Enleum HPA-23RM Reference Headphone Amplifier

Introduction

"Enleum" is a mix of the phrases "Enlightenment" and "Eum" (Korean for "Sound"). You might have heard of Soo In Chae’s work below "Bakoon" which was a collaboration between Soo In (founding father of Enleum) and Akira Nagai.

Description

The HPA-23RM (the "R" and "M" being shorthand for Reference and Mobile) is a singular headphone amplifier with two totally different amplification circuits – a voltage, and present output stage. The voltage stage is a MOSFET output stage primarily based on a simplified model of the JET2 bias circuit seen within the AMP-23R. The present output stage is derived from the HPA-21’s bipolar transistor circuit. While this system just isn’t one thing you’d lug round regularly, it’s transportable sufficient to be moved round and can be utilized on-the-go due to its built-in battery. Similar in dimension to a paper-backed novel, the Enleum measures 116mm x 164.5mm x 22mm and weighs 750 grams.

On the entrance panel, a toggle change selects achieve, whereas a recessed rotary knob features as each a quantity management and energy change. A 3.5mm socket is mated to the voltage stage, whereas a 1/4 inch socket is used for the present output stage. A row of LED lights point out cost standing, battery life and operation.

The inputs are positioned on the rear panel, with a USB-C socket used for charging, and a pair of RCA sockets and a 3.5mm socket used for the enter sign. There isn’t any selector change, so just one enter could also be used at a time. If the three.5mm socket is in use, that is given precedence over the RCA enter.

The current-output stage is able to 1W of energy, and half of that into the voltage output (right into a 30 ohm load).

In operation

Rotating the amount knob from its resting place to about 8 o’clock brings the unit into standby mode. The LEDs mild as much as point out the battery stage. The HPA-23RM makes use of a discrete resistor relay community to manage the amount and advancing the knob additional unmutes the unit , with an audible click on as you progress between every quantity stage. The handbook advises you to deliver the amount knob again to the standby place earlier than plugging and unplugging headphones to keep away from harm to the unit.

The unit is specified to function for as much as 5 hours of use in voltage output mode, and three.5 hours in present output mode, which matched my person expertise. Thankfully, the HPA-23RM might be charged whereas in use.

Sound Quality

Enleum recommends as a place to begin that the voltage output be used with IEMs / headphones which can be delicate, or have a various impedance curve, whereas the present output be used with headphones which have a flat impedance curve resembling planar headphones. This is after all not a tough rule, and Enleum does encourage you to experiment. Matching a headphone with a various impedance curve with the present output does lead to a frequency response that tracks the impedance curve, which could possibly be both or unhealthy factor relying in your goal. For instance, the Sennheiser HD8xx has an impedance peak at about 100 Hz and a falling impedance within the high-frequencies. Listening to those headphones by way of the present output provides you added bass and attenuated high-frequencies.

To be continued …

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March 17, 2024 at 01:30PM