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Gallien-Krueger Fusion 800S Review

Gallien-Krueger Fusion 800S Review

A wealth of tone-shaping possibilities—and not one but three 12AX7s—lurk in this featherweight 800-watt powerhouse.

Signal chain for all clips: 50/50 mix of onboard DI and a Sennheiser miked Mesa/Boogie Subway 115 cabinet, recorded with an Mbox straight into Logic X.
Clip 1: 2015 Squier Precision with flatwounds - voice filter engaged and 2 o'clock bump on the bass control.
Clip 2: 1979 Yamaha BB2000 - overdrive engaged, cut set at 3 o'clock, bump set at 2 o'clock, and contour at 2 o'clock.
Clip 3: Music Man StingRay 5 fretless - hi-mid set at 4 o'clock.


Incredibly musical overdrive. Detailed tone shaping. Retains sonic brand essence.

Involved control layout.


Gallien-Krueger Fusion 800S


Ease of Use:



In an era when bass amplifier manufacturers, in many cases, are taking pride in providing a neutral, uncolored, and clean tone, it’s certainly nice to be tasked with reviewing an amp from the brand that has always commanded a unique and unmistakable sonic footprint. Gallien-Krueger’s 800RB is arguably one of the most iconic bass amps in history for providing a very different tone than others on the tube side of the amp world, and it’s no wonder that some of my favorite picked-bass tones have come from GK players like Duff McKagan, Eddie Jackson, and David Taylor, just to name a few.

When Gallien-Kruger released the Fusion 550, with its redesigned tube preamp, a few years back, it was a noteworthy departure from the company’s previous output. During their first wave of manufacturing class-D amps, GK also introduced the MB Fusion 800, and now we have a new, updated line with the Fusion S Series, which includes three different versions of varying power. We choose the Fusion 800S for a look, and as an avid user of the company’s Fusion 550, I couldn’t wait to get my hands on it.

Two Colors, Two Personalities
The Fusion 800S has a Batmobile sleekness with its minimalistic, flat black housing, and weighs in at a very feathery 5 1/2 pounds. The front panel’s layout is somewhat complex, since each control actually has two functions. (Each rotary control lights up in blue or white to indicate which function is active.) For some bassists who are used to simpler layouts, it might take a little getting used to, but the Fusion 800S presents a big payoff in tonal options.

There’s not enough space for me to go through the functions of each control individually, but the broad strokes are as follows: On the far left, a clean input level dial called “voice” also doubles as an additional EQ pre-shaper for re-voicing the amp. A second level control is assigned to the amp’s overdrive section, which has one of the Fusion 800S’s three 12AX7s dedicated to it.

It’s a clean tone, but not a clinical tone, which, to me, is a great starting point for so many styles of music.

Two other controls—labeled edge/cut and level/body—further help fine-tune the overdrive channel. The 4-band EQ section houses four controls for bass/bump, lo-mid/contour, hi-mid/hi-cut, and treble/presence. Finally, the front panel is rounded out by indicator lights for temperature and power draw, as well as a master/mute control.

The rear of the amp houses all the necessary amenities, such as a pre/post switch and ground lift for the DI out, twist-lock speaker outputs, a tuner out, and an effects send/return. The rear panel also features some pleasant bonus items: an aux-in, a headphone out, and an input to engage the drive channel with the company’s LF-1 footswitch (available separately).

That GK Sound
For my first test drive, I chose a Squier Precision strung with flatwounds and a Mesa/Boogie Subway 1x15 cab, and set the P's onboard tone wide open to catch the sound of the strings and truly hear the personality of the amp. Plugging into the Fusion 800S completely flat was a pleasant experience, but it was missing a little something, so I boosted the bass control to about 2 o’clock and switched the input-level control to its alternate voice function.

By simply engaging the voice control, the Fusion 800S sounded just like a GK is supposed to sound in less than a second. The high mids and lower highs helped provide an edgy, crispy—but not too hi-fi—tone that gave the flatwound strings true attitude, even when I was playing fingerstyle fairly softly. It’s a clean tone, but not a clinical tone, which, to me, is a great starting point for so many styles of music. This tone setting also had ample warmth, but without being too pillow-y or muddy.

Classic Pick Territory
I purposely warmed up with the aforementioned tone before attempting the sound I wanted to hear more than anything out of this amplifier: the often-imitated-but-never-duplicated GK hard-rock pick tone. I grabbed my already aggressive-sounding 1979 Yamaha BB2000, again boosted the bass control to 2 o’clock, and engaged the overdrive channel. I also set the edge/cut control to cut, and set the level at 3 o’clock.

To my happy surprise, the amp’s overdrive added some of the sonic qualities of a slightly overdriven 10"-speaker, rather than that of an in-amp, very dirty distortion circuit that so many modern amps feature. The Fusion 800S’s distortion really retains the sound of the strings and the fundamentals of the clean signal to a very satisfying degree. The tubes in the preamp are certainly responsible for the great softness and slight compression that feel like pleasant speaker distortion when pushing the input hard. And this tone is especially usable when employing a pick and trying to emulate McKagan’s sound. A big grin spread across my face as I continued to dig into this clean tone with some hair on its chest. There’s just no other way to describe it, since it definitely isn’t what I’d refer to as “dirty” in the traditional sense.

Straight In
Thinking I might have been too quick to engage the voice control, I next set the Fusion 800S without any tone coloring—outside of a notable high-mid bump to about 4 o’clock—and plugged in my active, fretless Music Man StingRay. A clean and punchy tone with the traditional, very solid, and firm-feeling GK characteristics present in the low end was the result. The GK midrange and treble personalities were tamed, and the 800S performed impressively as a more straight-laced bass amp. Versatility box checked!

The Verdict
The marriage between GK’s tube preamp and class-D power section is a successful one. The amp breathes and behaves much like the older solid-state Fusion 550, but at a fraction of the weight. Though the immensity of the tone-shaping possibilities can be bewildering at first, they’re very usable if you play many different genres. For me, the winning feature on this amp is the overdrive section. It adds excitement to the tone withoutadding too much dirt, which is a tremendously musical and usable feature. Yes, the Fusion 800S sounds like a GK, but it has other tricks up its sleeve as well, and that should certainly please longtime GK fans.