Gallien-Krueger MB800 Bass Amp Head

Hands-On Review: Gallien-Krueger MB800 Bass Head

Posted on .

GK raises the bar with more power, more features, and more growl

By Terry Buddingh
International Music-Gear Journalist

Yogi Berra, the iconic baseball player, coach, philosopher, and soothsayer, once observed: “Predicting the future is hard because it keeps changing.”

But for GK founder/designer/visionary Bob Gallien, predicting the future of bass amp design is simply a matter of following the long path between past and present, then applying the latest tools and technologies to take the next logical step forward. With more than four decades dedicated to bass amp study and design, Bob can draw upon the full history of practical bass amp design—because he was there through it all, constantly addressing and solving the problems of the day and tirelessly refining, redefining, and advancing the art of contemporary bass amp design.

When GK introduces a new bass amp such as the Gallien-Krueger MB800 reviewed here, you know it’s going to be carefully and thoughtfully designed, and it’s going to tap into, extend, and reinforce the GK legacy. It’s also going to be sturdy and practical, offer truly useful features, and above all, it’s going to sound great and embody GK’s no-nonsense “tools not toys” philosophy.

Extended family

The Gallien-Krueger MB800 bass amp head (800 watts, 4.9 pounds) raises the bar for MB power—yet it’s still amazingly lightweight and effortlessly portable. The MB800 follows a trio of popular predecessors: the super-compact MB200 (200 watts, 2 pounds), the punchy MB500 (500 watts, 3.75 pounds), and the deliciously sweet MB Fusion (tube preamp, 500 watts, 4.5 pounds). All of these amps feature super-efficient state-of-the-art Class D power amps and switch-mode power supplies—the key components that contribute to their amazing power, compact size, and light weight.

Thirty years ago Bob Gallien devised the legendary active four-band tone control circuit that has become one of the key features that define the “GK sound.” Utilizing several integrated circuit op amp devices configured in series, this tone control circuit was voiced specifically for bass, and in that regard was a big step forward from previous passive tone controls. Instead of using integrated circuit op amps in the preamp and tone control section like most GK amps (excluding GK’s more recent tube-equipped Fusion models), the MB800’s preamp features discrete field effect transistors (FETs) in every stage. FETs are known for their “tube-like” character and provide a distinctively strong harmonic content when driven hard. For years FETs have played a key role in the classic GK Boost circuit contributing greatly to the trademark “GK growl.” The unique harmonic characteristic of this all-FET preamp sets the Gallien-Krueger MB800 apart from the other MB amps, and other recent GK amps as well. If you’ve been waiting for a GK amp with the potential for more grind, gristle, and growl as well as tight, girthy clean headroom—this one’s for you.

Leading technology

Leaders lead and followers follow, and sometimes you can wait for the technology to come to you—or you can go out and develop it yourself. For the MB800, Bob Gallien chose to develop a new control pot and switch design that features a ring of light around each control to indicate its status. Besides looking really cool onstage, these light-up pots and switches provide a quick review of all EQ, Contour, and Gain settings—even at a considerable distance. Cool indeed, and useful as well.

The MB800 has two footswitchable gain modes; these gain modes can also be selected by tapping the appropriate control knob, which lights up to indicate which gain mode is active. The Master volume control also has a light-up tap feature; tapping this control either engages or disengages the MB800’s limiter circuit, although the Gallien-Krueger MB800’s limiter circuit is so subtle and well-mannered I doubt many people would prefer it disengaged.


With its unique all-FET preamp, the MB800 offers an extremely wide range of happening clean and overdriven tones. With Gain A engaged and set low, I was immediately struck by the MB800’s impressive abundance of clean headroom and punch. Coupled with one of GK’s Neo 810 speaker cabinets, this combination was capable of unbelievably loud volume levels, while always preserving an inherently tight, controlled, and focused tone. Really—this amp kicks like a mule, with devastating punch and authority.

The preamp’s FETs come to life when Gain B is engaged and cranked high into overdrive territory; the tube-like grind and gristle come into play with loads of added texture that still retain the clarity and focus that are characteristic of the cleaner tones. Truly amazing—and a truly unique and cool amp.

The MB800 is a real winner, and it’s definitely going to be a tough act to follow; I’m not sure how anyone could top it. The question now is where does Bob go from here? The only thing for certain, as Yogi Berra would say, “It ain’t over ’til it’s over.”

Features & Specs

  • Unique all discrete FET preamp
  • -10dB Pad switch with illuminated clip indicator
  • Illuminated Mute switch
  • Illuminated controls including Gain A/B, Contour, EQ, Level B, and Master
  • Balanced XLR DI output jack, with Pre/Post and Ground switches
  • Effects loop
  • Headphone/line-out jack
  • State-of-the-art Class D power amp
  • Weight-reducing switch-mode power supply
  • 2 Speakon speaker output jacks
  • Footswitch included
  • 800 watts @ 4 ohms
  • 500 watts @ 8 ohms
  • 10-3/4"W x 1-3/4"H x 8-1/2"D
  • 4.9 lb.

GK’s unique, compact, and featured-packed MB800 offers an abundance of gig-worthy power and a wide range of excellent tones.

Tags: Amplifiers

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