Icon Pro Audio/Harrison 32Ci

Boring preamps have long been a given in audio interfaces, but all that is about to change...

Audio interfaces have had mic preamps built into them for almost as long as there have been audio interfaces. But for many years, it seemed as though manufacturers had signed a secret pact to make their preamps as boring as possible. Interface designers were slow to wake up to the fact that not every user wanted a completely transparent, neutral input stage, and that in fact many people were spending really rather a lot of money to augment their transparent, neutral input stages with third‑party mic preamps that offered a bit of character.

In the last few years, we’ve seen a sprinkling of interfaces with transformer‑balanced preamps that can add a little mojo to proceedings, including Steinberg’s UR‑RT models, Neve’s 88M and the forthcoming Heritage Audio i73 Pro. It’s still a surprisingly sparsely populated market sector, though, so the emergence of a new contender is very pleasing.

That contender is a collaboration between a relatively young company, Icon Pro Audio, and veteran console designers Harrison. In some ways, it’s a fairly conventional USB audio interface, but in place of the usual boring mic preamps, it employs the input stage from Harrison’s 32‑series consoles. So, as well as heritage preamps, it has an unusually extensive filter implementation featuring high‑ and low‑pass filters that can be swept right through the midrange. And, as we’ll see, it also has a few other unusual qualities.

Short Back & Sides

The 32Ci is a desktop device with a gently raked, squarish case measuring nearly nine inches by 10. The controls are housed on the top, the two headphone sockets are at the front, and all the other I/O is located on the slightly deeper rear panel. Build quality and industrial design are impressive, and there’s a real sense of class to the 32Ci that belies its competitive pricing.

One reason why boring preamps are the norm in audio interfaces concerns power requirements. As well as offering good specifications, modern off‑the‑shelf, chip‑based designs are very efficient, which is an especially important consideration in bus‑powered devices. If Icon Pro Audio had taken that route with the 32Ci, I’m sure they’d have been able to make it powered over USB, but the inclusion of the Harrison preamps necessitates an external PSU. The unit also gets noticeably warm in use, though thankfully there are no fans to kick in and ruin your best takes.

The 32Ci measures 291 x 243 x 92mm and weighs 1.83kg.

All of the 32Ci’s controls seem to use conventional pots, and there is nary an endless encoder to be seen. The master volume control is flanked by 12 LEDs which act as a pair of six‑segment meters. The two interesting preamps are fed from combi XLR/jack sockets, and can be switched into a high‑impedance mode to accommodate signals from electric guitars and basses. There’s an additional pair of inputs on quarter‑inch jacks; depending on the setting of a rear‑panel button, these can operate as balanced line‑level inputs accepting levels up to +24dBu, or as unbalanced ‘consumer’ inputs optimised for the ‑10dBV standard. On the output side, there are two pairs of quarter‑inch jacks in addition to the aforementioned headphone outputs. These are configured in a slightly unusual arrangement, which I’ll return to in a moment.

There’s also digital I/O, comprising a single ADAT optical in and out, MIDI in and out, and two USB Type‑C sockets. One of these is used to connect the 32Ci to the host computer, while the other is labelled OTG and is intended for streaming audio from the 32Ci to a phone or tablet. If you use an Apple device, you’ll need the official Camera Connection Kit or similar rather than a generic USB cable.

Buffering The Hits

Basic audio interfaces often handle cue mixing and low‑latency monitoring using only hardware controls. As the I/O count mounts up, though, this gets impractical, and so more complex interfaces have digital mixing and routing facilities, configured using a software control panel. The 32Ci is the only interface I’ve come across that falls into both camps at once.

How so? Well, inasmuch as there is mixing and routing functionality built into the 32Ci, it’s all‑analogue and controlled from hardware. However, you can also install a macOS and Windows program called IO Pro. This looks similar to the mixer utilities supplied with many other interfaces, but instead of adjusting settings on DSP in the interface, it runs entirely natively. It’s perhaps best thought of as a host‑based alternative to your DAW’s own mixer window that runs in parallel with your DAW.

The main Core Audio or ASIO driver presents a total of 14 physical I/O paths to and from your DAW at base sample rates (four analogue plus stereo OTG and eight ADAT), while a second ‘loopback’ driver presents four stereo virtual I/O paths, if selected. The 32Ci itself is blissfully unaware of the virtual I/O, but both sets appear in the IO Pro mixer. On macOS, therefore, the IO Pro mixer has a total of 12 mono and five stereo input channels; things get more complex on Windows, thanks to the need to integrate ASIO and WDM paths. There’s also a stereo master output and four stereo aux busses, each of which can be returned either to the master output or direct to a physical or virtual output path. Pressing the button labelled Mon adds what is in effect a second master channel that can be routed to a different physical output. This monitor channel has an undocumented pop‑up labelled Direct, which presents a 4x4 matrix with sliders, and appears to do nothing whatsoever in my system. Perhaps it has a function in the Windows version.

Clocking arrangements concerning the 32Ci and IO Pro are opaque. On macOS, Audio MIDI Setup allows you to select a clock source, but this only seems to relate to its relationship with the loopback driver and other Core Audio devices, and ADAT does not appear as an option. My tests suggested that if the 32Ci receives a valid ADAT signal at the sample rate your DAW is using, it’ll automatically clock to that and make the ADAT inputs available to record. If no ADAT source is connected, or there’s a sample rate mismatch, the 32Ci reverts to its internal clock and mutes the ADAT inputs. However, there is no visual indication at all to tell you what clock source is currently being used, and nor is there any useful information in the manual on the topic.

IO Pro is not a ‘control panel’ but a fully native software mixer.

Generous Host

Because IO Pro runs natively, it’s able to act as a plug‑in host. The input channels, auxes and master bus all have insert slots where plug‑ins can be inserted in VST2, VST3 or Audio Units formats. It also has its own buffer size setting, which is independent of the buffer size set by the DAW; so you could, for example, run IO Pro at a low buffer size and restrict yourself to using plug‑ins that don’t use lookahead, whilst your DAW operates at a higher buffer size and with no such restrictions.

Because IO Pro runs natively, it’s able to act as a plug‑in host.

The IO Pro installer also installs several plug‑ins designed specifically for working in this environment. These include a simple reverb called iVerb, a grid‑based one‑shot sample player called Stingers (which I couldn’t get to work) and, most surprisingly, a full‑blown modular signal processing and routing environment called Patch. This is itself a plug‑in host and chainer, and allows you to set up labyrinthine audio and MIDI routing paths.

All in all, though, IO Pro is a bit of an odd duck. It allows you to do some quite complex stuff that could be very handy for particular use cases, such as live streaming or podcasting. Yet, at the same time, it’s frustratingly lacking in basic features. For example, it doesn’t seem to be possible to link two analogue or ADAT channels together to make a stereo channel, and I couldn’t find any simple way to reset pan controls to their default positions. DAW playback bypasses IO Pro altogether, as a consequence of which there is no monitor control on offer there. There’s no solo/PFL architecture, and each channel has only a single pre‑/post‑fader button, which applies to all four aux sends on that channel. If you have a pointing device that supports sideways scrolling, such as the Apple Magic Mouse, you might expect this to scroll sideways across the mixer channels, but instead it does exactly the same as vertical scrolling, namely moving the nearest fader up and down.

Yes, There Are Two Paths You Can Monitor By

Assuming you’re not streaming live or casting pods, though, you always have the option simply to ignore IO Pro. Mac users don’t even need to install it, in fact, as the 32Ci is class compliant. The routing and monitoring facilities baked into the 32Ci hardware will be available regardless. There are two built‑in monitoring paths, one feeding the main outputs and the first pair of headphones, and the other feeding the second headphone output. Each of these paths has a potentiometer that allows you to set a balance between DAW playback and input signals from the mic preamps and line inputs. There’s no way to adjust the relative levels of the different inputs in the low‑latency monitor feed, and the 32Ci doesn’t offer any options as to where they’re panned: the two preamps are always heard centrally in mono, whilst the line ins are hard‑panned.

Beginning at the left of the rear panel we find a USB‑C port for computer connection and a second USB‑C port labelled OTG for interfacing with a phone or tablet. Moving on, there are ADAT I/O ports, full size MIDI I/O sockets, quarter‑inch main and ‘Alt’ outputs, quarter‑inch line inputs and a pair of combi inputs. A pair of headphone ports is found at the front of the unit.

Both pairs of rear‑panel analogue outputs are tied to the first of the two monitor paths. The first pair is intended for connection to speakers or other devices that expect a ‘professional’ signal level, and can deliver up to +24dBu for a 0dBFS signal. The second pair shares the same master volume control and carries the same audio signal, but at a less hot level intended for consumer devices, and are designated ‘alternate’ outputs. Under normal circumstances, the main outputs are active and the alternate outs muted; pressing the Alternate button reverses this situation.

This is an arrangement that might suit you perfectly, if for example you want to augment a pair of conventional studio monitors with a consumer grotbox for A/B mix checking, but equally it could easily become restrictive. There’s no way to alter the fixed level offset between Main and Alt outputs, nor any way to address the latter independently from your DAW.

Character References

As I’ve already mentioned, one of the reasons why manufacturers often use boring off‑the‑shelf chip‑based preamps in their interfaces is that their specifications are usually better than those of older console preamp designs. If what you’re after is a more interesting and colourful sound, it’s likely to be precisely the extra distortion and non‑linearity in the older design that is responsible for its character.

Perhaps excusably, then, Icon and Harrison have listed specifications for the preamp and for the A‑D conversion independently, even though there’s no way to use the one without the other. The converter specs are beyond reproach, with a dynamic range of 125dB available on the input side and a humongous 129dB on the output side. The preamp specs are less satisfying, partly because there are no measurements given for equivalent input noise or distortion, and partly because they’re copied from the 32Classic console, with references to a non‑existent fader being at unity.

The non‑existence of this fader is germane to the question of character. Many standalone rackmounting or 500‑series preamps offer an output attenuator, allowing the input gain to be driven harder without overloading downstream devices. Others offer insert points, where a compressor or other processor can be patched in to offer control over the level of the preamplified signal. The 32Ci has neither, so there’s no way to manipulate the amount of ‘hair’ the preamp is adding to your signal independently of the level feeding the A‑D converter. And as it happens, it’s not obvious what part of the circuit might contribute desirable distortion anyway.

Transformers?

Inasmuch as mic preamps add character, it is usually because they are based around components such as transformers or valves that can behave in a non‑linear fashion. Back in the ’70s, Harrison consoles went through at least three major design revisions. As far as I can discover, the first two iterations used a Jensen input transformer designated the JT‑115K‑E. Thanks to its 10:1 turns ratio, this provided 20dB of voltage gain and thus formed a key part of the preamp circuit. Then, in the third and most desirable iteration of the console, Harrison redesigned the input stage to be capable of transformerless operation: a 1:1 transformer could optionally be fitted in front of this, but wasn’t necessary and didn’t carry out any actual amplification.

Now part of the Audiotonix group, Harrison recently introduced an updated 32‑series console called the 32Classic, and have since announced a 500‑series reissue of the 32C preamp. As these use a Jensen JT‑MB‑CPCA transformer with a 1:1 turns ratio, they are presumably based on the third revision of the circuit.

At launch, Icon Pro Audio’s website stated that the 32Ci’s preamps were likewise “equipped with high‑quality transformers”, but there obviously isn’t space for them within its compact shell, and Icon confirmed to me that this was an error. So, presumably, they too have used the last revision of the preamp circuit, but without the optional transformer. Consequently, it’s not coloured in the sense of offering saturation or other non‑linear behaviour, but it’s certainly a high‑quality preamp, with plenty of gain, low noise and a decent amount of headroom. The gain pot has a 50dB range, which is extended further by a ‑20dB pad button, allowing signal levels up to 18dBu to be accommodated.

Moreover, the lack of obvious saturation doesn’t mean that the 32Ci’s input stage has no character — just that this character resides elsewhere. Specifically, it is imparted by the unusual filter implementation. The high‑pass filter can be swept from 25Hz all the way up to 3.15kHz, and there’s also the much less common option of a low‑pass filter, which can turn over anywhere between 20kHz and 160Hz. These provide plenty of tone‑shaping options on their own, but the icing on the cake is a button labelled Bump. This introduces what was apparently a common modification to Harrison consoles back in the day: a small resonant peak at the corner frequency of the high‑pass filter. This doesn’t transform it into a screaming Moog ladder filter, but it’s brilliant for those situations where you want to convey the impression of a rich, full low end without cluttering the mix up with unwanted sub frequencies. For example, I often find that DI’ed bass guitar can sound a bit too heavy below 100Hz or so; engaging Bump can trim that excess weight whilst adding more substance in the frequency range an octave up that’s audible on small speakers.

Summing Up

The 32Ci is an unusual product, and not only because it bucks the trend for interfaces to have boring preamps. Even after using it for several weeks, I’m not entirely sure what to make of it.

Let’s start by getting the negatives out of the way. The way Icon have augmented hardware direct monitoring with the separate IO Pro utility is distinctive, but the former is rather basic, and the latter feels undercooked at present. The two don’t work together in any way, and unless you need the loopback functions, there is little to be gained by monitoring through IO Pro rather than your DAW’s own mixer. Elsewhere, hardware features that would potentially be useful in a studio context, such as speaker switching, are undermined by inflexible or restrictive implementation.

When you’re getting two channels of Harrison preamplification and filtering for much less than a single 500‑series Harrison preamp, it’s hard to dispute that the 32Ci offers plenty of value for money.

But the positives shouldn’t be overlooked. Transformers or no transformers, the 32Ci sounds great, albeit without adding any noticeable warmth or substance to input signals. The filters are more rewarding and creative to work with than mere filters have any right to be, there’s ADAT I/O if you need to record more sources, and Icon Pro Audio have really thought about use cases other than music recording, with the OTG socket and some highly advanced software routing features available in case you need to patch in audio from multiple applications and send it over the Internet. And when you’re getting two channels of Harrison preamplification and filtering for much less than a single 500‑series Harrison preamp, it’s hard to dispute that the 32Ci offers plenty of value for money.

Information

£429 including VAT.

www.soundservice-msl.co.uk

www.iconproaudio.com

$499

www.iconproaudio.com

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