VTL MB-125 Owner's Manual

VTL
MB-125 Monoblock Power Amplifier

Owner’s Manual

MAKING TUBES USER FRIENDLY

VTL MB-125 Monoblock Power Amplifier

Information in this document is subject to change without notice. No part of this document may be reproduced or transmitted
in any form or by any means, electronic or mechanical, for any purpose, without the express written permission by VTL.

Version History:

Version 2.2: April 23, 2008

Copyright

© 2009 by VTL Amplifiers Inc. All rights reserved.

4774 Murrieta Street, Suite 10

Chino, CA 91710, USA

Phone [phone] • Fax [phone]

http://www.vtl.com/

e-mail: [e-mail]

Part Number OM-0010-201

Table of Contents

CHAPTER 1 .......................................................................................................................................1

INTRODUCTION....................................................................................................1

Symbol Conventions used in this guide ..................................................................................1

Electrical Safety Notice...........................................................................................1

Water and Moisture...................................................................................................1

Location and Ventilation........................................................................................2

Servicing...........................................................................................................................2

Operational Warnings.............................................................................................2

CHAPTER 2 .......................................................................................................................................3

GETTING STARTED.........................................................................................3

Unpacking the MB-125 from its box................................................................3

The MB-125 Front Panel.......................................................................................4

Check for tube placement.......................................................................................................4

MB-125 Back Panel...................................................................................................5

The MB-125 Back View....................................................................................................................5

Connecting Your Amplifier to your system..................................................5

Voltage Setting.............................................................................................................6

Power Source for your Amplifier......................................................................6

CHAPTER 3 .......................................................................................................................................7

OPERATING THE AMPLIFIER..............................................................7

Powering your system on.......................................................................................7

Ground Loop Hum.....................................................................................................8

Powering the system off..........................................................................................8

Tetrode-Triode Switching......................................................................................8

Bias Checking and Setting.....................................................................................8

Top view and Bias Measurement points of the MB-125 Amplifier .................................................11

CHAPTER 4 .....................................................................................................................................12

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CARE AND MAINTENANCE OF YOUR VTL

MPLIFIER...............................................................................................................12

A

BREAK IN PERIOD..........................................................................................12

Power-on Period.......................................................................................................12

Tube Types....................................................................................................................12

Tube Life........................................................................................................................12

Changing Tubes...................................................................................................................13

Changing the AC and B+ Fuses......................................................................14

Cleaning.........................................................................................................................14

Transporting MB-125............................................................................................14

CHAPTER 5 .....................................................................................................................................15

SPECIFICATIONS...............................................................................................15

CHAPTER 6 .....................................................................................................................................16

WARRANTY..............................................................................................................................16

APPENDIX.......................................................................................................................................17

Warranty Registration...........................................................................................17

Service Notes...............................................................................................................17

MB-125 Owner’s Manual
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CHAPTER 1

Introduction

Congratulations on your purchase of the VTL MB-125 Monoblock Power Amplifier.

he MB-125 Monoblock Amplifier, a powerful 125 watts per channel amplifier from the VTL
monoblock amplifier family, represents the entry level monoblock using our pure tube design. This

T

value and maximum performance. Please take a moment to read through this owner’s manual and please take
time to get familiar with the features of this product, so that you can become familiar with the operating and
maintenance procedures needed for the MB-125’s. After you have finished reading this manual please keep it
in a safe place for future reference.

The VTL team is proud that you have selected the MB-125 power amplifiers as a new member of your home
audio system. We sincerely hope that the VTL MB-125’s will contribute towards your enjoyment of music and
give you many hours of listening pleasure.

pair of high performance monoblock amplifiers is designed to deliver a most involving and true-to-live
listening experience to you. Proper care and maintenance of the MB-125’s will assure their lasting

Symbol Conv entions used in this guide

Certain symbols are used in this owner’s manual to draw your attention to important points being discussed.
For your own safety and that of your equipment you should note and heed the warnings that follow these
symbols.

The “Warning - Pay particular Attention” symbol used is

and the “Warning - Observe These Precautions For Your Safety” is

Electrical Safety Notice

Electrical voltage from power cables is hazardous. We recommend that the power cord connected to this unit
be used with a properly grounded outlet. To prevent electrical shock do not remove any of the covers of this
amplifier, especially while the unit is powered on.

Water and Moisture

The amplifier should not be used close to any water or moisture sources. If liquid enters the amplifier it must
be immediately unplugged and returned to your dealer for servicing. If this occurs you should under no
circumstances try to power the unit on before the unit has been properly serviced by a trained repair technician

- there are hazardous voltages present in this unit that can cause serious injury if they come in contact with you.

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Location and V entilation

Install this amplifier in a location which is stable and well ventilated. If the amplifier is placed in a
built-in installation, ensure that there is adequate room for a supply of air to flow through the
ventilation openings. Allow at least 9 inches clearance on the top and around the sides of the

amplifier. Be sure the amplifier is at least 10 inches away from your preamplifier to prevent possible
noise introduction into your system. Tiptoes or other isolation accessories may prove useful in reducing
mechanical vibrations. Do not place amplifiers directly on high pile carpets as this will block the
ventilation vents. Do not place the amplifier next to heat sources such as radiators, stoves or other appliances.
Do not place amplifier on the floor where small children can tamper with the equipment. If it is not possible
to place amplifier out of the reach of small children it is recommended that you remove power cables when the
equipment is not in use.

Servicing

Do not attempt to service the amplifier beyond the procedures described in this manual. For all other service
and questions, please contact your authorized VTL dealer or the factory.

Operational Warnings

 Do not touch the tubes after the amplifier is turned on. Tubes can get very hot while the amplifiers

are operating. Turn off the amplifier and allow the tubes to cool down before attempting to work with the
tubes.

 Do not attempt to disassemble the amplifier chassis or remove any covers from the amplifier.

Always consult with your VTL authorized dealer or the VTL factory support department before
attempting any service work on any VTL unit.

 Always connect your loudspeaker to the amplifier before powering the unit on. Operating any VTL power

amplifiers without a speaker load connected can damage the output transformer, and will not be covered
under the warranty. Also, ensure that no speaker cables can become loose during use and that there are no
intermittent faults with the cables.

 Tube amplifiers can be heavy and awkward to lift, with the weight unevenly distributed, and you should

not attempt to move the unit without help. Each unit of the MB-125 monoblock weighs approximately 50
lbs (22 Kg).

 Do not attempt to make or break any connections to the amplifier while the unit is powered on as this can

damage the amplifier and/or the rest of the system, and this damage is not covered by warranty.

 Do not flip the triode tetrode switches while the unit is powered on, as this can damage the switch and is

not covered under warranty.

 Do not exceed fuse ratings or attempt to bypass any fuses, as this can cause an extremely hazardous

condition and will void any warrantees. Use only the same type and rating of fuses as specified in the
owners manual and marked on the unit.

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