Description
Why It Matters
A great power amplifier should not call attention to itself.
It should be quiet.
It should be powerful.
It should control the loudspeaker.
It should preserve the signal.
It should have enough reserve power to handle real music and movie dynamics without strain.
That’s the AT4000 Series.
The fully balanced differential design reduces noise, increases signal purity, and gives the amplifier the stability needed to drive demanding loudspeakers with confidence. ATI rates the AT4000 Series at greater than 125 dB signal-to-noise ratio, less than 0.03% THD+N, and a damping factor of greater than 400.
The SAE Pedigree
Morris Kessler is one of the great amplifier designers in American high fidelity history.
Before ATI, Morris co-founded SAE — Scientific Audio Electronics — one of the respected American amplifier brands of the classic hi-fi era. That same engineering DNA continues today in ATI.
The Signature Series is personal. Morris’s signature appears on the front panel because these amplifiers represent his statement of what a serious modern power amplifier should be: clean, powerful, stable, durable, and built in America.
Sound & Vision noted Kessler’s SAE background and ATI’s long history of building amplifiers in the USA, including work for brands such as Crestron, Theta Digital, and Outlaw Audio.
What They’re Saying
“This amp never broke a sweat driving my 4-ohm speakers at insanely loud levels.”
— Sound & Vision, reviewing the ATI AT6005 Signature Series amplifier
“The ATI would be at the top of my list, due to its low noise and seemingly endless power output.”
— Sound & Vision
“Incredible power reserves with dead silent backgrounds.”
— Secrets of Home Theater and High Fidelity, reviewing the ATI AT6002 Signature Series amplifier
“No amplifier has ever been this quiet in my system.”
— Secrets of Home Theater and High Fidelity
“A fully balanced, dual mono amplifier with high-end build quality… it sounds like a statement product.”
— Secrets of Home Theater and High Fidelity
Built for Real Loudspeakers
The AT4000 Series is rated for 4-ohm to 16-ohm loudspeakers and is safe for all types of loads.
That matters.
Many high-performance loudspeakers present difficult impedance curves. Lesser amplifiers can sound compressed, strained, or edgy when pushed. The AT4000 Series is built for control, headroom, and composure.
Whether used in a high-end stereo system, a serious 5.1 home theater, or a full 7-channel surround system, the AT4000 Series gives each channel its own clean, authoritative power.
Balanced or Unbalanced Inputs
Each channel includes both:
Balanced XLR input
Unbalanced RCA input
A rear-panel selector lets you choose the input type for each channel. This makes the AT4000 Series compatible with a wide range of stereo preamps, AV processors, legacy systems, and modern balanced-output components.
AT4005: The Sweet Spot for Serious 5-Channel Systems
The ATI AT4005 is the natural choice for a serious 5-channel home theater or music-surround system.
It delivers:
5 channels of equal power
200 watts per channel into 8 ohms
300 watts per channel into 4 ohms
Balanced and unbalanced inputs on every channel
Made in the USA construction
7-Year Warranty
For customers who already own a great surround processor or AVR with preamp outputs, the AT4005 is a major performance upgrade. It removes the heavy lifting from the receiver or processor and gives the loudspeakers the clean current they need.
ATI AT4000 Signature Series — Features & Specifications
| Feature / Specification | ATI AT4000 Series |
|---|---|
| Number of Channels | 2 to 7 |
| FTC Full Bandwidth Power Output @ 8Ω | 200 watts RMS per channel |
| FTC Full Bandwidth Power Output @ 4Ω | 300 watts RMS per channel |
| Input Sensitivity for Full Rated FTC Output @ 8Ω | 1.6 volts |
| Frequency Response | ±0.1 dB, 20Hz–20kHz |
| Phase Response | +5 to -15°, 20Hz–20kHz @ 1W |
| Signal-to-Noise Ratio | >125 dB, referenced to FTC rated power, A-weighted |
| THD+N, 20Hz–20kHz | <0.03% |
| Intermodulation Distortion | <0.03% |
| Recommended Load Impedance | Safe for all types of loads; rated for 4Ω to 16Ω |
| FTC Power Bandwidth | +0, -3 dB, 5Hz–100kHz |
| Damping Factor | >400 |
| Crosstalk | Greater than -80 dB, 20Hz–20kHz |
| Voltage Gain — RCA Inputs | 28 dB ±0.2 dB |
| Voltage Gain — XLR Inputs | 28 dB ±0.2 dB |
| Slew Rate | >60 V/µS |
| Input Impedance | 28kΩ |
| Output DC Offset | Less than ±1mV |
| Remote Trigger | Activated from 3.3VDC to 24VDC via 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 ensure lower noise and crosstalk |
| Circuit Boards | Double-sided FR-4 glass-epoxy computer-grade boards, 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 bipolar and ThermalTrak™ output transistors optimize performance in real time |
| Power Supply Capacitance | 46,200 µF per channel |
| Power Cord | Dual detachable 3-wire cord |
| Power Requirements | Factory built for single voltage: 120VAC or 240VAC |
| AC Circuit Requirement | 1 × 20 Amp circuit |
| Power Consumption — Standby | ≤1W at 120VAC; ≤0.5W at 240VAC |
| Power Consumption — Idle | TBD |
| Chassis Dimensions — Inches | 17.0″ W × 7.75″ H × 18.0″ D |
| Chassis Dimensions — Millimeters | 440 W × 197 H × 457 D |
| Warranty | 7 years parts and labor against defects in parts or workmanship |
Model Weights
| Model | Net Weight | Shipping Weight |
|---|---|---|
| AT4002 | 51 lbs / 23.1 kg | 77 lbs / 35 kg |
| AT4003 | 71 lbs / 32.2 kg | 86 lbs / 39 kg |
| AT4004 | TBD | 90 lbs / 41 kg |
| AT4005 | TBD | 99 lbs / 45 kg |
| AT4006 | TBD | 109 lbs / 50 kg |
| AT4007 | 93 lbs / 42.2 kg | 119 lbs / 54 kg |
The AT4000 Series is not lightweight equipment. It is built the old-fashioned way: heavy chassis, serious power supply, substantial output stage, and real heat-sinked amplifier hardware.
The Essence Take
The ATI AT4000 Signature Series is for listeners who want real amplifier authority without moving into unnecessary excess.
It has the pedigree.
It has the build quality.
It has the power.
It has the warranty.
And it is made in the USA by one of America’s most respected amplifier companies.
For a serious home theater, a demanding music-surround system, or a high-performance stereo installation, the AT4000 Series is exactly the kind of amplifier we like to recommend: honest engineering, real power, and long-term value.
Penngray, AVS Forum –
ATI’s “True Balance” Differential Design Architecture
“Getting back more specifically to amps, I really need amplifiers that can do certain things for me, and the ATIs have all that, plus more. I want to go full balanced instead of single ended, and ATI handles that, plus the “true balance” differential design architecture of the amp really fits the bill for me. I want lots or headroom, and with three 200W channels per amp being fed off two gigantic toroidal transformers, there’s no bottom to this well–or at least I can’t find it.
About that 200W/channel–it’s not really true. Are they liars? Well, no, my actual measurements find them to be running about 210-220+W/channel, all channels driven from full range 20Hz to 20kHz noise. So it’s not your typical, lame 200W/channel with one channel driven only at 1kHz.
A nice surprise is the soft start circuitry. I have a single 20 Amp circuit dedicated to this system, and with the amps connected via DC triggers to the pre, a push of the on button brings the whole system up in an orderly fashion, without pops, thumps, thrown breakers, or house wide brown outs. I can take the Niles IPC6 sequencer right out of the system.
All in all, I got everything I needed in an excellent pair of amps at a great price, made locally in CA, USA. Plus, I didn’t pay extra for what I didn’t need: fancy billet Aluminum front, big prestige brand name, expensive marketing campaign, and huge overhead. Instead, when looking at them up close, I can see the quality construction, the attention to detail, the careful engineering, and the thoughtful, useful feature set.
These are well worth the $$$$.
“FWIW, I own $4000 amps and I own $500 amps… My ATI amp is the best value amp I have found out there. It has the lowest noise floor… I simply love them with my higher sensitivity horn designs. It’s the first amp in 5 years that had me saying that subjective, WOW!!”
Penngray, an AVS member with over 25,000 posts
Audio Visual Science Forum
Sound & Vision, David Vaughn –
Sound and Vision – ATI AT6005 Top Pick of the Year Award
“ATI’s Beastly AT6005 Amp, 116 Pounds of Pure Listening Pleasure by David Vaughn
If I were in the market for a new amp, the ATI would be at the top of my list, due to is low noise and seemingly endless power output. Highly recommended”
https://www.soundandvision.com/content/ati-at6005-amplifier
David Vaughn
Sound & Vision
Chris Heinonen & Dr. David Rich, Secrets of Home Theater & High Fidelity –
Secrets of Home Theater and High Fidelity – ATI AT6002
Chris Heinonen and Dr. David Rich reviewed our new Signature Series stereo amplifier. Here are their highlights:
“Innovative amp that offers incredibly high performance… High-end build quality.
…feels and sounds like a statement product… Incredible beast.
The AT6002 has the largest dynamic range of any amplifier I have ever heard. I could place my ear next to the tweeter of the Revel f208 and hear nothing when the system was idle. Not even a slight hiss. No amplifier has been this quiet in my system. Compared to my reference amplifier, the ATI AT6002 removed a layer of granularity. I could not make the amplifier lose its cool.
The 128.7dB SNR at 300 Watts has a bit equivalent of 21 bits, which is better than any DAC now on the market.
No power supply hum spurs are seen above -135dB, a remarkable result for a power amp at full power.
The ATI AT6002 …is a giant in the world of power amplifiers… (need) never be replaced.”
https://hometheaterhifi.com/reviews/amplifier/power-amplifier/ati-at6002-multi-channel-power-amplifier-review/
Chris Heinonen & Dr. David Rich
Home Theater Hifi