ARP

This review first appeared in Jule 2025 on HifiKnights.com. By request of the manufacturer and permission of the author, it is hereby syndicated to reach a broader audience. All images contained in this piece are the property of HifiKnights – Ed.

Reviewer: Dawid Grzyb
Transport: Innuos Statement, fidata HFAS1-S10U
DAC: LampizatOr Horizon360 w. Stradi 5U4G + Psvane Art TIII 4x KT88 / 2x 6SN7
USB components: iFi audio Mercury3.0
Network: Fidelizer EtherStream, Linksys WRT160N
Preamplifier: Trilogy 915R, Thöress DFP
Amplifier: Trilogy 995R, FirstWatt F7, Enleum AMP-23R
Speakers: Boenicke Audio W11 SE+, sound|kaos Vox 3afw
Headphones: HifiMan Susvara
Interconnects: LessLoss Entropic Process C-MARC, Boenicke Audio IC3 CG
Speaker cables: Boenicke Audio S3, LessLoss C-MARC
Speaker signal conditioning: LessLoss Firewall for Loudspeakers, Boenicke ComDev
Anti-vibration conditioning: 12x Carbide Audio Carbide Base under DAC, preamp and speakers
Power delivery: Gigawatt PC-3 SE EVO+/LC-3 EVO, LessLoss C-MARC, LessLoss Entropic Process C-MARC, Boenicke Audio Power Gate, ISOL-8 Prometheus
Equipment rack: Franc Audio Accessories Wood Block Rack 1+3
Review component retail: €2'500 for single-ended copper, €3'500 for balanced copper, €4'500 for single-ended silver, €6'900 for balanced silver

Most of the preamplifier breed is active. It's designed around volume controls based on discrete or IC-embedded resistor ladders. At the very narrow end of this sector we find a few passive specimens with no voltage gain. Amongst them, even fewer are TVC or AVC aka transformer or autoformer volume controls. Pure wire without gain? Let's find out. Prior to launching HifiKnights in early 2016, I had a firm idea on how to grow the site into a sustainable day job reasonably quick. My plan involved hitting up all our local manufacturers, introduce myself and offer them bilingual exposure in Polish/English. Back then our domestic scene already had around 75 brands so a lot of ground to cover. It worked. Marek and I are still here. More importantly, over the years I worked with LampizatOr, Cube Audio, Gigawatt, Stacore, Egg-Shell, Soyaton, JCAT, Audio Phonique, Gemstone and many more. While I enjoyed their products and the people who make them, Khozmo proved to be a particularly elusive audio house which had been on my radar ever since I can recall. In mid 2020 Srajan asked whether I'd heard about Hattor Audio by the same owner. The name rang a bell so I reached out. While Arek Kallas expressed interest, his hands at the time were full so we didn't proceed past first courtesies. Fast forward to early 2025. Arek asked whether I'd be interested to have a go at his latest—and as I was about to learn, very special—design. Absolutely. We recently met in Warsaw, he left me his goods and today's game was afoot.

That had me super excited and we'll shortly get to why. Let's first look at Arek's first company Khozmo established some 15 years back. While its portfolio features a power amp and quite a few passive preamps including rare TVC types, its bread and butter are various resistive attenuator modules built around AMRG, AMRT, PRP, Vishay or Z-Foil resistors in mono, stereo or quad so fully balanced versions. 64-step shunt/ladder attenuation systems with displays, remote control, source selection and active opamp stages follow. This clearly winks at DIYers who enjoy minting their own stuff with no-compromise boutique volume controls. Most importantly it's a busy source of OEM whereby many top-name brands rely on Khozmo components. As their supplier, Arek is obliged to play coy about their identities. Don't ask don't tell. Suffice it to say, the list of high-calibre brands doing business with him is anything but short. No wonder. The man's been around. His volume-control solutions have a reputation for being gorgeously made, extremely reliable and brilliant, all valid enablers to carve out a specialty career for himself.

It's not uncommon however for an OEM supplier to incorporate their own tech into a house brand. Enter Hattor Audio based on existing Khozmo goodies and then some. Hattor have been around for about a decade and their current line-up consists of six models: a standalone tubed buffer/gain preamp, the NT500 integrated amp, the MINI/Ultimate stereo/mono amps and the MINI/BIG preamps in passive or active guise. Adorable compactness, priced to sell and handsome heavily customizable exteriors are common to all. During our chat Arek explained that he really loves products that sound good and offer great value. He meant it. His most affordable passive MINI preamp packed with posh 64-step Vishay-based attenuator, remote wand, custom-made heat sinks and 3:2 i/o wants just €900. Silver/black options selectable for the chassis, knobs and fascia base and insert, the latter even in wood, come with. Should you find that sticker suspiciously low, fret not. The fully loaded MINI rocks top-shelf Amtrans AMRG resistors and an active stage with Staccato opamps for €2'400.

Although Hattor's BIG is the current dual-mono flagship preamp, it too starts out at €900. For that we get RCA i/o, remote control, a Vishay ladder, an external linear PSU and passive operation. Available colour variants remain as specified above. The front baffle can even feature a carbon-fibre or leather inlay at no extra cost. AMRT, AMRG or Z-Foil resistors add €500, €600 and €1'000 respectively. XLR i/o add €100, €400, €500 and €600 with Vishay, AMRT, AMRG or Z-Foil resistors. Should we go active, OPA2134/Staccato opamps eat up another €450 or €600. Fully loaded, the BIG with the best resistive attenuator retails for €3'200. Whilst that's serious Hattor coin, the new magnetic autoformer option sets the financial ceiling and is the key plot twist today. Welcome the Autoformer Reference Preamplifier aka ARP. It looks like the BIG so packs all of its finish options. With RCA or XLR i/o and copper-wound autoformers, it sells for €2'500 and 3'500. Silver windings raise the sum to €4'500 and 6'900. Active opamps aren't available. My sample had copper AVC because silver wasn't ready. No matter. These rarely used parts promise an awful lot either way. They were the very reason why I was so excited.