"I've been playing guitar on and off for nearly 15 years, and I have a bad case of G.A.S. (Gear Acquisition Syndrome). Over the years I've owned at least 20 guitars and even more amplifiers.

Some of my amps were bought and subsequently reviewed here on Amazon. In some of the reviews, such as my review of the Valeton TAR 20G amp head, I've mentioned that the amp made me wish I'd owned it sooner, as it would have kept me from buying a lot of other amps.

About five years ago, I sold a lot of my guitars off but couldn't bring myself to part with my veritable zoo of amps. And that's where the title of this review comes into play:

I've been so impressed with this amp, I've sold off nearly all my other amps. I never saw this happening.

This head can do everything I want and need from an amp. Although it's a head, it's internal five inch speaker allows me to jam in my bedroom, and it's adjustable power output easily allows me to push the amp's power section without leveling my house. It has a couple of line-out options, so playing with headphones and direct line-in recording via my DAW is easily done as well. It's MIDI in jack further expands the amp's flexibility when recording with my DAW as well! Finally, I can very easily hook this head up to one or both of my 3D printed guitar speaker cabinets, a 4x6 cab and a 2x10 cab. The effects loop allows for easy connection of my pedal board, either for jamming or recording.

In terms of features, I have one gripe, but it's a personal preference gripe so I won't deduct from my review rating for this: This head's controls are on the top. I very much prefer front face controls. Not a deal breaker, but I feel it's worth mentioning. Also, the cab response switch seems a little gimmicky. I can hear a difference when I play the head through it's internal speaker, and I hear no difference playing through my 3D printed cabs. I intend to experiment with this feature when I get around to really integrating this amp into my recording setup.

In terms of tone, I'm not going to dive in too deep here; If you want to know what the amp sounds like, watch videos and/or listen to clips and let your ears be the judge. But I have a few observations to share.

First off, the clean channel, while spectacular sounding, is clearly Roland's JC-120 chorus clean model. Because of this, the clean channel puts out some SERIOUS bass frequencies. When I run the clean channel through my 4x6 cab, the little 6" speakers fart and flab when I play on the low E string. I haven't tried playing my baritone guitar through this amp for this reason. (Note: I run standard tuning on all my guitars)

While you can easily break up the clean channel by diming the gain knob, I don't care for how it sounds. It sounds as literal as I write it: A JC-120 with the gain cranked. I find going to the Crunch channel and turning the gain way back is a much better alternative.

I feel there should be a more noticeable difference between the Lead and Brown channels. Yes, both are modelled for high gain applications, but I expected more of a creamy tone from the Lead channel, and more midrange emphasis on the Brown channel. This can be easily argued by anyone with an experienced ear though, so take this statement with a grain of salt as it's just what I hear and feel.

As for the acoustic channel....I am blown away. My middle-of-the-line Yamaha acoustic guitar sounds PHENOMONAL through this amp! I mostly keep my acoustic to not need an amp, but I'm finding myself reaching for my Yamaha more and more, expressly to play it through this amp. I saw myself using this channel once then forgetting about it. Not so! Again, VERY impressed here.

As for effects, they sound good. With my gearhead state, I can waste DAYS tweaking effects, so I've made it a point to just pick ones I like and leave them be. For this amp, I'm just using a spring reverb effect. I do like noodling around with the octaver and wah-wah effects as well. In general, all the effects sound like BOSS's engineers spent a good amount of time dialing them in. You can of course connect the amp to a PC, get the appropriate software and change the effects yourself. I don't intend on doing this. BOSS's DS-1 is even on the amp and sounds as infamous as ever! Sweet, sweet crunch, but with farty lows and ultra fizzy highs to ruin that crunch.

Some experienced guitarists or Internet surfers may read what I just wrote and ask "WHY did you drag that pedal into this!?". The answer is because it ties into my one solid gripe about this amp's tone:

The "Variation" button on this amp is a really annoying gimmick!!

All it seems to do is add more gain and a lot more treble to the amp's channels. It makes the Crunch channel sound like a clean amp with a stock DS-1 in front of it..... and that isn't a compliment!! In other words, the Variation button makes a good amp tone sound overly bright, tinny, and fizzy if overdrive or distortion is achieved. I give a big thumbs down to this feature. Either BOSS's sound engineers should rework this feature or remove it entirely. Every time I've tried playing ANY of the amp's channels with the Variation button engaged, I invariably reach to turn that feature off a minute later with a grimace on my face.

So, since I can't use the star rating with precision, I give this amp a 4.9 out of 5. If the Variation button either did nothing or simply switched to another bank of tones that I didn't care for, I wouldn't hold this feature against the amp. But where it literally makes any tone I've dialed in sound bad, I deduct a bit of my score from the amp for this.

But overall, I'm really pleased with this amp. I return to my earlier statement and say I always saw myself growing old with a house full of guitar amps, but I've been quite enjoying having more house space and I'm definitely enjoying the tones I get from this amp.....sans the Variation, thank you very much!"

"I’ve been playing tube amps since the ‘80’s. Various Mesa-Boogies mostly. I still have my Nomad 100 head, but I needed a lighter and more “low volume friendly” amp. I’ve also been looking at pedals lately, but don’t have tons of $. The MKII 100 fills all these slots. It’s also a lot lighter than my Boogie. Nothing will ever beat a 100 watt Mesa-Boogie cranked up, and I still have that available, but the Katana can hold its own. If you know how to dial-in amps, and/or use the Katana Librarian app, you can make this thing sound GREAT. While it can get LOUD, it sounds great turned down on .5 watts. Just using the panel you can dial in great sounds, and the Librarian app opens up an abundance of further tone shaping options. I also got the GA-FC EX and the Airstep Kat to open up switching options. I would highly recommend this amp even before you factor in that it’s $379."

"I've owned solid state amps for 40 years. Treating myself to a new Gibson LP recently, I really thought I would also get my first tube amp. I tried out a few tube combo amps and was not impressed with the limited channels/controls, high price, and heavy carrying weight. Factor in limited built-in effects like reverb only, regular maintenance to replace tubes, and transporting damage concern the decision to stay with solid state really was a no brainer.

The HUGE difference with this solid state amp compared to previous amps I've owned is the advanced Digital Signal Processing capability. Leveraging their years of expertise in DSP effects design and manufacturing, the Katana MKII is based on some of the latest technology there and I believe BOSS is well ahead of their competitors. There is so much packed into this amp. DSP based solid state amps have reached a new level beyond anything from the past. I ended up selling ALL of my old pedal effects and using the money to buy the BOSS GA-FC foot switch and FV-500L pdeal too. I absolutely love this amp and footswitch combination. I think the GA-FC at a minimum is a must to go with the amp. The FV-500L I use as an expression pedal for master volume control or I can switch the port that it's plugged into on the GA-FC for wah pedal or other pedal control. Setup of the expression pedal using the software is very easy and flexible to allow you to customize what and how you want to control a specific built in effect.

While you do not have to use the free software, I HIGHLY recommend you do. Only challenge was finding the software to download. It is not intuitive after getting to the website. Youll find different artists tones to download, but no easy to find link for the core software. Just click on any artist download then scroll ALL the way to bottom and you will find the core siftware. Other than this challenge, everyting else was breaze. You will need the appropriate USB cable though. It does not come with the amp. At least mine didnt. The software is very intuitive, easy to use, and is what allows you to set up all of the specific effects you want to control by the footswitch and capture your tone settings. You can capture tone settinga from the front pannel, but have greater customization via the software. Through the software you can change the finer settings of every effect, beyond what you can do on the Amp control panel.

The varations of tones and effects are absolutely outstanding. I've never had a better sounding or more capable amp. Now that I have it all 8 channels programmed with specific effects for each channel i can turn on or off by the footswitch, I do not even use the panel controls other than turning the power on and off.

With the 100W compared to 50W, getting 4 each channels and a Variation Amp Type button to great more storage tone combines is worth the extra money. It also gives you more than enough power to comfortably play over drums and bass in small to medium venue.

I also bought the specific cover for the amp. I believe this is the best sounding, most versatile, most capable, attractive, and best value amp on the market. I highly recommend this amp. Other than difficulty finding the software download initially, I cannot not find any issue or dissatisfaction with any aspect of this amp."