Gallien-Krueger 400RB series Operating Instructions - Page 2

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Operating Instructions

400RB

THE BASICS

Your new 400RB represents the latest advances that technol-

ogy has to offer. It was designed to provide the widest possible

range of usable sounds. The combination of three voicing filters

with four bands of active EQ is unbeatable for flexibility and

ease of operation. This amplifier has many features, all of which

are described here. A careful examination of this manual will

help you to get the most from them.

INPUT SECTION

This section contains the 1/4'' input jack and the input attenuator.

With the attenuator out the maximum input level is 1Vrms (3V

P-P). For larger input signals the input attenuator should be set.

This reduces the gain of the input stage by 10 dB, increasing the

input head room to 3V rms (10 P-P).

EFFECTS LOOP

Located on the rear panel, it is provided for the insertion of

effects. It is post EQ but pre boost and master. Using standard

guitar cords connect the effects input to the send and the effects

output to the return. The boost and master controls will effect

any signal put into the return jack. The level is 1.5V rms (4.5V

P-P) into 100K ohm.

DIRECT OUT

This output will put 500mv into 600 ohms unbalanced. It can be

used with a direct box or can be connected directly to the high

"Z" input of a mixer.

SPEAKERS

Two Speaker jacks are provided on the rear panel and will accept

a total load of 4 ohms. Lower impedances should not be used.

This unit can drive one four ohm speaker or two eight ohm

speakers, maximum. Higher impedances such as eight or sixteen

ohms are acceptable. No damage will result from operating the

amplifier with the speaker disconnected.

POWER SWITCH

The power switch and associated pilot light are located in the

lower right hand corner of the front panel.

FUSE

Located on the rear panel, never operate this amplifier with any

other than the recommended fuse.

120V operation - replace with type 3AG4A

240V operation - replace with type 3AG2A

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 above. The only maintenance required is cleaning.

We recommend a soft damp cloth and mild soap for cleaning the

outside surfaces. If you are going to pack your amplifier around

a lot, we recommend a road case to protect it from scratches and

road wear.

Setting up your Sound

Your amplifier is designed to sound about right with the tone

controls set flat (5). We therefore recommend you start with the

EQ set flat and the voicing filters out.

Helpful Hints

1. Don't be afraid to experiment with the EQ on your bass first.

Make sure that you have as close to the sound you want

from your bass before adjusting the EQ on your amp.

2. Set your playing level first. You may want to push up your

volume and boost levels while dropping back the master.

This will give a fatter sound but can add distortion. Some

players find this desirable, you will have to be the judge.

For the cleanest possible sound, operate the master on 10

(max). The boost control is footswitchable and can act as a

pre-set volume. The L.E.D. next to the boost control

indicated that boost is on.

3. Once your basic levels are set, work with the voicing filters.

The Lo Cut is a bass roll off and is used to control stage

rumble at high volume. Mid Cut puts a notch at about

500hz giving a mellow round sound. Hi Boost adds edge

and definition.

4. Having set your levels and filters, you are ready to fine tune

your tone. This is an involved procedure requiring you to

use your ears to tell you what is right. We have broken the

sound spectrum into four basic bands and provided active

controls for each. Adjustment procedures are repetitive and

require patience.

TREBLE : Boost and cut at 4khz, will add or remove

edge and definition.

HIGH MID : Boost and cut at 1khz. There is a lot of

sound in this band, it works on the lower

harmonics of your instrument and affects the

punch of your sound.

LOW MID : Boost and cut at 250hz. Basically this

band affects the body of your sound.

BASS : Boost and cut at 60hz. Affects only the bottom

end and will be used to account for varying

room accoustics.