KBR-3D
-WARNING-
The KBR-3D can produce extremely high sound pressure levels. Hearing protection is
advised. The KBR-3D must be earthed and connected to a correct power source.
-SPECIFICATIONS-
Design Range:
Rotary Channel Input 1 375 mV RMS 100K ohms
Input 2 Unlimited 50K ohms
Stereo Channel All inputs 175 mV RMS 100K ohms
Power amp inputs 420 mV RMS 22K ohms
Dry rotary output 420 mV RMS 600 ohms
1
Tube: 12AX7EH – 7025 – 5751
Power Amplifiers: 100/100 watt RMS main full range amplifiers
45-watt RMS > 800 Hz horn amplifier
Frequency Response: Full Range speakers 50-15 kHz + -5 dB
Horn driver 600 Hz-8 kHz
Speakers: 2 10” Eminence Beta 250-watt, 8 ohms
2 80-watt 3.5X3.5 Ferro-cooled horns, 8 ohms
1 80-watt MS 1.2 proprietary diaphragm horn driver, 8 ohms
Dimensions: 24” W 21” H 16” Weight 68 lbs.
Power: Fuse (Slo-Blow)
US 117 VAC 50/60 Hz 300 watt 5 amp
Europe 230 VAC 50/60 300 watt 2.5 amp
Japan 100 VAC 50/60 300 watt 5 amp
Fuse Location: The fuse is located in the power inlet module on the rear panel. Use only the
recommended size of fuse as stated above.
-DESCRIPTION-
The Motion Sound KBR-3D is a state-of-the-art amplifier for keyboard providing all of the
features necessary to reproduce stereo and rotary sound independently. The two channels employ
technology that is specifically targeted to reproduce and enhance the sound of instruments
normally associated with each channel. Hi-Fidelity stereo = piano, strings and synthesizer.
Rotary = organ. If your keyboard has multiple outputs, you can send stereo piano and strings,
etc., to the stereo channel from the standard left and right outputs of your keyboard. Organ
sounds (be sure to turn off the rotary simulator in your keyboard) may be assigned to an auxiliary
output and plugged into the KBR-3D’s rotary channel. Left/right line level inputs on the rear
panel allowing mixing boards for microphone and other instruments to be fed directly to the
KBR-3D’s power amplifiers. The rear panel has left and right XLR outputs and a mixer for the
rotary channel stereo horn microphones. There are two 10” 250-watt Eminence Beta speakers
and two 3.5X3.5” 80-watt Ferro cooled horns driven by 100/100-watt amplifiers provide stunning
clarity and transient response. A 12AX7EH tube pre-amp and 45-watt amplifier driving a 80watt MS-1.2 diaphragm for the rotary horn in conjunction with the enhanced stereo low rotor
simulator provide rich liquid REAL rotary sound.
2
-QUICK START-
1. Set all controls to the default number indicated on each control.
2. Set keyboard to 50% volume; plug into the KBR-3D’s appropriate channel.
3. Fine tune volume and tone controls to suite your taste.
-ROTARY CHANNEL-
The KBR-3D employs Motion Sound’s acclaimed PRO-3T rotating horn technology, including a
12AX7EH pre-amp circuit and the MS 1.2 proprietary diaphragm. The low rotor simulator is
specifically designed for the KBR-3D’s speaker cabinet and provides rich, liquid stereo
simulation.
Inputs:
1. Input “1” is designed for use with a single keyboard or organ module.
2. Input “2” when used alone (without input 1) attenuates the incoming signal by 50%. This
input impedance is reduced to 33K ohms.
3. Analog volume pedals are not recommended.
Speed Control: Connect the supplied dual button foot switch here. This is a TRS connector
where the sleeve is common or ground, the “tip” controls fast/slow operation and the
“ring” determines whether slow or stop is enabled.
Fast overrides all: When the fast speed is on (yellow fast indicator on the KBR-3D is lit), the
stop button does not have effect. When the fast button is pressed again (yellow indicator
off) the slow speed or stop is enabled depending on the position of the stop switch button.
This enables the horn motor and low rotor simulator to cycle between fast to slow, fast to
stop and slow to stop. The rotors will follow the acceleration times as set internally.
Disable Stop: If the stop function is not desired, a single contact switch can be used with a mono ¼’ jack.
The stop is disabled by the sleeve of the ¼” connector and the switch button then controls
fast/slow only.
Pre-Gain: Inputs 1 and 2 are fed to this control before reaching the 12AX7EH tube circuit. The pre-gain is
actually an attenuator allowing input levels to be virtually unlimited.
Contour: This knob controls the high frequency response of the rotary channel. The 147 position (approx.
5 kHz role off) is similar t o many older rotating speakers. If you would like a brighter sound,
choose the PRO-3 (approx. 7 kHz roll off) setting. The control also provides positions in between
to allow for today’s keyboards and personal taste in high frequency response.
3
12AX7EH Pre-Amp: There are no solid state devices in this unique tube circuit which utilizes a 12AX7EH
(or any of its derivatives) in a self-biased symmetrical clipping topology that behaves like a 147
tube output stage when overdriven. This design pro vides silky-smooth sound until pushed into
clipping, at first crunchy and at extremes provides a gnarly massive tube grind! A combination of
keyboard volume X volume pedal X pre-gain settings
12AX7EH.
Post-Gain: This control allows silky-smooth, clean tube sound with settings of 8-10 and utilizes the full
output range of the 45-watt RMS horn power amplifier. When turned down and used in
conjunction with the pre-gain and keyboard volume controls, the post-gain allows all levels of
overdrive to be played at any volume below the 45-watt amplifier’s clipping point and can provide
tube only overdrive at loud to very soft levels.
Many users like to set a level or “ceiling” with the pre-gain around 5 and about 50% volume on their
keyboard, a point where the 12AX7EH runs fairly clean and then be able to push the tube into clipping by
conveniently raising the volume on the keyboard. Again, overall volume can be changed with the post-gain
without affecting this “ceiling” level.
pre-gain post-gain
Clean Sound 1-5 8-9
Crunch 5-8 3-7
Gnarl 8-10 1-7
Settings depend on a signal source level of approximately 300 mV RMS fed into the KBR-3D rotary
channel inp ut 1 only (input 2 not used) .
determines the overall drive of the
Low Rotor Volume: The balance between sound from the rotating horn (> 800 Hz) and that of the low
simulator is adjusted here. Set the balance to default or to match your favorite classic rotating
speaker or personal taste.
Bass: The control effects bass frequencies below approx. 150 Hz. Generally set to “0”, this is also a
personal taste control. If you play with a bas player, leave the control between –10 to 0. If you
play solo and use pedals, try a settings of 0- +5. Bass reproduction uses a great deal of power—
use only what seems needed in each situation.
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