Gallien-Krueger 400RB-III SM Schematic

Service Manual

400RB-III Series

Table of Contents

Operating Instructions 3
Turn On / Calibration Procedure 20
Schematics 21
Bill of Materials 22

Note: As of 1/99, there are no Engineering Change Orders (ECOs) for this model. New ECOs will be re-

leased as they are issued.

400RB Series

Table Of Contents

Table of Contents

*All Features and specifications are subject to change without notice
**This list is subject to change without notice.

Introduction.....................................................................

Quick Start.......................................................................

Sound Tips.......................................................................

Safety Information..........................................................

Installation and Maintenance........................................

Front Panel Controls.....................................................

Rear Panel Controls......................................................

400RB Series Combos...................................................

Tech Talk.......................................................................

Specifications.................................................................

Notes..............................................................................

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Gallien-Krueger

2240 Paragon Dr.
San Jose, CA, 95131
phone: [phone]
fax: [phone]
www.gallien-krueger.com

2

Congratulations

400RB Series

Your purchase of a new Gallien-Krueger 400RB Series
product is surely the result of much careful consider­ation on your part. For our part, we at Gallien­Krueger are pleased that you chose us, and are
determined that you will be a satisfied customer. In
choosing a 400RB Series product, you own an
amplifier with many unique features, that can take
you where you have never been before.

To get the most out of your new purchase please take a
few minutes to read through this manual. If you are in a
hurry, we suggest you at least read through the Quick
Start section before setting up your new rig. This will
help get you started and give you a few quick tips, but is
not a substitute for reading the rest of the manual.

Your amplifier should have come with the following
items, please check the contents of the box to ensure that
you have everything.

Included with your 400RB Head:
400RB 1
Rack mount ears with hardware 2
Power cord 1
Owner’s manual 1
Warranty card 1
Safety instructions sheet 1

If your 400RB Series amplifier or combo did not
come with all the items listed, or if you encounter
problems while setting up your new equipment,
please contact your local dealer, or us as soon as
possible at:

Gallien-Krueger, Inc.
2240 Paragon Drive
San Jose, CA 95131
phone: [phone]
fax: [phone]
Internet: www.gallien-krueger.com
Email: [e-mail]

We wish you a lifetime of good playing and remem­ber to always have fun!

Introduction

Included with your 400RB Combo:
400RB/112, or /115 1
Power Cord 1
Owner’s Manual 1
Warranty Card 1
Safety Instructions Sheet 1

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Always Listening

I have never seen the point in doing things the way
others have done them. I also have not been very
interested in following the latest fad. I am a
Stanford educated engineer who worked his way
through school as a musician. Like all musicians, I
have lugged amplifiers up stairways and into car
trunks, always wondering why these things had to
be so heavy, bulky, and hard to handle.
As I am the principal innovator at

Introduction

reflect my attitudes and life experiences. I don’t model
my designs after other manufacturer’s products (as
some of our competitors are proud of reciting).
Instead, I believe new and old problems are best solved
with new solutions. Having taken our own path,
products enjoy a unique, unmatched sound, allowing
the artist using them every opportunity to make an
original statement.
Having supported my products for over thirty years, I
have learned from the story they tell.
is a reflection of that story, and has a commitment to
support that legacy. Just as the products I created
thirty years ago are still telling their story, the products
we create today will be talking to us tomorrow.
We’ll be listening,

GKGK

GK, our products

GKGK

Gallien-KruegerGallien-Krueger

Gallien-Krueger

Gallien-KruegerGallien-Krueger

400RB Series

GKGK

GK

GKGK

Robert Gallien

4

Quick Start

The 400RB Series is designed to be simple to operate.
All controls have a well defined purpose and are well
behaved. These directions will take you through the
basics and give you a good start for setting up your
sound.

400RB Series

Quick Start

First:

Set the power switch to Off and connect the supplied
power cable from the amplifier AC receptacle to an AC
power outlet of proper voltage and power rating (see
safety information on page 7 for details).

Next:

Connect your speaker cabinets to the amplifier
outputs marked 240W. Be sure not to exceed the
recommended speaker load listed below.

Maximum Recommended Speaker Load:

One 4 Ohm, or two 8 Ohm cabinets.

If you are using an RBH series cabinet, set the
crossover switch to full range.

Then:

Set all EQ controls and the Boost control to 12
o’clock. The Voicing Filters should be turned all the
way down to get a flat response. Set the Volume and
Master Volumes at 0. If you have a five string bass,
push the button marked String Bass in.

Now:

Set the master control to 12 o’clock and slowly bring
the Master volume up. Do not turn the Volume
control in the input section past 12 o’clock unless you
want an overdrive effect. If you have a bass with
passive electronics make sure the controls are all the
way up. If you have a bass with active electronics,
turn all of the EQ controls on the bass to the middle
or flat position.

At This Point:

You should be hearing your bass quite well. You can
use the Volume and Master to achieve a comfortable
sound level.
turn up the Master control first.

Remember:Remember:

Remember: If you need more volume,

Remember:Remember:

Next:

Using an instrument cable, connect your bass to the
Input jack and turn the power switch on and play. If
the clip LED flashes, push the button marked
in. This will prevent you from overdriving the preamp.

-10db-10db

-10db

-10db-10db

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400RB Series

Sound Tips

The 400RB Series has several unique features which,
if used properly, will obtain that sound you have been
searching for.

The Equalizer:

The Equalizer is used to fine tune your sound. When
adjusting it, do it just a little at a time. These are

Sound Tips

active circuits, and small changes can make a big
difference in your sound. With a little experimenta­tion you will find that this equalizer is very easy to
use, never sounds weird and provides you with a large
variety of great sounds, unique to GK.

Contour:

Increasing the Contour level will scoop out mid­range frequencies while boosting the highs and lows.
The sound, once again, is unique to GK and unavail­able on any other Bass amp.

String Bass:

The way a Bass amp deals with the instrument low
string is a critical part of it’s sound. In fact, a five
string instrument requires an entirely different low
end response than a four string instrument. No
equalizer can make the necessary adjustments to
accommodate both. However, the String Bass button
on the 400RB Series does just that. When it is out, the
400RB is voiced like the 800RB (the world’s classic
four string amp). Push it in and the 400RB is voiced
for five string instruments. For some playing styles
you may want it in, even with a four string instru­ment.

Boost/Master:

Turning up the Boost control, will add a little growl to
your tone. This is an unmistakable GK trade mark
sound, that you will grow to appreciate. Raising the
Boost while lowering the Master will add more growl
while keeping the sound level the same. Growl is
actually a small amount of even order harmonic
distortion, that sounds great through a woofer. For
most playing situations, the Master is set between 12 &
3 o’clock. The cleanest sound is obtained by setting
the Master above 12 o’clock, and going above 3
o’clock for maximum power situations.

Direct Out:

The 400RB provides a low noise, high quality
balanced direct out for connection to PA and record­ing consoles. With the Pre/Post EQ switch set to “Pre”
(Out), the direct output signal is fed directly from our
low noise, high headroom, FET input stage providing
a low noise output superior to external direct boxes
and impedance transformers. The Direct Output
signal is only effected by the -10dB Pad, and Tuning
Mute controls. This allows you to adjust your tone
and volume on stage without changing the Direct Out
signal level and confusing your sound man.

Changing the Pre/Post EQ switch to “Post” (In),
sends the “GK sound” and preamp response to the
Direct Out jack. This gives you complete control over
the Direct Out’s tone and volume. In addition, a
Ground (Gnd) Lift switch is included to remove hum
and buzz when connecting to equipment powered by
a different ground system.

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Safety Information

400RB Series

V erify Line Voltage and Amperage Before
Use:

Your new 400RB Series Bass Amp has been factory
configured for use with:

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Connecting the amplifier to a line with specifications
other than indicated above can create a safety and fire
hazard, and may damage the amplifier. If you have any
questions about the voltage requirements for your
specific model, or about the line voltage in your area,
contact your dealer before plugging the unit into a wall
outlet.

Verify AC Circuit Capacity Before Use:

The high power output of your amplifier may require
heavy current draw under Full-Load conditions. To
insure proper performance and avoid potential safety
hazards, we recommend connection to line circuits with
Amperage specified “as above”. Connecting multiple
amplifiers to the same circuit, or connecting the ampli­fier to the same circuit used by other heavy-power
devices, such as high-wattage lights, may cause circuit
breakers to trip. It is always a good idea to avoid using
any audio equipment on the same AC circuit as equip­ment with motors, such as air conditioners or refrig­erators. This will lessen to possibility of power
variation and electrical start-up noise affecting your
sound.

120 Volt/60Hz 20 Amp circuit for USA &
Canada.
230 Volt/50Hz 10 Amp circuit for Europe
& Australia.
100 Volt/50Hz 20 Amp circuit for Japan.
Proper AC circuit for all other countries.

Do Not Use Extension Cords:

To avoid safety hazards, use only the power cord
supplied with your unit. If a replacement cord is
used, make certain that it is of consistent quality
and gauge as the original. We do not recommend
using extension cords with this product. As with all
electrical devices, do not run power cords under
rugs or carpets or place heavy objects on them.
Damaged power cords should be replaced immedi­ately with cords meeting factory specifications.

Handle The AC Power Cord Gently:

When disconnecting the power cord from an AC
outlet, always pull the plug, never pull the cord. If
you do not intend to use the amplifier for a consid­erable length of time, disconnect the plug from the
AC outlet.

Do Not Open The Amplifier Enclosure:

There are no user-serviceable components inside
this product. Opening the amplifier enclosure may
present a shock hazard, and modification to the
product will void your warranty. If liquid enters the
unit, or any metal object such as a paper clip, wire,
or staple accidentally falls inside the enclosure,
disconnect the unit from the AC power source
immediately and consult an authorized service
station.

Unpacking:

The carton and packing materials used in shipping
your new amplifier were specially designed to
cushion it from the shocks and vibration that occur
during transport. We suggest that you save the
carton and packing materials for use in shipping,
in the event you move, or the amplifier needs repair.

Safety Information

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Installation and Maintenance

400RB Series

Installation:

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Installation & Maintenance

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To insure proper operation and to avoid
potential safety hazards, place the unit on a
firm, level surface. When installing the unit
in a rack, be sure the mounting hardware can
support the amplifier’s weight. To save space
in your rack, the 400RB’s feet can be
removed using a Philips head screwdriver.
Make certain that proper space is provided
for ventilation. The 400RB Series requires at
least ½ inch clearance above for proper
ventilation. Never block the fan vent holes in
the top or front of the amplifier. If the
amplifier will be installed in a rack or other
enclosed area, make sure that there is
sufficient air movement within the enclosure
to allow proper cooling. Consult your dealer
for more information.
Avoid installation in extremely hot or cold
locations, and areas that are exposed to direct
sunlight, or near heating equipment.
Avoid moist or humid locations.
Remember, power amplifiers generate heat.
The heat sink fins and ventilation slots that
form part of the enclosure are specially
designed to remove this heat. Placing other
electronic equipment near these heat­dissipation systems may possibly affect the
long-term reliability of both your amplifier
and the other equipment.

Cleaning:

When the unit gets dirty, wipe it with a clean, soft and
dry cloth. If necessary, first wipe the surface with a
soft cloth slightly dampened with mild, soapy water,
followed by a fresh cloth with clean water. Wipe
immediately with a dry cloth. Never use benzene,
thinner, alcohol, or other volatile cleaning agents.
Do not use abrasive cleaners, as they may damage the
finish of metal parts. Avoid spraying insecticides near
the unit.

Maintenance:

Your new amplifier is rugged. It was built to give you a
lifetime of trouble-free operation, if it is operated in
accordance with the instructions contained in this
manual. The only maintenance required is cleaning. If
you are going to move your amplifier around frequently,
we recommend a road case to protect it from scratches
and road wear.

Moving the Unit:

Before moving the unit, be certain to disconnect any
interconnection cords with other components, and
make sure that you disconnect the unit from the AC
outlet.

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Front Panel Controls

400RB Series

Front Panel Controls

1-Balanced Direct Out:

An electronically balanced output, that you can run
to your P.A. system.

2-Pre/Post EQ Button:

Selects the direct out signal from before or after the
EQ.

3-Input:

A standard ¼” input jack and input attenuator
button. The button is generally left out, except in rare
cases when the clip LED flashes.

4-T uning Mute Button:

Set this switch to “On” when tuning up. No signal
will be sent to the speakers, or the P.A. system.

5-Volume:

Sets pre-amp gain after the input stage. It is used in
conjunction with the input pad, to optimize the
amplifier’s headroom.

6-V oicing Filters:
String Bass:

Setting

this button voices the pre-amp for basses with
“B” tuning. Leave it out and the amp is voiced like the
800RB, for 4 string basses.

Contour:

Drops the mid-range frequencies while boosting lows
& highs.

Presence:

Adds edge and definition to higher frequencies.

Active Equalization:
7-T reble:

Boost and cut at 7kHz+14dB shelving type. Add or
remove edge and definition.
8-High Mid:8-High Mid:

8-High Mid:

8-High Mid:8-High Mid:
Boost and cut at 1 kHz +6dB -10dB, “Q Optimized,”
band pass type. Works on lower string harmonics,
and effects the punch of your sound.

9-Low Mid:

Boost and cut at 250Hz +6dB -10dB, “Q Optimized,”
band pass type. Works on the main body of your
sound.

10-Bass:

Boost and cut at 60Hz +10dB, shelving type. Controls
low end push.

Outputs:
11-Boost:

A post EQ gain stage using GIVE technology which
adds “growl” as it is turned up.

12-Master:

Controls output level of the amplifier.

13-Effects Loop:

Send and return jacks provided for the insertion of
effects after the EQ, but before the boost section.
Some effect units have gain, turning the BOOST
down, will compensate for this.

14-T uner Output

Output to tuner.

15-Power Switch

Turns the amplifier on or off. Should a problem
occur during operation press this switch out first.

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