RADFORD WOODSIDE MA50 RENAISSANCE

Pre owned. In fair condition. It shows several signs of wear, as visible in the photos. Supplied without the original packaging.

The Woodside MA50 Renaissance is a tube monoblock power amplifier developed as an evolution of the earlier Radford designs by John Widgery, who had previously managed the Radford factory and been responsible for the design of the output transformers used in the STA-25 series. The project is developed to overcome some of the limitations found in earlier Renaissance amplifiers, with particular attention to the power supply, circuitry, and load control.

The power supply adopts a fully regulated and decoupled configuration developed by American designer Arnold Weisenberg. A solid-state regulator limits interaction between the various circuit stages and reduces the internal impedance between them. The toroidal power transformer provides a current capacity approximately five times greater than the idle requirement and features three separate filament windings, respectively dedicated to the two pairs of output tubes and the driver stages. Total filtering capacitance reaches 750 µF at 450 V.

The input stage uses a directly coupled ECC811 tube with an active load based on a 12AX7 dual triode. This is followed by a 12AU7 configured as a cathode follower, a solution intended to reduce the Miller effect and maintain stable high-frequency performance. The signal is then fed to the phase splitter through a polypropylene capacitor.

The output stage employs two matched pairs of Tesla EL34 power pentodes in a parallel push-pull configuration operating in Class A. The circuit incorporates automatic biasing, eliminating the need for manual bias adjustment when the output tubes are replaced.

A specific feature of the design is the multi-section output transformer developed by John Widgery. Its secondary features a single pair of output taps designed for connection to loudspeakers within the impedance range typical of modern speaker systems, rather than the traditional multiple 4, 8, and 16-ohm taps. This configuration is combined with low internal impedance and a high damping factor, with the aim of improving control of the loudspeaker drivers at low frequencies.

The chassis features gold-finished side panels and side handles inspired by the Radford tradition. The handles facilitate handling of the amplifier and can also serve as supports during maintenance work on the underside of the chassis. The upper section is protected by a black perforated metal grille that leaves the tubes visible while promoting heat dissipation.

The internal layout separates the power transformer and printed circuit board from the output tubes and large output transformer. The transformers use solder terminals rather than flying leads, with silver conductors used for the connections. The tube sockets are not mounted directly to the circuit board, helping to limit the transfer of heat generated by the tubes to the solid-state components.

The chassis ventilation is designed to promote a chimney effect around the EL34 tubes. Air is drawn through openings in the base, passes through the ventilated areas around the tube sockets, and exits through the upper grille. The internal connections and circuitry are carefully assembled, with selected components and dedicated connections between the circuit board, tube sockets, and transformers.

The output section uses five-way binding posts for loudspeaker connections, while the circuit configuration and power supply are designed to provide stable operation. The amplifier architecture is intended to keep signal paths short and effectively separate the different electrical sections.

The Woodside MA50 Renaissance delivers a balanced and detailed presentation, with controlled low-frequency response and good intelligibility and separation even with complex musical programmes. The design also provides an articulate midrange and smooth high-frequency response, making it particularly suitable for use with electrostatic loudspeakers and high-sensitivity dynamic systems.

The Woodside MA50 Renaissance is therefore a tube monoblock power amplifier based on four EL34 tubes per channel in a parallel push-pull Class A configuration, featuring a regulated and decoupled power supply, specially designed transformers, automatic biasing, and a mechanical construction focused on vibration management, thermal dissipation, and circuit stability.

Technical specifications:

• Configuration: tube monoblock power amplifier; 4 × EL34 in the output stage
• Output power: 50 W continuous into 8 Ω at 1 kHz, THD ≤0.2%; 75 W continuous into 4 Ω at 1 kHz, THD ≤0.2%
• Dynamic headroom: 1.6 dB
• Peak output current: 15 A
• Frequency response: 8 Hz–56 kHz
• Input impedance: 100 kΩ
• Input sensitivity: 750 mV; equivalent voltage gain 28.5 dB
• Slew rate: 15 V/µs
• Power consumption: not specified
• Dimensions: 420 × 220 × 270 mm (W × H × D)
• Weight: approx. 15 kg