Hands-On Review:Gallien–Krueger Micro Bass Heads

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Compact heads deliver high performance at affordable prices

By By Terry Buddingh
International Music-Gear Journalist


Gallien-Krueger Micro Bass Heads

Gallien-Krueger has consistently been on the leading edge of bass amp  design and technology for more than 40 years, and that decades-long  tradition continues with the ultra-compact, ultra-lightweight,  full-featured, and super-affordable MB series heads. Featuring  state-of-the-art Class D power amps, these surprisingly powerful  micro-sized heads offer effortless portability and a full complement of  essential features—all at amazingly affordable prices.


The MB200 and MB500 boast GK's time-tested and gig-proven solid-state preamp and tone control circuitry, while the MB Fusion borrows its all-tube preamp from GK's heavyweight hybrid Fusion 550  (but without the Fusion 550's programmable, motorized tone controls).  Built to endure the rigors of the road, these serious tone machines  fully embody Bob Gallien's "tools, not toys" design philosophy, and all  three heads are loaded with essential modern-day real-world gigging  accouterments like balanced XLR DI outputs and combination 1/4" to  Speakon speaker output jacks.


The MB200 is amazingly small; it's smaller than many DI boxes, standalone  preamps, and pedals, and it's thin enough to slip easily into most gig  bag pockets. Weighing a mere 2 pounds, it's difficult to imagine a more  travel-friendly bass head. Despite its small size, GK still managed to  include everything a gigging bass player needs: there's a -10dB pad  switch to accommodate high-output active basses, an on/off switch for  GK's classic Contour pre-shape circuit, plus GK's legendary 4-band tone  control section. The MB200 also has a balanced DI output with pre/post  EQ selector button; a 1/8" auxiliary input for CD, MP3, or other  players; and a switchable line-out/headphone jack. The MB200 has a  single 1/4" to Speakon combo jack.


It may look tiny, but the MB200 is indeed a serious—and versatile—tone tool. Conservatively rated at  200W @ 4 ohms, the MB200 is surprisingly loud, with amazingly strong and  weighty low-end response. It looks small, but it sounds massive. The  MB200 is bound to find its way into to a wide range of applications. You  could use it as a full-featured DI box, enhancing your sound with GK's  excellent sounding Contour and tone controls, or you could use the Line  Out to drive a large power amp when extra volume might be required. I'm  sure these pint-sized powerhouses will find their way into guitar,  keyboard, and other applications as well. Considering its effortless  portability, gig-worthy power, potential for adaptability, and  affordable price, the MB200 will surely find a place in even the most  extensive bass gear arsenals. This is a real no-brainer—everybody should  have an MB200.


With its Mute button, Effects Loop, Tuner Output, defeatable Limiter,  Master Volume control, and footswitchable Boost with secondary Master  Volume control, the MB500 offers a boatload of additional features to go along with its extra  power. With an honest 500W @ 4 ohms, the MB500 kicks like a mule with an  authoritative and forceful punch. This head likes to rock and rock  hard; it really comes to life when you crank it up, and it seems to dare  you to do so. Weighing-in at 3.75 pounds, and breaking the buck-a-watt  price barrier, the MB500 packs a lot of value into an incredibly  portable high-power package.


The footswitchable Boost feature greatly expands the MB500's  range of tonal options. Increasing the Boost knob setting increases the  trademark GK growl, and this added texture provides some colorful  contrast when switching from a cleaner, non-boosted setting. It's useful  for more rock-flavored tone, soloing, or contrasting mid-song section  and textural changes.


The post-EQ, pre-Boost Effects Loop works great with a wide range of devices, and greatly expands the MB500's  range of options. The MB500 has two combination  1/4" to Speakon  speaker output jacks, so it can easily power two speaker cabinets.

MB Fusion

The MB Fusion grafts an all-tube preamp onto the same power amp section used in the MB500,  so the power is the same: 500W @ 4 ohms. Using three 12AX7 tubes  running at high voltage, the MB Fusion's preamp is essentially a  tube-driven adaptation of GK's classic solid state preamp circuit  design. The feature set is similar to the MB500, except the MB Fusion  has selectable Contour control mid-dip center frequencies (500Hz or  800Hz), and separate switches labeled Presence and Deep (for a 4dB boost  @ 10kHz and 30Hz, respectively).


The MB Fusion has two footswitchable Gain and Master volume controls. These allow you  to instantly switch between two flavors of tube overdrive (or clean  tones) with the tap of a switch. Like the MB500,  the MB Fusion is capable of a wide range of tones and textures. The MB  Fusion's cleaner tones impart a delectable sense of hi-fi sweetness,  texture, dimension, and dynamic nuance that tube lovers will surely  recognize and enjoy. Using a pick and cranking up the Gain knob elicits  wicked grind and growl that clearly evokes the textures of far less  portable all-tube bass icons.

Features & Specs

  •   •  Passive and active switches
  •   •  Preamp Gain control
  •   •  Contour control (on/off button on MB200)
  •   •  Active 4-band tone controls
  •   •  Balanced XLR DI output jack
  •   •  State-of-the-art Class D power amp
  •   •  Weight-reducing switch-mode power supply
  •   •  Combination  1/4" and Speakon speaker output jacks
  • MB200
  •   •  200W @ 4 ohms
  •   •  140W @ 8 ohms
  •   •  7.75" x 8" x 1.75"
  •   •  2 lb.
  • MB500
  •   •  500W @ 4 ohms
  •   •  350W @ 8 ohms
  •   •  11" x 9" x 1.75"
  •   •  3.75 lb.
  • MB Fusion
  •   •  All-tube preamp
  •   •  500W @ 4 ohms
  •   •  350W @ 8 ohms
  •   •  11" x 9.75" x 1.75"
  •   •  4.5 lb.

GK's compact yet featured-packed MB heads offer gig-worthy power and tone in surprisingly lightweight and  exceptionally high-value packages. Click or call now to order with the  assurance of Musician's Friend's Dual Guarantees that ensure your total  satisfaction and the lowest price.