Hands-On Review:
Gallien–Krueger MB800 Bass Head

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 the past and present, and then applying the latest tools and technologies to take the next logical step forward. And 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. So for Bob Gallien, the future may indeed keep changing, thanks to ever evolving and emerging technologies and such, but his tireless pursuit of bass amp perfection has never faltered. Simply put: Bob knows bass amps, through and through, and no one else on the planet can rightfully claim to match his decades of single minded dedication to the advancement of the art of bass amp design. So when GK introduces a new bass amp, such as the 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 MB800 (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 a unique bass-friendly active four-band tone control circuit, and that now-legendary circuit quickly became 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 (which were typically borrowed/copied from standard guitar amp designs and not particularly suited nor properly voiced for bass).
But instead of using integrated circuit op amps in the preamp and tone control section, like most GK amps (excluding some very early models and GK’s more recent tube equipped Fusion models), the MB800’s preamp features discreet field effect transistors (FETs). FETs are renown for their “tube like” character, and they can also provide a distinctively strong harmonic content when driven hard. FETs play a key role in GK’s classic Boost circuit, and in that circuit they contribute greatly to the trademark “GK growl.” The unique overdrive characteristics of this all FET preamp set the 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 … 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 on stage, these light-up pots and switches provide you with a quick review of all control 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 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 especially wide range of happening clean and overdriven tones. With Gain A engaged and set low, I was immediately struck with 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 really come to life when Gain B is engaged and cranked high into overdrive territory; the tube-like grind and gristle really comes into play with loads of added texture that still retains the clarity and focus that is 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 only question now is where does Bob go from here? The only thing for certain, as Yogi Berra would say, is “it ain’t over ‘til it’s over.”
GK’s unique, compact, and featured packed MB800 offers an ample abundance of gig worthy power and a wide range of excellent tones.


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