VTL S-400 II series User manual

VTL
S-400 Series II Reference Stereo Amplifier
O w n e r ’ s M a n u a l

S-400 Amplifier Owner’s Manual
VTL i
MAKING TUBES USER FRIENDLY
VTL S-400 II 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 1.0 August 26, 2014
Part Number: OM-S-400
Copyright ©2014 by VTL Amplifiers Inc. All rights reserved.
4774 Murrieta Street, Suite 10
Chino, CA 91710, USA
Phone [phone] • Fax [phone]
Email: [email protected] • http://www.vtl.com

S-400 Amplifier Owner’s Manual
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TABLE OF CONTENT
CHAPTER 1 ......................................................................................................................................................................... 1
INTRODUCTION.............................................................................................................................................................. 1
Symbol Conventions used in this guide......................................................................................................................................... 4
Electrical Safety Notice................................................................................................................................................................ 4
Water and Moisture...................................................................................................................................................................... 4
Location and Ventilation .............................................................................................................................................................. 4
Servicing....................................................................................................................................................................................... 5
Operational Warnings.................................................................................................................................................................. 5
CHAPTER 2 ......................................................................................................................................................................... 7
GETTING STARTED........................................................................................................................................................ 7
Before starting.............................................................................................................................................................................. 7
Unpacking the unit from the crate................................................................................................................................................ 7
Changing Top Cover Screws ...................................................................................................................................................... 10
Quick Start.................................................................................................................................................................................. 11
CHAPTER 3 ....................................................................................................................................................................... 15
OPERATING THE AMPLIFIER ........................................................................................................................................ 15
Rear panel controls and connections.......................................................................................................................................... 15
Rear Panel Functions ............................................................................................................................................................................................17
1. Fuse Tester ....................................................................................................................................................................................................17
2. Changing input between balanced and single-ended....................................................................................................................................17
3. Changing amplifier phase.............................................................................................................................................................................17
Front panel controls and indicators........................................................................................................................................... 18
Front Panel Controls.........................................................................................................................................................................................18
Front Panel Indicators.......................................................................................................................................................................................18
AC Voltage Setting...................................................................................................................................................................... 19
AC Power Source........................................................................................................................................................................ 20
Connection to the AC........................................................................................................................................................................................20
Powering On the Amplifier......................................................................................................................................................... 20
Ground Loop Hum...................................................................................................................................................................... 23
Setting the Operating Mode........................................................................................................................................................ 23
Muting the Amplifier................................................................................................................................................................... 24
Tube Bias and Top deck Indications........................................................................................................................................... 24
Using the DF switches................................................................................................................................................................ 27
DF Switch Settings ..........................................................................................................................................................................................27
Remote Control and Communications........................................................................................................................................ 29
Using a 12V trigger to power the amplifier on or off.......................................................................................................................................29
Using the Amplifier with an infrared Remote Control.....................................................................................................................................29
Using the amplifier with RS232 control...........................................................................................................................................................30
Diagnostic and programming Functions.................................................................................................................................... 32
Basic Programming functions...........................................................................................................................................................................32
Basic Diagnostic functions ...............................................................................................................................................................................34
Advanced Functions and Diagnostics...............................................................................................................................................................37
Fault Indications......................................................................................................................................................................... 39
Not ready modes....................................................................................................................................................................................................39
INVERTed Phase..................................................................................................................................................................................................40
TUBE green Fault.................................................................................................................................................................................................40
TUBE red Fault.....................................................................................................................................................................................................41
HEAT Fault...........................................................................................................................................................................................................42
POWER faults.......................................................................................................................................................................................................43
Tube Service Reminder.........................................................................................................................................................................................44
Reset / Clearing faults ................................................................................................................................................................ 44
Powering the amplifier off.......................................................................................................................................................... 45
CHAPTER 4 ....................................................................................................................................................................... 47

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CARE AND MAINTENANCE OF YOUR VTL AMPLIFIER.................................................................................................. 47
Break In Period .......................................................................................................................................................................... 47
Tube Life..................................................................................................................................................................................... 47
Changing Tubes.......................................................................................................................................................................... 48
Changing the Screen, Plate, Logic, B+ Input, Filament Fuses .................................................................................................. 51
Cleaning ..................................................................................................................................................................................... 52
Troubleshooting.......................................................................................................................................................................... 52
CHAPTER 5 ....................................................................................................................................................................... 55
SPECIFICATIONS .......................................................................................................................................................... 55
CHAPTER 6 ....................................................................................................................................................................... 57
WARRANTY................................................................................................................................................................. 57
APPENDIX......................................................................................................................................................................... 58
Appendix I: Quick Reference - Summary of indicators.............................................................................................................. 58
Appendix II: Individual tube hour log ....................................................................................................................................... 60
Warranty Registration................................................................................................................................................................ 61
Service Notes.............................................................................................................................................................................. 61

CHAPTER 1
Introduction
Congratulations on your purchase of the VTL S-400 Series II Reference Amplifier – the modern vacuum tube amplifier
designed to bring high performance and ease of use to serious music lovers such as yourself.
From all of us at VTL, we are proud to offer our S-400 Series II Reference power amplifier – the ultimate expression of
everything we know about power amplifier design, designed to deliver the most advanced technology and thinking in
power amplifier design today. S-400’s bold and ultra fast sound and commanding vocal and visual presence are
appreciated by the most serious and discerning music and film lovers. We thank you for selecting this amplifier for your
home audio/theater system, and we wish you many hours of enjoyment for years to come.
In order to get the most benefit from your purchase, we recommend that you take sufficient time to familiarize yourself
with the features of this product. Please take a moment to read through this owner’s manual, as it contains all of the
installation procedures needed to connect your new amplifier to the rest of your system, as well as the many functions
that the amplifier can perform. After you have finished reading this manual it should be kept in a safe place for future
reference.
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The Design Goals and Benefits
When the VTL design team began developing the concepts for a next-generation Reference amplifier, the following
design goals were laid out:
• The Reference amplifier should deliver a new sonic standard worthy of its marque as a member of the VTL
Reference family – it should provide unsurpassed sound quality into real-world loads, as well as excellent
measurements on the test bench
• The amplifier must be able to drive a wide range of speaker types to their optimal performance, with
consistent performance under a wide range of conditions
• The amplifier must be self-optimizing and provide a full range of diagnostics for maintaining peak
performance and providing user feedback, without the need for the user to have to know the inner workings
of the amplifier.
• The operation of the amplifier must be intuitive and user-friendly while providing flexibility in its control
functions, for integration with modern home theater systems
• Complete in-system diagnosis via front panel or remote to make remote use and maintenance easy.
These goals have been fully realized in the new S-400 power amplifiers.
S-400 Series II Circuit overview:
An all-tube amplifier, S-400 is the culmination of VTL’s most advanced thinking in performance engineering, with self-
optimization, fault diagnosis and user feedback designed to bring the ultimate performance and convenience to the
user.
The Series II version of the S-400 features a complete re-working of the entire signal path. Upgrades include a fully
balanced differential input stage driving a differential phase splitter and a lower impedance push-pull output stage with a
dramatically improved, fully balanced and enhanced interleaved and coupled output transformer.
The S-400 Reference stereo amplifiers gain further sonic benefits with a shorter, faster and fully balanced negative
feedback loop, with zero global negative feedback. The negative feedback loop completely eliminates ringing and
requires no capacitor compensation to maintain critical phase integrity and information. The result is an amplifier that
remains stable even under the most demanding loads.
Adjustable precision-regulated plate, screen and bias supplies hold the output tube operating point constant even under
AC and main power supply fluctuations, and stabilizes the critical power supplies yielding tonal stability and sonic
integrity especially during complex, dynamic signal conditions.
Another new feature in Series II is a user adjustable Damping Factor feedback control that allows the user to adjust the
amplifier’s output impedance by varying the amount of negative feedback. Impedance can now be precisely set to suit
the listener’s taste, and to improve control of the loudspeaker loads to deliver best performance. The three possible
settings are:
1. LOW -- Lowest damping factor, good loudspeaker control, most natural sound.
2. MED -- Better loudspeaker control, with some impact on sound quality
3. HI -- Best loudspeaker control, with a little more impact on sound quality, but on speakers that need the
control the sonic improvement is clear
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Tube life is dramatically extended by optimized operating voltages and timed, low current inrush limiting, with low idle
current draw on all stages. An ever-warm position further lowers idle current and keeps all voltages present to keep the
circuit warm when not in use.
Comprehensive fault sensing monitors internal and external conditions, protects the circuits, and alerts the user under
any adverse conditions. In the case of any malfunction of any of the output tubes the amplifier is shut down to protect
the circuitry and faults are indicated on the front panel, along with the blinking LED on the top deck next to the tube
that caused the fault shutdown, to make diagnosis and tube replacement easy.
The logic-controlled automatic bias system is designed to keep the tubes at peak performance and operates completely
outside of the signal path. The tube biasing circuit checks and adjusts the tube bias values automatically during the
power on sequence, as well as when the amplifier is at idle (i.e. when no music signal is being amplified.) and drops out
of the circuit path when music signal is detected.
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Symbol Conventions 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 can be hazardous. We recommend that the
power cord used with this unit be connected to a properly grounded AC outlet.
There are hazardous voltages present in the unit, and to prevent electrical shock, do not
remove the cover of this amplifier, and under no circumstances while the unit is
powered on.
Warning – Under no circumstances should any attempt be made to
circumvent the ground system to the AC line for any reason. Using a
ground lifted system can be potentially extremely dangerous, both to persons that might
come in contact with the unit, and to the unit itself, and proper RF shielding cannot be
attained without a secure ground connection.
Damage to the unit that is the result of improper AC connection and grounding will not be covered under the
warranty.
Prior to connecting this amplifier to any audio or video equipment in your system, make
sure this unit’s power (and the rest of the equipment connected to its input and output
channels) is turned off. Adding or removing input or output cables to the amplifier while
the system is powered on can cause damage to the amplifier and possibly also to the rest of
the system.
Water and Moisture
The amplifier should be kept away from sources of water or moisture. If liquid enters
the unit it must be immediately returned to your dealer for servicing. In this case you
should under no circumstances try to power the unit on - there are hazardous
voltages present in this unit that can cause serious injury if they come in contact with
you.
Location and Ventilation
Warning – To avoid risk of failure due to overheating, do not stack chassis
components
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The amplifier emits heat and needs proper ventilation to ensure long operational life.
Ensure that the amplifiers are installed in a location that is stable and well ventilated. If the
amplifier is placed in a built-in installation, ensure that there is adequate room for air to flow
through the ventilation openings. Allow at least 12 inches clearance on the top and around
the sides of each chassis of each amplifier. The warranty does not cover units that are
damaged due to overheating from incorrect installation.
Tiptoes or other isolation accessories may prove useful in reducing mechanical vibrations or other external
vibrations that might affect sonic performance, and we have found that such accessories can offer definite
beneficial sonic improvements when used correctly. In all cases you should be sure to install this amplifier in a
location that is stable, as warranty does not cover damage due to the unit falling.
Do not place the amplifier next to heat sources such as radiators, stoves or other appliances.
Do not place the amplifier where small children might be able to tamper with the equipment. If it is not possible
to place the 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
 It is critical for proper sonic performance of this component that it be properly
configured for the mode of operation while playing. If a balanced signal is
applied to the inputs the amplifier must be configured for balanced operation,
and vice-versa.
 Always make all connections before powering the amplifier on. Connecting or
disconnecting the amplifier while powered on can damage the output stage, and will
not be covered under the warranty. Ensure that no interconnect cables can become
loose during use and that there are no intermittent faults with the cables.
Warning: The S-400 Series II amplifier is a fully balanced design with a balanced output.
Care should be taken so that neither output is ever grounded.
Warning: Do not connect a sub-woofer to the output of the amplifier unless you are sure
that the subwoofer input is fully balanced and that neither phase can become
grounded.
Please consult your authorized VTL dealer or the VTL factory customer support department if you have any
questions on the fully balanced connection of the amplifier.
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 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.
 Do not touch the tubes after the amplifier is turned on. Tubes can get very hot while
the amplifier is operating. Turn off the amplifier and allow the tubes to cool down before
attempting to work with the tubes.
 Tube components can be heavy and awkward to lift, with the weight unevenly distributed,
and you should not attempt to move the unit without help. The amplifier weighs
approximately 250 lbs. (113 Kg).
 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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