Atoll IN400 Evolution Integrated Amplifier, Black

The Atoll IN400 Evolution is the largest integrated amplifier in the Atoll lineup: 2×160 watts at 8 ohms, sixteen MOSFETs, and two 1050 VA toroidal transformers in a symmetrically built dual-mono chassis.

Nineteen and a half kilograms, 10 millimetres of aluminium on the front, and inside it's almost all power supply. Anyone who's ever lifted one knows where the money went — and it wasn't the packaging.

Why the IN400 Evolution?

Because nothing stands in the way anymore. The preamp stage runs discrete in Class A, the power stage in Class A/B with eight MOSFETs per channel, and 96,680 µF of smoothing capacitance keeps the supply voltage stable even when an orchestra comes in all at once. Two balanced XLR inputs take high-quality sources directly, five RCA inputs handle the rest, and the bypass ties it into the home cinema.

What you'll hear

Composure. The IN400 Evolution sounds the same at low and high volumes — just louder. Bass with structure instead of mass, a midrange with no strain at all, and a soundstage that doesn't end at the speakers. At 4 ohms it steps up to 2×300 watts instead of limiting. That's exactly what separates a great amplifier from a loud one.

Who is the IN400 Evolution for?

For large rooms, for low-efficiency or impedance-critical speakers — and for anyone who wants to buy once and then have peace of mind. Plain talk: it doesn't come with streaming built in; digital inputs are an option card. In a 20-square-metre room with simple bookshelf speakers, it's plain overkill — the IN200 or IN300 Evolution does the job just as well there. And at 44 centimetres wide and 37 centimetres deep, it needs a rack that can actually support it.

Our verdict

This isn't an amplifier you replace every five years. Trevor Butler wrote on 30 April 2025 in The Ear: "The IN400 Evo is in the highest echelons for its price bracket and can't be recommended highly enough." Alfredo Mascia put it in a nutshell on 13 July 2025 on HiFi-IFAs: "Dynamics without drama, control without harshness – a character that endures." Before buying in this class, we should talk about your room and your speakers: 044 680 22 00 or WhatsApp 076 534 22 00 – HD Zürisee in Wädenswil.

Technical data

• Type: analogue stereo integrated amplifier, symmetrical dual-mono construction
• Output power: 2 × 160 watts at 8 ohms, 2 × 300 watts at 4 ohms
• Power stage: 16 MOSFETs (8 per channel), discrete Class A/B circuit, preamp stage in Class A
• Power supply: 2 × 1050 VA toroidal transformer plus 1.6 VA for control logic
• Smoothing capacitance: 96,680 µF
• Analogue inputs: 2 × balanced XLR, 5 × RCA line (1 × AUX among them, switchable to phono card), 1 × bypass
• Digital inputs: not from the factory – retrofittable via option card DA100 or DA200
• Outputs: 1 pair of speaker terminals, 2 × RCA pre-out, tape out, 12V trigger
• Output level: pre-out adjustable, tape out fixed
• Headphone output: present, 6.35 mm jack
• Frequency response: 5 Hz – 100 kHz (−3 dB)
• THD: 0.05% at 1 kHz
• Signal-to-noise ratio: 100 dB
• Input impedance: 357 kOhm, input sensitivity 450 mV
• Slew rate: 2 µs
• Standby: under 0.5 watts (eco mode)
• Option cards: phono P50 (MM) or P100 (MM/MC), DAC DA100 or DA200
• Chassis: 10 mm thick aluminium front in bi-colour design
• Colour: Black
• Dimensions (W × H × D): 440 × 130 × 370 mm
• Weight: 19.5 kg
• Warranty: 2 years
• Included: Atoll IN400 Evolution, remote control, power cable, user manual

Frequently asked questions

How much power does the Atoll IN400 Evolution have?
2×160 watts at 8 ohms and 2×300 watts at 4 ohms. Eight MOSFETs work per channel, fed by two 1050 VA toroidal transformers and 96,680 µF of smoothing capacitance. That reserve is why it doesn't get harsher even under difficult loads.

What distinguishes the IN400 Evolution from the IN300 Evolution?
Above all the power supply: 1050 instead of 440 VA per transformer and 96,680 instead of 86,150 µF. Plus two balanced XLR inputs instead of one, a 10 mm instead of 8 mm thick front, and 3.5 kilograms more weight. Sonically, it's about composure at high levels.

Can I connect a turntable to the IN400 Evolution?
Yes, with a phono card. The P50 turns the AUX input into an MM input, while the P100 can additionally handle MC with switchable termination impedance. Without a card, you connect an external phono preamp to one of the five line inputs.

Does the IN400 Evolution have digital inputs?
Not from the factory. They come via the DA100 or DA200 option card. The DA200 brings two coaxial and two optical inputs, USB-B, and Bluetooth. Please note: Atoll doesn't officially list the DA200 for the IN400 Evolution – we clarify approval with distribution before installation.

Why buy the Atoll IN400 Evolution at HD Zürisee?
Because an amplifier in this class needs speakers, a room, and cabling that keep up. We'll look at your chain, tell you honestly whether the step is worthwhile, and take care of delivery, installation, and service with our own technician.

Pairs well with

It deserves floorstanding speakers that can actually draw on its reserves. As a source, the Atoll CD400 Evolution from our CD players or a streamer fits well – wired symmetrically with the right cables.