ThermalTrak™ output devices are incorporated in Signature Series amps to provide an integrated device for temperature sensing with the output transistor resulting in real-time bias performance


The AT4000 Signature series amplifiers, available with 2 to 7 channels.


They share the design philosophy and circuit sophistication of ATI’s award-winning AT6000 Series amps at a reduced power of 200W RMS per channel at 8 ohms and 300W RMS at 4 ohms.

Furthermore, their “signature series” designation with a facsimile of Kessler’s signature on the main panel attests the special nature of these amplifiers.

ATI Signature Series are fully balanced, differential amps, advanced from previous designs which were essentially balanced bridged amplifiers.

Signature Series uses only a single input stage with dual-differential output stages.

This design approach retains the advantages of balanced designs and reduces noise by 50%.

Using current feedback rather than voltage feedback, Signature Series amps respond faster with a virtually unlimited slew rate which makes them capable to reproduce todays best music and film sound.

ThermalTrak™ output devices are incorporated in Signature Series amps to provide an integrated device for temperature sensing with the output transistor resulting in real-time bias performance.

Combining these advancements with dual DC servos reduces DC offset at the output to insignificant levels.

The use of a modular PCB layout with amplifier and power supply parts on the same card with edge to edge isolation of AC and signal input provides improved signal-to-noise ratio.

Dual toroidal transformers, dual power switches and dual AC power cords bring a complete dual-mono design to the AT4002 and AT6002.


Multi-channel amplifiers up to the 7-channel AT4007 and AT6007 models may be connected to independent 20 amp circuits for greater sustained output power than would be possible than from a single AC circuit.

4000 Series amps are rated at 200 Watts RMS from 20Hz to 20kHz with no more than 0.03% THD at 8 ohms with all channels driven and 300 Watts RMS at 4 ohms under the same conditions.

Signal-to-noise ratio is typically -126dB referenced to full output so that each Signature Series amp is capable of playing back the full dynamic range available on today’s lossless recordings.

AT4000 SIGNATURE SERIES Specifications

AT4000 SIGNATURE SERIES Specifications

Numbers of Channels 2-7

FTC Full Bandwidth Power Output@ 8Ω (Watts RMS) 200

FTC Full Bandwidth Power Output@ 4Ω (Watts RMS) 300

Input Sensitivity for Full Rated FTC Output Power – 8Ω 1.6 Volts

Frequency Response ±0.ldB 20Hz – 20kHz

Phase Response +5 to -15°, 20Hz – 20kHz @ 1W

Signal-to-Noise Ratio (Ref FTC Rated Power, A-Wtd) >125dB

Total Harmonic Distortion + Noise (20Hz – 20kHz) <0.03%

Intermodulation Distortion <0.03%

Recommended Load Impedance Safe for all types of loads. Rated for 4Ω to 16Ω

Power Bandwidth FTC +0,-3 dB 5Hz – 100kHz

Damping Factor >400

Crosstalk Greater than –80 dB from 20 Hz to 20 kHz

Voltage Gain (RCA Inputs) 28dB ±0.2dB

Voltage Gain (XLR Inputs) 28dB ±0.2dB

Slew Rate >60V/µS

Input Impedance 28kΩ

Output DC Offset Less Than ±1mV

Power Requirements 240VAC 1x 20 Amp Circuit

Power Consumption (Standby) ≤1W (120 VAC), ≤0.5W (240 VAC)

Power Consumption (Idle) TBD

Chassis Dimensions (W x H x D) inches 17.0″ X 7.75″ X 18.0″

Chassis Dimensions (W x H x D) millimeters 440 X 197 X 457

Additional information


AT4002 – 2 Channel Power Amplifier, AT4003 – 3 Channel Power Amplifier, AT4004 – 4 Channel Power Amplifier, AT4005 – 5 Channel Power Amplifier, AT4006 – 6 Channel Power Amplifier, AT4007 – 7 Channel Power Amplifier



AMPLIFIER TECHNOLOGIES INC At ATI, they make heavy-duty amplifiers with proven circuitry, meticulous assembly and rigorous testing designed to deliver state-of-the-art audio for years, all designed by them and built in their own US factory. It’s a simple story, American amplifiers built by American people. They hope you enjoy listening.


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