The Audio-GD Master 9P is an excellent fully balanced headphone amplifier and combo amplifier, featuring the newly developed ACSS design, which provides a sound that is as accurate and transparent with XLR as with ACSS. It also benefits from an optimized power supply to provide an extremely clean and stable electrical signal to all audio circuits.

The amplifier stage of the Master 9P has a unique current gain stage (ACSS) for the shortest possible signal path and a particularly neutral and faithful sound reproduction. This ACSS amplifier has a very low distortion level and is soldered directly to the main PCB. The gain and preamplifier stages here operate in Class A. The output transistors operate with a high rest current. The special design of this stage avoids switching distortion.

The ACSS used in the Master 9P architecture is a feedback-free technology using discrete amplifiers. The combination of ACSS and a feedback-free circuitry allows for beautiful dynamics, detail and sonic neutrality, while ensuring low distortion and high linearity. The ACSS stage uses four groups of high quality Class A PSUs. This parallel connection provides a high input impedance to prevent power supply pulses from affecting the gain stages.

Linear Fidelity output stage

The Master 9P uses Linear Fidelity technology on its output stages. These have no feedback but maintain a very low level of distortion and offer excellent linear performance.

A powerful amplifier

The use of high power components combined with a robust power supply ensures a high current output, allowing the Master-9P to accompany demanding loudspeakers. The Master 9P uses four channels of feedback-free output stages consisting of eight ON Semiconductor transistors, each with a power handling capacity of 230W/15A. The whole set reaches a capacity of 100000µF and two transformers are used with a power of 600W.

Impedance matching

In order to limit the impact of different output impedances depending on the DAC used, the Master 9P uses four groups of Class A FET cascode buffers. All input signals pass through these FET buffers to achieve a low output impedance.

Volume control

The Master 9P's volume control system acts at the input stage of the analog amplifier via a potentiometer allowing signal attenuation through relays and resistors. Here the volume control uses a variable passive I/V conversion at the output of the ACSS amplifier and does not degrade the signal quality.

Shielding

The Master 9P features complete separation of the left and right channels of the amplifier, power supply and transformer. It also uses a heavy aluminum alloy chassis to prevent transformer eddy currents from interfering with the PCB.