On September 1st that bit hit the fan; and not because first units began shipping. It's because on that day, Enleum's new website went live and Red Dot added the amp to its annual list of award winners. "The Enleum HPA-23RM headphone amplifier is for desktop use and for use on the go for high-fidelity headphone listening. A clearly structured user interface facilitates intuitive operation. The precision-manufactured aluminum housing is based on square shapes that provide an attractive contrast with the undulating heat sinks on the sides. All screws are located on the underside to keep the appearance clean and minimalist. This headphone amplifier meets the needs of a discerning audiophile target group both acoustically and aesthetically. The high-precision workmanship is particularly convincing." The year prior, the AMP-23R had won. Before he emailed actual specs—and knowing him to be a diehard miniaturization freak—my eyes judged Soo In's design to size as three stacked CD jewel cases faced side-on in its rippled mid section. The five frontal cubes and rear apron with logo then enlarged that footprint but not by much. How off was my assessment without size reference? It'd be a hifi Flachmann [German for hip flask] even if the real thing added 20-30%. It certainly looked like a hi-tech gadget for a debonair secret agent of the Royal Philharmonic Forces. License to thrill?
Actual photo not render.
Fill with music. Uncork with ¼" plug. Pick low-Ω voltage or high-Ω current mode. Open ears. Imbibe. Be safe. Don't drive under the long-term influence of elevated SPL. It's not just ports and insufficiently hard metal tweeters which ring. Also, I shall never understand walkers or joggers with earbuds. Don't they mean to hear bicycles, cars and other potential hazards approach out of sight? About outa sight, how big of a parka pocket would one need to take this Enleum for a walk? Unlike exposed jobs, this volume wheel certainly looks accident-proofed against unintended pocket change.
On exposed jobs, watchful observers might place bets on whether Soo In's bonsai rig with Wattson's Madison will lead to a collab on his long-expected DAC. Madison is hi-tech, compact and seriously engineered, all things Mr. Chae treasures. Given how Wattson's Swiss parent company Engineered SA are in the OEM biz, envisioning an Enleum-badged Madison with current-mode outputs perhaps battery power doesn't seem too farfetched. But that's sheer speculation. Back on hard facts, here's what Soo In had for the HPA-23RM. In the firm's naming convention, it unpacks as HeadPhone Amp, product size 2, circuit generation 3, Reference class, Mobile capable:
"Except for the output stage, it packs the latest tech of the AMP-23R and the battery supply cutting-edge ultra-low noise regulators. It even employs a solid-state relay-based attenuator. However, these special parts are extremely difficult to procure, hence production only by September. We've secured parts to build 250 amplifiers this year. Hopefully that will cover expected demand. We are still testing output devices before settling on the best for production. Playtime will depend on this so isn't fully confirmed yet. No BPS-02 power cycling but one can extend playtime with an external battery pack over USB C. The power supply voltage will about match what the HPA-21's was so we expect similar output power but that too will finalize once we lock in the output devices."
The little amp that could.
From our 2013 HPA-21 review, "in a power current source, an input voltage causes the amplifier to deliver a proportional output current. Of course this would occur with an ordinary amplifier driving a pure resistance too but a speaker isn't purely resistive. It possesses numerous reactive elements due to inductance and capacitance in the electrical circuit and the reaction to motion of the voice coil in a complex mechanical system. Fed by a voltage amplifier, the current through the driver's voice coil is not directly or instantly proportional to the input to the amplifier. Ordinarily loudspeakers are designed around this assumption but the pistonic model of loudspeaker design also assumes that the acoustic output mirrors the acceleration of the voice coil/cone assembly over a specific range. This is reflected by the current through the voice coil. The most precise way to develop that specific current is with a current-source amplifier. Such an amplifier ignores the impedances in series with the circuit, the resistance and inductance of the wire and voice coil and the back electromotive force (EMF) produced by the cone motion. Most speakers are designed around voltage sources but there are a few instances where a current source can be used to advantage. One of the best is the category of full-range high-efficiency drivers."
