July
2020

Country of Origin

UK

icOn4 Pro

Reviewer: Srajan Ebaen
Financial interests: click here
Sources: Retina 5K 27" iMac (4GHz quad-core with Turbo boost, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 14.4), PureMusic 3.02, Audirvana 3, Qobuz Hifi, Tidal Hifi, COS Engineering D1, Denafrips Terminator, Soundaware D300Ref,  AURALiC Vega, Jay's Audio CDT 2 MkII & DAC-2 SE
Preamplifier: Vinnie Rossi L2 Signature with WE 300B/VT52 or Elrog ER300B/50; Nagra Classic, Wyred4Sound STP-SE Stage II, Vinnie Rossi LIO (AVT module); April Music Stello HP100 MkII
Power & integrated amplifiers: Pass Labs XA30.8; LinnenberG Audio Liszt monos; FirstWatt SIT1 monos, SIT-3, F5, F6, F7; Goldmund/Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics NC500 monos; April Music Stello S100 MkII;  Crayon Audio CFA-1.2; SAG AIO; Bakoon AMP-13R
Loudspeakers: Audio Physic Codex; Acelec Model One; Cube Audio Nenuphar; Kroma Audio Mimí; Albedo Audio Aptica; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V & VI & Submission; German Physiks HRS-120; Eversound Essence; Fram Midi 150 & 120
Cables: Complete loom of Allnic Audio ZL3000/5000 and Zu Event; KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Black Cat Cable redlevel Lupo; Ocellia OCC Silver
Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps/sub, Puritan Audio Labs PSM156 & PS106-DC
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands 
Sundry accessories: Acoustic System resonators
Room: 4 x 6m with high gabled beam ceiling opening into 4 x 8m kitchen and 5 x 8m living room, hence no wall behind the listening chairs
Review component retail: €1'599 to ~€3'000 depending on configuration

People don't just buy what they need. They buy what they want. Which needn't be the same. Case in point? Active preamps. Most modern digital sources will drive most modern amplifiers to full output. No extra gain is required, just signal cut/attenuation plus source selection. What do active preamps do in this context? Look at it this way. 2 + 8 – 9 = 1. Two is your source signal voltage. One is the signal strength needed to play at your desired loudness. Adding more gain symbolized by eight only to knock it down by nine is wasteful. A passive simplifies the math. 2 – 1 = 1. It's pure signal cut, no boost. At the very least it's more efficient so greener. It also should incur fewer losses from less signal manipulation and produce less noise and distortion.

Alps potentiometer | Khozmo switched resistor ladder | multi-tapped attenuation transformers into manual selector switch | integrated Slagleformer module with tidy ribbon wire as used by John Chapman

In this group fall simple potentiometers and more complex resistor ladders with inputs and outputs; light-dependent resistors aka LDR; multi-tapped transformers and autoformers. John Chapman's Tap-X under the Bent Audio brand was a TVC aka transformer volume control which I reviewed. Later its Stevens & Billington TX103 parts became unavailable. John subsequently adopted autoformers by David Slagle. Eventually those also became an option on Vinnie Rossi's Lio for which John contributed. I reviewed that too. Then John got too busy with OEM work so discontinued his own products. His Tap tapped out. X marks the spot.

Today there's the Bespoke Audio Company in the UK whose principals previously worked at Stevens & Billington on their magnetic passives. Now they wind their own attenuation transformers for bespoke passive linestages with mixed RCA/XLR i/o. AM Hi-End have a single-ended and fully balanced TVC. Audio Consulting in Switzerland have the SIlver Rock.  Back in the UK, Townshend have two RCA-based passives. And there's Pál Nagy who has resurrected the Bent Audio platform of Slagleformers with ±7.5dB balance control and pre-paired Apple remote.

His icOn4 can be ordered with 3:2 or 4:1 RCA i/o and offers 40 x 1.5dB steps actuated by ultra-fast Vishay Fet switches. There's also a display for volume, balance and input, MCU-driven firmware to add instant mute, AV bypass, night/sleep modes, even an Android control app. If you're a passifist, it creates one more harbor where to drop anchor and expand the hunt for Red October as your perfect passive pre.

AM Hi-End passive with RCA/XLR in dual-mono pure manual mode