Tube socket

In both cases this allowed the tube's output circuitry to be isolated from the input (grid) circuit more effectively.

The earliest tubes, like the Deforest Spherical Audion[3] from c. 1911, used the typical light bulb Edison socket for the heater, and flying leads for the other elements.

Other tubes directly used flying leads for all of their contacts, like the Cunningham AudioTron from 1915,[4] or the Deforest Oscillion.

[5] Type C6A xenon thyratrons, used in servos for the U.S. Navy Stable Element Mark 6, had a mogul screw base and L-shaped stiff wires at the top for grid and anode connections.

[6] Mating connectors were machined pairs of brass blocks with clamping screws, attached to flying leads (free hanging).

Before alternating current (AC) line/mains-powered radios were developed, some four-pin tubes (in particular, the very common UX-201A ('01A)) had a bayonet pin on the side of a cylindrical base.

The socket used that pin for retaining the tube; insertion finished with a slight clockwise turn.

The wire leads from the tube were soldered into the pins, and the evacuation tip was protected inside the post.

[citation needed] Octal and miniature tubes are still in use in tube-type audio hi-fi and guitar amplifiers.

[16] The pin geometry was the same as for octal, but the pins were thinner (although they will fit into a standard octal socket, they wobble and do not make good contact), the base shell was made of aluminium, and the center hole had an electrical contact that also mechanically locked (hence "loctal") the tube in place.

The loctal tube's structure was supported directly by the connecting pins passing through the glass "button" base.

Loctal tubes had shorter connecting lengths between the socket pins and the internal elements than did their octal counterparts.

Keying by omitting a pin is also used in 8- (subminiature), 10-, and 12-pin (Compactron) tubes (a variant 10-pin form, "Noval+1", is basically a nine-pin socket with an added center contact).

The pinched-off air evacuation nub is at the top of the tube, giving it its distinctive appearance.

Miniature tubes were widely manufactured for military use during World War II,[20] and also used in consumer equipment.

[21] In June 1940 RCA released its battery-operated Model BP-10, the first superheterodyne receiver small enough to fit in a handbag or coat pocket.

[24] After the war miniature tubes continued to be manufactured for civilian use, regardless of any technical advantage, as they were cheaper than octals and loctals.

The B7G (or "small-button" or "heptal") seven-pin miniature tubes are smaller than Noval, with seven pins arranged at 45-degree spacing in a 9.53 mm (3/8th inch) diameter arc, the "missing" pin position being used to position the tube in its socket (unlike octal, loctal and rimlock sockets).

The nine-pin miniature Noval B9A base, sometimes called button 9-pin, B9-1, offered a useful reduction in physical size compared to previous common types, such as octal (especially important in TV receivers where space was limited), while also providing a sufficient number of connections (unlike B7G) to allow effectively unrestricted access to all the electrodes, even of relatively complex tubes such as double triodes and triode-hexodes.

This base type was used by many of the United States and most of the European tubes, e.g., 12AX7-ECC83, EF86 and EL84, produced commercially towards the end of the era before transistors largely displaced their use.

The Rimlock (B8A) base is an eight-pin design with a pin circle diameter close to Noval, and uses a nub on the side of the envelope to engage with a guide and retaining spring in the socket wall.

Early tubes with this base type typically had a metal skirt around the lower ~15mm of the envelope to match the socket wall, and this offered a degree of built-in screening, but these were fairly soon replaced by "skirtless" versions, which had a characteristic widening in the glass to compensate physically for the absence of the skirt.

Rose, Saltzberg and Burnside from RCA created the acorn tube by using far smaller electrodes, with radial short connections.

[26] A different approach was taken by the designers of the lighthouse tube, such as the octal-base 2C43,[27] which relied on using concentric cylindrical metal contacts in connections that minimized inductance, thus allowing a much higher frequency.

They could also be used in small-signal applications at lower frequencies, as in the Ampex MR-70, a costly studio tape recorder whose entire electronics section was based on nuvistors.

Some low-power reflex klystrons such as the 2K25 and 2K45 had small-diameter rigid coaxial outputs parallel to octal base pins.

Subminiature tubes with long wire leads, introduced in the 1950s, were often soldered directly to printed circuit boards.