pickups. With the switch in the active position, the preamp presents a lower gain (approx –10db) which is tailored to
active pickups. A bass with active pickups is essentially one that offers extreme flexibility in it’s onboard tone control
and utilizes a battery in order to power the active electronics of the bass preamp to increase the signal of the lower
impedance pickup.
SPECIAL NOTE
-
In the past several years many bass instrument manufactures have begun of-
fering preamps with hot to very hot signals. The result is that the instruments’ onboard electronics and the amount of
cut and boost used on the instrument could dramatically affect how you set your gain and EQ controls on any bass
amplifier, including the GBE 1200.
Input Signal Mute Switch
— The input section also includes an “input mute” switch. With this switch, you can place
the amplifier (and the direct output) in standby mode between sets without having to change any of your volume
settings. This feature is especially handy when using the tuner output since you will still be able to use your tuner
without having sound come from the amplifier or P.A. system. A red LED turns on when the input mute is active,
reminding you that you are in “stand-by” mode.
Channel and Mix Switches
— The “TUBE/FET” switch in the channel section switches the preamp between the
tube preamp and the FET preamp. The ”mix” switch in the channel section combines the two preamp channels
together. The mix switch must be disengaged (out) for the “TUBE/FET” channel switch to operate. Each preamp has
it’s own sound and character. Alternating between the two distinct voicings allow for creative flexibility in obtaining
your tone. Additionally, mixing the two channels together yields additional tonal possibilities. Bright blue tally LED’s
show at a glance which mode you have selected. Both switches must be in the out position in order for the 5 button
footswitch to work properly.
FET Channel Input Gain Control & O/L LED
— The “FET GAIN” control, in conjunction with the red “O/L LED”
(overload), allow you to adjust the FET preamp input gain sensitivity to the instrument you are playing. Basses
can have an output level from a few thousandths of a volt to several volts. Generally, you want to see only an
occasional flash of the red O/L LED when you really hit the string hard. Distortion of the preamp gain stage will occur
when the red O/L LED is illuminated constantly, so plan accordingly. The best signal to noise ratio will result with the
above method. Setting your playing volume in the FET channel will be a combination of the “FET GAIN” control, the
“FET VOLUME” control and the “MASTER VOLUME” control, depending in part on individual preference. A blue LED
lights when the FET channel is active.
TUBE Channel Input Gain Control & O/L LED
— The TUBE channel operates the same as the FET channel,
except that it is more often desirable to operate the “TUBE GAIN” control higher, intentionally overdriving the tube
preamp for a more overdriven and distorted sound. This action is indicated visually by the red “O/L LED” and
generally requires a higher setting on the “TUBE GAIN” control and a lower setting on the “TUBE VOLUME” control.
A blue LED lights when the TUBE channel is active.
SETTING YOUR INPUT SIGNAL
– Use the following guidelines to set your amplifier input stage for the type of bass
used and your personal playing style.
1)
Select either Active or Passive input gain depending upon the bass used.
2)
Set your instruments controls (volume and tone) where you normally prefer to run them.
3)
With the Channel Gain setting at “0” and your amplifier EQ positions centered at 12 o’clock, begin
turning the gain control up to a level in which the O/L LED is illuminating with your hardest notes
played. It is okay for the O/L LED to flash occasionally BUT it should not be on constantly.
Now set your channel volume and master volume settings for the desired output level (loudness)
that you wish to produce.
4)
Now, turn your attention to the EQ section and make the adjustments for the desired tone. Because
this is an active EQ network any large settings of cut or boost will affect the gain level of the preamp
and the O/L lights at the input stage.
5)
After setting your EQ it may be necessary to go back and adjust your input gain level accordingly. It
should be noted that the Global Signal Shape circuits will not affect the input gain BUT will affect the
Master output level and clip indicator if used with extreme settings.
Note—due to the flexibility of the GBE 1200’s channel selecting and mixing capabilities BOTH channels O/L LED’s
may illuminate even though you are only playing one channel. This feature allows you to know that signal is active in
both channels and the second channel’s gain level is set at a predetermined level (by you) before you switch to it or
mix it in.
Active 5 Band Equalization
— The “active 5 band equalization” used in the GBE 1200 amplifier is composed of 1
shelving low frequency control, 3 peaking midrange controls and 1 shelving high frequency control. These filters are
not interactive and are effective as an advanced tone control system. The filters have a cut/boost range of +/- 15dB
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