Vacuum Tubes Good to Know Trivia

The OddMix Vacuum Tubes Replacement Substitutions Tables section has a wide variety of popular tube substitutions for rare antique, vintage, exotic, original, discontinued and collector's vacuum tubes, electron tubes, audio tubes and Fleming valves. It is quite possible that we have the tubes you need under a different substitute number.

Many of these thermionic vacuum devices were made by RCA, GE, Sylvania, Philco, Philips, Tungsram, Valvo and others to be used in radio receivers, transmitters, short wave sets, amateur ham radio, car radios, television sets, audio amplifiers, guitar amplifiers, instruments and special purpose circuits.

Good to know, helpful vacuum tube trivia:

These are mostly - but not always - correct (at least for US type numbered tubes);

1. - The first numeral indicates the rounded filament voltage.

2. - The fourth numeral indicates the number of used pins within a tube assembly.

Example: the 6BD11 compactron uses 11 pins - thus it can only be successfully substituted with another active 11 pin unit. Beware of substitute types that offer less active contacts than the original!

3. - All numeral tubes are high reliability and/or industrial types, are preferred substitutes (when available).

4. - MANY tubes were better made then their counterparts - as brand reputation for some - was more important than to "get rich quick"...

5. - Letters after the fouth numeral either indicate the enclosure type, or used to track the design changes. They do not change the pinout, thus useable for substitution. Example: 6AU6 and 6AU6A are the same tube structurally. Only some electrical parameters are "improved". 6L6 was the original steel enclosed beam power tube. A 6L6 GA, GB, etc. are all "coast reduced improvements", cheaper make that cost more, but work fine for substituting.

6. - It takes more time, money and effort to produce a better vacuum, but the result are - much better tube!

7. - The gain (S) of a vacuum tube is a function only of it's geometry. Factory design sets the tube's gain. 8. - Vacuum tubes may operate (properly) from a few volts anode supply to a few thousand volts.

9. - Elektrometer tubes are able to provide an input impedance of better than 1012 Ohms input impedance (resistance) with proper tube selection and careful circuit design.

10. - At the height of the tube era, major tube companies used to make - and brand - (legally) their "competition's" devices to fool (and defraud) the unsuspecting public. GE made a lot of RCA tubes and vice versa. So did the other tube makers...

11. - OddMix tubes are almost all old inventory originals, from a bygone era, thus they are excellent for antique radio and television restoration projects or for setting up a vacuum tube museum.

12. - Once OddMix inventory sells out, there is no plan to replace it - thus first come first serve, buy them before too late...

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