14
400RB-IV Series
Tech Talk
Tech Talk
Voicing Filters:
Voicing filters are used to completely re-voice the
amplifier. In the case of the Contour and String Bass
controls, the effect is dramatic.
The Contour is used to completely revoice the ampli-
fier. 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 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 response than a four string instrument. No
equalizer can make the necessary adjustments to
accommodate both, however the String Bass button
on the 400RB-IV Series does just that. When it is out,
the 400RB-IV is voiced like the 800RB. Push it in and
the 400RB-IV is voiced for five string instruments. For
some playing styles you may want it in, even with a
four string instrument.
Low Noise Operation:
The 400RB-IV Series uses a high gain, high head-
room, 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”
electronics do not need the input attenuator to be set.
The benefit to you is less hiss from your horn, and
over all, much less noise.
“G.I.V.E.” Technology:
As in all GK pre-amps, the 400RB-IV 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. Working in concert
with our unique Four Band Active Equalizer, and
three stage Voicing Filter Section, G.I.V.E. technology
produces a consistently pleasing bass tone.
Cool Running = Reliability:
The 400RB-IV Series uses a “dual rail power supply”
that generates about half the heat of conventional
amplifiers. Low output signals run off a low voltage
supply, and high level signals run off a high voltage
supply. This keeps the amp running a lot cooler and
makes it much more reliable. To cool the amp when
its being driven hard, we’ve designed a temperature
sensitive 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-IV’s protection circuitry constantly
monitors for unsafe operating conditions such as
short circuits, miss-wired speaker cables, blown
speakers, improper ventilation, and incorrect speaker
configurations. In addition, protection is provided
during power up/down. If the 400RB-IV senses any
unsafe operating conditions, the output signal is
immediately muted and the power light changes from
Blue 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
amplifier 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.
In Closing:
You should now have a thorough understanding of
how your new 400RB-IV 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].
