AMPEG CLASSIC SVT-VR SVTVR_OM.pdf

SVT-VR

Bass Guitar Amplifier

Owner’s Manual

SVT-VR Bass Guitar Amplifier

"voltage dangereux" non isolé d'ampleur suffisante pour constituer un risque

pour alerter les utilisateurs de la présence d'instructions importantes pour le

accompagnant l'appareil.

TABLE OF CONTENTS

Important Safety Instructions ........................................................................................................... 2–3

Introduction / Features ........................................................................................................................ 4

The Front Panel .............................................................................................................................. 5–6

The Rear Panel ............................................................................................................................... 7–8

Suggested Settings / Personal Settings ......................................................................................... 9–10

Important Information About Tubes and Tube Products .................................................................. 11–15

Troubleshooting ................................................................................................................................16

Block Diagram .................................................................................................................................. 17

Technical Specifications ....................................................................................................................18

Service Information ........................................................................................................................... 19

IMPORTANT SAFETY INSTRUCTIONS

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with a dry cloth.

7. Do not block any ventilation openings.
Minimum distance (5 cm) around the apparatus
for sufficient ventilation. The ventilation should
not be impeded by covering the ventilation
openings with items, such as newspapers,
table-cloths, curtains, etc. Install in accordance
with the manufacturer’s instructions.

8. Do not install near any heat sources such
as radiators, heat registers, stoves, or other
apparatus (including amplifiers) that produce
heat. No naked flame sources, such as lighted
candles, should be placed on the apparatus.

9. Do not defeat the safety purpose of the
polarized or grounding-type plug. A polarized plug
has two blades with one wider than the other. A
grounding-type plug has two blades and a third
grounding prong. The wide blade or the third
prong are provided for your safety. If the provided
plug does not fit into your outlet, consult an
electrician for replacement of the obsolete outlet.

10.

Protect the power cord from being walked
on or pinched particularly at plugs, convenience
receptacles, and the point where they exit from
the apparatus.

11.

Only use attachments/accesso­ries specified by the manufacturer.

12.

Use only with a cart, stand,
tripod, bracket, or table specified
by the manufacturer, or sold with
the apparatus. When a cart is used,
use caution when moving the cart/apparatus com­bination to avoid injury from tip-over.

13.

Unplug this apparatus during lightning storms
or when unused for long periods of time.

14.

Refer all servicing to qualified service
personnel. Servicing is required when the
apparatus has been damaged in any way, such
as power-supply cord or plug is damaged, liquid

2

PORTABLE CART

WARNING

has been spilled or objects have fallen into
the apparatus, the apparatus has been exposed
to rain or moisture, does not operate normally,
or has been dropped.

15.

Do not overload wall outlets and extension
cords as this can result in a risk of fire or electric
shock.

16.

This apparatus shall not be exposed
to dripping or splashing, and no object filled
with liquids, such as vases or beer glasses,
shall be placed on the apparatus.

17.

This apparatus has been designed with Class-I
construction and must be connected to a mains
socket outlet with a protective earthing connection
(the third grounding prong).

18.

The MAINS plug or an appliance coupler is
used as the disconnect device, so the disconnect
device shall remain readily operable.

19. The use of apparatus is in tropical and/or
moderate climates.

20.

For the terminals marked with symbol of “ ”
may be of sufficient magnitude to constitute
a risk of electric shock. The external wiring
connected to the terminals requires installation
by an instructed person or the used of ready­made leads or cords.

CAUTION AVIS

RISK OF ELECTRIC SHOCK. DO NOT OPEN

RISQUE DE CHOC ELECTRIQUE. NE PAS OUVRIR

CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK DO NOT REMOVE COVER (OR BACK)

NO USER-SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL

ATTENTION: POUR EVITER LES RISQUES DE CHOC ELECTRIQUE, NE PAS ENLEVER LE COUVERCLE.

AVIS: POUR EVITER LES RISQUES D'INCENDIE OU D'ELECTROCUTION, N'EXPOSEZ PAS CET ARTICLE

NOTE — This amplifier is intended for professional use only.

Laite on liitettävä suojakoskettimilla varustettuun pistorasiaan.

Apparatet må tilkoples jordet stikkontakt.

Apparaten skall anslutas till jordat uttag.

AUCUN ENTRETIEN DE PIECES INTERIEURES PAR L'USAGER.

CONFIER L'ENTRETIEN AU PERSONNEL QUALIFIE.

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

Le symbole éclair avec point de flèche à l'intérieur d'un triangle équilatéral
est utilisé pour alerter l'utilisateur de la présence à l'intérieur du coffret de

d'éléctrocution.

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 appliance.

Le point d'exclamation à l'intérieur d'un triangle équilatéral est employé

fonctionnement et l'entretien (service) dans le livret d'instruction

A LA PLUIE OU A L'HUMIDITE

SVT-VR Bass Guitar Amplifier

NOTE: This equipment has been tested and found to comply
with the limits for a Class B digital device, pursuant to part 15 of
the FCC Rules. These limits are designed to provide reasonable
protection against harmful interference in a residential installation.
This equipment generates, uses, and can radiate radio frequency
energy and, if not installed and used in accordance with the
instructions, may cause harmful interference to radio
communications. However, there is no guarantee that interference
will not occur in a particular installation. If this equipment does
cause harmful interference to radio or television reception, which
can be determined by turning the equipment off and on, the user
is encouraged to try to correct the interference by one or more of
the following measures:

• Reorient or relocate the receiving antenna.

• Increase the separation between the equipment and the
receiver.

• Connect the equipment into an outlet on a circuit different
from that to which the receiver is connected.

• Consult the dealer or an experienced radio/TV technician for
help.

CAUTION: Changes or modifications to this device not expressly
approved by Yamaha Guitar Group, Inc. could void the user's
authority to operate the equipment under FCC rules.

This apparatus does not exceed the Class A/Class B (whichever
is applicable)
apparatus as
Canadian Department

limits for radio noise emissions from digital

set out in the radio interference regulations of the

of Communications.

CONSIGNES DE SECURITE IMPORTANTES

- LIRE, SUIVRE TOUTES LES INSTRUCTIONS ET LES PRECAUTIONS D’UTILISATION

- NE PAS UTILISER PROCHE D’UNE SOURCE DE CHALEUR ET NE PAS BLOQUER OU OBSTRUER LE SYSTEME DE VENTILATION SUR CET APPAREIL. POUR UNE

UTILISATION CONFORME, CET APPAREIL NECESSITE ENVIRON 7CM D’ESPACE BIEN VENTILE AUTOUR DE SON SYSTEME DE REFROIDISSEMENT, AINSI QU’UN COURANT
D’AIR FRAIS CONSTANT

- NE PAS UTILISER CET APPAREIL PROCHE D’UNE SOURCE LIQUIDE

- NETTOYER SEULEMENT A L’AIDE D’UN CHIFFON DOUX ET SEC ET NE PAS UTILISER DE PRODUITS MENAGERS

- CONNECTER UNIQUEMENT LE CABLE D’ALIMENTATION FOURNI SUR UNE PRISE AVEC MISE A LA TERRE, ET COMPATIBLE AVEC LA TENSION, L’INTENSITE ET LA

FREQUENCE REQUISES INDIQUEES SUR LA FACE ARRIERE DE L’APPAREIL

- S’ASSURER DE NE PAS MARCHER, PLIER OU TIRER SUR LE CABLE D’ALIMENTATION

- DEBRANCHER L’APPAREIL LORS D’UNE TEMPETE OU LORS D’UNE TRES LONGUE PERIODE DE NON UTILISATION

- UTILISER UNIQUEMENT DES ACCESSOIRES SPECIFIES PAR LE FABRICANT POUR UNE UTILISATION EN TOUTE SECURITE ET POUR EVITER DES BLESSURES

- ATTENTION: AFIN DE PREVENIR TOUT RISQUE DE CHOCS ELECTRIQUES OU DE DEBUT D’INCENDIE, NE PAS EXPOSER CET APPAREIL A LA PLUIE ET A L’HUMIDITE

- TOUT ENTRETIEN DOIT ETRE FAIT PAR UN TECHNICIEN QUALIFIE

- NOS AMPLIFICATEURS PEUVENT PRODUIRE DE TRES HAUTES PRESSIONS ACOUSTIQUES QUI PEUVENT CAUSER DES DOMMAGES AUDITIFS PERMANENTS OU

DEFINITIFS. L’UTILISER AVEC UNE GRANDE PRECAUTION EST CONSEILLE ET DES PROTECTIONS AUDITIVES SONT RECOMMANDEES POUR UNE UTILISATION A FORT
VOLUME.

- ATTENTION: CET APPAREIL REQUIERT UNE PRISE MURALE AVEC MISE A LA TERRE, AUX NORMES ACTUELLES ET COMPATIBLE AVEC LES SPECIFICATIONS

ELECTRIQUES SE TROUVANT EN FACE ARRIERE DE L’APPAREIL. LA PRISE ELECTRIQUE DOIT RESTER ACCESSIBLE POUR DEBRANCHER L’APPAREIL EN CAS DE DEFAUT
PENDANT L’UTILISATION

- CET APPAREIL DOIT ETRE DEBRANCHE SI IL N’EST PAS UTILISE

Elimination correcte du produit : Ce symbole indique que ce produit ne doit pas être éliminé avec les ordures ménagères, comme le prévoiT la directive WEEE (2012/19/
EU) et votre loi nationale.

Ce produit doit être remis à un site de recyclage des déchets électriques et des équipements électroniques (EEE).

Un mauvais recyclage de ce type de déchet peut avoir de possibles impacts négatifs sur l’environnement et la santé humaine dus aux émanations de substances.

Dans un même temps, votre coopération à un recyclage correct de ce produit contribuera à la bonne utilisation des ressources naturelles.

Pour connaître l’endroit où il est possible de recycler ces équipements, merci de contacter votre mairie, les services de recyclages ou le service des déchets ménagers.

ATTENTION — Le présent appareil numérique n’émet pas de
bruits radioélectriques dépassant las limites applicables aux
appareils numériques de class A/de class B (selon le cas)
prescrites dans le réglement sur le brouillage radioélectrique édicté
par les ministere des communications du Canada.

Exposure to extremely high noise levels may cause permanent
hearing loss. Individuals vary considerably in susceptibility to
noise-induced hearing loss, but nearly everyone will lose some
hearing if exposed to sufficiently intense noise for a period of
time. The U.S. Government’s Occupational Safety and Health
Administration (OSHA) has specified the permissible noise level
exposures shown in the following chart.

According to OSHA, any exposure in excess of these
permissible limits could result in some hearing loss. To ensure
against potentially dangerous exposure to high sound pressure
levels, it is recommended that all persons exposed to equipment
capable of producing high sound pressure levels use hearing
protectors while the equipment is in operation. Ear plugs or
protectors in the ear canals or over the ears must be worn when
operating the equipment in order to prevent permanent hearing
loss if exposure is in excess of the limits set forth here:

Duration, per
day in hours

8 90 Duo in small club
6 92
4 95 Subway Train
3 97
2 100 Very loud classical music

1.5 102
1 105 The boss screaming at his minions about

0.5 110

0.25 or less 115 Loudest parts at a rock concert

Sound
Level dBA, Slow
Response

Typical Example

manual deadlines

Correct disposal of this product: This symbol indicates that this product should not be disposed of with your household waste,
according to the WEEE directive (2012/19/EU) and your national law. This product should be handed over to an authorized col­lection site for recycling waste electrical and electronic equipment (EEE). Improper handling of this type of waste could have a
possible negative impact on the environment and human health due to potentially hazardous substances that are generally asso­ciated with EEE. At the same time, your cooperation in the correct disposal of this product will contribute to the effective usage
of natural resources. For more information about where you can drop off your waste equipment for recycling, please contact your
local city office, waste authority, or your household waste disposal service.

3

SVT-VR Bass Guitar Amplifier

Introduction

Congratulations!

This versatile and powerful bass amplifier delivers up to 300 watts of unsurpassed quality,
offering the classic vibrance of tubes, as well as contemporary features.

The SVT-VR amplifier is an ideal companion to the SVT-410HLF, SVT-610HLF, SVT-810AV
or SVT-810E cabinet, available separately.

Like all Ampeg products, your SVT-VR amplifier is designed by musicians and built
using only the best of components. Each amplifier is tested to confirm that it meets our
specifications, and we believe that this amplifier is the absolute best that it can be. In order to
get the most out of your new amplifier, please read this manual before you begin playing.

Best of luck in all of your musical endeavors!

Sincerely,

The dedicated team at Ampeg

You are now the proud owner of an Ampeg SVT-VR bass guitar amplifier.

Features

• TWO-CHANNEL OPERATION: Two separate channels with independent tone and
volume controls.

• BRIGHT AND NORMAL INPUTS: Each channel offers a choice of inputs: normal or
high-end enhanced [bright].

• ULTRA HI, ULTRA LO AND BASS CUT (CH. 1 ONLY) SWITCHES: Lets you tailor your
sound in many different ways with the touch of a button.

• MIDRANGE FREQUENCY SELECT “1•2•3” SWITCH (CH. 1 ONLY): Allows you to
select the operating range for the midrange control for increased tonal flexibility.

• BIAS ADJUSTMENT CONTROLS: Lets you adjust the tube bias and balance for optimal
operation.

• SLAVE OUT: Use for powering another amp from the SVT-VR’s preamp.

• POWER AMP IN / PREAMP OUT: A separate preamp may be connected to the power
amp in jack and the preamp out jack may be connected to a slave amp.

• TRANSFORMER BALANCED LINE OUT: Independent level control – balanced XLR
output jack – switchable pre– or post–EQ – ground lift for balanced XLR.

• HEAVY-DUTY SPEAKER JACKS: Speakon jacks for more reliable connections at higher
output.

4

The Front Panel

1 2 3 4

7 8 9 13 14

5 6 10 11 12 15 16

SVT-VR Bass Guitar Amplifier

1. ONE: (The Channel One Input jacks):
The signal output from an instrument
or a line-level signal may be connected
to this 1/4" input by means of a
shielded instrument cable. Either the
bright or normal jack may be used.
The bright jack enhances the high
frequencies of the input signal. The
signal at these jacks is sent into the
channel one preamp section [tone
and volume controls].

2. TWO: (The Channel Two Input jacks):
The signal output from an instrument
or a line-level signal may be connected
to this 1/4" input by means of a
shielded instrument cable. Either the
bright or normal jack may be used.
The bright jack enhances the high
frequencies of the input signal. The
signal at these jacks is sent into the
channel two preamp section [tone
and volume controls].

3. VOLUME: Use this control to adjust the
output level of channel one.

4. TREBLE: Use this to adjust the high
frequency level of channel one. This
provides up to 12 dB of boost, or
12 dB of cut at 4 kHz. The high
frequency output is flat at the center
position.

5. MIDRANGE: Use this to adjust the
midrange frequency level of channel one.
This provides up to 20 dB of boost, or
20 dB of cut at the selected frequency

[8]. The midrange frequency
output is flat at the center position.
Rotate the control counter-clockwise
for a “contoured” sound (more distant,
less midrange output) or clockwise for a
sound which really cuts through.

6. BASS: Use this to adjust the low
frequency level of channel one. This
provides up to 12 dB of boost, or
12 dB of cut at 40 Hz. The low
frequency output is flat at the center
position.

7. ULTRA-HI: This switch, when engaged
[right side down], enhances the amount
of high frequency output of channel one.
The amount of boost is dependent on
the setting of the volume control [3].

8. 1•2•3: This switch selects the
frequency that will be affected by the
midrange control [5]. The available
frequencies are 220 Hz [left side of
the switch engaged], 800 Hz [switch
in the center position], or 3 kHz (right
side of the switch engaged].

9. BASS-CUT/OFF/ULTRA-LO: Engaging
the left side of this switch decreases
the low frequency output of channel
one. Engaging the right side of this
switch enhances the low frequency
output of channel one. The switch is
inactive in the center position.

10. VOLUME: Use this control to adjust the
output level of channel two.

5

The Front Panel continued

1 2 3 4

7 8 9 13 14

5 6 10 11 12 15 16

SVT-VR Bass Guitar Amplifier

11. TREBLE: Use this to adjust the high
frequency level of channel two. This
provides up to 12 dB of boost, or
12 dB of cut at 4 kHz. The high
frequency output is flat at the center
position.

12. BASS: Use this to adjust the low
frequency level of channel two. This
provides up to 12 dB of boost, or
12 dB of cut at 40 Hz. The low
frequency output is flat at the center
position.

13. ULTRA-HI: This switch, when engaged
[right side down], enhances the amount
of high frequency output of channel two.
The amount of boost is dependent on
the setting of the volume control [10].

14. ULTRA LO: This switch, when engaged
[right side down], enhances the low
frequency output of channel two.

15. STANDBY SWITCH: Use this switch to
turn the standby power on or off. Flick
the switch up to turn the standby on.
The standby mode allows the tubes to
warm up or remain warm without high
voltage being applied to them. This
helps extend tube life. This switch should
be OFF when first turning the amplifier
on. Allow the unit to warm up for at least
20 seconds before switching to the ON
position. During short periods of
non-use, the amp should be put into
standby mode.

16. POWER SWITCH: Use this switch to
turn the overall system power on or
off. Flick the switch up to turn on the
power. The power switch should be
engaged prior to the standby switch
(as mentioned above, #15). This
switch must be turned off to reset
the amp after a Fault condition. The
adjacent lamp illuminates green when
the amplifier is on and is not in
standby mode.

6

The Rear Panel

17 19 20 21 22 23 2426 282725 2918

SVT-VR Bass Guitar Amplifier

17. IEC POWER INPUT CONNECTOR: This
is where you connect the supplied AC
power cord. Plug the male end of the
cord into a grounded AC outlet.
DO NOT DEFEAT THE GROUND PRONG
OF THE AC PLUG!

18. FUSE: This protects the unit from
damage due to overload conditions or
power line surges. If the fuse blows,
replace it only with the same size and
type.

19. POLARITY: Place this switch in the
position that provides the least electrical
buzz from the unit.

20. BIAS / BALANCE SECTION: These
controls and sets of LEDs allow the user
to properly bias the power amp. See
“Setting Tube Bias and Balance” on page
15 for a complete description of how to
use this section.

21. SLAVE OUT: The slave out is for
slaving two amps together: it connects
both their power amps and their
preamps.

22. POWER AMP IN: This jack connects
directly to the internal power amp for
use with an external preamp. When
using an external source, connect the
OUTPUT of the source to this jack using
a shielded instrument cable to feed the
signal into the power amp section. The
internal signal is disconnected when a
plug is inserted into this jack.

23. PREAMP OUT: This jack is a direct
post master preamp output for use with

an external power amp. Connect the
external amp’s input to this jack using a
shielded instrument cable.

24. TRANSFORMER BAL OUT: This signal
may be used to feed an external power
amplifier, mixing console or house PA
system.

The signal level at this jack is controlled

by the level control [25] and may be
pre– or post–EQ depending on the
setting of the pre/post switch [26].
Additionally, the lift/gnd switch [27] is
available to reduce any noise that may
occur at the transformer bal out.

25. LEVEL: Use this control to adjust
the signal level at the transformer
bal out jack [24]. This control works
independently from the front panel
volume controls [3, 10].

26. PRE (CH. 1) / POST: The signal at
the transformer bal out jack [24] can
be set to either Pre-EQ or Post-EQ with
this switch. With the switch in the OUT
position, the signal at the jacks is
Pre-EQ. This is a direct output not
affected by any volume or tone
controls. With the switch in the IN
position, the signal is Post-EQ and is
controlled and modified by the volume
and tone controls.

27. LIFT / GND: When this switch is
engaged, it connects the ground
connection at the transformer bal
out jack [24]. This may help reduce
residual hum and buzz sometimes
picked up in line out signal cables.

7

17 19 20 21 22 23 2426 282725 2918

The Rear Panel continued

SVT-VR Bass Guitar Amplifier

28. IMPEDANCE SELECTOR: Use this
switch to match the output impedance
of the amp to the speaker(s) being used
(2 or 4 ohms). For help in deciding the
total impedance of your system, consult
the chart below.

Cabinet Number of Total

Impedance Cabinets Impedance

2 ohms 1 2 ohms

4 ohms 1 4 ohms

4 ohms 2 2 ohms

8 ohms 2 4 ohms

8 ohms 4 2 ohms

29. SPEAKER OUTPUTS: Two 1/4" output
jacks and one Speakon® output jack
supply speaker-level power to the
cabinet. The rated power output is 300
watts rms into 2 or 4 ohms.

The two identical outputs are wired in

parallel, and you can use either one, or
use both. Make sure the total speaker
impedance load is 2 ohms or greater.

Use speaker cables with Speakon or

1/4" TS ends to make the connections.
Do not use instrument cables as they
may overheat.

NOTE: In some areas, 1/4" speaker jacks

are not appropriate for use on amplifiers
with high output power levels. For this
reason, use the Speakon jack instead.

(Speakon® is a registered trademark of Neutrik AG.)

8

Suggested Settings

Standard:

*

Back Pickup

Fretless:

*

SVT-VR Bass Guitar Amplifier

Hard Edge:

“Scooped”:

*

*

= as needed

*

9

Personal Settings

SVT-VR Bass Guitar Amplifier

10

SVT-VR Bass Guitar Amplifier

Important information about tubes

A brief history of the tube:

In 1883, Thomas Edison discovered that electrons would flow from a suspended filament when enclosed
in an evacuated lamp. Years later, in 1905, John Ambrose Fleming expanded on Edison’s discovery and
created the “Fleming Valve”. Then, in 1907, Dr. Lee de Forest added a third component – the grid – to
“Fleming’s Valve” and the vacuum tube was a fact of life. The door to electronic amplification was now
open.

During World War II, data gleaned from their intensive research on the detectors used in radar systems
led Bell Telephone Laboratories to the invention of the transistor. This reliable little device gained quick
support as the new component for amplification. The death of the vacuum tube seemed imminent as
designers, scientists, and engineers reveled in the idea of replacing large, fragile glass tubes with these
small, solid-state devices.

However, there were (and still are) many serious listeners who realized that the sound produced by a
“transistor” amplifier is significantly different from that produced by a tube amplifier with identical design
specifications. They considered the sound produced by these new solid-state devices to be hard, brittle,
and lifeless. It was determined that solid-state devices produced a less musical set of harmonics than
tubes. When pushed past their limits, they tend to mute the tone and emphasize the distortion.

Tubes, on the other hand, produce a more musical set of harmonics, the intensity of which may be
controlled by the player. This characteristic adds warmth and definition to the sound which has become
the hallmark of tube amplifiers. When tubes are driven into clipping, the harmonic overtones can be both
sweet and pleasing or intense and penetrating, depending on the musician’s taste and playing technique.

Over the years, application engineers have designed a number of outstanding solid-state amplifiers that
sound very, very good. Some use special circuitry which enables them to simulate distortion
characteristics of a tube amplifier. However, the tube amplifier, still held in the highest esteem by many
musicians, offers a classic “vintage” sound in a contemporary market.

Tube types and usage:

Tube amplifiers are based primarily on two types of tubes – preamplifier tubes and power tubes. The
tubes used in preamplifiers (12AX7, 12AU7, 12AT7, etc.) are smaller than the power tubes. These tubes
amplify the signal from the instrument and shape the sound. They are inherently microphonic (mechani­cally pick up and transmit external noises). Since these tubes are used in the critical first stages of a tube
amplifier’s circuitry, it is very important that any replacements are high-quality, low noise/low microphonic
tubes for this application. Although tubes of this quality may be difficult to find and typically cost more
than “off-the-shelf” tubes, the improvement in performance is worth the investment.

Preamplifier tubes are also used to drive the power tubes. When used in this application, a 12AX7 will
produce a more distorted tone than a 12AT7 which produces a clearer, sweeter sound. A 12AU7 is even
cleaner and brighter than a 12AT7, giving more definition to the sound. It is possible to change the sound
of the amplifier by changing the type of preamp and/or driver tubes. When making any modification to
your equipment, it is highly recommended that you consult with a qualified service center.

11

Tube types and usage continued...

SVT-VR Bass Guitar Amplifier

Power tubes

These tubes convert the low-level, conditioned signal from the preamplifier into a level that is sufficient to
drive the speakers. There are several types of power tubes available, each of which offers a different per­formance/sound characteristic. For example, the EL34 power tube produces a great classic rock sound.
When an EL34 is driven into distortion, it produces a unique sound (“crunch”). When compared to the 6L6,
the EL34 distorts more quickly, exhibits a “looser” low-end response and produces more harmonics at mid
and high frequencies (“creamier” sound). These differences become more noticeable at higher volumes.

The 6L6 tubes produce a big low-end thump and have very good dynamic range. They offer a more tradi­tional “American Rock” sound. The 6V6 tubes produce a creamy sound with nice distortion. On the other
hand, the KT88 produces a big low-end but sounds more like an EL34 in the mid and high frequencies.

The 6550 power tubes are more rugged and stay cleaner sounding, even at full power. When they do dis­tort, the sound produced is more solid and has a tighter low end; more of a “heavy metal” type distortion
with lots of power.

Some power tubes are available in matched sets. These tubes have been extensively tested for optimum
performance and longevity.

When replacing power tubes, please replace them with a tested, matched pair and have the amp rebiased
by a qualified service center. It is possible to change the sound of the amplifier by changing the type of
power tubes. When making any modification to your equipment, it is highly recommended that you consult
with a qualified service center.

are the largest tubes used in an amplifier, generate the most heat and wear out the fastest.

The nature of tubes – why (and when) to replace them:

Tubes are made up of a number of fragile mechanical components that are vacuum-sealed in a glass
envelope or bubble. The tube’s longevity is based on a number of factors which include how hard and
often the amplifier is played, vibration from the speakers, road travel, repeated setup and tear down, etc.

Any time you notice a change in the amplifier’s performance, check the tubes first.

If it’s been awhile since the tubes were replaced and the sound from the amplifier lacks punch, fades in
and out, loses highs or lows or produces unusual sounds, the power tubes probably need to be replaced.
If the amplifier squeals, makes noise, loses gain, starts to hum, lacks “sensitivity”, or feels as if it is
working against you, the preamplifier tubes may need to be replaced.

The power tubes are subjected to considerably more stress than the preamplifier tubes. Consequently,
they almost always fail/degrade first. If deteriorating power tubes aren’t replaced, they will ultimately fail.
Depending on the failure mode, they may even cause severe damage to the audio output transformer
and/or other components in the amplifier. Replacing the tubes before they fail completely has the potential
to save time, money and other unwanted troubles. Since power tubes work together in an amplifier, it is
crucial that they (if there is more than one) be replaced by a matched set. If you are on the road a lot, we
recommend that you carry a spare matched set of replacement power tubes and their associated driver
tubes.

After turning off the power and disconnecting the amplifier from the power source, carefully check the
tubes (in bright light) for cracks, white spots inside the glass or any apparent damage. Then, with the
power on, view the tubes in a darkened room. Look for the preamplifier tubes that do not glow at all or
power tubes that glow excessively red.

12

SVT-VR Bass Guitar Amplifier

The nature of tubes continued...

Whenever replacing power tube(s):

• Always have the amplifier’s bias voltage checked by a qualified service center. Improper bias voltage
will cause degradation in performance and possibly damage tubes and/or the amplifier. (See the section
below titled “The importance of proper biasing” for more information on this subject).

• We highly recommend replacing the driver tube(s), as well. The driver tube determines the shape and
amplitude of the signal applied to the power tube(s) and has to work almost as hard as the power tube(s).

You may check the preamplifier tubes for microphonics by turning the amplifier on, turning up the gain and
tapping lightly on each tube with the end of a pencil or a chopstick. You will be able to hear the tapping
through the speakers, which is normal. It is not normal for a tube to ring like a bell after it is tapped. If it
does ring, then it is microphonic and should be replaced. Remember to use only high quality, low
microphonic tubes in the preamplifier section.

Even though power tubes are rarely microphonic, they should be checked, anyway. The power tubes may
be checked for microphonics just like the preamp tubes.

In the case of very high gain amps, you may be able to reduce the amount of noise generated by simply
swapping the preamp tubes around.

The importance of proper biasing:

For the best performance and longest tube life, proper biasing is imperative. Bias is the negative
voltage which is applied to the power tube’s control grid to set the level of idle current. We cannot over
emphasize the difference in warmth of tone and dynamic response that come with proper biasing. If
the bias is set too high (overbiased), the sound from the amp will be distorted at all levels. If the bias is
set too low (underbiased), the power tubes will run hot (the plates inside the tubes may glow red due to
excessive heat) and the sound from the amplifier will lack power and punch. The excessive heat greatly
reduces tube life – from a few days to as little as a few hours in extreme cases. Setting the bias on the
amp is like setting the idle on a car. If it’s too high or hot, it’s running away with you and if it’s too low or
cold it will choke when you step on it.

The bias is adjusted at the factory in accordance with the type of power tube(s) installed in your
amplifier. It is important to point out that tubes of the same type and specification typically exhibit
different performance characteristics. Consequently, whenever power tubes are replaced, the bias
voltage must be checked and re-adjusted to accommodate the operating parameters of the
replacement tubes. The bias adjustment should be performed only by qualified service personnel
with the proper, calibrated test equipment.

13

SVT-VR Bass Guitar Amplifier

Survival Tips for Tube Amplifiers

To prolong tube life, observe these tips and recommendations:

• Match the impedance of the speaker cabinet(s) to the amplifier. Improper impedance matching
will contribute to early tube degradation and may cause premature tube failure.

• Make sure the speaker(s) are properly connected prior to turning on the amplifier.

• After playing the amplifier, allow sufficient time for it to properly cool down prior to moving it.
A properly cooled amplifier prolongs tube life due to the internal components being less
susceptible to the damage caused by vibration.

• Allow the amplifier to warm up to room temperature before turning it on. The heat generated by
the tube elements can crack a cold glass housing.

• Replace the output tube(s) before the performance degrades or the tubes fail completely.
Replace the tube(s) on a regular basis; at least once per year or as often as every 4 to 6
months if you play long and hard every day.

• Always have the bias checked after replacing the output tubes (unless the amplifier is equipped
with “self-biasing circuitry”). This should be done ONLY at a qualified service center. Improper
biasing could result in the tubes running too hot, which greatly reduces the life of the tubes – or
too cold, which results in distorted sound regardless of level settings. Do not play the amplifier
if it exhibits these symptoms – get the bias checked/adjusted immediately to prevent tube failure
and/or other damage.

• If the locating notch on the base of the power tube breaks off, replace the tube. This significantly
reduces the risk of damaging the amplifier by incorrectly inserting the tube.

• Protect the amplifier from dust and moisture. If liquid gets into the amplifier proper, or if the
amplifier is dropped or otherwise mechanically abused, have it checked out at an authorized
service center before using it.

• Proper maintenance and cleaning – in combination with routine checkups by an authorized
service center – will ensure the best performance and longest life from the amplifier.

CAUTION: Tube replacements should be performed only by qualified service personnel who are
familiar with the dangers of hazardous voltages that are typically present in tube circuitry.

14

SVT-VR Bass Guitar Amplifier

Changing the Tubes

Tubes wear out in direct proportion to how often and how hard you use the amplifier. Power tubes
should be checked at least once a year – more frequently if you use the amplifier nearly every day.
When power tubes wear out, the amplifier will begin to grow weak, lack punch, fade up and down, or
lose highs and lows. Power tubes work together in a push/pull configuration and should be replaced
at the same time with matched or balanced tubes. Your dealer can recommend the best replacement
tubes for your amplifier.

Preamp tubes aren’t worked as hard as power tubes and typically last longer. When a preamp tube
wears out, the amplifier may squeal, get noisy, lose gain and sensitivity, or just quit working. A service
center can determine which tube(s) may need replacing.

To get to the power tubes in the SVT-VR, the rear screen must be removed and the tube retainer(s) must
be moved out of the way. Qualified service persons may follow these steps to change the tubes:

• Turn the amp off, unplug it and let it cool for at least 5 minutes.

• Remove the screws which hold the perforated metal screen to the rear of the cabinet.

• Set the perforated metal screen aside.

• Remove the tube retainer(s) by lifting them off the tube(s) and moving them to one side.

• Grasp the tube at its top and gently work it out of its socket by rocking it slightly back and forth as
you lift up on it.

• When inserting new output tubes, align the tab in the tube’s plastic base with the slot in the socket
and press the tube gently but firmly into place by pushing down on its top.

• Replace the perforated metal screen and screws.

• Power up the amplifier and let it sit for at least 20 minutes. Bias the amplifier as directed in the
section below.

Setting Tube Bias and Balance

Tube Bias:

Allow the amplifier to warm up to proper AC line voltage for at least 20 minutes. With no signal
present, adjust each bias control until its adjacent LED illuminates.

The Bias 1 control affects the three power tubes on the left (as viewed from the rear). The Bias 2
control affects the three power tubes on the right (as viewed from the rear).

Balance:

Insert a 40 Hz signal into the amplifier. Adjust the volume control for approximately 25VRMS output.
Slowly adjust the balance control until its adjacent LED illuminates.

15

SVT-VR Bass Guitar Amplifier

Troubleshooting

In the unlikely event that your SVT-VR should malfunction, take a few minutes to
troubleshoot it before you call for service. You can save yourself time and money by
doing it yourself, and often the cure for the problem is something quite simple. If you
think the problem may be worn out tubes, see page 12–13 for symptoms of tube failure.

If the problem isn’t covered above, or if the steps lead you here, then contact your
Ampeg dealer for service information. Also, you should refer the amp for servicing if it
gets dropped, has liquid spilled into it, or sustains damage to its power cord.

16

Block Diagram

BRIGHT

NORMAL

BRIGHT

NORMAL

OUT

POWER

PREAMP

AMP IN

MID-

RANGE

OUT

SLAVE

SVT-VR Bass Guitar Amplifier

SPEAKERS

2 OHM

4 OHM

BALANCE

2

BIAS

AMP

POWER

1

BIAS

(SPEAKON

1+

JACK)

2+

1- 2-

ONE

1•2•3

TREBLEBASS

VOLUME

HIGH

ULTRA

LOW

ULTRA

PRE

POST

BAL. OUT

TRANSFORMER

GND

LIFT

LEVEL

TWO

TREBLEBASS

VOLUME

HIGH

ULTRA

LOW

ULTRA

17

SVT-VR Bass Guitar Amplifier

SVT–VR Technical Specifications

Output Power Rating 300 watts rms minimum continuous @ <5% THD
into 2 or 4 ohms, 0.25VRMS input

Total System Gain
Channel one: 66 dB @ 1 kHz with volume up and tones flat
Channel two: 59 dB @ 1 kHz with volume up and tones flat

Signal to Noise Ratio
Channel one: 75 dB typical
Channel two: 75 dB typical

Maximum Gain [5% THD] 78 dB @ 1 kHz, levels up, tone controls centered;
–3 dB @ 20 Hz, 15 kHz

Tube Complement 12AX7 (4), 12AU7 (4), 6550 (6)

Tone Controls
Channel one:
Bass: +12 / –12 dB @ 40 Hz
Midrange: +20 / –20 dB @ 220 Hz, 800 Hz
or 3 kHz
Treble: +12 / –12 dB @ 4 kHz
Ultra Hi: +15 dB @ 8 kHz (volume @ 50%)
Ultra Lo: –20 dB @ 600 Hz
Bass Cut: –20 dB @ 40 Hz
Channel two:
Bass: +12 / –12 dB @ 40 Hz
Treble: +12 / –12 dB @ 4 kHz
Ultra Hi: +15 dB @ 8 kHz (volume @ 50%)
Ultra Lo: +11 dB @ 40 Hz (relative)

Power Requirements [Domestic]: ~100–120 VAC, 50–60 Hz, 400W
[Export]: ~200–240 VAC, 50–60 Hz, 400W

Size (H x W x D) 11.5 in / 292 mm (with feet) x 24.0 in / 610 mm /
x 12.75 in / 324 mm

Weight 85 lb / 38.6 kg (approximately)

18

SVT-VR Bass Guitar Amplifier

SVT–VR Service Information

Service Information

I

f you are having a problem with your SVT-VR, you can go to our website (www.ampeg.com)
and click on Support for service information, or call Technical Support at 1-818-575-3600
Monday – Friday during
outside of the U.S., contact your local distributor for technical support and service.

The

SVT-VR is covered with a durable fabric-backed vinyl material.

Never spray cleaning agents on the SVT-VR. Avoid abrasive cleansers which would damage the finish.

Ampeg continually develops new products and improves upon existing ones. For this reason, the specifications
and information in this manual are subject to change without notice.

normal business hours, Pacific Time

, to receive assistance. If you are

Clean with a dry lint-free cloth.

“Ampeg” is a registered trademark of Yamaha Guitar Group Inc. All other brand names mentioned are trade­marks or registered trademarks of their respective holders and are hereby acknowledged.

www.ampeg.com

©2018 Yamaha Guitar Group Inc.

26580 Agoura Road • Calabasas, CA 91302-1921

Part No. 2038873 Rev. D 07/18

19

SVT-VR

Bass Guitar Amplifier

Owner’s Manual