13
400RB Series
Tech
Talk
Cool Running = Reliability:
To cool the 400RB weve designed a temperature sensi-
tive fan cooling system. When the amp is under a light
load, the fan is off or running at a low speed, reducing fan
noise. As the amp works harder, the fan speed increases
to keep everything cool.
Smart Protection Circuitry:
The 400RB’s protection circuitry constantly monitors
for unsafe operating conditions such as short circuits,
miswired speaker cables, blown speakers, improper
ventilation and incorrect speaker configurations. In
addition, protection is provided during power up/
power down. If the 400RB senses any unsafe operat-
ing conditions, the output signal is immediately
muted and the power light changes from Green to
Red. The amplifier will remain muted until the fault
is removed. If the protection circuit activates while
playing, turn the amplifier off and check the ampli-
fier speaker output connections. Be sure that you are
not exceeding the maximum recommend load
described in this manual. If the problem persists,
contact GK directly for technical advice.
Low Noise Operation:
The 400RB Series uses a high gain, high headroom,
low noise input stage. It has such a large dynamic
range (60v p-p) that very few instruments can
overdrive it. Even most basses with “active” electron-
ics do not need the input attenuator to be set. The
benefit to you is less hiss from your horn, and overall,
less noise.
In Closing:
You should now have a thorough understanding of
how your new 400RB Series amplifier works and what
advantages it can offer you in getting “your” sound.
We thank you for reading the Owner’s Manual and
wish you the best of times! Please send us your
comments via www.gallien-krueger.com or email us
at [email protected].
Tech Talk
Voicing Filters:
Voicing filters are used to completely revoice the
amplifier. In the case of the Contour and String Bass
controls, the effect is dramatic.
The Contour control tunes between two different
shaping circuits, with greatly different response. With
the control all the way up, the low end is slightly
boosted, the mids are dropped and the high end is
pushed up. This is a contour response not available
with a normal equalizer, and is only found in GK
amplifiers.
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 re-
sponse 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 (worlds 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…at least now, you have a
choice!
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Technology:
As in all GK pre-amps, the 400RB Series pre-amp
incorporates what we call G.I.V.E (Gate Induced Valve
Effect) Technology. We use field effect devices with
the gate biased in a way that emphasizes the optimum
harmonic content of the signal.
