Integrated amplifiers — ToneWinner AD-2PRO+

The AD-2PRO+ is an integrated amplifier from Tone Winner, the Chinese manufacturer based in Guangzhou. It is the latest version of the AD-2, a design refined over some twenty years. Its fully balanced circuit can run in pure Class A, in Class AB, or in an automatic mode that switches between the two, chosen from the remote, and it also includes a DAC with USB input and an MM/MC phono stage.

Key specs that matter

Output is 240 W per channel into 8 ohms in Class AB and about 60 W per channel in pure Class A. Frequency response runs from 15 Hz to 95 kHz, signal-to-noise exceeds 100 dB and THD is 0.05% or lower (1 kHz, A-weighted). The analogue inputs are one balanced XLR and three RCA, plus MM/MC phono. Digital inputs comprise two optical, one coaxial and USB, served by an ESS ES9038 DAC that supports PCM up to 32-bit/768 kHz and DSD512. Subwoofer outputs are available in balanced and unbalanced form. The chassis measures 444 x 254 x 460 mm and weighs 35.9 kg.

Engineering and use context

Symmetry runs through the entire signal path, from a differential input to a bridge-tied load output stage in which two amplifier sections drive each speaker in opposite phase. Left and right channels have independent power supplies, each with its own 860 W toroidal transformer, with 120,000 uF of audio-grade filter capacitance and high-power output transistors in parallel for current capability. Nine Texas Instruments OPA1656 operational amplifiers form the balanced gain stages of the preamplifier and DAC sections. In Class A the output transistors conduct over the full signal cycle, which removes crossover distortion at the cost of lower output and more heat, while Class AB delivers full power. The automatic setting switches between them according to signal level. A power amplifier mode, also selected from the remote, bypasses the volume control for use with an external preamplifier or AV processor. Large heatsinks and a patented wide-voltage power design that accepts mains from 110 V to 240 V complete the build.

Pairing

In Class AB the amplifier can drive low-sensitivity floorstanders in rooms up to about 40 m2, while the Class A mode suits efficient speakers of 90 dB or more. The subwoofer outputs make 2.1 systems straightforward, and the heavy chassis needs a sturdy shelf.

Alternatives

Tone Winner's AD-3PRO+ is the smaller integrated amplifier, with 165 W per channel and a DAC section.