Audio Research VT100 User manual

Modele VT100
AMPLIFICATEUR DE PUISSANCE STEREO
Modell VT100
STEREO-ENDVERSTARKER
Modello VT100
AMPLIFICATORE DI POTENZA STEREO
Modelo VT100
AMPLIFICADOR DE POTENCIA ESTEREOFONICO
Model VT100
STEREO POWER AMPLIFIER
3900 ANNAPOLIS LANE NORTH/ PLYMOUTH, MINNESOTA 55447-5447 I PI-/ONE, 763-577-9700 FAX [phone]

Model VT100
Contents
Stereo Power Amplifier .......................................... 1
Sommaire
Amplificateur De Puissance Stereo .............................. 6
Inhalt
Stereo-Endverstarker ........................................... 11
In dice
Amplificatore Di Potenza Stereo
............................... 16
Contenido
Amplificador De PotenciaEstereof6nico ........................ 21

Model VT100
VACUUM TUBE
POWER AMPLIFIER
WARNING
TO PflEVEHl' FIREAND $HOCK ttAZ.UID, DO NOT
exPOSE THIS DIMCE TO RAIN OR MOIST1JR1i.
UNIT
LMUST 81< OP£RAT£D IN A NOIUZOHTAl.POSITION.
-00 NOT OPaiATE WIT1l COVERSREMOVED·
UNIT CONTAINS VOLTAGES WHICH MAY BE HAVofiDOUS.
RIGHT OUTPUT
0 4 a
+ +
CAUTION 4 OHM TAP IS GRDUNIIED INTERIW.t.Y.
DO NOT CONNECT TO LOADS WITH COMMON GROUND.
·~ .IUMI'£IIFOR
BIIIGI..I<-£NDE0
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audio research
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POWIOR
MODEL VT100
STEREO AMPLIFIER
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audio research
MINNETONKA, MINNESOTA
MADE IN U.S.A..
0
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0
100!C.n
RIGHT
INPUT
LEFT
~ ~
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200KO
MODEL VT100
HIGH DEFINITlON"
~
JUMPER fOil
S(loj(l.U;-aft!OO
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CAUTION
FOR PROn::.CTlDN AGAINST FIRE HAZARD
REPLACE ONLY Wllll SAME RATlNG FUSES.
POWER CONSUMPTION 750 WATTS
MAXIMUM, 60160 HZ
LEFT OUTPUT
0 4 a
+ +
CAUTION 4 OHM TJU' IS GROUNDED INTERNALLY.
DO NOT CONNilCT TO LOAOS WITH COMMON GROUND.
0
0

Addendum to VT100 Owner's Manual
pertaining to
VT1 OOMKIII version.
The information in the VT100 Owner's Manual applies to the VT1 OOMKIII,
but with the following additional features and specification changes for
the MKIII version:
Removable lEG power cord
Cooling fan
A SAUSE input switch replaces the shorting links needed in ·the .XLR
connectors for SE operation in previous versions,
The VT100MKIII uses four 6H30 tubes, replacing the eight 6922 tubes
found in the VT100 and VT100MKII. The output tube complement of
eight 6550 output tubes remains unchanged; Because
of differing heater ·
currents, 6H30 tubes cannot be used in the VT100 or VT100MKII, nor can
6922 tubes be used in the
VT1 OOMKIII.
A larger value line fuse (the value is stated on fhe chassis next to the
fuse post).
Power Supply Energy Storage: approximately 540 joules.
Weight: 66.7 lbs. (30.3 kg) Net; 83.7 lbs. (38.0 kg) Shipping.
(OVER)
IS-273·1 JC-009290

REMOTE TURN-ON CONNECTIONS
The VT1 OOMKIII has a built-in 12VDC remote turn-on/off circuit for operation by a
master control system in a home theater or large audio system. Use a 3.5mm (.140")
diameter mono mini-plug to connect to the +12V
IN jack on the rear of the VT1 OOMKIII.
Two identical paralleled jacks are provided to allow chaining connections to control two
or more
VT100MK111s or other equipment.
The +12V
IN jack should be connected to the +12VDC output of the master control system,
using a continuous +12VDC signal at 12mA per
VT1 OOMKIII for the duration of amplifier
on-time. Do not use a momentary or data pulse control signal.
The front power rocker switch on the VT1 OOMKIII must be off to use the remote turn-on.
The front power,·.rocker switch
may still be used when the remote turn-on is connected,
but the remote will not turn the
VT1 OOMKIII off if the front power rocker switch is left on.
The front power rocker switch will not turn the VTfOOMKIII off if the remote system is on.
The +12VDC remote jacks have polarity protection, so. they
.vvill not operate if a -12VDC
signal is accidentally connected,
or if the control wires are reversed. The 12V remote
relay in the VT1 OOMKIU has click suppression to protect circuits in the master .control
. : system. · · ·
OUTPUTTUBE BIAS ADJUSTMENT
.Instead of adjusting bias to 130mVDC at each of two resistor test points as in the VT100
and VT100MKII, the VT100MKIII has four bias adjustments consisting of four bias
adjustment pots labeled 1-4, and four corresponding resistor test points, one above
each pair
of output tubes (each test point is labeled 1-4 and marked 65mV). Adjust
each of the four pots to read 65mV at each of these corresponding test points. (Refer
to 'Output Tube Bias Adjustment' section
in manual for remainder of procedure,
voltmeter requirements and cautionary statement before preceding.)
15273-1 1C-009290

Important: VT100MKIII fuse value change
The VT1 OOMKIII linefuse values have been changed from 7A to
1 OA on 1 OOV and 120V units, but remain unchanged at T6.3A on
220V, 230V and 240V units. This unit is already equipped with
the higher-value fuse.
This information supercedes
the original smaller fuse values
printed in the owner's manual and on the rear of the amplifier
chassis by thefuse holder post.
IS-289 50-1 051 01

WARNING!
DO NOT ATTEMPT TO OPERATE THIS
VT100 MKIII AMPLIFIER BEFORE INSTALLING
THE
VACUUM TUBES IN THEIR PROPER SOCKETS.
TOP EDGE
REAR
e . .·e
. @ . TOPEDGE e
----¥------------- --------------------------------------------- -------------Q----
v@ FRONT ·@V
RELATIVE POSITIONS OF ALL (12) TUBES LOCATED ON TWO
CIRCUIT BOARDS AS VIEWED FROM THE FRONT AND
LOOKING DOWN FROM ABOVE THE AMPLIFIER.
SEE YOUR OWNER'S MANUAL FOR COMPLETEINSTRUCTIONS
FOR SAFE INSTALLATION AND OPERATION.
IS-272 1 C-Q05190

Model VT100
Preface
Please take time to carefully read and understand the
following instructions before you install or attempt to oper-
ate this equipment. Becoming familiar
with the product
and its correct operating procedures will help assure you of
maximum musical enjoyment and reliable operation. The
effort you invest now will be well rewarded in the years
ahead.
Packaging
Save all the packaging in a dry place. Your Audio
Research amplifier is a precision electronic instrument and
should be properly cartoned any time shipment is made.
Because ofits weight. it
is highly probable that the unit will
be damaged during shipment if repackaged in cartoning
other than that designed for the unit.
You may not have occasion to return the unit to the factory
for service. but if
that should prove necessary. or other
occasion to ship it occurs. the original packaging may save
your investment from unnecessary damage, delay and
expense.
Unpacking
The VT100 is packed within two cartons (inner and outer}
which have impact-absorbing panels in between. Because of
the weight ofthe unit and because it is a precision electron-
ic instrument it is necessary to take reasonable care of its
unpacking and preparation for use.
It is best to have a large, open work area with two people
available to help. Set the carton upright in the center of the
work area and with a small knife carefully slit the taped
edges of the outer carton's top flaps. Fold the flaps to the
sides and while holding the inner carton in place. roll the
unit upside down.
You can now lift the outer carton off and
set
it and the filler panels aside. Now slit the inner carton's
taped seams on the bottom (now facing upward}. Again,
fold the
flaps over and while holding the unit in, roll it over
as before.
You can now lift the inner carton off to find your
VT100 sitting upright. undamaged and uncartoned. Careful-
ly remove the plastic wrap. Now, while it is fresh in your
mind, reassemble the carton system for future use.
Accessories
1 -Phillips-head screwdriver for cover removal
1-Plastic screwdriver for bias adjustments
User replaceable spare fuses include:
2- 4 Amp MDQ slo-blo with 220V and 240V unit
2- 6I/4 Amp MDQ slo-blo with 100V and 120V units
2- Gold-plated shorting jumpers for single-ended
operation
Warnings
1. To prevent fire or shock hazard. do not expose your
VT100 to rain or moisture.
2. This unit contains voltages which can cause serious in-
jury or death. Do not operate with covers removed. Refer
servicing to your authorized Audio Research dealer or
other qualified personneL
3. The 16-gauge. 3-conductor power cord on your VT100 is
equipped with a standard 3-prong grounding plug. If
used normally. it will provide a safe earth ground con-
nection of the chassis. Refer to the section on "AC Power
Connections" for detailed information.
4. For continued protection against fire hazard.
replace fuses only with the same type and rating of fuses
as specified.
Preparation for Use
Your VT100 amplifier is shipped with the vacuum tubes
packed in foam blocks. These
must be unpacked and
installed before you attempt to operate the amplifier.
Included are four matched pairs of 6550C output tubes. and
eight' 6922 dual triodes used in the input through driver
stages. Proceed according to the following instructions.
.
DO NOT ATTEMPT TO OPERATE THIS
EQUIPMENT BEFORE INSTALLING THE VACUUM
TUBES IN THEIR PROPER SOCKETS.
TOP EDGE
Diagram indicates relative positions of all (16) tubes located
.
on two circuit boards as viewed from the front and looking
down from above the amplifier.
1. Using the Phillips-head screwdriver provided,
remove the top cover assembly. setting it and the
retaining screws aside.
1

Model VT100
2. Carefully remove each vacuum tube from its
protective foam and match its location "V'' number (writ-
ten on the base of the tube) to the "V" number printed
next to each socket on the circuit board
(see accompany-
ing tube location diagram). Firmly seat each tube in its
matching socket. taking
care to "key" the tube pins to
the socket hole. Retain the foam blocks with other pack-
ing materials for possible future use.
3. Once
all vacuum tubes have been installed, reposition
the top cover assembly over the chassis and. fasten with
screws.
Note: In general. contact enhancers are not recommended
for use on vacuum tube contact pins. With continual expo-
sure to heat and air. these substances can form gummy.
dust-collecting residues which actually reduce contact and
degrade sonic performance. Proper external use of these
preparations -on interconnect plugs. speaker connections,
etc. - is subject to the discretion of the owner. Contact
Audio Research for specific recommendations.
Panel Controls
The front panel has:
I - Switch: I- Powerline On-Off
I-lndicator: I- Power "On" LED (Green)
Use of Controls
POWER ON- OFF SWITCH, Initiates/terminates AC line
power to the amplifier. Power "On" function
is indicated by
illuminated green
LED above switch.
Note: Audio Research does
not recommend leaving your
VT100 on 24 hours a day as is the custom of some audio-
philes to achieve maximum sonic performance on demand.
While this
is often recommended for solid-state equipment,
Audio Research does not recommend this procedure for
vacuum tube power amplifiers. (2,000 hours oftube life will
pass by in 84
days!)
Installation
To insure normal component life and safe operation this
unit
must be operated only in a horizontal (upright) posi-
tion. Adequate air flow and proper cooling thereby can
occur only if there is no restriction around the unit. Allow
at least 12 inches of unrestricted ventilation space above
the VT100 top coverduring operation.
The six (6) special non-marring elastomer feet
provide adequate ventilation spacing only from a smooth,
hard surface. Never operate
the unit while it is sitting on
a soft, irregularsurface such as a mg or carpet.
2
If the unit is to be operated in an enclosure such as an
equipment
rack. make certain that adequate air flow above
and below the unit
is provided. The ambient operating
temperature should never exceed l20°F
or 49°C. Audio
Research Corporation
Rack Mount Ventilators (RMV-3)
must be used above and below each unit. Improper installa-
tion will cause premature tube failure and will affect your
warranty. as well
as the service life of the unit.
It is normal for a vacuum tube power amplifier to run quite
warm. and if used for prolonged periods. hot to the touch.
All components within are. however. operated at safe. con-
servative levels and will not be improperly affected there-
by, providing the requirements outlined above are
adhered to.
Connections
The rear panel has:
2- RCA Input connectors for single-ended
connection. L& R
2- XLR Input connectors. for balanced connection. L& R
6 -Output binding posts (+) and
H. L & R. for 4 or
8 ohm speaker connection
l
-Power line cord
I -Power line fuse holder
IMPORTANT: Use the best available speaker wires and in-
terconnects. Audio Research cannot emphasize this
enough. As better components and systems are developed.
it becomes increasingly important to avoid the limitations
of inferior system interconnections. For best results we rec-
ommend Audio Research LitzLink 2® interconnects
and LitzLine 2® speaker cables.
It is important sonically that your entire system be con-
nected so that the audio signal arriving at the speakers has
correct, or "absolute" polarity
(i.e .. non-inverted).·Connect
the black or "-" speaker terminal to the wire that connects
to the
"0" terminal on the VTlOO. Connect the red or "+"
speaker terminal to the wire that connects to the "4" or "8"
ohm impedance terminal on the VT100. Use the best avail-
able speaker cables and tighten all connections securely to
ensure best sonic results.
MATCHING: It is important to use as close as possible an
impedance match between the amplifier and speaker for
optimum transfer of power to the speaker with minimum
distortion. In the case of speaker systems with significant
variations in impedance throughout
the frequency spec-
trum. such as most electrostatic types. the best impedance
match should be determined by listening.

Model VT100
Connect the VTlOO input to the preamplifier or electronic
crossover. using only the highest grade of audio intercon-
nect cables. To avoid sonic degradation use the shortest
practical length of cables.
AC POWER CONNECTIONS: It is essential that the VT100
amplifier be connected to a wall AC power receptacle. or a
similar heavy-duty source. If it
is connected to convenience
receptacles on preamplifiers. etc.. the
full sonic capabilities
of both the VT100 and the preamplifier may be compro-
mised. Furthermore. the proper control of start-up and
shut-down surges may not occur unless the Power switch
on the front ofthe
VT100 is actually used for on/off control
of the amplifier. The
AC power source for the VT100 ampli-
fier should be capable of supplying 10 amperes for 100 or
120 volt units. or 5 amperes for 220 or 240 volt units.
For
the very best performance on domestic 100 or 120 volt
circuits. the VT100 should be connected to its
own AC
power.circuit branch, protected by a 15 amp breaker. The
preamplifier and other audio equipment should be connect-
ed to a different power circuit and breaker. Avoid the use
of extension cords. If they must be used on a temporary
basis, use
14-gauge or heavier cords.
The VT100 utilizes a compatible grounding system
that
generally does not require a "ground lifter" adapter plug on
the
AC power cord to minimize hum. The power cord on
your VT100 has a standard three-prong grounding plug to
provide maximum safety when it
is connected to a ground
wall receptacle. If there
is any question regarding the safety
of grounding procedures, be certain to seek competent help
with
the installation.
If electronic crossovers or other AC powered equipment is
used with the VT100 it may be necessary to use "ground
lifter" adapters on
the power plugs of that equipment to
minimize system hum. Generally. the lowest hum is
achieved when the only direct connection between audio
common "ground" and true earth ground occurs in the
preamplifier. through its grounded power cord. Other
equipment in the system should have some form of isola-
tion to prevent ground loops and associated hum.
Always place the Power On-Offswitch on the panel of
the VT100 in the "0[[" position before connecting the
power line cord to ACpower.
Single-Ended Operation
Single-ended inputs should be used with a preamplifier (or
electronic crossover, etc.) having single-ended outputs
which does not invert overall phase or polarity. When us-
ing single-ended inputs, make sure the shorting jumper
pins supplied for single-ended operation are installed on
the rear panel of the amplifier between
the bottom and
right socket holes ofthe balanced input jack.
on both chan-
nels. as shown in the accompanying rear panel diagram.
Balanced Operation
Balanced inputs can be used with a preamplifier (or
electronic crossover.
etc.) having balanced outputs. When
using the balanced inputs. remove the shorting jumper pins
before connecting balanced
XLR connectors. Disconnect
any single-ended cables.
Operating Procedure
1. Make sure you have read and complied with the IN-
STALLATION AND CONNECTIONS instructions prior
to attempting operation.
2. Make sure your VTlOO is properly connected to a high-
current power receptacle via the attached power cord
(see
CONNECTIONS).
3. Your preamplifier should be "On" and muted and/or set
at minimum gain.
4. Turn the Power switch from "Off" to "On." The green
power
LED indicator should glow immediately. Note: If
the power indicator
LED fails to light. turn the Power
switch to "Off" and check the appropriate fuse for possi-
ble failure.An extra fuse for A. C. power is included with
your
VT100.
5. Your VTlOO should now operate satisfactorily. However.
a full stabiliZation or warm-up time of approximately one
hour
is recommended for best sonic performance.
Servicing
Because of its careful design and exacting standards of
manufacture. your
VTlOO amplifier should normally re-
quire only minimal service to maintain its high level ofper-
formance.
CAUTION: The VT100 amplifier contains sufficient levels
of voltage and current to be lethal.
Do not tamper with a
component or part inside
the unit. Even with the power
turned off. a charge remains in
the energy storage capaci-
tors for some time. Refer any needed service to your autho-
riZed Audio Research dealer or other qualified technician.
Replacement vacuum tubes may be obtained through your
authorized retailer or directly from Audio Research
Cus-
tomer Service. For best performance, the 6550C output
tubes should be matched pairs.
Additional questions regarding the operation. maintenance
or servicing of your amplifier may be referred to
the Cus-
tomer Service Department of Audio Research Corporation
at 612-939-0600 (CST).
3

Model VT100
Output Tube Bias Adjustment
As shipped from the factory, the output bias
adjustments are set for a nominal 65mA per 6550C tube.
Under these idle conditions the tubes are each dissipating
approximately 27 watts of their 41 watt rating (35
watt plate, 6 watt screen). This point of operation provides
"enriched" Class AB
1,
and will satisfy the most critical
listener.
For best results, operate and adjust the VT100 at the
normal rated line voltage listed on the rear panel. Adjust-
ment must be made under zero-signal conditions after at
least
15 minutes ofuninterrupted stabilization time.
A digital voltmeter capable of accurate measurements with
lmVDC resolution is preferred for accurate adjustment
(must have 3112 digit display). Use the plastic alignment
tool provided to make the adjustment. The test points are
accessible from
the top of the circuit boards above the out-
put tubes. For the VTlOO and VTIOOMKII adjust the bias at
one place on each channel for an average reading of
!30mVDC (0. 13 Volt DC) between test points (across 0.5
ohm resistor). For the VT!OOMKIIl adjust the bias in 2
places on each channel for 65mVDC (.065VDC) between
test points (across 0.50 ohm resistor). Caution, resistor
is
420V above ground.
Cleaning
To maintain the new appearance of this unit, occasionally
wipe the front panel and top cover with a soft. damp (not
wet) cloth to remove dust. A mild, non-alkaline soap solu-
tion or dilute isopropyl alcohol may be used to remove
fingerprints or similar smudges. Cleaners containing abra-
sives should not be used as they will damage the anodized
finish of the front panel. A small, soft paint brush
is effec-
tive in removing dust from bevels, the recessed nameplate
and other features ofthe front panel.
4
Limited Warranty
Audio Research Corporation products are covered by a 3-
Year Limited Warranty (all products except CD players,
transports, and vacuum tubes). a
2-Year Limited Warranty
(CD players and transports), or a 90-Day Limited War'ranty
(vacuum tubes). This Limited Warranty initiates from the
date of purchase, and
is limited to the original purchaser, or
in
the case of demonstration equipment, limited to the
balance of warranty remaining after original shipment to
the retailer or importer.
In the United States, the specific terms, conditions and
remedies
for fulfillment of this Limited Warranty are listed
on
the warranty card accompanying the product in its
shipping carton, or may
be obtained from the authorized
retailer or from the Audio Research Customer Service
Department. Outside the United States, the authorized
importing retailer or distributor has accepted the responsi-
bility for warranty of Audio Research products sold by
them The specific terms and remedies for fulfillment of
the Limited Warranty may vary from country to country.
Warranty service should normally be obtained from the
importing retailer or distributor from whom
the product
was purchased.
In the unlikely event that technical service beyond the
abil-
ity of the importer is required, Audio Research will fulfill
the terms and conditions of the Limited Warranty. Such
product must be returned at the purchaser's expense to the
Audio Research factory, along
with a photocopy of the
dated purchase receipt for the product, a written descrip-
tion of the problern(s) encountered, and any information
necessary
for return shipment. The cost of return shipment
is the responsibility ofthe purchaser.

Model VTlOOMKIII
Specifications
POWER OUTPUT: 100 watts per channel continuous from
20Hz to 20kHz. 1kHztotal harmonic distortion typically 0.3% at
100 watts, below 0.03% at 1 watt.
Approximate actual power available at "clipping" 120 watts
(1kHz). (Note that actual power output is dependent upon
both
line voltage and "condition" i.e.: if power line has high
distortion, maximum power will be affected adversely, although
from a listening standpoint this is not very critical.)
POWER BANDWIDTH: (-3dB points) 12Hz to 60kHz.
FREQUENCY RESPONSE: (-3dB points at 1 watt)
1Hz to 80 kHz.
INPUT SENSITIVITY: 1.7V RMS (Bal, 0.87V RMS SE) for
rated output. (24.3 dB
Bal gain, 32.2dB SE gain into 8 ohms.)
INPUT IMPEDANCE: 200K ohms Balanced, 1 OOK ohms
Single-ended.
OUTPUT TAPS: 8 ohms, 4 ohms.
OUTPUT REGULATION: Approximately 0.8dB 8 ohm load to
open circuit (Damping factor approximately 11 ).
OVERALL NEGATIVE FEEDBACK: 15dB.
SLEW RATE: 8 volts/microsecond.
RISE TIME: 4 microseconds.
HUM & NOISE: Less than 0.2mV
RMS- 103dB below rated
output
(IHF weighted, Bal input shorted).
POWER SUPPLY ENERGY STORAGE: Approximately 540
joules.
POWER REQUIREMENTS: 105-125VAC 60Hz (210-250VAC
50Hz) 650 watts at rated output, 800 watts maximum, 440
watts at "idle':
TUBES REQUIRED:
4- Matched pair 6550C- Power
Output; 4 -
6H30 Driver.
DIMENSIONS : 19" (48.3 em) W x 8. 75" (22.2 em) H x 19.5"
(49.5 em) D. Handles extend 1.5" (3.8 em) forward.
WEIGHT: 65.91bs. (30.0 kg) Net; 82.0 lbs. (37.3 kg) Shipping.
Specifications subject to change without notice.
©2000 Audio Research Corporation.