28 May PONENT-10. Class A Power Amplifier.

Many excellent home audio amplifier designs have been published over the past few years. However, some of these designs have become obsolete due to changes in component availability, and others are intended to provide power levels that exceed the requirements of a typical living room. Furthermore, most of these designs have tended to become more complex, adding too many, perhaps unnecessary, things. Under the circumstances it seemed worth considering how simple a design could be made which would provide adequate power output together with an above reproach standard of performance, and this study has resulted in the present design.

Class B amplifiers

The main advantage of class B amplifiers is that the power dissipation is very low and the overall power conversion efficiency is high. Unfortunately, there are also some disadvantages such as crossover distortion, excess current demand when the output signal increases, which causes excess heating, so protection circuits are necessary, increasing the complexity of the design, thus leaving being simple and economical to build.

Class A amplifiers

An alternative approach to the design of a power amplifier that combines good performance with simple construction, is to use the output transistors in a class A configuration. This avoids the problems of asymmetry in almost complementary circuits, thermal runaway in transient overloads , crossover distortion and signal-dependent variations in current demand in the power supply. However, it is less efficient than a class B circuit, and the output transistors must be mounted on large heat sinks.

Following our line of products based on monobloc aluminum chassis, we present a 10W class A amplifier, with a very simple design and low feedback. Totally handcrafted and based on a configuration from the 1970s, the transistors that best resembled that era have been selected. Includes an oversized power supply with filtering Mundorf capacitors. Ideal amplifier for use with high-sensitivity speakers or for near-field listening, such as in recording studios.

Technical Specifications
(measures at 230 VAC with a 8 Ω load)

• Input impedance: 50 kΩ
• Input sensitivity: 1.5V for maximum power
• Output power: 1 W @ 0,086% THD, 10 W @ 1,55% THD, 1 kHz, 8Ω
• Frequency response: 10 Hz – 200 kHz (–1 dB)
• Gain: 15.6 dB
• Power consumption: 100 W
• Fuse: Slow 2 A (230 VAC)
• Dimensions (W x D x H): 430 x 300 x 90 mm
• Weight: 25 Kg
• Warranty: 3 years