EF37A Mullard NOS NIB Low Noise Audio Pentode

One (1) Tube – Rare Vintage Mullard EF37A

A rare early production Mullard EF37A, preserved in its original old-type box with factory wrapping paper. The box was opened only for photography, the tube itself has never been used or tested.

Manufactured at the renowned Philips Eindhoven plant, with clearly visible etched factory codes confirming its authenticity.

Mullard designated the EF37A as a high-gain, high-impedance pentode designed for audio-frequency preamplifier stages. The electrode system features anti-microphonic construction, and the specially designed bifilar-wound heater reduces hum to negligible levels - a hallmark of Mullard’s precision engineering.

When configured in triode mode, the EF37A reveals an exceptionally refined and natural sound, combining remarkable transparency, lush harmonic richness, and a beautifully fluid midrange.

These early EF37A tubes are highly regarded for their low noise, smooth tonal balance, and musical expressiveness, making them an excellent choice for high-end preamplifiers, phono stages, and classic audio restorations.