45 Watts Per Channel of Tube Power

The xDuoo A35 is a fully integrated vacuum tube amplifier designed for two-channel audio systems. Built around a hand-wired analog circuit, it combines a 12AX7 voltage amplification stage, dual 12AU7 driver tubes, and four matched EL34 output tubes in a push-pull configuration rated at 45 watts per channel. Alongside its traditional tube architecture, the A35 incorporates an ESS ES9018K2M DAC, Bluetooth 5.1 connectivity, and infrared remote control support, allowing it to serve as both a conventional stereo amplifier and a modern digital audio hub.

Hand-wired EL34 amplification

The A35 uses a fully tube-based signal path with distinct stages assigned to voltage gain, signal driving, and power output. A single 12AX7 handles voltage amplification, two 12AU7 tubes drive the output stage, and four EL34 power tubes operate in a push-pull topology. Push-pull output stages improve efficiency and output capability by having pairs of tubes share amplification duties across opposite halves of the waveform, allowing the amplifier to deliver 45 watts per channel while maintaining the operating characteristics associated with EL34-based designs.

Ultra-linear operation and transformer design

The A35 operates in ultra-linear mode, a configuration that connects portions of the output transformer directly into the output stage to balance power output, linearity, and distortion performance. This operating mode has long been used in EL34 amplifiers because it provides greater output control while retaining the tonal characteristics associated with tube amplification.

Custom EI transformers use imported silicon steel cores and high-purity enameled copper windings. Vacuum impregnation and low-magnetostriction construction help suppress mechanical vibration and transformer-induced noise, contributing to quieter operation and improved long-term stability. These transformers form a critical part of the amplifier's power delivery and output stages, directly influencing channel consistency and overall electrical performance.

Integrated ESS DAC and Bluetooth connectivity

An ESS ES9018K2M DAC provides onboard digital decoding for modern music sources. The DAC's low-distortion architecture allows digital signals to be converted within the amplifier itself, eliminating the need for an external DAC in many systems while preserving a fully integrated signal chain.

Wireless playback is supported through Qualcomm Bluetooth 5.1 with SBC, AAC, aptX, and aptX HD codec compatibility. Support for higher-bandwidth codecs such as aptX HD allows compatible devices to transmit audio with greater data throughput than standard Bluetooth implementations, while Bluetooth 5.1 provides stable wireless connectivity for smartphones, tablets, and portable music players.

Protection systems and component selection

The amplifier incorporates a relay-based protection circuit that introduces a 60-second startup delay. This warm-up period allows the vacuum tubes to reach stable operating conditions before audio playback begins. Additional protection circuitry monitors for overload and short-circuit conditions to help protect both connected speakers and internal amplifier components.

Internally, the A35 uses audio-focused components including Japan-made filter capacitors selected for tube amplifier applications. A reinforced metal chassis, shock-resistant tube mounting structure, and gold-plated terminals further support long-term reliability while helping reduce the effects of vibration and electromagnetic interference during operation.

Availability

The xDuoo A35 is available now on Apos.