AUDIO-GD Master 19 Class A Headphone Amplifier[2nd hand]

* True balanced ACSS design
* Pure Class A (9W @ 40 Ohm)
* Preamplifier & Headphone Amplifier
* 2 gain modes for high and low sensitivity

Overview
Fully balanced, pure Class-A design with discrete analog stages without OPAs or coupling capacitors in the signal channels.
Non-feedback ACSS analog output stage.
A total of 8 perfectly matched 150W transistors (total 1200W) as output stages to achieve high Class-A output power.
Uses two R-core transformers (total 100W) as separate power supplies for digital control components and left/right channels.
4 groups of pure Class-A power supplies feed the audio circuits.
Over 35,000 μF of NOVER audio-grade capacitors ensure abundant and stable power delivery.
Uses the highest quality components and precisely matched transistors, OCC wires.
Four-channel, 100-step, digitally controlled relay-based volume control avoids channel imbalance and improves sound quality.
Super Exponential Volume characteristic allows easy volume adjustment on very high-power headphones/speakers without changing the gain mode.
16.25 dB gain in two amplification modes can drive low-sensitivity headphones very effectively.
5 input groups: RCA x2, XLR x2, ACSS x1
Preamplifier output: XLR / RCA / ACSS
Headphone amplifier output: XLR 4-pin x1 / 6.3 mm x1

Specifications
* S/N Ratio: >130 dB
* THD: <0.003 %
* THD+N: <0.005 %
* Gain: Low Gain: +16 dB (XLR), High Gain: +25 dB (XLR)
* Volume characteristic: 100-step Super Exponential
* Headphone Amp Output Power (Balanced, Pure Class A): 40 Ω: 9000 mW, 100 Ω: 3800 mW, 300 Ω: 1250 mW, 600 Ω: 630 mW
* Headphone Amp Output Power (Single-ended, Pure Class A): 40 Ω: 2500 mW, 100 Ω: 1050 mW, 300 Ω: 350 mW, 600 Ω: 175 mW
* Preamplifier Output Level (Max): 10 V @ RCA, 20 V @ XLR, 2.4+2.4 mA @ ACSS
* Output Impedance: 1 Ω
* Input Impedance: 90 kΩ @ XLR, <10 Ω @ ACSS
* Frequency Response (XLR input): 20 Hz - 20 kHz (±0 dB)
* Extended Frequency Response: 1 Hz - 220 kHz (+0 dB, -3 dB)
* Channel Separation: >130 dB
* Channel Imbalance: <0.05 dB
* Power Requirement: Version 1: 100-120V AC 50/60 Hz, Version 2: 220-240V AC 50/60 Hz
* Power Consumption: 45 W @ 240V or 120V
* Transformer Power: 100 W (2 transformers)
* Package Weight: Approximately 7 kg
* Dimensions: W360 x L360 x H85 mm (fully aluminum)
* Accessories: Power cord x1