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MF MD HG Warehouse SaleLast Chance 01-23-15
Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head   (Open Box)
Ships Internationally
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Product# 581055

Gives you an all-tube preamp, 4-band EQ, and 500W of power.

The 500W Gallien-Krueger MB Fusion tube preamp incorporates the same all-tube preamp of the GK Fusion 550 and maintains the amazing portability of the MB2-500. The ultra-light bass amp delivers 500W at 4 ohms, 350W at 8 ohms, and is equipped with an all-tube, 3x12AX7 preamp. The GK MB Fusion bass head also has a 4-band active EQ, variable contour with mid frequency select, and Deep and Bright switches, so you've got total tonal control.

  • 500W Digital power amp
  • All tube preamp (Three 12AX7s) w/ 4-band Active EQ
  • Footswitchable Boost w/ Volume control
  • Variable contour with mid frequency select
  • Deep and Bright switch
  • Mute switch
  • Active/passive switch (-14dB)
  • Effects loop
  • Line out, headphone out and Tuner out
  • XLR out with pre/post EQ and ground light
  • 2 Speakon outputs
  • Footswitch included

Get portable, powerful tone that goes wherever your sound takes you—add the MB Fusion to the cart now.


MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head

  • 4 lb.

Review Snapshot®

by PowerReviews
Gallien-KruegerMB Fusion 500W Tube Preamp Ultra Light Bass Amp Head

(based on 7 reviews)

Ratings Distribution

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Reviewed by 7 customers

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(31 of 31 customers found this review helpful)


This Head Rocks

By RockinRick

from Shingle Springs Ca

About Me Experienced

Verified Buyer


  • Easy To Use
  • Excellent Sound
  • Good Warmth
  • Portable
  • Powerful


    Best Uses

    • Amateur Recording
    • Performances
    • Rock-blues-just Play

    Comments about Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head:

    Im older (62) yes OLD and been playing a long time.Still have the Ampeg but wanted something lighter.....This is my 2nd GK head and I love it.
    Tube preamp- plenty of power...SUPER lite.....what more could you ask for....PERIOD

    Comment on this review

    (2 of 21 customers found this review helpful)


    GK MB Fusion 500W Amp

    Comments about Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head:

    I would recommend the amp, but I still need to see how well it holds up over time.
    Nice features, but I can't give it a 10 because it doesn't have a clip light or a limiter/compression feature.
    I've only used it once so far, but it sounded great and it held up fine for a 4 hour gig. Bought it as a back up for my Mesa Boogie M-Pulse 600.
    Fair price for what you get.

    Comment on this review

    (9 of 34 customers found this review helpful)


    GK MBFusion

    By jon heake

    from chandler az

    Comments about Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head:

    I bought this amp ( MB Fusion ) a around the 18th of Nov, its now 21 dec and i have returned it. Here's my reason why though. It sounds great, is very loud, has super bass responce, and every feature is very useable on this amp. I returned it simply because the tone wasn't exactly what i was looking for. I had never used GK before so i was kind of taking a gamble, and with MF's great return policy i figured, hey why not? Its no fault of GK though. It was me. However, It was missing a couple features i usually like in an amp(on board-compressor and a clip indicator led). The 2 channels with the provided foot switch was really a nice touch and the tubes in this amp really give it a nice warm sound.

    So all in all, if Gk is the tone you love then pick up this amp. It really is a great little amp and I almost kept it even though it wasnt really the tone i was after. Like I said though, great product and i highly recomend it. Unless you are like me and generally dislike Flea's tone. Gk amps sound like him, or rather, he sounds like GK.
    I would have given it a 10 if it had an on board compressor and a clip indicator light.
    very well built, the pots were nice and smooth and all of the buttons seemed tight and not loose.
    I think the head is a little pricey for its power rating but its still a very good buy.

    Comment on this review

    (49 of 50 customers found this review helpful)


    Thank You GK

    By Patrick Burns

    from Washington DC area

    Comments about Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head:

    Overall I simply can not find fault with this product. As a profession musician paying my bills with my bass, it's really hard to find fault in a fully functional, beautifully made, and super light-weight amp, which comfortably sits in my backpack. I use a 8 ohm Hartke XL series 2x10 and run a Source Audio BEF, Snarling Dog Bootzilla Wah and a Digitech Jamman (through effects loop) with phenom sound and tone. The "Deep" and "Presence" filters are exceptional additions to the GK's tone shaping super-powers. Additionally using the included pedal to swap between channels it is easy to dial in a overdriven tube tone in channel B and swap on the fly for solo moments or stand out moments.
    Two Channels, included quality footswitch (and cable), tones of tone sculpting ability, a clear and well written owners manual, intuitive design, and four pounds! Amazing. The features are better than advertised.
    I have never owned anything from GK before and this is an outstanding introduction to their product line, however, since the product comes prepared for rack mount system and at this price it seems like a rack mounting system should have been included. A local music shop told me NOT to rack mount the system as the tubes heat will become an issue...but then that begs the question of why does it come prepared for a rack system?
    Just based on size, portablility, and most importantly TONE this bass amp is simply unbelievable. I regret waiting this long to get a light weight amp. I can't believe I lugged around a 45lbs box for the last 5 years when I didn't need to! I feel like at the price this is a bit pricey and definitely made me think a while before dropping the coin, however, now that I own it I am kicking myself for waiting!

    Comment on this review

    (46 of 48 customers found this review helpful)


    The Buck Stops Here!!!!

    By *TheEdge*

    from Ypsilanti, MI

    Comments about Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head:

    If you're looking for a light weight, full featured, powerful amp for your rig, look no further. This GK MB Fusion has got to be the best thing in it's class. The tone is amazing. Very good choice of EQ bands. The 350watts @ 8ohms drives my Eden 410XST very well. Haven't tried it at 500watts (will probably never need it). The tube preamp (3 tubes) sound is very warm and you can set the B-gain/B-Master get a good tube distortion and switch between the A and B sides. This thing rocks. I've been an Eden owner since '95, this is my first GK amp. I'm glad I didn't choose the Eden WTX series or Markbass light weights. I play all types of music, Jazz, R&B, Classic Rock, Metal, Pop. This Mb Fusion will fill the job well.

    Comment on this review

    (54 of 55 customers found this review helpful)


    These Are HOT

    By Basses & Bulldogs

    from Caledonia Wisc.

    Comments about Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head:

    This is my first G-K bass amp. I took delivery on this wonderful little piece of gear about 3 weeks ago. I was very anxious to try it out on two back to back weekend gigs - one being a 3 piece blues band in a local club with one 4 ohm eden 212xlt and the next gig with a 9 piece band in a large classic hall with my 4 ohm 6-10 Goliath Senior. I would usually bring a Ampeg SVT-3 Pro to both of these jobs and a Carl Martin Compressor/Limiter box that loads pre amp tubes well for Great sustain at any volume. I played a custom black warmoth J Bass for the blues gig. In the larger hall a newer RIC 4003 and amber Contemporary series Hofner violin Bass. I found no issues with the power cord or the supplied footswitch.The MB Fusion was a bit pricey but now I know the whole story. I really was amazed at how much punch this little book sized amp has. I got compliments at both jobs from band members and friends. The 2 volume - 2 master volumes set-up is great w/footswitch for pre-set boost or solo. The MB Fusion pumps out a solid 500 watts/4 ohms and 4 very usable bands of EQ. It has alot of the sound I was used to with the Ampeg. At 4 1/2 lbs. It fits right in my Anvil briefcase. Do not let the size of this bass head keep you from buying one of these. In my 44 Yrs.of bass playing this is a milestone type product - I'm very excited to have one and want to push those 3 pre amp tubes again as soon as I can.

    Comment on this review

    (39 of 41 customers found this review helpful)



    By porksoda6

    from Bay Area

    Comments about Gallien-Krueger MB Fusion 500W Tube Preamp Ultra Light Bass Amp Head:

    It's a truly amazing, powerful,ultra portable little unit at only 4lbs! Yes, that's right Four pounds! GK quality and reliability! I highly recommend it! It Rocks!

    Comment on this review

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