Arcam A25: Integrated amplifier that differs from its predecessor

The Arcam A25 integrated amplifier differs from its predecessor, the Arcam SA20 model, in its new industrial design, the presence of a bluetooth module version 5.2 and USB version C. The source selection buttons have been replaced with a round knob on the left side of the front panel of the amplifier.

The Arcam Radia A25 amplifier offers the best performance and best sound in the Arcam Radia amplifier line, surpassing the Arcam A5 and Arcam A15. Unlike its smaller Class A/B amplification siblings, the A25 is Class G and boasts 100W per channel. The specificity of this design is that until the power reaches 20 W per channel, the device operates in pure A-class, and then moves to class AB. Solid, backlit knobs add a touch of luxury to the anodized aluminum body, and a compact remote control is included. The front panel has a headphone output (mini-jack).

Class G is a derivative of Class A/B, but before we explain, please let us first take a look at the other amplifier classes. Class A is used for low power consumption systems. Many valve amplifiers are Class A with a single output device. This amplifies the entire audio signal waveform. Class A sounds the best, but is very inefficient and requires a large power supply. As a result, Class B was developed, which uses two or more output devices. Each of the output transistors processes half of the audio waveform. As a result, it is more efficient, but may suffer from crosstalk. This led to the development of Class A/B, where Class A is used at low outputs and Class B is gradually introduced at higher volumes.

Class G is similar to Class A/B except that it increases amplifier efficiency by using multiple power rails and thus optimizing the power supply. Class G uses at least two different buses, and each higher voltage bus is turned on as the volume increases. The advantage is increased efficiency at higher power output. You’ll experience a smoother, more dynamic, and overall much more musical sound than other amp models.

The Arcam A25 amplifier integrates two-way Bluetooth, which uses the latest 24-bit HD aptX 5.2 codec to deliver the best sound possible. This allows you to stream music from your smartphone, tablet or other Bluetooth-enabled device – you can also connect to Bluetooth headphones, which is a useful feature for close listening in the evening.

The onboard DAC is powered by the high quality ESS ES9280A DAC chipset, one of the best sounding DACs available today. Three digital inputs are included along with three standard line inputs, allowing you to enjoy the best sound from a wide range of music sources through the input of your choice – either directly at line level or taking advantage of the excellent built-in DAC via the digital input.

Arcam has not forgotten vinyl lovers, and the Arcam A25 built-in amplifier is equipped with a high-quality phono preamplifier designed to work with millimeter cartridges. There are two types of cartridges – moving magnet (MM) and moving coil (MC). The latter has less power and will require a separate phono stage – this is a possible upgrade path.

Arcam A25 Specifications

Continuous Output Power: (0.5% THD), per channel into 8 ohms 100 W
Harmonic Distortion, 80% power, 8 ohms at 1 kHz 0.002%
S/N Ratio 110 dB
Analog Inputs: 3 (RCA pairs ), Phono (MM) input
Digital inputs: USB-C, Coaxial (RCA), Optical (Toslink)
Bluetooth 5.2 with aptX™ adaptive technology and AAC
Supports DSD for USB-C only: 1024, 512, 256, 128, 64
Output for headphones – Maximum output level (rms) at 32 Ohm/300 Ohm: 2.5 V/5V – Load range: 16Ω – 2 kOhm
Mains voltage: 100 V or 110-120 V or 220-240 V, 50-60 Hz
Power consumption (max): 500 W
Power consumption (standby): <0.5 W
Dimensions W x D (including speaker terminals) x H (including feet): 431 x 344 x 83 mm
Weight (net): 9 kg