Aurorasound HFSA-02 Integrated Amplifier

Product Overview

This is a conventional integrated amplifier with an all-vacuum-tube design. The input stage uses a 12AX7, the phase-inverting stage uses a 12AU7, and the output stage features an EL34 push-pull configuration with a Lundahl output transformer, all UL-connected, delivering a total output of 31W + 31W.

The amplifier frame is made of 22 mm-thick solid maple, while the top plate is constructed from 4 mm-thick solid aluminum, creating a rigid, flex-free body structure. This construction firmly supports the heavyweight transformers and sensitive vacuum-tube components, enabling the amplifier to reproduce a solid, tight mid-low range and delicate high frequencies.

This carefully handcrafted, complete, and orthodox vacuum-tube amplifier not only meets the needs of today’s digital high-resolution era but also provides sufficient functionality and performance for analog playback. It has been designed and manufactured as a representative vacuum-tube amplifier that will remain timeless for decades and can be enjoyed for many years to come.

Features

Various Input Options

As a basic integrated amplifier, it is equipped with a selector switch and volume control for four RCA line inputs. Three options are available:

1. XLR balanced input ×1 + RCA ×3

2. Phono input (MM) + RCA ×3

3. RCA/XLR input ×1 for use as a power amplifier

The panel can be replaced to suit each option, so please choose in advance. Changes can also be made later. The input circuits for each option are solid-state.

Circuit

The input stage uses 12AX7 tubes in parallel, lowering the tube’s internal impedance and achieving low noise while increasing drive power to the next stage. The phase-inverting stage employs a Mullard-type 12AU7 for stable signal transfer to the final stage. The final stage uses EL34 tubes in an ultra-linear connection with a Lundahl output transformer, achieving high power with low distortion.

The EL34 tubes are self-biased, allowing them to be easily replaced with EL34s from other brands without any adjustments. A bias voltage checkpoint is provided next to the socket so that the EL34’s operating condition can be checked over time. By using a conventional circuit and standard vacuum tubes, stable operation and long-term maintainability are ensured.

Specification Parts

Resistors are selected from Vishay, PRP (USA), and TAKUMAN (Japan); film capacitors from WIMA (Germany); and electrolytic capacitors from TDK-EPCOS (Germany). These selections are based on quality and reliability.

The power transformer and choke transformer are custom-made in Japan by Aurora Sound, and the rectifier diodes are made by ROHM, offering very low noise and high voltage resistance. All terminals are carefully selected and feature high-quality, thick gold plating.