T+A Amplifiers

M 40 HV

Flagship mono power. Hybrid valve/transistor.

The M 40 HV is T+A's flagship power amplifier and the only hybrid design in the HV series. Its input stage uses an all-valve cascode circuit with 6SN7 vacuum tubes operating in Class A, feeding an HV J-FET voltage amplifier with triode characteristics, and finally a current amplifier stage with twenty ring emitter bipolar output transistors. The result is 550W into 8 ohms and 1,000W into 4 ohms from a single channel — with the first 60W in pure Class A. A damping factor exceeding 115, slew rate of 65 V/us, and 180,000 uF reservoir capacity ensure absolute authority over any loudspeaker. Two units required for stereo.

At a Glance

●550W/8 ohm, 1,000W/4 ohm mono

●6SN7 valve input stage (Class A)

●20 ring emitter output transistors

●Damping factor > 115

●Pure Class A up to 60W

●Made in Herford, Germany

Key Features

Hybrid Valve/Transistor Topology

All-valve 6SN7 cascode input stage in Class A, HV J-FET voltage amplifier with triode characteristics, and twenty ring emitter bipolar output transistors — the only hybrid design in the HV series.

550W / 1,000W Mono Power

550W RMS into 8 ohms, 1,000W into 4 ohms from a single dedicated channel. Pure Class A up to 60W, transitioning seamlessly to Class AB.

Damping Factor > 115

Significantly higher than any other HV amplifier, delivering iron-fisted grip and control over the most demanding loudspeaker loads.

180,000 uF Reservoir

50% more reservoir capacity than the A 3000 HV or PA 3100 HV, ensuring limitless current delivery on the most extreme dynamic peaks.

Technologies Inside

High Voltage Technology

Tube linearity. Transistor power.

T+A's HV amplifiers operate at dramatically higher voltages than conventional designs — up to 100V in preamplifiers and 360V in power amplifiers. This forces the audio signal to exercise less than 20% of each transistor's operating curve, staying in the most linear region. The result is tube-like linearity and naturalness with transistor power, bandwidth, and reliability — virtually no negative feedback required. Built entirely from discrete components with individually selected audio J-FET transistors, encapsulated gold-contact relays, and precision discrete resistor volume control.

Most solid-state amplifiers operate their transistors across a wide portion of their transfer characteristic, which introduces non-linearity that must be corrected with large amounts of negative feedback — a technique that reduces distortion on paper but can compress dynamics and add its own sonic signature. T+A's approach is fundamentally different: by raising the supply voltage to 360V in power amplifiers (compared to the typical 60–80V), the music signal uses only the most linear 20% of each transistor's operating curve — the region where a transistor behaves almost identically to a vacuum tube. This means negative feedback can be reduced to near-zero levels, preserving the signal's original dynamics, micro-detail, and spatial information. Every HV circuit is built from discrete components rather than integrated circuits: individually selected and matched audio-grade J-FET transistors, hermetically sealed gold-contact relays for signal switching, and a precision discrete resistor ladder for volume control that maintains perfect channel balance and signal purity at every level.

DASS Galvanic Isolation

Digital and analogue. Completely separated.

T+A's Digital-Analog Separation System uses ultra-fast Silicon Labs digital isolators to establish complete galvanic separation between digital and analogue device sections. Each domain has its own completely separate power supply and mains transformer section, preventing any digital noise from contaminating analogue signal paths.

In any device that combines digital processing with analogue audio — streamers, DACs, integrated amplifiers — the high-speed digital circuits generate electromagnetic noise that can couple into the sensitive analogue signal path through shared ground planes, power supply rails, and even physical proximity. Most manufacturers attempt to manage this with careful PCB layout and filtering, but some coupling is inevitable when digital and analogue circuits share a common electrical ground. T+A's DASS eliminates this problem at the most fundamental level: ultra-fast Silicon Labs digital isolators transfer the audio data across a galvanic barrier — there is literally no electrical connection between the digital and analogue sections. Each domain has its own dedicated mains transformer and completely independent power supply, meaning digital switching noise has no conductive path to reach the analogue circuitry. The digital isolators are fast enough to pass high-resolution audio data without introducing jitter or timing errors. The audible benefit is a lower noise floor and a blacker background, revealing low-level detail and spatial cues that would otherwise be masked by digital contamination.

HV Series

The absolute reference.

T+A's flagship amplifiers operate at dramatically higher voltages than conventional designs — up to 360V in power stages. This forces the audio signal into the most linear region of each transistor's operating curve, achieving tube-like naturalness with solid-state power and bandwidth. Fully discrete construction with individually selected J-FET transistors, gold-contact relay switching, and double-mono architecture. The pinnacle of T+A engineering.

Gallery

A closer look at the M 40 HV.

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For complete specifications and technical details, visit the official T+A website.