Diagram of Vacuum-Tube DiodeDiagram of Vacuum-Tube TriodeInside of a vacuum tube with plate cut open.A two-tube homemade radio from 1958. The tubes are the two glass columns with the dark tops. The leads at the bottom connect to the low-voltage filament supply and to the high-voltage anode supplyAn RCA 12AX7 dual-triode tube (1947)

Discover great deals on the many top brand items available only on eBay!


This site contains sponsored affiliate links.

Tubes

In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. more...

HomeHome
Accessories & CablesAccessories & Cables
AmplifiersAmplifiers
CD Players & RecordersCD Players & Recorders
Cassette DecksCassette Decks
CrossoversCrossovers
DVD Players & Recorders DVD Players & Recorders
Digital Music...Digital Music...
Digital Video Recorders, PVRDigital Video Recorders, PVR
EqualizersEqualizers
Headphones, HeadsetsHeadphones, Headsets
Home Audio MiscHome Audio Misc
Home Theater ProjectorsHome Theater Projectors
Home Theater in a Box Home Theater in a Box
KaraokeKaraoke
MiniDisc PlayersMiniDisc Players
OtherOther
PreamplifiersPreamplifiers
ProcessorsProcessors
RadiosRadios
ReceiversReceivers
Remote ControlsRemote Controls
Satellite Radio Satellite Radio
Satellite, Cable TVSatellite, Cable TV
Shelf, Compact SystemsShelf, Compact Systems
Speakers & SubwoofersSpeakers & Subwoofers
Televisions TVTelevisions TV
Tuners, AM/FMTuners, AM/FM
TurntablesTurntables
VCRsVCRs
Vintage ElectronicsVintage Electronics
8-Track Players8-Track Players
Amplifiers, Tube AmpsAmplifiers, Tube Amps
Books, Manuals, MagazinesBooks, Manuals, Magazines
CapacitorsCapacitors
Cassette DecksCassette Decks
Drivers & HornsDrivers & Horns
Other VintageOther Vintage
Preamplifiers, Tube PreampsPreamplifiers, Tube Preamps
RadiosRadios
ReceiversReceivers
Reel-to-Reel Tape RecordersReel-to-Reel Tape Recorders
SpeakersSpeakers
TelephonesTelephones
TelevisionsTelevisions
TransformersTransformers
TubesTubes
NOS TubesNOS Tubes
Other TubesOther Tubes
Tube SocketsTube Sockets
Vacuum TubesVacuum Tubes
General ElectricGeneral Electric
MullardMullard
Other BrandsOther Brands
RCARCA
SylvaniaSylvania
Western ElectricWestern Electric
Tuners, Tube TunersTuners, Tube Tuners
TurntablesTurntables
Wholesale LotsWholesale Lots

Once used in most electronic devices, vacuum tubes are now used only in specialized applications. For most purposes, the vacuum tube has been replaced by the much smaller and less expensive transistor, either as a discrete device or in an integrated circuit. At the start of the 21st century there has been renewed interest in the vacuum tube, this time in the form of the Field-emitter microtube.

Operation

Vacuum tubes, or thermionic valves, are arrangements of electrodes in a vacuum within an insulating, temperature-resistant envelope. Although the envelope was classically glass, power tubes often use ceramic and metal. The electrodes were attached to leads which passed through the envelope in a way that was sealed air tight. On most tubes, the leads were designed to plug into tube sockets for easy replacement.

The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air. When hot, the filament releases electrons into the vacuum: a process called thermionic emission. The resulting negatively-charged cloud of electrons is called a space charge. These electrons will be drawn to a metal plate inside the envelope if the plate (also called the anode) is positively charged relative to the filament (or cathode). This results in a current of electrons flowing from filament to plate. This cannot work in the reverse direction because the plate is not heated and cannot emit electrons. This very simple example described can thus be seen to operate as a diode: a device that conducts current only in one direction.

Development

John Ambrose Fleming, scientific adviser to the Marconi company invented the diode in 1904 based on an observation by Thomas Edison (Edison received U.S. Patent 307031 from this observation). The unidirectional current and construction of the original diode led to Lee DeForest placing another electrode, a bent wire or screen, between the filament and plate electrode in 1906. DeForest discovered that the current flow from filament to plate depended on the voltage applied to the grid, and that the current drawn by the grid was very low, being composed of the electrons which are intercepted by the grid. As the applied voltage of the grid varied from negative to positive, the current of electrons flowing from the filament to the plate would vary accordingly. Thus the grid was said to electrostatically "control" the plate current. The resulting three-electrode device was therefore an excellent and very sensitive amplifier of voltages. DeForest called his invention the audion, but it is better known as a triode. The tube equivalent of a transistor, triodes were used in early tube amplifiers.

Read more at Wikipedia.org


[List your site here Free!]

Qty=4 Nos Rca 12Au6 Vacuum tubesQty=4 Nos Rca 12Au6 Vacuum tubes $15.00 New ListingVintage Tubes - VarietyNew ListingVintage Tubes - Variety $349.00
Pair 102L Western Electric Audio Tubes Both test v strong w same date GuaranteedPair 102L Western Electric Audio Tubes Both test v strong w same date Guaranteed $349.00 New ListingPair Burroughs Ultronic B7971 Nixie TubesNew ListingPair Burroughs Ultronic B7971 Nixie Tubes $289.99
New ListingElectronic Vacuum Tubes Lot Of 51 (Mixed Rca And Ge)New ListingElectronic Vacuum Tubes Lot Of 51 (Mixed Rca And Ge) $60.00 4 x Tesla El83 Tubes4 x Tesla El83 Tubes $30.00
Matched Pair Tung Sol 12Ax7 / Ecc83 pre-amp tubes, Brand New in Box !Matched Pair Tung Sol 12Ax7 / Ecc83 pre-amp tubes, Brand New in Box ! $49.95 U.S. Manufactured Western Electric 300B triode Pair. New in Box and never usedU.S. Manufactured Western Electric 300B triode Pair. New in Box and never used $570.00
New ListingLot of 69 Transmitter TubesNew ListingLot of 69 Transmitter Tubes $99.00 New Listing6 Vintage Electric Radio & Television Electron Tube W/ Boxes - Mixed LotNew Listing6 Vintage Electric Radio & Television Electron Tube W/ Boxes - Mixed Lot $0.99
New ListingWestern Electric 396A Tube UsedNew ListingWestern Electric 396A Tube Used $49.50 New ListingLot Telefunken Tube Valve Valvola RÖHre Lampe Valvula Valvula 350 Pc Some SealedNew ListingLot Telefunken Tube Valve Valvola RÖHre Lampe Valvula Valvula 350 Pc Some Sealed $500.00
New Gain Matched Quintet (5) Jj Electronics Tesla 12Ax7 Ecc83-S Vacuum TubesNew Gain Matched Quintet (5) Jj Electronics Tesla 12Ax7 Ecc83-S Vacuum Tubes $98.12 8 pcs Matched Set x 6P14P Ussr vintage tubes ~ El84 /6Bq5 Ussr Tube8 pcs Matched Set x 6P14P Ussr vintage tubes ~ El84 /6Bq5 Ussr Tube $22.00
Qty 25 - Empty White Vacuum Tube Boxes - Kt88 6550 2A3 807 & SimilarQty 25 - Empty White Vacuum Tube Boxes - Kt88 6550 2A3 807 & Similar $29.95 New ListingTelefunken Ribbed Plate 12Ax7 Tube plus a Siemens 12Ax7 Tube -Tested and matchedNew ListingTelefunken Ribbed Plate 12Ax7 Tube plus a Siemens 12Ax7 Tube -Tested and matched $120.00
New Listing10 Vacuum tubes Philco Raytheon pulled from radio setNew Listing10 Vacuum tubes Philco Raytheon pulled from radio set $29.00 New Qty 2 Sylvania 5R4Gyb Usa Matched Pair Side O Getter Black Plates Nos TubesNew Qty 2 Sylvania 5R4Gyb Usa Matched Pair Side O Getter Black Plates Nos Tubes $63.36
New ListingLot Of Vintage Vacuum Tubes - New Old Stock In Boxes - Lot Of 80 Tubes!New ListingLot Of Vintage Vacuum Tubes - New Old Stock In Boxes - Lot Of 80 Tubes! $27.50 Ken-Rad Rca Sylvania 1629 Vt-138 Vintage Magic Eye Tube (Nos, many available)Ken-Rad Rca Sylvania 1629 Vt-138 Vintage Magic Eye Tube (Nos, many available) $20.00
New ListingVt-52 Western Electric Audio Output TubeNew ListingVt-52 Western Electric Audio Output Tube $399.00 1 Nos Nib Toyo 6E5 Eye Tube Vt-215 Tested Super Bright Volume Prices 120 day Wty1 Nos Nib Toyo 6E5 Eye Tube Vt-215 Tested Super Bright Volume Prices 120 day Wty $28.89
New ListingKt88 6550 Ars Audio Research Matched Pair Tubes Tested Leslie SpeakerNew ListingKt88 6550 Ars Audio Research Matched Pair Tubes Tested Leslie Speaker $120.00 New MatchEd Quad Electro Harmonix El34 Eh tubes valves El34EhNew MatchEd Quad Electro Harmonix El34 Eh tubes valves El34Eh $119.99
Ge Jan 6829 Vacuum Tubes - Vintage Twin Triodes for Audio Amps & PreAmpsGe Jan 6829 Vacuum Tubes - Vintage Twin Triodes for Audio Amps & PreAmps $9.99 1 x Ez40 Valvo / Philips (La Radiotechnique) - Nos1 x Ez40 Valvo / Philips (La Radiotechnique) - Nos $35.00
New Listing4 x Tubes " Tungsram Kl1 " New.New Listing4 x Tubes " Tungsram Kl1 " New. $52.00 5814A Ecc82 Toshiba triple mica "O" Getter made in Japan Ampltrex tested At10005814A Ecc82 Toshiba triple mica "O" Getter made in Japan Ampltrex tested At1000 $300.00
New Listing5 Pcs Nos Ge Jan 6Ah6Wa audio radio Preamp Tubes new from factory case!New Listing5 Pcs Nos Ge Jan 6Ah6Wa audio radio Preamp Tubes new from factory case! $24.95 New 2x Mullard El84 / 6Bq5 | Matched Pair / Duet / Two | Power Tubes | Free ShipNew 2x Mullard El84 / 6Bq5 | Matched Pair / Duet / Two | Power Tubes | Free Ship $59.99
Rca Dr2000 dr 2000 Numitron Tube lot of 6 Tested goodRca Dr2000 dr 2000 Numitron Tube lot of 6 Tested good $70.00 New 4x Jj El84 / 6Bq5 | Matched Quad / Quartet / Four | Power Tubes | Free ShipNew 4x Jj El84 / 6Bq5 | Matched Quad / Quartet / Four | Power Tubes | Free Ship $74.99
1 Nos 1960 Tung-Sol 5687 17.5mm Black Plate Pair D-Getter Ring for Audio Note1 Nos 1960 Tung-Sol 5687 17.5mm Black Plate Pair D-Getter Ring for Audio Note $79.00 Pair Nos Nib We Western Electric Jw359A Sub-Miniature Vacuum Tubes (Many Avail)Pair Nos Nib We Western Electric Jw359A Sub-Miniature Vacuum Tubes (Many Avail) $25.00
Lot Of 4:958A Vt-212 Acorn Vacuum Tubes 1944 Vintage Military Grade Triodes JozLot Of 4:958A Vt-212 Acorn Vacuum Tubes 1944 Vintage Military Grade Triodes Joz $20.00 New ListingTested Mixed Lot of 16 Vintage Electron Vacuum Tv/Radio Tubes, Tested, Lot # 1New ListingTested Mixed Lot of 16 Vintage Electron Vacuum Tv/Radio Tubes, Tested, Lot # 1 $89.99
Lot Of 2:unopened Varian Eimac Jan8245 Tedrode Electron Tube 4Cx250K 8245 500Lot Of 2:unopened Varian Eimac Jan8245 Tedrode Electron Tube 4Cx250K 8245 500 $65.00 New ListingTwo Vintage Rca 12Au7A Vacuum TubesNew ListingTwo Vintage Rca 12Au7A Vacuum Tubes $100.00
General Electric Ge 12At7 Vintage TubeGeneral Electric Ge 12At7 Vintage Tube $10.88 Matched Pair Black Plate Sylvania Military 6005, 6Aq5W, 6095 Audio Output TubesMatched Pair Black Plate Sylvania Military 6005, 6Aq5W, 6095 Audio Output Tubes $15.99
Pair 6L6Gc Sovtek Russia Tubes Brand New From Factory Case Multiple AvailablePair 6L6Gc Sovtek Russia Tubes Brand New From Factory Case Multiple Available $25.00 $20.00
Sylvania Silvertone 1482 Amp Tubes Set 6V6Gt 6X4 6Au6 12Ax7 (x2) -Used Test NosSylvania Silvertone 1482 Amp Tubes Set 6V6Gt 6X4 6Au6 12Ax7 (x2) -Used Test Nos $99.95 Matched Pair Mullard 12Ax7 tubes, Brand New in Box !Matched Pair Mullard 12Ax7 tubes, Brand New in Box ! $49.95
Nos Match Quad *D* Getters 5 Star 6201 Ecc81 12At7 3 Mica Tubes Usa Made 1950'SNos Match Quad *D* Getters 5 Star 6201 Ecc81 12At7 3 Mica Tubes Usa Made 1950'S $110.90 4 x Reflector 6E6P-E Tubes4 x Reflector 6E6P-E Tubes $20.00
Vintage 1962/1963 Nos Rca Clear Top 12Au7A Platinum Grade Brand New Preamp TubesVintage 1962/1963 Nos Rca Clear Top 12Au7A Platinum Grade Brand New Preamp Tubes $29.95 Pair of Nos Groove Tube Gt-12Au7A / 12Au7 Audio Vacuum Tubes (Many Available)Pair of Nos Groove Tube Gt-12Au7A / 12Au7 Audio Vacuum Tubes (Many Available) $19.55
Jj El84 Power Tubes - Matched PairJj El84 Power Tubes - Matched Pair $38.90 (1) Electron Tube Ge Jan 5670w Twin Triode Vacuum tubes. Nos(1) Electron Tube Ge Jan 5670w Twin Triode Vacuum tubes. Nos $12.00
Vintage Radio Tube Set - 100% Tested Good 5 Piece Set Vacuum Tubes- Test StrongVintage Radio Tube Set - 100% Tested Good 5 Piece Set Vacuum Tubes- Test Strong $23.50 New ListingNos Pair Rca 6681/12Ax7A TubesNew ListingNos Pair Rca 6681/12Ax7A Tubes $129.00
Pm El34 6Ca7 Vintage TubePm El34 6Ca7 Vintage Tube $49.99 New ListingExcellent! 1959 Matched Pair Webcor / Mullard El84 6Bq5 Code rX1 R9E TubesNew ListingExcellent! 1959 Matched Pair Webcor / Mullard El84 6Bq5 Code rX1 R9E Tubes $79.99
Click to see more Tubes items at www.ebay.com
Prices current as of last update, 05/31/25 5:20pm.

See also...
NOS Tubes, Tubes, Vintage Electronics
Other Tubes, Tubes, Vintage Electronics
Tube Sockets, Tubes, Vintage Electronics
Vacuum Tubes, Tubes, Vintage Electronics

Home Contact Resources Exchange Links ebay