The inventors of guitar DSP outdo themselves with a new guitar processor built for the most demanding professional stage and studio work.
By Stephen Lynch
Ever since Line 6 unveiled Helix in June, 2015, anticipation has been intense. After all, these guys have been at the front of the pack in guitar DSP going back to the days of the game-changing POD. But as cool as that little bean-shaped box is, Helix is of another order entirely. With this new flagship guitar processor, Line 6 clearly has its sights aimed at touring pros and weekend warriors who demand the utmost in tone, performance and reliability.
With the Helix street date slated for the spring 2016, I jumped at the chance to get my hands (and feet) on a preview unit. My sample was the floor-based Helix. A rack-based version, fittingly named the Helix Rack, is also available for preorder as I write this. It will make sense for guitarists and studio owners who foresee integrating Helix into extensive stage rigs or studio gear. The Helix Control, also currently on preorder status, is designed as a single-cable remote to run the Rack and its more compact footprint should be ideal on crowded stages.
Six years in the making
In the epic R&D process that Helix entailed, the Line 6 team was brutal with itself. Dissatisfied with the speed of the initial user interface, they scrapped it, going back to the drawing board twice more before they were completely satisfied with the look, feel and speed of the GUI.
According to Ben Adrian, one of the sound designers on the project, the team found it took roughly a month to nail every aspect of an amp. Their analysis was exhaustive and included the obvious power and preamp stage circuitry and tone stacks as well as those nuances introduced by the circuit designs, both intentional and unintentional—effects such as RC filtering that are an intrinsic part of an amp’s character. Line 6 was intent on identifying and recreating the happy electronic “accidents” that give each modeled unit its singular character. This level of analysis and DSP sophistication is unprecedented in a guitar multiprocessor.
Effects received similar scrutiny. The Helix model of the original Univibe is a poster child for Line 6’s obsession with capturing the behavior of actual circuits rather than merely going for a similar sound. The original ‘60s Univibe stomp used four photocells surrounding a standard incandescent light bulb. As voltage to the light fluctuated causing it to dim and brighten, the photocells generated signals responsible for that distinctive, wobbly fuzz tone Hendrix exploited so thoroughly. To capture the Univibe’s electronic behavior involved the creation of standalone models of light bulbs, bucket-brigade chips and transistors. As I soon discovered, these exhaustive steps pay big dividends when you plug in.
Under the hood
To achieve the level of detail and playing dynamics Helix delivers takes a whole lot of data-crunching power. In creating a truly convincing model, it’s not just a matter of understanding how an effect or amp sounds, but also why it behaves and sounds the way it does. The process of describing an effect’s sound so that it can be modeled using DSP is challenging, but it has been done with varying degrees of accuracy for a while now.
What’s been missing before Helix is an in-depth understanding of what’s happening in amp and effect circuits and their components under changing loads and other conditions. Things like frequency, power supply ripples, phase response and linearity, all of which all contribute to the overall character of a given sound. Speaker cabs are another great example. The classic sounds generated by vintage cabinets are influenced by things never before measured in such detail. Stuff like the phase cancellation that occurs in multi-speaker cabinets, edge reflections, the wood, the glue, even the powder-dry, fragile speaker cone paper all play a role in making a Fender Bassman cab, for example, sound the way it does.
Line 6 has gone further by studying subtle interactions between amp and effects components and guitar control pots as they’re rolled off. Understanding, for example, how a specific transistor, tube, rectifier or resistor behaves under various loads—what their gain profiles look like among other things—is critical in replicating the real playing dynamics of real analog gear. Replication of these dynamics is remarkable right down to the impact of individual tube sag. A dual-processor engine coupled with lean code helps ensure that these sophisticated models perform flawlessly and latency-free.
Upon unboxing, Helix impresses as being one rugged piece of gear. The solid aluminum case and steel base feel tank-tough in the way pro-grade stage gear should. The switches and knobs look like they’ll hold up to serious tour-induced abuse.
Taking in the top panel, I was struck by its simplicity and uncluttered look. The 800 x 480-pixel color LCD display requires no squinting. Everything's easy to read and interpret thanks to a GUI with a lot of smarts. Functions for the minimal controls that surround the display, including a joystick, are largely replicated when you put the unit’s stomp switches in to edit mode, which we’ll address in a moment.
Use your feet, use your hands
Editing and parameter setting in a DAW or traditional guitar processor can be a hassle when you’ve got your guitar or bass strapped on. With Helix, you can do all your editing with your foot—very cool in live situations. But when you’re at home or in the studio, Helix transforms into a desktop unit by setting the stomp switches in edit mode. Doing so turns them into touch-sensitive controllers—just the thing for in-depth tone tweaking and parameter setting. Jumping between blocks and building complex signal chains is as easy as touching a footswitch with your finger. Very, very clever.
You can use the top-panel joystick to navigate between presets and parameters too. It allows single-handed navigation, selection and move operations. This sort of flexibility is a recognition that we all have our own workflow preferences onstage and in the studio. I found getting around the interface pretty much a no-brainer after quickly getting a feel for its elegantly simple architecture.
Taking a spin
For starters, I built a basic signal chain with a phaser and compressor going into a dual-rectifier high-gain amp model, then out to a powered speaker for testing purposes. I started out with a Shure 57 model placed one foot off the cone. I then tried a Royer model positioned at three feet. In both cases moving between positions and mic types was both audible and visceral—you could feel those mics being moved through space.
Sensing that I was missing some midrange with the Royer, I tried moving the Shure in closer to the cone, immediately punching up the mids. What formerly involved moving mic stands can now be achieved by simply dialing in mic model positions. Awesome.
Authentic playing dynamics have always been a big challenge in guitar DSP. Not with Helix. The amps behave like real amps: When you dig in they get grittier and louder. When you back off the notes actually decay like a real amp.
Curious to see just how good Helix models are, I plugged my guitar into the Channel 4 preamp of my Mesa Road King Dual Rectifier set to its “Modern” high-gain setting and ran my output via the powered speaker. I then called up the Dual Rectifier model in the Helix and routed that straight into my physical amp’s FX loop return—thus sending it through the same power amp and speaker the "real" amp's preamp flowed through. Switching between the two signal paths was a revelation. With just a little tweaking, I could get the virtual and actual amps to feel and sound identical, while being output via the same speaker. Pretty convincing!
The Road King is a four-channel amp, and I tried assigning what Mesa calls its Tweed Clean tone to Channel 1. I then called up the Helix equivalent of the Tweed Clean, and again, A/B-ing between the two channels I found I could dial in identical sounds AND feel on either channel—again being routed through the same power amp and speaker. Not only does the Helix totally nail the sound of the Mesa, but with its huge array of effects, the sky’s the limit on where you can go from there.
I quickly fell in love with putting the stomp switches into edit mode. I found the touch interface was sensitive and reliable, letting me tweak away endlessly, creating chains and fine tuning effects. The foot controller can be set to manage just about any function on the fly: how much fuzz you’ve got in your fuzz, how fast your delay repeats, and so on. Create a setting and assign it to the pedal with a button press—this thing works the way your brain thinks it ought to.
Because we had limited time to audition Helix before having to return the review sample, I didn’t have a chance to test the four-cable connection method that allows Helix to be incorporated as an extension of your physical amp. This would allow me to swap out the four actual preamp channels in my physical amp with three or four virtual preamps—all of this happening ahead of my physical amp’s power stage. Those four discrete effects loops offer a lot of opportunity for turn-on-a-dime effects and fun!
Signal routing any way you want it
While the Helix is clearly intended to take over as the heart of your guitar rig, that doesn’t mean you have to give up any of your stomps or other current goodies. With those four effects loops and the super-intuitive GUI, integrating them into the Helix signal chain is a piece of cake. You can also add up to three external expression pedals. With its built-in 8 x 8 USB interface and comprehensive back-panel I/O, physical connection scenarios are pretty much endless.
Take those four effects loops for instance. You can connect up to four discrete pedal chains or you can split them up and assign them any way you want in your I/O scheme. With four independent signal paths, multiple instruments can be processed simultaneously, and your wet and dry signals can be routed via analog or digital I/O.
Typical of the pro-level design Helix evidences, the analog guitar input has a huge 123dB of dynamic range plus variable impedance. You should be able to squeeze the last drop of tonal goodness out of just about any pickup type while keeping noise at bay. A mic input with phantom power and digital control over its analog gain stage is a nice plus that extends your connection possibilities.
For Variax guitar owners, there’s a dedicated connector with which you can call up models and tunings and control effects. The connector also provides power to your Variax. S/PDIF I/O, an L6 Link AES/EBU out, and USB port make studio connections straightforward.
GUI and chewy
Helix is capable of replicating compression, sustain, and picking dynamics with impeccable realism. But if getting to those chewy tones is a chore, that would be a turnoff. With four stereo signal paths available for every preset, the possibilities are mindboggling. (We’ll get to reamping in a minute.)
The bad old days of delving deep into submenus to create elaborate signal chains is history. With Helix, everything is right in front of you: big, bold, legible and deeply informative.
The GUI makes signal chain setup and monitoring a piece of cake.
At a glance you see your complete signal chain with all routing details in the display along with all your currently loaded and active presets clearly shown with very legible electronic scribble strips. You can also customize the colors of the switch LEDs to match your preferences.
Everything’s easy to read with the unit on the floor—a big help on darkened stages. Text is very legible and the signal chain icons are intuitively designed. It’s a convention in these sort of reviews to say you barely looked at the manual or help screens. In this case, that’s absolutely true.
Virtual cabs you can practically touch
Over the last few years Impulse Response (IR) technology has been getting tone tweakers excited, and Line 6 has built it into Helix with its HX processing engine. Briefly, IR involves sampling speaker cabinets in conjunction with various industry-standard mics positioned at specific physical points in relation to the cabinet. The idea is to render an exact sonic recreation of the original cabinet in a given space. By themselves, IR files don’t sound like much, but when used as plug-ins, they infuse your sound with new levels of realism.
Line 6 engineers have figured out how to deliver 2048-point IR while keeping a firm hand on DSP usage for latency-free performance. Cabinet resonances and output are captured with a broad assortment of mics positioned at 12 different distances from each cabinet. As I found in moving virtual mics around, impeccable low-end response tracking means Helix will replicate real-world proximity effects as you mics to their closest positions. Hard-core tone tweakers can even load their custom IR files into Helix.
Reamping couldn’t be easier using Helix. With preassigned routing, the Drive channel is automatically recorded then mixed with reamped signals on the assigned outputs with essentially no configuration needed. Because of its robust I/O and signal-chain building capabilities, you can do all sorts of wild and wooly wet/dry signal-routing variations to exploit the super-flexible matrix. I could have spent hours exploring the possibilities.
Bristling with MIDI power
Helix, as you would expect, works flawlessly in real-time MIDI-control situations. Patch editing is where it really shows its mettle. You can send up to six independent commands while recalling patches that aren’t currently assigned to a footswitch. This allows you to control external digital mixers, swap a synth patch, or perhaps trigger a looper or sequencer.
If you’ve been on the fence about going the guitar-processor route, Helix is the piece of gear to make you pull the trigger. Once you immerse yourself in its huge range of sounds, routing options and astounding responsiveness to playing dynamics, I’m betting your stage rig will never be the same. Any guitarist who needs to cover a broad range of tones and effects with superb realism should give Helix an audition.
Try Helix risk-free
We recognize that Helix will be a significant investment for some players. With the Musician’s Friend 45-Day No-Hassle Guarantee, you’ll have the time to thoroughly audition it for yourself. We’re guessing that if your perceptions match ours, Helix will rapidly become the core of both your stage and studio guitar rigs.
Features & specs
- Dual DSP-Powered HX Modeling Engine With up to 4 Discrete Signal Paths, 45 Amps, 30 Cabs, 16 Mics, and 70 Effects
- Imports User and 3rd Party 1024/2048 Cab IRs (Impulse Responses)
- 12 Capacitive-Sensing Footswitches and Customizable Scribble Strips - Touch to Edit, Hold to Assign, Press to Engage
- Hands-Free Pedal Edit Mode Lays out Effect Parameters Across Switches and Expression Pedal
- Ultra-Fast Footswitch and Controller Assignment
- Up to 3 Expression Pedals, CV/Expression out, External Amp Switching, and Deep MIDI Control
- Extensive I/O for Seamless Integration With Your Entire Rig—10 Inputs/12 Outputs (Including Four FX Loops) Plus 8-In/8-Out USB Audio Interface
- AES/EBU, S/PDIF, and Variax VDI
- Industry-Leading 123dB of Dynamic Range on the Guitar Input, for Tremendous Depth and Ultra-Low Noise
- Tour-Grade Construction