GK MB Fusion vs GK Fusion 550

pshep68 · #1 10-16-2012, 09:47 AM

Can anyone chime in with regards to the differences in sound/tone (not volume) of both of these amp?

scottfeldstein · #2 10-16-2012, 09:55 AM

Good question. One obvious difference is the 550 has moar tubes in the preamp. I wonder how this affects the ability to overdrive the signal there... My guess is, a bit. And that the real differences between these heads are the other features. The EQ looks more or less the same. But you do get a variable level DI and the biamp feature.

pshep68 · #3 10-16-2012, 10:00 AM

Would more tubes in the preamp of the 550 mean a warmer sound?

scottfeldstein · #4 10-16-2012, 10:02 AM

Maybe, but I'm out of my depth. Surely someone else knows.

pshep68 · #5 10-16-2012, 10:15 AM

I just checked online and I do believe that both the mb fusion and the fusion 550 have the same number of tubes in the preamp ... correct me if I'm wrong.

scottfeldstein · #6 10-16-2012, 10:28 AM

You are correct. I was wrong. Both appear to have three 12AX7's.

Jared Lash · #7 10-16-2012, 10:31 AM

My understanding is that they have the same preamp with the Fusion 550 having the power section from the 1001 RB-II (I believe) and the MB Fusion having the class D power module used with the MB500 or MB800 (for the new MB Fusion 800)

Other than that (and the 550's motorized knobs for switching settings) I think they are more or less the same.

I think the EQ points are the same so the only difference would be from the power sections. I've tried both but not in a true A/B setting so I couldn't tell you any subtle differences. Based on my experience they sounded the same to my ears.

scottfeldstein · #8 10-16-2012, 10:33 AM

My gut feeling is they probably sound very, very similar and that the differences between them are the other features. Biamp, knob memory, adjustable DI, etc.

PlungerModerno · #9 10-16-2012, 10:38 AM

From what I hear the main difference in preamp between the two is the motorized controls for channel switching. The 550 has it, the mb not.

The power amp sections are obviously different but are supposed to be pretty close - I've never got to A/B them (or try a 550) but the GK people seem to think the are along the same lines:

http://www.youtube.com/watch?v=TsaoxD4BYws

I'd agree, but only a blind A/B with a bunch of different settings and the like

ljazz · #10 10-17-2012, 02:29 AM

I have not played them in order to do a direct a/b, however, I've played both, and believe the primary difference is basically the same when comparing the mb500 and the 700rbII (which I have directly compared)...... more tonal "heft" in the class H power sections. I've also run the mbfusion's pre through the return on the 700rbII, and it was awesome sounding. I've been saying this in other threads........ I would love to see a simplified 550...... go to the channel switching like in the mbfusion, and keep it in a 2 space unit under 20 lbs..... I'd be all over it.

PlungerModerno · #11 10-17-2012, 02:47 AM

Quote:

Originally Posted by ljazz

I have not played them in order to do a direct a/b, however, I've played both, and believe the primary difference is basically the same when comparing the mb500 and the 700rbII (which I have directly compared)...... more tonal "heft" in the class H power sections. I've also run the mbfusion's pre through the return on the 700rbII, and it was awesome sounding. I've been saying this in other threads........ I would love to see a simplified 550...... go to the channel switching like in the mbfusion, and keep it in a 2 space unit under 20 lbs..... I'd be all over it.

That is an interesting idea - and I wouldn't be surprised if GK were to go down that road in the future. Micros are doing well and if the mb fusion 800 is anything to go by - GK may see those models as higher priority to a fusion 1050 or a middle ground head like the one you propose.

I'd be happy with any of them (and am with my mb fusion 500).

mouthmw · #12 10-17-2012, 03:47 AM

I think Fusion 550 shares the same poweramp as 700rb ii, not 1001rb ii since it's 500W.

Anarchyok · #13 10-17-2012, 05:30 AM

Quote:

Originally Posted by mouthmw

I think Fusion 550 shares the same poweramp as 700rb ii, not 1001rb ii since it's 500W.

It's from the 1001rbii but tuned down from 700 to 500 apparently.

I own both the mb fusion and the fusion 550.

Tonally very similar as you'd expect but the 550 has more heft in its feel and response - it feels like it just wants to keep giving.

The mb fusion is great when I want light weight, which is 95% of the time, but when I simply want power, I go for my 550

valipe · #14 10-17-2012, 01:06 PM

I did A/B test. Fusion 550 sounded fuller, open sound with bottom. Fusion MB sound drier, tighter but very nice also. I bought Fusion 550. It was a great addition to my amp selection two Mesas and TC Electronic Rebelhead. Fusion 550 is quite heavy and big, but I don't mind. Sometimes good sound is not feather light.

jdwinva · #15 04-11-2013, 09:05 AM

I own both. Other than the motorized knobs on the 550 the primary differentiator, the Fusion 550 has more heft in the power section. I know, they both are rated at 500 watts into 4 ohms but they sound amazingly similar with more headroom going to the Fusion 550. That said, the MB Fusion does 95% of what the Fusion 550 does IMHO.