The affordable and stylish Spark 40 packs Positive Grid’s powerful modelling software into a convenient, portable practice amp. What’s not to like?
My own miniature Tonehenge is a lovely boutique tube amp, plus a custom 2x6 cab and an oversized 1x12 cab with a Celestion Alnico Cream. It would pass the cork‑sniffing test of all but the most lofty gear snobs but, sometimes, even a top‑degree tone‑mason can’t be bothered to deal with tubes and cabs. The amp is unreasonably loud, it gets hot, and fooling with attenuators to bring the output of the cabs down to a sensible volume for practice defeats the point of their lush tone somewhat. Plus if you want to move any of it… well, let’s just say I skipped the gym during lockdown. So small practice amps still have a place in my life and after some incredibly positive experiences with Positive Grid’s Bias Amp modelling plug‑in, I figured it couldn’t hurt to try their take on the idea.
Launched around a year ago, the Spark 40 combines a power amp with DSP amp and effects modelling, along with some interesting practice‑oriented features. It had something of a rocky start to life, because the crowdfunding campaign was so popular that it took quite a while for everyone to receive their units. That’s all out of the way though, and the Spark is now available to buy in shops. I recently did just that.
Conceptually, the Spark is pretty simple: you plug in your instrument, as with any amp, and a DSP modelling engine gives access to most guitar and bass tones you can dream up. The resulting sound is pumped out by a 40W solid‑state amplifier driving two four‑inch full‑range speakers in a stereo configuration.
You can access presets using the hardware controls but can do much more tweaking using the Bluetooth smartphone app. With the app, you can also pull tones from a vast online library, and the Spark can even listen to your playing and create a basic backing track for you, or help you to learn a well‑known song using its Smart Jam feature (see box). There’s also a USB connection, which allows you to record the emulated amp sound directly into your DAW as audio, without the influence of the Spark’s own cab‑and‑speaker combination. No driver is required for Mac/iOS, but there’s an ASIO driver for suitably low‑latency performance on Windows. This feature is a great bonus, since the modelling is good enough that you could easily use this amp to make records, and they’d more than likely sound better than if you attempted to mic a cab at home!
The Spark looks like a real amp, and Positive Grid have done a great job of hiding just how high‑tech it is inside; knowing guitarists generally to be a conservative bunch I’d guess this is a conscious choice. All the knobs feel solid and consistent and the build feels decent generally. There’s a carry handle and, at 5.2kg, the Spark 40 is neither so light as to feel cheap nor so heavy as to be a burden. When I bought mine, they threw in the carry case for free, and this is a snug fit — great for lugging it to the studio and back, taking it on holiday as hand baggage, or maybe transporting it to a quiet jam.
If you really can’t be bothered with the app or any customisation of tones you’d be missing out, but you can stick to using the amp’s physical controls if you want. With the left‑most knob you can choose one of seven on‑board factory presets: one for acoustic, one for bass and five for electric guitar, with increasing levels of distortion. These presets remain fundamentally as they’re set up, but each one features a controllable mod effect, delay and reverb, and lets you dial the EQ (bass, mid and treble) and virtual pre‑ and power‑amp stages to taste. At the other side is an Output knob, which controls the volume put out by the Spark’s solid‑state amp, while a Master knob emulates the master output of the virtual tube amp, with all the attendant effects on distortion characteristics. There’s also a dual‑purpose button for delay tempo and accessing the built‑in tuner.
A line input on the rear means you can play along to a backing track without having to use the app, and you can control its volume relative to your instrument. There’s no dedicated line output, but the headphone output (which has plenty of juice on tap) could serve as one. There’s no footswitch support either, so you won’t be switching channels or effects on the fly — unless you want to modify the unit (see the ‘Spark Mods’ box). As with a regular amp, though, you can always use a favourite effects pedal for a different sound, or as a boost for extra gain.
You can do much more using the iOS/Android control app, and setting this up is simple, with the usual...