Nuvistor

The nuvistor is a type of vacuum tube announced by RCA in 1959. Most nuvistors are basically thimble-shaped, but somewhat smaller than a thimble. Triodes and tetrodes were made, although tetrode nuvistors are rare. The tube is made entirely of metal and ceramic. Making nuvistors requires special equipment, since there is no intubation to pump gases out of the envelope. Instead, the entire structure is assembled, inserted into its metal envelope, sealed and processed in a large vacuum chamber with simple robotic devices.

Nuvistors are among the highest performing small signal receiving tubes. They feature excellent VHF and UHF performance plus low noise figures, and were widely used throughout the 1960s in televisions (beginning with RCA's "New Vista" line of color sets in 1961 with the CTC-11 chassis), radio equipment and high-fidelity equipment, primarily in RF sections. They competed with the solid state revolution, and along with GE's Compactron, probably held it at bay for a few years. RCA discontinued their use in television tuners for its product line in late 1971. One famous application was in the Ampex MR-70, a costly studio tape recorder whose entire electronics section was based on nuvistors. Another limited application of this tube pertained to studio grade microphones from that era, the AKG/Norelco C12a being a good example, which employed the 7586. It was also later determined that (with extensive modification) the nuvistor made a sufficient replacement for the obsolete Telefunken VF14 tube, which could be found in the famed Neumann U47 studio microphone.

Example Nuvistor types:

7586 - First one released, medium mu triode
7587 - Sharp cutoff tetrode
8056 - triode for low plate voltages
8058 - triode, with plate cap & grid on shell, for UHF performance
7895 - 7586 with higher mu
2CW4 - Same as type 6CW4, but with a 2.1 volt / 450 milliampere heater. Used in television receivers with series heater strings
6CW4 - high mu triode, most common one in consumer electronics
6DS4 - remote cutoff 6CW4
6DV4 - medium mu, intended as UHF oscillator, shell sometimes gold plated