UESUGI U-BROS-17

Pre owned. In good condition. Shows some signs of wear. Original packaging not included.

Two units are available, both in similar cosmetic condition.

With 220V transformer.

The U-BROS-17 monaural power amplifier represents the evolution and refinement of the U-BROS-11 model. The amplifier’s design begins with a first stage consisting of ECC83/12AX7 valves connected in parallel, while the input and phase inversion stages use cathode-connected ECC82/12AU7 valves. The power stage employs EL34/6CA7 valves in a three-pole parallel push-pull configuration, carefully selected in matched pairs with identical current values after an extensive “aging” process using a dedicated machine developed by the Uesugi Research Laboratory, eliminating the need for a DC balance circuit.

Compared to the previous model, the parallel connection of the first-stage valves with ECC83/12AX7 and a 14 dB negative feedback (NFB) level improve the signal-to-noise ratio and overall amplifier stability. The output transformers are designed to maintain nearly constant primary inductance, ensuring stable characteristics even with slight variations between the two push-pull valves. The power supply section uses a high-inductance choke coil to provide clean and stable DC output, while the internal resistance of the power transformer and choke is minimized to keep the voltage steady across all channels.

The U-BROS-17 features two parallel inputs and supports bi-amp drive. The transformers, jointly developed by the Uesugi R&D Laboratory and Tamura Manufacturing Co., are built to reliability standards equivalent to those used in space satellites. The high-quality 1.6 mm thick iron chassis is handcrafted with rounded corners, polished welds, and a metallic finish that harmonizes with the hammer-tone transformer casing. Internal wiring is divided into separate blocks for the power supply, bias, and amplification stages, handcrafted by skilled artisans with extremely short paths between the first stage and the level control, without using shielded cables, ensuring maximum sonic integrity.

The U-BROS-17 uses American-made EL34/6CA7 valves (GE Corporation) with higher tolerance margins, allowing a rated output of 40 W, higher than the 30 W of the previous model. The four power valves in parallel push-pull are arranged asymmetrically relative to the output transformer, eliminating the slight blur typical of parallel push-pull systems. The result is a highly refined monaural amplifier that delivers extremely delicate, transparent, and detailed sound, reproducing every musical nuance with naturalness and precision.

Technical specifications:

• Type: monaural power amplifier
• Output stage: EL34/6CA7 valves (3-pole connection); parallel push-pull operation
• Input sensitivity: 1 V
• Input impedance: 100 kΩ
• Rated output: 40 W (continuous output)
• Output impedance: 4 Ω, 8 Ω, 16 Ω
• Frequency response: 20 Hz – 20 kHz (at any level control position)
• Distortion: ≤ 0.1%
• Damping factor: approx. 15
• Residual noise: ≤ 0.2 mV (8 Ω load without harmonic components)
• Maximum power consumption: approx. 140 W
• Dimensions (W × H × D): 435 × 232 × 175 mm
• Weight: approx. 22 kg