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GK Fusion S now available!

OK, I bought one, the 800 Watt version.

Quick & Dirty Impressions:

- It sounds amazing right out of the box with no effort at all.
- The owners manual in my box is clearly not a "final" version, and the descriptions of each knob's feature are pretty unsatisfying. I've been playing bass since dinosaurs walked the earth, and there are quite a few head scratchers in these descriptions. Hopefully they will update this. They could take a huge lesson from Mesa Boogie in this area.
- Along these lines, it is going to take me some time to figure out how all of the features work and interact with each other.
- The plastic knobs feel a little cheap to me. The "push" engage feature of the controls, gives a more flexible (almost wiggly) feel to the knob. I don't know the mechanics behind this, but no one wants to feel a wiggly anything on their amp. We will see how they hold up.
- I tried some of the presets from the demo version, and although they sounded different in my house (different bass, recording interface), they sounded similar and quite good. I used an active, passive and piezo bass, and was happy with the sound using all of them.
- When using headphones, there were a couple items that I didn't love. 1) The Standby Switch doesn't work through the headphone send. So even though the light changes from blue to white when you engage it, the audio still comes through the cans. This was an unpleasant discovery when I turned my amp off while wearing my phones and received a squeal/squelch into my earbone. 2) no matter how I set the Trim, Normal and Master volumes for a clean sound, I could hear a low level distortion in the signal. Maybe it was my phones, I will check it out through the speakers and other headphones, and see if I can still hear it.
- The Overdrive Channel: It has its own foot-switch and cable which is nice and works well. The thing with the overdrive channel is it is not programmable, so even though I can preset the Overdrive Level, Edge/Cut, and Level/Body settings, I have to use whatever other settings are currently on the rest of the amp. So there is not much opportunity to use the switching to get a very different sound and EQ, just the same sound you are currently using with overdrive added. I honestly am not too crazy about the sounds I am getting from this section, but I am still in a learning curve. But for example, the Level/Body features are on the same clickable knob. So if I want to set my overall output level, I cannot effectively use the "Body" feature because that will also raise or lower the output. So if you like the body level high, your output will be too loud. Yes, I can adjust the master or send volume, but then when I click off the overdrive channel back to the Normal channel, my volume will be too low. I can imagine that I will not get much use out of this overdrive channel, unless I have a eureka moment.
- Small item: The Standby light is ALWAYS on when the amp is plugged in to power. It goes off when you go out of standby mode, but when I am done playing and pack up, that damn white light is still shining like a beacon to those lost at sea! I wish I could turn it off.

So, still early, still exploring, but I can confidently say that the amp sounds really, really good, is light and portable, looks amazing. It sounds like a GK, has balls, edge and power, and I like it a lot.
 
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You'll note that the 10% THD spec on the Mesa specifically includes preamp overdrive. Your comparison of 1% to 10% isn't exactly apples to apples as GK would be incapable of including an overdrive circuit and claiming 1% THD using the same terms as Mesa. The reality is that as-written neither company's specs are exactly comparable, unless I've missed something more specific from GK.

I think the functional difference is that one rolls on as input gain increases and the other is switchable on and off.
 
OK, I bought one, the 800 Watt version.

Quick & Dirty Impressions:

- It sounds amazing right out of the box with no effort at all.
- The owners manual in my box is clearly not a "final" version, and the descriptions of each knob's feature are pretty unsatisfying. I've been playing bass since dinosaurs walked the earth, and there are quite a few head scratchers in these descriptions. Hopefully they will update this. They could take a huge lesson from Mesa Boogie in this area.
- Along these lines, it is going to take me some time to figure out how all of the features work and interact with each other.
- The plastic knobs feel a little cheap to me. The "push" engage feature of the controls, gives a more flexible (almost wiggly) feel to the knob. I don't know the mechanics behind this, but no one wants to feel a wiggly anything on their amp. We will see how they hold up.
- I tried some of the presets from the demo version, and although they sounded different in my house (different bass, recording interface), they sounded similar and quite good. I used an active, passive and piezo bass, and was happy with the sound using all of them.
- When using headphones, there were a couple items that I didn't love. 1) The Standby Switch doesn't work through the headphone send. So even though the light changes from blue to white when you engage it, the audio still comes through the cans. This was an unpleasant discovery when I turned my amp off while wearing my phones and received a squeal/squelch into my earbone. 2) no matter how I set the Trim, Normal and Master volumes for a clean sound, I could hear a low level distortion in the signal. Maybe it was my phones, I will check it out through the speakers and other headphones, and see if I can still hear it.
- The Overdrive Channel: It has its own foot-switch and cable which is nice and works well. The thing with the overdrive channel is it is not programmable, so even though I can preset the Overdrive Level, Edge/Cut, and Level/Body settings, I have to use whatever other settings are currently on the rest of the amp. So there is not much opportunity to use the switching to get a very different sound and EQ, just the same sound you are currently using with overdrive added. I honestly am not too crazy about the sounds I am getting from this section, but I am still in a learning curve. But for example, the Level/Body features are on the same clickable knob. So if I want to set my overall output level, I cannot effectively use the "Body" feature because that will also raise or lower the output. So if you like the body level high, your output will be too loud. Yes, I can adjust the master or send volume, but then when I click off the overdrive channel back to the Normal channel, my volume will be too low. I can imagine that I will not get much use out of this overdrive channel, unless I have a eureka moment.
- Small item: The Standby light is ALWAYS on when the amp is plugged in to power. It goes off when you go out of standby mode, but when I am done playing and pack up, that damn white light is still shining like a beacon to those lost at sea! I wish I could turn it off.

So, still early, still exploring, but I can confidently say that the amp sounds really, really good, is light and portable, looks amazing. It sounds like a GK, has balls, edge and power, and I like it a lot.
Nice review. I'll be especially curious if you were able to get a completely clean tone figured out if you're interested in following back up in the future.
 
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I have a Fusion 550 which I love the tone but it's a heavy beast. I think the reason I like it is that it also has 3 pre-amp tubes loke the new Fusion S series. Warm punchy tone. So I am wondering if one of these new Class D-Tube pre-amp heads will give me the same tone and doing it at only 5lbs. It comes in 500, 800 and 1200 watts. I think one would be fine with the 500. I barely get the 550 past 2 and it's 500wts. Thoughts?
 
I foresee many GK used amp heads up for sale for those wanting a newer GK head, Me I'm too in love with my boat anchor of my GK Fusion 550, But those new fusion + can cause me to sell my extra MB Fusion 800 at a great price , Oh and if you want a tube compressor, have mark bass one for sale, just sitting around ! See here I am saving you folks money !
 
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I have a Fusion 550 which I love the tone but it's a heavy beast. I think the reason I like it is that it also has 3 pre-amp tubes loke the new Fusion S series. Warm punchy tone. So I am wondering if one of these new Class D-Tube pre-amp heads will give me the same tone and doing it at only 5lbs. It comes in 500, 800 and 1200 watts. I think one would be fine with the 500. I barely get the 550 past 2 and it's 500wts. Thoughts?
If you notice on the GK site, they still offer the 550, why its a beast of an amp! one of these days I am going to have some fun tube rolling in it, and I am betting its weight is from either a large E and I transformer or a huge dang Tordroidal Transformer.
 
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- The plastic knobs feel a little cheap to me. The "push" engage feature of the controls, gives a more flexible (almost wiggly) feel to the knob. I don't know the mechanics behind this, but no one wants to feel a wiggly anything on their amp. We will see how they hold up.
Wiggly knobs, built in overdrive - are these amps tools or toys?
I guess I'll stick with my 700RB ...
 
OK, I bought one, the 800 Watt version.

Quick & Dirty Impressions:

- It sounds amazing right out of the box with no effort at all.
- The owners manual in my box is clearly not a "final" version, and the descriptions of each knob's feature are pretty unsatisfying. I've been playing bass since dinosaurs walked the earth, and there are quite a few head scratchers in these descriptions. Hopefully they will update this. They could take a huge lesson from Mesa Boogie in this area.
- Along these lines, it is going to take me some time to figure out how all of the features work and interact with each other.
- The plastic knobs feel a little cheap to me. The "push" engage feature of the controls, gives a more flexible (almost wiggly) feel to the knob. I don't know the mechanics behind this, but no one wants to feel a wiggly anything on their amp. We will see how they hold up.
- I tried some of the presets from the demo version, and although they sounded different in my house (different bass, recording interface), they sounded similar and quite good. I used an active, passive and piezo bass, and was happy with the sound using all of them.
- When using headphones, there were a couple items that I didn't love. 1) The Standby Switch doesn't work through the headphone send. So even though the light changes from blue to white when you engage it, the audio still comes through the cans. This was an unpleasant discovery when I turned my amp off while wearing my phones and received a squeal/squelch into my earbone. 2) no matter how I set the Trim, Normal and Master volumes for a clean sound, I could hear a low level distortion in the signal. Maybe it was my phones, I will check it out through the speakers and other headphones, and see if I can still hear it.
- The Overdrive Channel: It has its own foot-switch and cable which is nice and works well. The thing with the overdrive channel is it is not programmable, so even though I can preset the Overdrive Level, Edge/Cut, and Level/Body settings, I have to use whatever other settings are currently on the rest of the amp. So there is not much opportunity to use the switching to get a very different sound and EQ, just the same sound you are currently using with overdrive added. I honestly am not too crazy about the sounds I am getting from this section, but I am still in a learning curve. But for example, the Level/Body features are on the same clickable knob. So if I want to set my overall output level, I cannot effectively use the "Body" feature because that will also raise or lower the output. So if you like the body level high, your output will be too loud. Yes, I can adjust the master or send volume, but then when I click off the overdrive channel back to the Normal channel, my volume will be too low. I can imagine that I will not get much use out of this overdrive channel, unless I have a eureka moment.
- Small item: The Standby light is ALWAYS on when the amp is plugged in to power. It goes off when you go out of standby mode, but when I am done playing and pack up, that damn white light is still shining like a beacon to those lost at sea! I wish I could turn it off.

So, still early, still exploring, but I can confidently say that the amp sounds really, really good, is light and portable, looks amazing. It sounds like a GK, has balls, edge and power, and I like it a lot.
I had one brought in to try out. Will be playing around with it this weekend. I definitely agree with you on the knobs. The overall build seems solid but the knobs sure feel cheap.
 
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I had one brought in to try out. Will be playing around with it this weekend. I definitely agree with you on the knobs. The overall build seems solid but the knobs sure feel cheap.
Is it the plastic of the knobs or how they turn/how solid they are on the post? I've been thinking hard about one of these but cheap feeling exterior vs cheap mechanics are different things and unfortunately I can't try one where I live.
 
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Is it the plastic of the knobs or how they turn/how solid they are on the post? I've been thinking hard about one of these but cheap feeling exterior vs cheap mechanics are different things and unfortunately I can't try one where I live.
Definitely how they turn. I suppose as was said in the above review, it is likely because the knobs are also “push” as well. They turn very freely. I’m comparing to a fusion 550 and an Svt7pro.
Very quick trial though tonight with everything flat was fairly impressive tone.
Will give some feedback at the end of the weekend.
Cheers
 
I bought the 1200 this week. Initial impression is good so far, still working out the tones. As @TNCreature mentions, I wish the owners manual contained more info about tone knob descriptions. power switch is hard to locate on the back. Also, the standby light is annoying...it even stays on after you unplug the amp.
 
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I bought the 1200 this week. Initial impression is good so far, still working out the tones. As @TNCreature mentions, I wish the owners manual contained more info about, power switch is hard to locate on the back. Also, the standby light is annoying...it even stays on after you unplug the amp.

Mine died in a week, Sweetwater replaced it.
Another thing I forgot to mention, no included bag (nor one for sale yet) or speaker cable at this price point is disappointing.
 
I foresee many GK used amp heads up for sale for those wanting a newer GK head, Me I'm too in love with my boat anchor of my GK Fusion 550, But those new fusion + can cause me to sell my extra MB Fusion 800 at a great price , Oh and if you want a tube compressor, have mark bass one for sale, just sitting around ! See here I am saving you folks money !

I just bought a 550 Fusion last Friday. It's still posted on GK's website, so it's still viable and a an awesome sounding amp. Weighing in at 24 lbs, it's not the lightest amp but, it's far from the heaviest I've played. I've got solid-state amps that weight quite a bit more.

What's keeping me from the going all-in on the class D market is the pricing and durability of the current offerings. The good news is that prices on the 800RB's are becoming more accessible.
 
If you notice on the GK site, they still offer the 550, why its a beast of an amp! one of these days I am going to have some fun tube rolling in it, and I am betting its weight is from either a large E and I transformer or a huge dang Tordroidal Transformer.

I'm loving mine! I'm thinking of rolling some Gold Lions or NOS GE's. I can tell you that these have a large toroidal transformer and are very well designed and thought out. The motorized knobs aren't a make or break feature but, it's cool that they added them. Make sure to remove the four screws by the rear exhaust port when you take off the lid. There is a 90-degree bracket that is built into the lid.

It's a great compliment to my 1200SEB, which is considered to be one of the early class D designs.