Audeze THE KING, Manual

Introduction

The King Headphone Amplifier was designed for Audeze by 

world-renowned circuit designer Bascom King. His long experience 

dates back to a time when tubes ruled the amplifier world. That, 

along with advances in solid-state technology, led to The King’s 

unique combination of both. 

The King is a class-A hybrid design featuring E88CC triode tube 
inputs driving MOSFET output devices. The tube section is a 
differential stage that’s directly coupled to the MOSFET drivers. A 
current source ensures proper tube bias and improves their 
linearity. A DC servo circuit is in the loop between the input and 
output stage to keep DC offset as close to zero as possible 

(typically less than 5mV.)
 

Output devices are matched IRFZ20 MOSFETs chosen for their 
linearity and reliability. A symmetrical regulated power supply 

delivers ±16V DC to the output devices and there are no capacitors 

in the signal path. This results in a virtually flat frequency response 

throughout the range of our Audio Precision APX 525 audio 
analyzer: -0.1dB at 1Hz to 80kHz.

Left and right channels are on separate PCBs and each has its own 

voltage regulators to reduce crosstalk between channels. Each PCB 

features a protective shield of perforated, powder-coated magnetic 
material.

The toroidal transformer is massively oversized, molded in epoxy 
and shielded to further improve signal-to-noise ratio. The main 
power supply and protection PCBs also feature shields of perforated 
powder-coated magnetic material.
 
A microprocessor provides overload protection. Voltage across a 

1 ohm resistor connected to the source of the output MOSFETs is 

constantly monitored. The relay connecting the output to the 

headphone is powered off if it becomes higher than a predeter

-

mined value. The same relay disconnects the output until the servo 

eliminates DC offset as the amplifier powers on. 

Headphone impedance connected to the output is checked during 
the initial power-on delay. If the impedance is lower than 10 ohms 
the microprocessor won’t activate the relay. We recommend that 
you leave your headphone connected during power-on as The King 

checks for potential cable shorts.

There are two red and green LEDs that indicate the status of the 
output relays on both channels. During the initial power-on phase 
the red LEDs are on and that can be seen through holes in the top 

cover. After the relays connect the output to the headphone the red 

LEDs extinguish and green LEDs are lit.

The LED SPL Meter on the front panel indicates actual SPLs (Sound 
Pressure Levels) delivered by the LCD-4 on both channels. A 
removable calibrated display for other Audeze headphones will be 

offered at a later date. 
 
The King delivers a full 6 watts at 20 ohms and will drive any 
headphone with ease.