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Gallien-Krueger MB Fusion Hybrid Ultra-Light Bass Amplifier Head


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  • All-tube preamp combined with digital power amp design
  • Four band active EQ section allows you to shape and mould your tone
  • Dual footswitchable gain settings with master volume controls
  • Headphone/line out/chain output allows you to connect a direct (unbalanced) line out to unbalanced inputs on recording devices
  • Tuner pedal output with tuner mute switch for silent tuning
  • Send and return jacks for connecting an outboard FX chain
  • Contour control decreases mid-range frequencies whilst boosting low and high frequencies
  • -14dB pad switch for use with basses equipped with active pickups
  • Presence control adds sparkle to upper frequency range
  • Deep setting creates extended lower range to accommodate lower register of 5 or 6 string basses
  • Lightweight design with a rugged chassis to offer maximum protection
  • Includes footswitch, power supply and owner's manual
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Delivery & Returns

Delivery to UK mainland addresses* is FREE on orders over £75 and up to 30kg. (As a guide, a standard electric guitar weighs approx. 3-5kg).

Delivery on orders below £75 are charged at £4.45!

Delivery to Northern Ireland, the Scottish Highlands & Islands, Isle of Man, Isle of Wight, Channel Islands and the Republic of Ireland. is weight dependant and will be indicated at the checkout

Delivery above 30kg to ANY location will vary according to weight and will be indicated at the checkout

LocationPriceStandard Delivery
UK mainland*FREE on orders over £75 £4.45 on orders under £751-3 working days
Northern Ireland, Scottish Highlands & Islands Isle of Man Isle of Wight Channel Islands Republic of Ireland£12.95 – any order value up to 30kg Over 30kg - please call1-3 working days
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The Gallien-Krueger MB Fusion Hybrid Ultra-Light Bass Amplifier Head combines the tube preamp power of the much-loved GK Fusion series amps with the ultra-light poweramp circuitry of the awesome MB Fusion. Not only does it have the capability to produce a massive 500-Watt output, but it is small enough to fit in your gig bag too.

Small but perfectly formed

The MB Fusion is host to a range of features that allow you to shape and mould the perfect tone to meet your needs. Whether you're practising at home, jamming with friends, recording in the studio, or playing on stage, the discreet dimensions and functionality of this little gem means that you can take it anywhere, and have everything you need in one solid little amp head. The control interface across the front panel enables ready access, whilst the rear panel connection keep all cables and leads free and clear.

Pad switch and Mute

Next to the standard jack input you'll find the -14dB On/Off switch, which allows you to pad the input when using active pickup equipped basses. Alternatively, if you're using a passive pickup equipped bass, simply turn the switch off again. The pad button flashes red when the input is overdriven. The Mute switch allows you to silently tune or unplug your bass, preventing a signal from being sent when it is activated. The bright red indicator informs you when the Mute button is active.

Gain A and B

The MB Fusion is equipped with two footswitchable Gain settings: A and B. Each setting also has a corresponding Master control knob, which controls the overall output volume of the amplifier, depending on which Gain setting is active. The Gain settings enable you to inject some overdrive into the preamp circuitry to create greater warmth and add some sizzle to your tone.

Highly versatile EQ

The MB Fusion features a four-band EQ which is finely tuned to attenuate specific frequency ranges across Bass, Low-Mid, Hi-Mid and Treble. The Bass control allows you to boost or cut around 60Hz by +10dB, delivering a fatter and looser response or a tighter low-end sound. The Low-Mid control boosts and cuts around the 250Hz +6dB/-10dB, which allows you to soften the lower-mid range or create more saturation. The Hi-Mid control boosts and cuts at the 1kHz range, which allows you to hone in on your lower string harmonics to deliver greater punchiness to your tone. The Treble control boosts and cuts at 7kHz, which allows you to soften the upper frequencies and remove high-end pop or definition, particularly useful for when you want to temper your slapping technique's response.

Top Panel Controls

Across the top panel of the MB Fusion there are four additional controls: Contour, Presence, Deep and Limiter. The Contour switch activates a tube-driven version of the circuit seen in Gallien-Krueger's legendary RB series. When the control is at zero, the response across the frequency range is 'flat', but as it is increased, the mid-range is scooped out to give greater emphasis to low-end and high-frequency tones. As the mids are scooped out the volume level is maintained at a constant level to prevent fluctuations in the signal level.

Presence delivers brilliance to the high-end for greater articulation, which is particularly favourable when performing passages or soloing in the upper frets. The Deep control extends the low frequency range further to accommodate extended range basses such as 5 or 6 string models. However, even those with 4 string models will appreciate the extra girth offered by this setting, enabling you to create deep, rolling basslines.


Along the rear panel there are a range of connections including: a Direct Output (XLR) that allows a balanced output to be sent directly to a P.A. system with a standard microphone cable; a Headphone/Line Out/Chain Out jack with a switch that allows you to send a direct (unbalanced) line output to an unbalanced input. The Chain output enables connection to a Gallien-Krueger MBP powered extension cabinet. The Headphone output allows you to silently monitor your playing for quiet practise. The Speaker output allows you to output directly to a speaker cabinet.

The MB Fusion is equipped with Send and Return jacks; Send can be used to output a signal from the preamp to be fed into an FX chain post EQ, whilst the Return jack sends the signal before the Boost section. The Tuner output sends a feed from the signal stage to a tuner pedal for silent tuning during performances.

The Gallien-Krueger MB Fusion Hybrid Ultra-Light Bass Amplifier Head combines smooth tube warmth with exceptional digital poweramp technology, resulting in a highly detailed, lush tonal palette. The level of control available is remarkable for an amp of this size, but from the legendary team at GK, we wouldn’t expect anything less. Each model is supplied with a footswitch and power supply, as well as a comprehensive owner's manual.

ModelMB Fusion Hybrid Ultra-Light Bass Amplifier Head
Dimensions (H x W x D) 44.45 x 279.4 x 228.67 mm
Output Power 350W @ 8 Ohms
500W @ 4 Ohms
Input Section Maximum Input Level: 0.6V Rms
With -10dB pad: 1.6V Rms
Input Impedance: 1M Ohms
Send Output Impedance: 220 Ohms
Return Input Impedance: 50K Ohms
Tuner Output Impedance: 10K Ohms Direct Output Impedance: 500 Ohms
Equalizer Bass: +/-10dB @ 60Hz
Lo-Mid: +6dB/-10dB @ 250Hz
Hi-Mid: +6dB/-10dB @ 1KHz
Treble: +/-14dB @ 7KHz
Voicing FiltersContour: +2dB @ 50Hz / -10dB @ 500Hz / +3dB @ 7 KHz
Noise-90 dB reference to 500W/350W, “A” Weighted
Amplifier Protection Full short circuit, thermal and RF protection.
Stable into reactive and mismatch loads.
Five second muted warm-up.
CoolingVariable speed fan.
Power Requirements240W (Full Power)
Included Accessories Footswitch
Power Supply
Owner's Manual
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