Heritage H47 Microphone

The defining elements of the H47 are its M7 capsule, the selected vacuum tube, and the BV08 transformer.

The M7 enables switching between different polar patterns – cardioid, omnidirectional, and figure-eight. While modern microphones often use RK-47 capsules, we have remained faithful to the original M7 design to preserve the authentic sound signature.

Elite musicians and studios will surely be impressed by the fact that our H47 can be crafted with 3 options:

1. Classic vintage version – one can switch between the cardioid and omnidirectional pattern with a switch on the grille.
2. Pragmatic version – the microphone is set to a cardioid in a standard position. When one turns the microphone upside down, it automatically and silently switches to an omnidirectional position with no need for a switch.
3. Expanded pattern version – appreciated by producers and music masters, this version allows all polar patterns to be controlled from the power supply, from the cardioid to the omnidirectional setting and all points in between with a smooth potentiometer.

In addition, an exclusive component is the BV08 transformer, carefully matched to the impedance of our selected tube. Since replacing the Telefunken VF14 requires recalculating the transformer’s windings, we’ve ensured that the BV08 retains the original impedance characteristics, delivering a smooth and balanced tone.

The result? A microphone with exceptionally low self-noise, a frequency response reminiscent of the world’s greatest studio legends, and a distinctive character that brings warmth, depth, and authenticity to any recording.

Historical Overview

After World War II, as broadcasting and studio technology rapidly developed, there was a growing demand for new types of microphones. Before the war (in Berlin) and during the war (in Gefell), Neumann was already known for producing high-quality microphones, often referred to as “bottle” microphones.

At the time, Germany’s power grid was in poor condition—some areas had AC voltage, others had DC, both at 110V. Interestingly, this was an advantage because vacuum tubes of the era, with double-spiral filaments, typically operated at 55V. By wiring them in series, transformers weren’t needed. This unique voltage situation played a key role in the development of the legendary U47 microphone, which operated using a single 105V DC power supply. This voltage powered the metal pentode Telefunken VF14, providing both plate voltage and capsule polarization. The carefully designed circuit allowed users to switch between directional patterns—cardioid and omnidirectional, or cardioid and figure-eight (U48).

The pentode was chosen for its compact size and optimal filament voltage of 55V at 50mA. It was used in a triode configuration and operated at only about 65% of its rated specifications, making it possible to power the microphone with batteries. Unfortunately, after about a decade, production of the VF14 at Telefunken ceased. Attempts to recreate it in a glass version in Ulm were unsuccessful.

Finding a Replacement for the Telefunken VF14

When these tubes became unavailable, finding a suitable replacement was a challenge. During Georg Neumann’s lifetime, the nuvistor was considered as an alternative. This miniature vacuum tube, developed alongside the first transistors, had great potential but was quickly overshadowed by the rise of solid-state technology. While nuvistors were used in early American color televisions, they weren’t specifically designed for audio applications and often suffered from excessive noise and microphony.

Through extensive research and testing, we identified a unique vacuum tube as a worthy alternative to the legendary Telefunken AC701 and Japan’s 6D-H3. Like these historic tubes, the one used in the H49 and H47 features a special internal structure. It was designed specifically for high-fidelity audio applications, with reinforced electrodes to prevent resonance, grid leakage, and unwanted internal noise.

Many engineers attempting to replicate the Telefunken U47 have experimented with nuvistors (13CW4 or later 8393) or tubes like UF14, EF14, EF12, EF42, EF80, and EF800. However, these pentodes were originally designed for industrial rather than audio applications. They typically exhibit higher internal noise and different operating points, making them less suitable for high-end microphone design.

In a true condenser tube microphone, the capsule, tube, and transformer form an interdependent triad. Changing just one of these components can drastically alter the microphone’s sound.

We consider the Telefunken AC701 a benchmark when developing similar tubes. Alongside Hiller tubes, it was one of the very few vacuum tubes explicitly developed for microphone applications. This inspired our selected vacuum tube, now used in both the H47 and H49 microphones.

With reinforced electrodes that resist resonance and microphony, our tube delivers exceptional low-frequency stability and a clean, natural sound.