i73 Pro One: $649
i73 Pro 2: $999
i73 Pro Edge: $1499
heritageaudio.com

The uncompromising Class A design and super-sweet tonal characteristics of the Neve 1073 preamp have seen it modelled and recreated by many-a plugin developer and circuit designer, all keen to capture something of the sound and kudos of this legendary nugget of recording history.

Heritage Audio has built an extensive assortment of outboard hardware around just such an homage to Neve’s masterpiece, namely its 73 preamp. The latest addition to this collection is the i73 Pro range of audio interfaces, but the console-grade Class A preamps are just the start of what makes them so intriguing.

What features do the Heritage i73 Pro audio interfaces have?

The i73 Pro range covers three variants, starting with the i73 Pro One. This offers a single i73-equipped mic/line/instrument input and a second, transformerless auxiliary line input, along with a pair of main monitor outputs and a headphone output.

The i73 Pro 2 – the unit we have in front of us – replaces the One’s auxiliary input with a second i73-equipped mic/line channel, and has a larger enclosure to accommodate this.

Finally, the top-of-the-line i73 Pro Edge adds an instrument input to the second i73 channel, as well as an additional pair of transformerless line inputs, a pair of auxiliary line outputs, a second headphone output, and ADAT in/out supporting up to eight additional digital inputs and outputs (dependent on sample rate).

All mic/line inputs are of the XLR/jack combo variety and are rear-mounted, as are the line output jacks. The Hi-Z instrument inputs, which feed into the i73 preamp via their own integrated JFET circuit, and headphone outputs are front-mounted for maximum convenience.

Power is supplied by an external 12-volt DC transformer, and all models provide MIDI in and out via a mini-DIN breakout cable (included). Host connection is via a USB-C socket, with both USB-C to USB-C and USB-C to USB-A cables bundled in. What’s good here is that all of these potential sources of interference are positioned as far away from the analogue signal path and i73 preamps as the enclosure allows.

How does the i73 Pro look and sound?

The look of the i73 Pro is highly reminiscent of vintage 70s gear, with chunky metal casings trimmed with faux wooden end pieces, a classic blue-grey paint job, and knob caps that closely resemble those used on the original 1073. Even the preamp transformers are on display, their green tops protruding slightly from the casing, partially for improved heat-sinking, but mostly because Heritage Audio likes how this looks. So authentic is this retro styling that it seems strange it isn’t accompanied by the combined aroma of Bakelite and dust cooking on hot circuit boards!

Sticking with authenticity, the i73’s input gain is controlled via a Marconi/Elma-style rotary switch that delivers precise gain adjustments in 5 dB steps, with the preamp’s output level controlled separately by an attenuator pot. This arrangement allows for detailed gain staging and, with input gain cranked up and output level reduced accordingly, faithfully delivers the characteristic colouration and warm, sparkling saturation for which the 1073 is famous.

Our only complaint here is that with some line sources, the maximum 20 dB of line input gain can be too little to really get the preamp cooking. Using a high-impedance instrument input or connecting lines to the mic inputs via a DI box can get around this, though.

What is i73 Pro’s bundled software like?

The software package that comes with i73 Pro consists of a bundle of six Heritage Audio plugins, along with the i73 Mixer app that manages monitor mixes and provides access to settings not available via hardware controls.

The plugins come in native VST, AU and AAX formats for use in a DAW, but four are also provided as onboard DSP processors, with each i73-equipped input channel providing four slots for latency-free hosting of these processors.

BritStrip, based on Heritage Audio’s hardware of the same name, extends the vintage console ethos of i73 Pro with ’73-style EQ and a diode bridge compressor based on Heritage Audio’s Successor bus compressor. If you want your front-end to inject more classic analogue character you can load the HA1200 Tape Saturator plugin, modelled on the Ampex 1200 multitrack tape machine.

Guitar and bass players are well catered for too, with the awkwardly-named Small Recording Amp Serial# C17744 providing a classic Fender Tweed Champ guitar combo, and HA15 Pro delivering an authentic model of a vintage valve-driven Ampeg B-15 bass rig.

A nice feature of the DSP implementation is that the i73-equipped inputs are presented to the host DAW as both dry and processed buses. Recording these simultaneously means you can set up what you think will be a polished sound during tracking whilst leaving your options open in case you change your mind later on.

As well as allowing the DSP plugins to be loaded and configured, and managing monitor/cue mixes (each stereo output pair has its own independent mix), the i73 Mixer also provides two auxiliary sends on each input channel. These feed to a pair of auxiliary mixer channels that feature a slot for hosting a single plugin running natively on the computer instead of within the onboard DSP. Aux channels can’t be recorded, but they are just the ticket for adding reverb, delay and other effects in a headphone mix. Simply select something from your existing plugin collection and you’re away.

Should you buy a Heritage Audio i73 Pro audio interface?

We did find a few quirks during testing, although nothing drastic that can’t be worked around. For example, the interface can be fussy about connecting via certain USB hubs; a problem if your computer has a limited number of USB ports. Also, when the hardware sample rate is changed, such as when creating a new project in your DAW, the i73 Mixer has to be restarted in order to re-sync with the hardware, which feels clumsy.

These issues aside, working with the i73 Pro is enormously satisfying. The DSP plugins are well chosen to give your rig a flexible front-end, and we love how the preamp gain staging delivers genuine, authentic transformer overdrive. This provides a richness, warmth and sparkle that’s as hard to beat as it is to describe. The whole thing is just… well… classy!

Key features

All:

• USB-C host connection
• Up-to 192 kHz sample rate at up-to 32-bits per sample
• MIDI in/out

Plugins:

• BritStrip 1073-style EQ and diode bridge compression based on Heritage Audio Successor.
• HA1200 Tape Saturator based on Ampex 1200
• HA15 Pro based on Ampeg BA-15
• TAPEoPLEX tape delay modelled on Echoplex EP-4
• Small Recording Amp Serial # C17744 modelled on Fender Tweed Champ guitar amp
• HA240 Gold Foil Verb modelled on EMT-240 Gold Plate reverb

i73 Pro One:

• 1 mic/line/instrument input driving i73 Class A preamp
• 1 auxiliary line input
• Stereo monitor output
• 1 headphone output

i73 Pro 2:

• 1 mic/line/instrument input driving i73 Class A preamp
• 1 mic/line input driving i73 Class A preamp
• Stereo monitor output
• 1 headphone output

i73 Pro EDGE:

• 2 mic/line/Hi-Z inputs driving i73 Class A preamps
• 2 auxiliary line inputs
• Stereo monitor output
• 2 auxiliary line outputs
• 2 headphone outputs
• ADAT in/out

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