All ATI amplifiers are fully designed and assembled in the USA. ATI Signature Series are our very best amplifiers. Musical and powerful, ATI Signature Series is transparently revealing.


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

Power Cord
Dual detachable, 3-wire cord.
7-Year Warranty
Parts and labor against defects in parts or workmanship.

4RU 7.00” (178mm) Rack Mount
8.00” (203mm) Standard Height

Shipping Weight
77 to 119 lbs (model dependent)

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.

Remote Trigger
Activated from 3.3VDC to 24 VDC via a heavy-duty relay
Protection Circuits
Optically – coupled with full automatic reset.
Toroid Transformers
40% more efficient than EI type. Separate bi-filar windings for each channel guaranty lower noise and crosstalk.
Circuit Boards
Double-sided, FR-4 glass-epoxy, computer-grade boards are assembled in-house.
Soft Start Circuitry
Ultra soft turn on reduces in-rush current to a minimum. Multiple units can be turned on without tripping circuit breakers eliminating the need for sequencing.
Power Transistors
High-current, bi-polar and ThermalTrak™ output transistors insure optimized performance in real-time.
Power Supply Capacitance
46,200 µF (microfarads) per channel.
Power Cord
Dual detachable, 3-wire cord.
7-Year Warranty
Parts and labor against defects in parts or workmanship.
Numbers of Channels
FTC Full Bandwidth Power Output@ 8Ω (Watts RMS)
FTC Full Bandwidth Power Output@ 4Ω (Watts RMS)
Input Sensitivity for Full Rated FTC Output Power - 8Ω
Frequency Response
Phase Response
Signal-to-Noise Ratio (Ref FTC Rated Power, A-Wtd)
Total Harmonic Distortion + Noise (20Hz - 20kHz)
Intermodulation Distortion
Recommended Load Impedance
Power Bandwidth FTC
Damping Factor
Voltage Gain (RCA Inputs)
Voltage Gain (XLR Inputs)
Slew Rate
Input Impedance
Output DC Offset
Power Requirements
Power Consumption (Standby)
Power Consumption (Idle)
Chassis Dimensions (W x H x D) inches
Chassis Dimensions (W x H x D) millimeters
Net Weight (lbs/kg)
Shipping Weight (lbs/kg)
1.6 Volts
±0.ldB 20Hz - 20kHz
+5 to -15°, 20Hz - 20kHz @ 1W
Safe for all types of loads. Rated for 4Ω to 16Ω
+0,-3 dB 5Hz - 100kHz
Greater than –80 dB from 20 Hz to 20 kHz
28dB ±0.2dB
28dB ±0.2dB
Less Than ±1mV
Factory built for single voltage - 120 VAC or 240VAC
1x 20 Amp Circuit
≤1W (120 VAC), ≤0.5W (240 VAC)
17.0" X 7.75" X 18.0"
440 X 197 X 457
AT4002: 51/23.1
AT4003: 71/32.2
AT4004: TBD
AT4005: TBD
AT4006: TBD
AT4007: 93/42.2
AT4002: 77/35
AT4003: 86/39
AT4004: 90/41
AT4005: 99/45
AT4006: 109/50
AT4007: 119/54
TitleDescriptionVersionSizeHitsDate addedDownload
AT4000, Standard Front, Line Drawing AT4000 Dimensioned Line Drawing1.51 MB130007-02-2021 DownloadPreview
AT4000 Manual AT4000 Manual3.31 MB229602-14-2020 DownloadPreview