A1.5 Two-channel Power Amplifier

Like its bigger brother, the M1.1 Reference power amplifier, there’s a lot more to the A1.5 than meets the eye – just in a more compact and more affordable form

“Importantly, the improvements result in a more musically engaging delivery. The A1.5 is nothing short of a giant killer amp. Yup: miracles do exist! Even at 3 minutes into the listening session, I already knew that there was no way back!”


Product Description

Faced with exactly the same challenges as the M1.1, the A1.5 embodies the same sophisticated, modular and scalable approach. It might be (slightly) smaller than the M1.1 and around two-thirds of its weight, but it’s still four amplifiers in one. It still offers the same adaptable, software controlled topology, adjustable input configuration and gain, user selectable global feedback ratio and cost-effective upgrade path. It offers exactly the same, incredibly short signal path, fully discrete, fully balanced and fully complementary circuit, built with the same carefully selected components to the same exacting standards. Even the casework, although shorter, has the same footprint, uses the same construction and includes the same mechanical grounding/stacking system. In fact, in every important way, the A1.5 is, quite literally, an M1.1 writ small – or, in Hollywood terms, “Honey, I shrank the amp…”.

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Physical And Conceptual Modularity

  • Modular input boards to match system topology (one or two inputs as required)
  • Output stage can deliver 2x 150W RMS into 8 Ohms stereo, 150W into 8 Ohms mono (high-current), 550W mono (bridged) or 2x 150W bi-amped (single input, differential channel gain and global feedback settings)

Analog Input Stage

  • Pure class A, fully symmetrical circuit topology
  • Fully discrete, ultra low noise, high slew rate design
  • DC coupled with no series capacitors in the audio signal path
  • Gain adjustable through 24dB in 0.5dB steps

Analog Output Stage

  • Pure class A ultra low noise driver and class AB pure follower power stage
  • ExactBias circuitry ensures constant bias, independent of room temperature and amplifier loading
  • Constant monitoring of output power and temperature
  • User configurable display will show amplifier status, power output etc
  • Customized Argento loudspeaker binding posts, accept spades and banana connectors

Power Supply

  • 1700VA power transformer mounted on separate, mechanically isolated chassis bed to eliminate mechanical vibration
  • Magnetically and electrostatically shielded transformers to reduce noise and EM interference
  • Hyper fast, soft recovery diode bridge rectifiers meet dynamic demands without strain
  • Twin 82,000uF custom-built, ultra low ESR reservoir and filtering capacitors

User Adjustable Global Feedback

  • Ratio of Global to Local Feedback can be adjusted from 0% to 100%, in six steps (0, 10, 20, 40, 70, 100%) via the user interface or control app
  • Allows user optimization of amplifier/speaker interface, especially lowfrequency damping relative to speaker/room interaction
  • Each channel can be adjusted individually to control specific drivers/ranges in bi-amplification modes

Light Touch Protection

  • No output relay in signal path; full short circuit protection
  • Non-invasive output stage voltage, current and temperature monitoring protects your amplifier – and your speakers

Optional Hardware Monaural Analog Input Board

  • Option board needed for stereo and active applications (only buy the inputs you need)
  • XLR, RCA and 75 Ohm BNC inputs
  • Balanced pass-through for daisy-chaining amplifiers in multi-amp systems
  • Existing A1 amplifiers factory upgradable to full A1.5 specification

Technical Specifications

Nominal input voltage
2.2V RMS balanced
1.1V RMS single-ended

Input impedance
94kΩ balanced
47kΩ or 300Ω single-ended

Output power
2x 150W / 8Ω, 2x 275W / 4Ω, 2x 450W / 2Ω in stereo and bi-amp modes
1x 275W / 4Ω, 1x 450W / 2Ω, 1x 700W / 1Ω in monaural mode
1x 550W / 8Ω, 1x 800W / 4Ω, 1x 1200W / 2Ω in bridged mode

DC to 450kHz (-3dB) at 1W into an 8Ω resistive load

Signal to Noise Ratio
> 115dB in stereo and bi-amp modes
> 118dB in bridged mode

Total Harmonic Distortion + Noise
< 0.1% (0% global feedback)
< 0.01% (100% global feedback)

Max power consumption

440 x 440 x 198mm (W x D x H), 47kg

A1.5 Specific Downloads

CH-Control App

Meet the CH-Control App – a control application that allows users direct access to every aspect of their CH system’s set up and use via any Android portable device. The software control systems used to set and monitor the operational parameters of each and every CH component offer the perfect opportunity for remote operation via a portable App.

To use the CH-Control App, all you will need is an Android device and to connect your CH components to an Ethernet network. That can be done either through the Ethernet control board fitted as standard to all CH units, or through the network streaming board that can be installed in C1.2, C1.2 Mono or I1 units. We would always recommend using a dedicated tablet and network for your music streaming and system control requirements.

Once your CH system is all hooked up, the App gives you touch screen access to every setting on every CH component, from your listening seat, a huge benefit when it comes to whole system set up or optimization for individual recordings. Either way, the CH-Control App allows you to make easier and more accurate judgements: Total control, quite literally at your fingertips.

The features of every CH product are accessible through the CH-Control App:

  • Built-in UPnP controller to stream dematerialized music, create playlists, etc.
  • Set volume level, select sources, reverse phase, mute, etc.
  • Access to all the advanced set-up parameters in every CH product.
  • Works on a standard Ethernet network.
  • The CH-Control App is freely available on Google Play or on our website.