In Summary

With some audio interfaces offering instrument-specific inputs, we decided to see how they can affect an instrument’s sound. Using an interface with other options as well, we plug in, listen, and compare.

Going Deeper

If The Plug Fits…

When going direct with instruments, engineers can of course use any input with a 6.35mm (quarter inch) jack connection, but that’s not the whole story. While any connector that fits will work (such as on a DI, or even a console or interface line input) more accurate results can be achieved with an input that is optimised for instruments such as guitars and basses- especially passive ones. These outputs have specific needs that can be met by the destination, and plugging into the wrong thing just because it fits can degrade the sound noticeably.

JFET - What Is It, And Why Bother?

If you don’t like numbers look away now. Audio sources and destinations work best where the latter resists, or opposes the incoming signal, by a factor of around 1:10 (opinions will vary on the ratio). If the destination doesn’t oppose or impede the source enough, it will ‘load’ the source by trying to draw more current than is available.

With their high output impedances that rise even higher as frequency increases, guitars need very high impedance destinations that run into the mega-ohm (MΩ) range. Widely-used op-amp designs can do a great job with mic and line sources, but instruments need very high-Z destinations to avoid loading the instrument. This will avoid things like high frequency fall-off and a generally dull, uninspiring sound.

Step forward the JFET design, giving instrument inputs what they need. As it happens, these can also behave and respond similarly to input stages found on valve (tube) guitar amps, making the experience even better for artists.

Beyond JFET - IK Multimedia AXE I/O ONE

Described by IK Multimedia as a “multiple topology instrument preamp”, AXE I/O ONE is a 1 in, 3 out guitar-specific interface. As well as having a switchable JFET instrument input, it also has separate active (10 kΩ) and passive instrument modes. What is unique is its Z-TONE control with variable impedance from 1 MΩ (SHARP) down to 2.2 kΩ (BOLD) available. It also features a separate dedicated re-amp output allowing artists to properly drive their amp input.

Below are some audio examples with passive guitar and passive bass, all recorded in PASSIVE mode. All use single coil bridge pickups using a 3 metre lead. The PURE examples were recorded with the Z-TONE control at its centre position. All sounds are straight off the pickups with no other processing on the audio.

IK Multimedia AXE I/O ONE Features

Software

AmpliTube 5 SE includes 80 pieces of gear that cover a range of stomp and rack effects, amps, cabs, speakers, mics and rooms with chains built using drag and drop. TONEX SE uses AI Machine Modelling offers thousands of rigs and the modelling of existing ones including amps, cabs or pedals. These can be played inside TONEX and AmpliTube. Ableton Live Lite is also included.

Hardware

• 1-in/3-out USB audio interface.

• Z-TONE impedance-adapting input enhances pickups’ true sound.

• PURE and JFET input stages for modern or vintage tones.

• ACTIVE/PASSIVE pickup selector.

• Class-A mic preamp.

• High-definition 24-bit/192 kHz audio conversion.

• Amp Out with ground loop interrupter.

• MIDI Input and Output to connect keyboards, E-drum kits, controllers and more.

• 2 programmable inputs for expression pedals and/or single/double switches.

• Includes AmpliTube 5 SE, TONEX SE and Ableton Live Lite.

Better Than A DI?

Although the received wisdom of using a DI box for going direct will always work, some DI boxes will turn in better results than others by design. Traditional passive transformer DIs may present a load to Hi-Z instruments that is too low to avoid the effects mentioned above. Often, it’s active boxes that will work best in concert with passive guitar output stages thanks to their generally higher input impedances.

AXE I/O ONE recognises a need for solo creator studios to have one box that can take a mic or instrument input that doesn’t affect the way direct sources will sound. Its variable impedance Z-TONE circuit does make an audible difference to recorded pickup sounds. This is more stark than some of the subtleties available from some variable mic pres I’ve tried, although the rather oddly-named SHARP and BOLD labels would be better labelled as BRIGHT and DARK.

In the amp modelling software, I think the ‘Buy Me Now’ bursts of white noise that happen across unbundled models are a bit of a shame, where a 30 day trial might persuade more people to commit. That aside, the AXE I/O ONE’s driver is pretty spritely, making the sounds that you do have enjoyably responsive with minimal latency.

Back to the hardware. While Hi-Z inputs are almost a standard feature on many desktop interfaces, it’s hard to think of any other box in any price bracket that has so many options to massage guitar sounds on the way in as well as in the box. Knowing how discerning many guitarists are about their instruments, a tool like AXE I/O ONE could be one to check out for anyone who wants their front end to leave their instrument’s sound as nature intended.

Pricing & Availability

AXE IO ONE price point for the full package is €/$129.99 ex VAT (129.99 GBP inc VAT). You can learn more at IK Multimedia’s website.

A Word About This Article

As the Experts team considered how we could better help the community we thought that some of you are time poor and don’t have the time to read a long article or a watch a long video. In 2023 we are going to be trying out articles that have the fast takeaway right at the start and then an opportunity to go deeper if you wish. Let us know if you like this idea in the comments.