Compactron

12AE10 Compactron tube (a dual pentode), made by GE

Compactrons are a type of thermionic valve, or vacuum tube, which contain arrangements of diodes, triodes, or pentodes in multiple combination arrays, as well as high or low-voltage and power types.

History

The Compactron is a 12-pin Duodecar base vacuum tube family introduced in 1961 by General Electric in Owensboro, Kentucky ^[1] to compete with transistorized electronics during the solid state transition.^[2] Television sets were a primary application.

Use was prevalent in televisions because transistors were slow to achieve the high power and frequency capabilities needed particularly in color television sets. The first portable color television, the General Electric Porta-Color, was designed using 13 tubes, 10 of which were Compactrons.

Compactron's integrated valve design helped lower power consumption and heat generation (they were to tubes what integrated circuits were to transistors). Compactrons were also used in a few high end Hi-Fi stereos.^[2] They were also used by the Ampeg guitar amplifier company in some of their guitar amps. No modern tube based Hi-Fi systems are known to use this tube type, as simpler and more readily available tubes have again filled this niche.

Notable features

The evacuation tip is in the center of the circular pin pattern.

A distinguishing feature of most Compactrons is the placement of the evacuation tip on the bottom end, rather than the top end as was customary with "miniature" tubes, and a characteristic 3/4" diameter circle pin pattern.

• Most Compactrons ranged in glass envelope diameter from 1 ¹⁄₈" to 2 ³⁄₄" depending upon the internal configuration. Variations of the Compactron design were made by Sylvania and by some Japanese firms.

Examples

Examples of Compactrons type types include:

• 6AG11 high-mu twin triode
• 6BK11 triple triode
• 6C10 high-mu triple triode by Sylvania, etc.... not related to the Edison Swan (later Mazda) 6C10 triode-hexode
• 6M11 twin triode - pentode
• 6K11 triple triode
• 6LF6 beam power tetrode with anode cap
• 8B10 twin triode - twin diode
• 12AE10 twin pentode
• 38HK7 pentode diode

Due to their specific applications in television circuits, many different Compactron types were produced. Almost all were assigned using standard US tube numbers.

Technological obsolescence

Integrated circuits (of the analogue and digital type) gradually took over all of the functions that the Compactron was designed for. "Hybrid" television sets produced in the early to mid-1970s made use of a combination of tubes (typically Compactrons), transistors, and integrated circuits in the same set. By the mid-1980s this type of tube was functionally obsolete. Compactrons simply don't exist in any TV sets designed after 1986. Other specialist uses of the tube declined in parallel with the television set manufacture. Manufacture of Compactrons ceased in the early 1990s. New old stock replacements for almost all Compactron types produced are easily found for sale on the Internet.

Of note, in the 1960s, the 6BK11 Triple Triode Compactron tube was used by the Ampeg amplifier company in some of their guitar amps. Ampeg is the only guitar amp manufacturer that used this tube in their amps. The 6BK11 is in increasingly short supply today as an NOS replacement for stock tubes. NOS tubes are very important in guitar amps because they keep the amp performing as it was designed, which means it will produce the desired tone. There is a whole "cottage industry" that exists in producing vacuum tubes that are replacements for stock guitar amp tubes. The cottage industry exists because class A, open-ended, hand-wired, tube-driven guitar amps have a warm sound that is preferred by many musicians.^[3] The warmer sound of older amps means they command a premium resale value on the open market, and so in turn, any parts in the amp that may wear out over time or with use (including the vacuum tubes), also command similar values. The 6BK11 is a good example of this.

References

Notes