iFi Pro iCAN Signature

Headphone amps are found in many devices, so what can a standalone one offer those with cash to splash?

UK‑based iFi currently offer around 50 products aimed at the hi‑fi market, but some may appeal to the professional audience too. I was recently sent their flagship Pro iCAN Signature headphone amp/preamp to review, and this latest model is a high‑power, high‑quality, balanced‑headphone amp that doubles up as a preamp and simple monitor controller. Compared with their original iCAN, it features audiophile‑grade components throughout, an upgraded power supply, selected valves, an infrared remote control and a Pentaconn 4.4mm balanced headphone socket (more on that below). iFi have clearly put a lot of effort into the design, and the asking price reflects that!

Overview

The Pro iCAN Signature looks roughly half‑rack width but it’s taller than 1U, measuring 213 x 193 x 63mm and weighing 1.9kg. The substantial top panel features arced cooling slots and a glass bubble view port revealing the valves. Instead of conventional feet, a thick “quad‑damped isolation base mount” is glued to the base with two elastomer layers (silicone and ethylene/vinyl acetate) for damping and vibration isolation, and two metal layers (aluminium and a ferrous alloy) for electromagnetic screening.

Rear‑panel connectivity comprises four selectable stereo inputs: three unbalanced on RCA phono sockets, and the fourth balanced on female XLRs. Both balanced and unbalanced preamp outputs are provided on male XLRs and RCA phonos. Power comes from an external high‑quality line‑lump SMPS unit generating 15V DC at 4A, and accepting any mains voltage from 100‑240 V AC via a standard C14 IEC inlet. A captive output lead delivers the DC power through a standard (non‑locking) coaxial plug. Unusually, alongside the coaxial power input socket there’s a second loop‑through power output, intended to supply optional accessories such as iFi’s electrostatic headphone energising module. Something akin to an HDMI socket just below passes audio to that module, too.

The preamp has an array of selectable inputs and outputs on its rear.

On the front panel, a trio of XLR sockets for headphone connections is flanked symmetrically by four silver knobs. The larger outer pair select the input source (left) and listening volume (right), while the smaller inner knobs configure bass compensation EQ (XBass) and a stereo‑width enhancement facility (3D), which I’ll return to shortly. Two miniature toggle switches select the signal path mode and adjust the overall gain, and there are two more headphone socket options alongside. The on/off power‑standby button is cunningly concealed in the bottom left‑hand corner (the iFi logo top‑left lights when active), and the infrared remote control receiver window occupies the opposite corner.

Internally, the iCAN employs discrete surface‑mount analogue circuitry, configured with a fully differential (ie. balanced) signal path throughout. Consequently, the high‑quality ALPS volume control is a six‑ganged affair, with four tracks used for the balanced left/right audio signal paths, and the remaining two for control‑system positional information (the knob is motorised and can be moved using the remote control).

You’ll have spotted my mention of valves earlier: the pair of selected and matched military‑spec GE5670 dual‑triode valves can be selected for the front‑end of the signal path as an alternative to a solid‑state J‑FET topology. The second stage of preamp circuitry (which handles the EQ and 3D processing) uses bipolar transistors, while a MOSFET Class‑A output stage powers the headphone outlets. Apparently, this amplifier is biased to operate mostly as Class‑A, but slides into Class‑AB for low impedance phones at very high levels. All three amplifier stages are DC‑coupled, avoiding coupling capacitors in the signal path.

Modern equipment rarely uses fully differential signal paths, not least because it’s an expensive approach needing twice as much audio circuitry and careful gain matching throughout. But it offers several potential technical advantages, including lower distortion, reduced crosstalk, greater headroom, and higher output power. On that last point the Pro iCAN’s specifications state it delivers a maximum output voltage (in balanced mode) of over 20V RMS (around +28dBu), with a maximum peak current of 1.4A. That equates to an astonishing 14W of peak output power into 16Ω (balanced) headphones! Perhaps not surprisingly, then, the unit’s idling power consumption is toasty by modern energy‑saving standards, at 22W, pulling up to 50W when running flat out.

Headphone Connectivity

By my reckoning, the Pro iCAN has seven headphone connectors. Four are intended for connecting ‘balanced’ headphones in various ways, but they’re all a bit unusual in one way or another. Starting with the smallest, conventional headphones or in‑ears with a TRS mini‑jack can be plugged into a 3.5mm socket below the small XBass knob. This is marked SE for ‘single‑ended’, meaning a single amp per channel, rather than ‘balanced’. This output also features the company’s ‘S‑balanced’ and ‘iEMatch’ technologies. The latter is essentially a fixed attenuator in the signal path, since IEMs are usually pretty sensitive and iFi don’t want to melt the user’s ears with excessive power!

‘S‑balanced’ is a contraction of ‘single‑ended compatible balanced’, and essentially it’s a TRRS socket with the rearmost ring and sleeve both wired to ground — so that it works correctly with both standard three‑wire TRS and four‑wire PRO3.5 plugs. iFi claim this also reduces...