Disclosure: Fency Music, linked on this page, is our sister store. Liverpool Music does not currently earn affiliate commission from any retailer mentioned here.
The Boss Katana and the Positive Grid Spark are the two amps most new players end up choosing between, and they cost roughly the same. That is where the similarity ends. The Katana is a proper guitar amp that happens to have an app. The Spark is an app that happens to have a very good speaker attached. Which one suits you depends far less on tone than on where you will play and how you like to practise.
I am a songwriter, and I build FencyGuitar, a guitar learning app, so I spend a lot of time thinking about what keeps people practising. That is the angle here. I will compare the two ranges tier by tier, using UK prices checked on 25 October 2026, and I will be clear about where each one falls short.
The Short Answer
Buy the Katana if you expect to play with a drummer, rehearse with friends or play a small gig within the next year. Buy the Spark if you mostly play at home, learn from songs and videos, and want an amp you can carry from room to room. Here are my three picks.
| Amp | UK price | Best for |
|---|---|---|
| Boss Katana 50 Gen 3 | £289 | Players heading towards rehearsals and small gigs |
| Positive Grid Spark 2 | £239 | Home practice, learning songs, playing along with backing tracks |
| Positive Grid Spark GO | £95 | Tight budgets, headphone practice and travel |
The rest of this comparison explains the reasoning, and when each of these picks is the wrong one.
Two Very Different Ideas of a Practice Amp
Boss
Boss started out in Japan in 1973 and became part of the Roland group a few years later. It is best known for its compact pedals, which have been on stage floors for decades, and that background shows in the Katana. When Boss launched the Katana in 2016, it built a solid state amp that behaves like a traditional amp: one big speaker, physical knobs for gain and EQ, and a set of effects you can reach without touching a phone. The current Katana Gen 3 range keeps that approach and adds deeper editing through the free Boss Tone Studio software.
Positive Grid
Positive Grid came from software. It made its name with BIAS, a set of amp and effects modelling apps, before moving into hardware. The original Spark arrived at the end of 2019 and was designed around the phone in your pocket from day one. Its party trick was never just the sound. It was Smart Jam, which generates a bass and drum backing that follows your playing, and Auto Chords, which shows you the chords to songs you stream. The Spark 2 builds on that with more power, a better speaker arrangement and a built in looper.
So the question is not really which company makes better amps. It is whether you want a guitar amp first, or a practice companion first.
Sound and Volume
The biggest physical difference is the speaker. The Boss Katana 50 Gen 3 uses a single 12 inch speaker driven by a 50 watt Class AB power amp. The Positive Grid Spark 2 is also rated at 50 watts, but it uses a pair of 4 inch speakers with a horn and bass ports, in a much smaller cabinet.
That difference matters most at volume. A 12 inch speaker moves more air, so the Katana sounds like a guitar amp in the room: full low mids, a sense of the sound filling the space, and enough headroom to be heard over a drummer at a rehearsal. The Spark sounds detailed and polished up close, more like a good hi fi speaker. At bedroom levels that can actually be an advantage, because the stereo spread makes effects such as chorus and delay sound lovely. Push it to band volume, though, and it runs out of weight long before the Katana does.
Boss has a clever answer to the volume problem at home. The Katana's Power Control switch has 0.5 watt, half power and full power settings, so you can get the feel of a pushed amp at a volume that will not upset the neighbours. The Spark handles low volume well too, simply because its speakers are designed for close listening.
On tone, both are capable of convincing cleans, crunch and high gain. The Katana Gen 3 offers six amp characters, each with a variation, for twelve voicings in total, plus five effect sections on the front panel. The Spark leans on a large library of amp models and effects in the app, and on presets shared by other players through ToneCloud.
If you plan to use pedals in front of either amp, our Blues Driver vs Tube Screamer vs Klon comparison covers which drive pedals pair best with modelling amps.
Matching the Amp to Your Music
Both amps cover a wide range of styles, but each has its sweet spots.
Clean and indie. The Spark's stereo speakers flatter clean tones with chorus, delay and reverb, and for jangly chords at home it is a joy. The Katana's clean channel has more body and feels more like a real amp when you dig in, which helps if you play with a pick and like a bit of push.
Blues and classic rock. Here the Katana's single 12 inch speaker earns its keep. Crunch tones have the low mid weight that makes a Strat or Les Paul sound full, and the Power Control lets you get that sound at a sensible volume. The Spark does this well at low volume but loses some of the punch as you turn up.
Metal and high gain. Both have convincing high gain models. The Katana's Brown and Lead characters are tight and responsive, while the Spark gives you access to a huge number of community presets for specific artist tones. For palm muted riffs at volume, the bigger speaker wins again.
Acoustic guitar and vocals. The Katana includes an acoustic character, which is useful if you switch between electric and acoustic. The Spark can work as a speaker for backing tracks, but neither replaces a proper acoustic amp or a small PA for singing.
Songwriting and demos. This is where my own priorities come in. When an idea arrives, the fastest route to capturing it wins. The Spark's looper and drum patterns let you sketch a verse and chorus in a few minutes. The Katana's USB connection gives you a cleaner path into a recording app.
Learning and Practice Features
This is the Spark's home ground, and it is the reason so many beginners buy one.
Built in Bluetooth audio. The Spark is also a Bluetooth speaker. Stream a song or a lesson video from your phone and play along through the same speaker, with your guitar and the track mixed together. The Katana has an aux input and can add Bluetooth through an optional adaptor, but it is not built in.
Smart Jam and Auto Chords. In the Spark app, Smart Jam listens to what you play and generates a bass and drum part to match. Auto Chords shows chord charts for songs you stream. These are the features that turn practice from running scales into making music, and from my work on FencyGuitar I can say that this is exactly the moment where many learners either stick with it or give up.
Looper and drums. The Spark 2 adds a Groove Looper with built in drum patterns, so you can record a chord part and solo over it without any extra gear.
The Katana's approach. The Katana gives you a headphone output with cabinet simulation, a USB connection for recording, and Boss Tone Studio for detailed editing. It is a more serious tool and a less playful one. You will need a separate app or a computer for backing tracks and lessons.
The trade off is that the Spark relies on its app for a lot of its best features. If you dislike using your phone while you play, or you want to plug in and turn knobs, the Katana is far more satisfying.
Portability and Power
The Katana 50 Gen 3 weighs about 11.6kg and runs from the mains. It has a handle and moves easily between rooms or into a car, but it is not something you would carry on a bus for fun.
The Spark 2 is roughly half that weight and much smaller. It can also run from an optional battery, which was £69 at guitarguitar, so you can take it into the garden or a friend's flat without hunting for a socket. If you share a home and your practice spot changes from day to day, that convenience is a big deal.
For travel or late night practice, both brands make even smaller options, which I cover next. Our best practice amps roundup also looks at quieter and more portable alternatives from other brands.
The Small Models
Positive Grid Spark GO
The Positive Grid Spark GO was £95 at guitarguitar, which makes it the cheapest way into the Spark ecosystem. It is a tiny battery powered amp that works through the same app, with Bluetooth audio and the smart practice features. It is happiest as a headphone amp or a desk speaker. The Positive Grid Spark MINI, at £149, is a step up in size and volume.
Who should skip this: anyone who wants to play with other people. These are personal practice tools.
Boss Katana Mini X
The Boss Katana Mini X was £139 and is the most capable small amp in the Katana family, with a larger speaker than the original Katana Mini (£129) and battery power. Boss also makes the Boss Katana Go, a headphone amp that plugs straight into your guitar, at £109.
Who should skip this: players who want the full app experience. The small Katanas are simpler and more knob based.
At this size, the Spark GO wins on price and features, and the Katana Mini X wins on sounding like a small amp rather than a speaker.
The Main Event: Katana 50 vs Spark 2
Boss Katana 50 Gen 3
At £289 at guitarguitar, the Boss Katana 50 Gen 3 is the amp I would recommend to anyone who thinks they might play with a band. It is loud enough for rehearsals with a sensible drummer, it has four tone memories you can switch with an optional footswitch, and its controls are all on the top panel. You can set a sound in seconds without unlocking a phone.
It also has a headphone output, a USB connection for recording, and an input that bypasses the preamp if you later get a modelling pedal. One limitation to know: the Katana 50 has no effects loop and no dedicated line out. If those matter, you need the Katana 100.
Who should skip this: players who mostly practise alone at a desk, and anyone who needs to carry their amp regularly.
Positive Grid Spark 2
At £239, the Positive Grid Spark 2 is £50 cheaper than the Katana 50 and is the better learning tool. Compared with the original Spark, it adds more power (50 watts instead of 40), a revised speaker design, eight hardware presets instead of four, and the Groove Looper. The original Positive Grid Spark was still on sale for £199 and remains a good buy if you do not need the looper.
Who should skip this: anyone planning to rehearse with a drummer, and anyone who wants a traditional amp feel.
The Bigger Models
Boss Katana 100 Gen 3
If you know you will gig, the Boss Katana 100 Gen 3 at £379 is the more sensible step. It adds more power, eight tone memories, an effects loop and a line out for connecting to a PA or interface. There is also a 2x12 version at £449.
Positive Grid Reactor
Positive Grid's answer at gig level is not a bigger Spark. It is the Reactor, a new range of 12 inch combo amps launched in June 2026. Andertons listed the Positive Grid Reactor 50 at £299 and the 100 watt version at £379 at launch, and guitarguitar was selling bundles with a footswitch and wireless link. It has built in Bluetooth, an effects loop and line out on both sizes, and a new approach to modelling that builds tones from amp circuit behaviour.
It is too new for long term reliability reports, so I would treat it as the more experimental choice. The Katana 100 is the proven one.
Quick Comparison Table
| Boss Katana 50 Gen 3 | Positive Grid Spark 2 | |
|---|---|---|
| UK price | £289 | £239 |
| Power | 50 watts, with 0.5 watt and half settings | 50 watts |
| Speaker | One 12 inch | Two 4 inch with horn |
| Weight | About 11.6kg | Roughly half the Katana |
| Battery | No | Optional, sold separately |
| Bluetooth audio | Optional adaptor | Built in |
| Practice tools | Headphone out, USB, Tone Studio | Smart Jam, Auto Chords, Groove Looper, ToneCloud |
| Band volume | Yes, at rehearsal level | Not really |
| Best for | Rehearsals, small gigs, knob lovers | Home practice and learning |
What I Don't Like About Either Amp
Katana. The Katana 50 lacks an effects loop and a line out, which feels stingy at this price. Bluetooth needs an extra adaptor. Boss Tone Studio is powerful but not friendly, and some players find it confusing at first. And at 11.6kg it is more amp than many bedroom players need.
Spark. The Spark's best features live in the app, so a phone becomes part of your rig. Its small speakers sound impressive up close but thin out at volume. The battery costs extra. And because the amp leans on software, its usefulness depends on Positive Grid continuing to support the app well.
Both. Neither is a substitute for a valve amp if you are chasing that specific feel, and neither has a speaker you can easily upgrade.
Who Should Skip Both
Players chasing a classic valve sound. A small valve combo will suit you better. Our Blues Junior vs Princeton Reverb comparison is a good starting point.
People who want lots of sounds on a pedalboard. A multi effects unit with headphones may be cheaper and more flexible. See our Valeton GP-50 vs Boss GT-1 vs Zoom G1X Four comparison.
Silent practice only. If you only ever play late at night, a headphone amp or guitar headphones may be all you need.
Buying Used in the UK
Both amps are popular enough that the used market is full of them. When I checked, guitarguitar had a pre owned original Spark at £149 and a pre owned Katana Mini at £69, and you will find plenty more on Reverb, eBay and Facebook Marketplace.
Before buying a used modelling amp, check these points:
Generation. Make sure you know whether a Katana is Gen 1, 2 or 3, and whether a Spark is the original or the Spark 2. Older units are fine amps but have fewer features, so pay accordingly.
App support. Connect it to the current app and confirm it pairs and updates. A used Spark that will not connect loses most of its appeal.
Controls and jacks. Turn every knob, press every button and wiggle the cable in the input. Crackles and dropouts are common faults on well used amps.
Battery health. On battery models, ask how long it lasts on a charge. Batteries wear over time.
A private sale gives you far fewer rights than buying from a shop, so buy from a retailer with a returns window where you can.
So, Katana or Spark?
Learning at home, mostly alone. The Positive Grid Spark 2. The practice tools are genuinely useful and the Bluetooth speaker means it earns its place in the room even when you are not playing.
Planning to rehearse or gig. The Boss Katana 50 Gen 3, or the Katana 100 if you need a line out and effects loop.
Very small budget or travel. The Positive Grid Spark GO for app features, or the Boss Katana Mini X for a simpler amp.
There is also a third route that suits players who want amp, effects, drums and a looper on the floor rather than on a shelf. Fency Music, our sister store, carries the JOYO Jam Buddy II, a pedal sized amp with stereo speakers, drum patterns, looping and Bluetooth backing tracks.
Still choosing a guitar to go with your amp? Our Squier vs Epiphone comparison covers the most popular first guitars.
Why Liverpool Music
Liverpool Music is run by Zhong Gu, a songwriter who also builds FencyGuitar, a guitar learning app. We think a lot about the gap between owning gear and actually practising with it, and that is the lens we use here.
We checked prices against UK retailers on 25 October 2026, mainly guitarguitar, with Andertons for the Reactor launch prices. We cross checked specs against manufacturer and retailer listings, and when a point comes from owner reports rather than our own hands, we say so. Fency Music is our sister store, which is why we say so at the top of the page. We do not currently earn affiliate commission from any retailer we mention. If a price or spec has changed, tell us and we will correct it.
FAQ
Is the Boss Katana louder than the Spark?
Yes, the Boss Katana is effectively louder in a room. Both the Katana 50 Gen 3 and the Spark 2 are rated at 50 watts, but the Katana's 12 inch speaker moves far more air, so it holds up next to a drummer. The Spark sounds great up close but loses weight at band volume.
Can I use the Spark without the app?
Yes, you can play the Spark without the app using its top panel controls and stored presets. However, the features that make it special, such as Smart Jam, Auto Chords and the deeper tone editing, all live in the app. If you never want to use a phone while you play, the Katana is the better fit.
Is the Katana good for beginners?
Yes, the Katana is a very good beginner amp, especially for players who like physical knobs. It is simple to dial in, it sounds like a real amp and it will still be useful when you start playing with others. It lacks the Spark's built in learning tools, so you will need a separate app for lessons.
Can I record with either amp?
Yes, both amps can send audio to a computer over USB, so you can record without a microphone. That makes either one a simple home recording setup. For higher quality results or more flexibility, many players eventually add an audio interface and record the amp's line out or a modelling pedal instead.
Which is better for practising with headphones?
Both work well with headphones, and both use cabinet simulation so the sound is natural rather than fizzy. The Spark has the edge if you want to stream backing tracks over Bluetooth into the same headphones. The Katana has the edge if you prefer to set your tone with knobs.
The Bottom End
The Katana and the Spark are both excellent, which is why this argument never ends. The honest split is simple. The Katana is the better amp, and the Spark is the better practice partner. If your near future involves a rehearsal room, a drummer or an open mic, buy the Katana and grow into it. If your near future is a bedroom, a phone full of songs and the goal of playing every day, buy the Spark and let it make practice fun. The right amp is the one that gets you playing more often.
