Description

The Class A-2 headphone amplifier and preamplifier is based on in-house developed ACSS technology.
This is a pure class A design built with discrete analog stages without amplifiers operational or coupling capacitors in the signal path.

It seems like a complicated project, but in reality it is probably the simplest in the world.
The simplest and shortest signal path produces the most neutral and least colored sound!

HIGHLIGHTS
2500 mW pure class A headphone amplifier and preamplifier
ACSS technology developed internally by Audio-gd
Design with non-negative feedback
Complete design of discrete transistors

Improvement may result in changes in specifications and design without notice.
S/N ratio >125 dB (minimum volume)
THD <0,008%
Gain L Gain: +14dB
H Gain: +20dB
Headphone amplifier output power
(Pure Class A) 25 ohm: 2500 mW
40 ohm: 1600 mW
100 ohm: 650 mW
300 ohm: 325 mW
600 ohm: 160 mW
Preamp output level (max) 8V @ RCA
Input impedance 47K ohm on RCA
<10 ohms at ACSS
Frequency response 20Hz – 20KHz
( +/- 0,3 dB )
10Hz – 125K
(+0dB, -3dB)
Power Requirements 1 version 100-120 V AC 50/60 Hz
2 220-240 V AC 50/60 Hz version
Power consumption 20W at 240V or 120V
Package weight approximately 3,5 kg
Dimensions L240 X W360 X H80 (mm, black aluminium)
Accessories Power cord X1

IMPEDANCE MATCHING
There are DACs of very different quality. They have different designs and output impedances. To avoid negative effects on sound quality due to differences in DAC output impedance, we designed a pair of differential diamond buffers in the input of the A-2. All RCA input signals pass through these buffers, resulting in a very low output impedance, even if the source has a high or low output impedance.
Diamond differential buffers operate in pure class A and have a short signal path. this way we can maintain the sound quality without coloration (dry and harsh).

CLASS A ANALOG OUTPUT STAGES
The A-2 has diamond differential output stages in its design.
The output stages have two pairs of 20W transistors offering 2500MW at 25 ohms Class A, drive most headphones (run in pure class A), it doesn't matter if you have low sensitivity headphones

ACSS – Current Amplification

Audio-GD has developed an advanced current-driven amplification technique. Also known as ACSS, Audio-GD Current Conveyor System Signal. This special technique ensures that the signal travels a much shorter path and ensures more transparent, faster, and more neutral reproduction. A similar technique is used, for example, by KRELL. Most components in Current Conveyor technology are current mirrors. Current Conveyor technology is not a new technology; in 1966, Professor KC Smith and ASSedra published the concept of "analog circuits in motion."dalicurrent situation”.

HIGH PRECISION VOLUME CONTROL
Volume control is achieved by a high-quality ALPS-27 potentiometer.

R-CORE TRANSFORMER
The DAC is made of a low-noise, low-leakage, R-core tuned transformer. A total of 65W of power is supplied to all digital components and the left and right analog boards. DC power is distributed by separate power regulators. These are all pure Class A, low-noise shunts, powered by linear power supplies. The result is ultra-high speed and clean power for all individual components.

Specifications

Amplification type	Class A
RMS power per channel	2500 W
Reference load	25 ohm
Analog inputs	RCA
Rapporto S/N	125 dB
Harmonic Distortion (THD)	0.008%
Frequency response	20Hz - 20KHz
Input impedance	47 kOhm
Electricity consumption	20 W
Weight	3.5 kg
Dimensions (WxHxD)	240 x 360 x 80 mm
Trim	black aluminum
Alimentazione	100-120V AC 50/60Hz / 220-240V AC 50/60Hz