Introduction

The A-48S marks the fifth generation of Accuphase’s pure Class-A power amplifiers, marrying refined sonic elegance with increased drive capability. Its robust, monolithic chassis houses six parallel push-pull MOS-FET output devices per channel, delivering smooth, uncoloured power from 50 W into 8 Ω up to 400 W into 1 Ω—so you hear every nuance of your music, even at the lowest listening levels.

Design

Built around a zero-feedback, current-feedback topology, the A-48S employs an instrumentation-grade amplifier front end that drives a six-parallel MOS-FET output stage in pure Class A. A massive toroidal transformer feeds separate power rails for the amplification and metering circuits, while 68,000 µF of filtering capacitance per channel ensures rock-steady voltage under dynamic load. Dual large-scale analog meters and a front-panel gain selector (Max/–3 dB/–6 dB/–12 dB) put precise control and real-time monitoring at your fingertips.

Application

Ideal for both stereo and bi-amping configurations, the A-48S feeds any loudspeaker with authority and finesse. Dual speaker terminals per channel let you drive two sets of speakers or configure bridged/mono operation for up to 800 W into 2 Ω. Whether powering compact monitors or full-range towers, it excels at revealing transient detail, inner harmonics, and deep bass impact.

Technology Overview

• Class A MOS-FET Output Stage
  Six parallel push-pull MOS-FETs deliver linear power: 50 W/8 Ω, 100 W/4 Ω, 200 W/2 Ω, 400 W/1 Ω—without transitioning out of Class A.
• Current-Feedback Amplification
  Enables wide bandwidth, minimal phase shift, and stable operation into challenging speaker loads.
• Balanced Remote Sensing
  Maintains perfect voltage at the speaker terminals by sensing and compensating for cable losses.
• MCS+ Circuitry
  Improves open-loop gain and distortion characteristics by cascading MOS-FET stages in a discrete topology.
• Protection & Monitoring
  Speaker outputs are protected by MOS-FET switching, and large analog meters display instantaneous output power with high visibility.

Key Features

• Pure Class A operation with six parallel push-pull MOS-FETs per channel
• Wide, linear power delivery: 50 W → 400 W across loads from 8 Ω to 1 Ω
• Instrumentation-grade front end and current-feedback loop
• Separate power supplies for amplification and metering circuits
• 68,000 μF filtering capacitors per channel for stable voltage under dynamic peaks
• Damping factor of 1,000 for tight bass control
• Dual speaker terminals per channel for bi-amping or bridged mono
• Front-panel gain selector with four range settings
• Large analog power meters with selectable sensitivity
• MOS-FET-based protection circuitry for reliable operation