Head to Head – Guitar Interfaces

Audio interfaces have long featured high impedance instrument inputs, but what if this add-on was the main event? Guitarists may be the customer they have in mind, reports Robbie Stamp, but these interfaces may have a wider appeal

This issue we look at two interfaces, both with one goal: to help guitarists recording via a high-impedance input. The Axe I/O comes from IK, the makers of Amplitube; they have a long history in amp simulation. Audient, though, come from the analogue mixing console world and marry AD/ DA and analogue know-how with the guitar cab simulation experience of Two Notes. How do they perform?

Guitar preamp

The Axe I/O and Sono take different approaches to the guitar (instrument) input path. The Axe offers two inputs: one fixed at 1MΩ impedance, the other variable from 1MΩ to 22kΩ, essentially thickening/dulling the tone as it loads the pickups. In combination with the subtle harmonic distortion of the JFET switch (select Pure for clean) the Z-Tone control can dial back an overly bright bridge pickup, or add weight to a single coil.

The Sono has one instrument input but gives it a real valve preamp with three-band EQ. Two triodes of a 12AX7 valve sit either side of the EQ, giving scope for high quality analogue tone shaping and harmonic distortion, especially when driving the input stage hard with pedals.

Simulation

Axe I/O bundles with Amplitube 4 Deluxe, giving a large range of quality amps, cabs, pedals, mics and rooms. The two controller inputs and front panel Preset knob are mapped by default within Amplitube for easy integration, though these can be mapped to any MIDI CC.

Sono uses DSP to provide Two Notes’ Torpedo power amp and speaker cabinet simulation in the box. The drive knob controls the power amp distortion and three user presets can be stored onboard. The base set of virtual cabs is more than enough to get started with, though more can be purchased. The sims, alongside the valve preamp, are satisfyingly realistic and expressive.

Preamp to re-amp

Both interfaces possess instrumentlevel amp outputs, making re-amping possible without an external level converter box. This can mean sending out to an amp to mic up and record back via the mic preamp(s), or processing through pedals and returning via the Hi-Z input(s). In both cases the Sono has the advantage of using its valve preamp stage for extra EQ and distortion for pedals, or adding valve saturation to one of the mic preamps, which is a boon for recording in general.

Audio interface

There are balanced TRS Line main outs, an unbalanced floating amp-level TS out and stereo headphone on both, and though, on a software level, they both have four line outputs, only Axe I/O provides separate jacks for them (outs 3 & 4 are TS unbalanced); Sono routes them to the headphone amp.

Input-wise the Sono makes the bigger offer with an optical TOSLINK socket for stereo S/PDIF or ADAT (eight channels up to 48kHz, four up to 96kHz); good for adding preamps or effects units in a larger setup.

Monitoring and mixing

Being aimed at guitarists, these interfaces need flexible monitoring and routing, for switching between tracking, re-amping and mixing. At first they offer the same hardware monitoring controls (monitor level, headphone level and input/DAW mix), but Sono has a separate cue mix and talkback channel in software for a more studio-like engineer/artist monitoring format.