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Uncrating and carrying the amplifier to the upstairs listening room saved us an iron-pumping session at the gym. Getting the two 31cm tall and 9.15cm wide T-1610 upstairs was much easier. After unboxing the tubes, installing them was simple. The four nearly pencil-thick and 2.5cm long pins protruding from the equally massive copper base fit nicely and offered enough grip to insure safe placement, a comforting thought when dealing with €1000/ea. tubes.

The SX-Eco uses the same chassis as all other KR Audio amplifier types. Like the rest of the Kronzilla family, the SX-Eco thus uses its chassis turned narrow side to the front, with the cooling fins along the deep cheeks. Beneath the towering power tubes is a standby switch and matching LED indicator. At the back things are just as basic. From left to right there are the mains rocker switch, the IEC inlet, a tiny ‘eco’ switch, the loudspeaker terminals with a little door in their middle and finally a pair of RCA inputs. On top there are the two T-1610 triodes with two finned enclosures for the output transformers and a single large enclosure for the power transformer. All is very basic and simple, an impression enhanced by the matte black finish.

Inside things get a bit more exciting as it is there the solid-state driver department sits. The Kronzilla is a hybrid design using Fets to deliver current and triodes for the accompanying voltage in a dual mono setup. In fact there are more dualities aside from the left-right and Fet-triode combos. One is that the T-1610 tube itself consists of two parallel triodes stacked one atop the other packed in one huge glass envelope. In fact the T-1610 is a twin 805 triode, hence the 1610 nomenclature. The final duality is the special eco addition controlled by that tiny switch at the back. With it the amplifier can be set to Fet-triode hybrid mode or fet-à-fet full transistor mode. In this mode the tubes which usually run pretty toasty are taken out of the circuit completely and stay on ice at room temperature. All signal handling is done by the solid-state circuitry. Switching from one mode to the other must be done fully powered down of course.

The user thus decides whether to harness the full potential of a DHT SET in class A mode or run the more genteel aka cooler thermal behavior of full transistor mode that won't turn the Kronzilla into an unnecessary space heater. Unnecessary because this lower energy consumption mode was designed for casual listening to the likes of (internet) radio. That at least was the idea Cor Dekker ventilated to KR Audio’s designer Marek Gencev which has since materialized in the SX-Eco.

With the Kronzilla sitting on a sturdy wheeled platform it was easy to vary sources and available loudspeakers. In our listening room three setups are followed by Avantgarde Duo Omega, Arcadian Audio Pnoe and Vaessen Aquarius speakers. Sources are PS Audio PWT/PWD, a Feickert/Zu turntable and the Devialet D-Premier in its role as phono stage, preamp and streamer. It was a mere matter of rolling the amplifier towards one of these setups and making all necessary connections.

Before connecting the amplifier we made sure the impedance setting located behind the little door between the terminals as a pair of screws was set to 8Ω, the highest available. For starters the SX-Eco was mated to the Avantgarde and PS Audio setup. When the amp was switched on there was a very prominent and fairly loud hum filling the room. We double-checked connections, cable routing, reconnected interconnects. Nothing worked out. The 50Hz hum proved persistent. Luckily Cor Dekker had the solution. Power the Kronzilla from another electrical group. Once that suggestion was followed we had a soothing lack of hum. On top of that even at close range the SX-Eco in SET mode was dead quiet. In Fet mode a slight hiss was noticeable nearby but not at formal listening distance. This was a very good result since a 107dB speaker is a merciless noise sniffer than can waylay more than one good amp..