For his first series-produced microphone, the U47, Georg Neumann used the Telefunken VF14 universal current tube in order to keep the circuitry as small as possible. However, due to large parameter fluctuations and poor noise values, he demanded a strict re-selection of the tubes already manufactured (radio receivers were manufactured with the remainder, as before). The product, the VF14K / VF14M, is today one of the most expensive and sought-after spare parts on the audio market. Due to the special way the U47/U48 microphones work, they cannot easily be replaced by modern tubes. At the same time, the few VF14 tubes offered at horrendous prices are also subject to extreme quality fluctuations for tubes due to the production conditions and often come from dubious suppliers.

As a solution Telefunken Elektroakustik offers a new version of the Telefunken VF14K replacement tube, which uses the old steel tube case including the same base as the historical tubes. Inside this reissue, however, is a modern pentode from the broadcast range, which has been carefully selected by Telefunken with regard to the sound characteristics of the original tubes. The new VF14K replaces, without any adjustments, the old tube types, but delivers the same amplification and overtone behaviour as the original.