do not connect it to the AC power source yet!

§Connect the audio cables from your preamplifier’s output to the corresponding input connector on the amplifier.

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§Connect the wires from your speakers to the appropriate outputs on the amplifier. It is absolutely essential that you observe correct polarity in these connections.

Example: If you connect your left front output of your preamplifier to channel 4 input on the amplifier, remember to connect your left front speaker wires to channel 4's outputs. Always observe polarity when connecting speakers, connect amplifiers (+) to the speakers (+) and amplifiers(-)to speakers(-).

§Double check all connections.

§Connect a playback unit (CD, VLD, Tuner, etc...) to the preamplifier. Turn the volume on the preamplifier to minimum. Turn on the preamplifier, then the amplifier (in that order). Set the source on the preamplifier to the playback unit you’ve just connected. Turn the volume up slowly and listen for music from all channels. If this is not the case, double check your installation.

§Should you encounter any problems that cannot be traced to the source or the material being played, consult the “TROUBLESHOOTING” section on page 10.

Note: When turning equipment ‘off’, the amplifier should always be turned off first, then the preamplifier. When turning equipment ‘on’, the preamplifier should always be turned onfirst, then the amplifier.Before turning anything on, insure the preamplifier is at a low volume level.

Control muting

A control is provided on each Reference 7250/7260 series II amplifier to allow remote switching of mute on/off. The preamplifier’s control output, such as is provided with B&K series preamplifiers, can be utilized to provide a control signal to the Reference 7250/7260 series II. If more than one amplifier is being controlled, the control signal can be extended to include each successive unit by simply running a 1/8" MINI - JACK cable from the CTRL OUT connector of the first amplifier to the CTRL IN connector of the next unit (commonly referred to as ‘daisy chaining’). An example of how to connect two amplifiers is illustrated in figure E.

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