Vacuum tubes: Radio tubes, TV tubes, Audio tubes

Are tubes used in radio or TV different from audio tubes used in power amps and preamps?
If they are different (i.e., if tubes used in radios and TVs are different from tubes used in amp/preamps) what are the use of radio and TV tubes?
I don't see any people caring about tube radios and tube TVs as they care about tube amps, but I see a bunch of ads in eBay for selling radio/TV tubes, and just wonder.

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Many of the tubes from radio and TV are used in audio components. Designers through experimentation found these tubes had the pleasant qualities needed to play music. There are so many TV tubes that became the central design of high-end audio circuits.
In the days of tube designed FM radio and TV, there were millions of tubes manufactured to service these components. Now, in modern times these original tubes are coveted due to the small supply of NOS tubes that test well.
NIB (new in box) is what every audiophile wants. It means the tube was originally manufactured in a specialized factory with date codes and has never been used.
NOS (new old stock) is the next gem quality tube. It is an original period tube, but it’s use or non-use can’t be verified. The tube is tested to see if it measures as new. This is why a trustworthy dealer is important.

Re; radio tubes on Ebay. There are still vintage FM radios in collectors and audiophile's homes. Not to mention Ham radio operators and collectors. They need these tubes to keep their gear up and running.

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The best vintage tubes were designed for military, they are the highest quality (normally more expensive). So besides radio and tv there are critical military equipment that demands the highest quality tubes, stable, durable etc. I have some NOS japanese tubes from the 70’s, marketed as audio tubes especially for hi-fi audio, the manufacturer guarantee they are low microphonic and low noise (for example NEC 6BQ5 Hi-Fi Green series). As you know there is an amps in TV and Radiolas, so these tubes are audio tubes (fine for your modern high-end amps and phono stages, depends on the type of the tube).
And Russia will be manufacturing tubes for a long time since their military electronics still use tube circuits.
To add to the good comments above, during the many decades in which tube-based radios and TVs were produced countless different tube types came into existence, and were used in countless different radios and TVs. A small fraction of those tube types, but still a significant number of them, are used in today’s high quality audio components.

That tends to be most true in the case of small signal tubes, that are used in preamps and other line-level components. But a number of power tubes that had been used in certain radios are still used in high quality audio power amplifiers. Examples being the types 45 and 2A3, which were used in high end radios of the early to mid 1930s, and the 6L6 which was used in certain radios starting a few years later. Some of those radios, produced by manufacturers such as E. H. Scott (no relation to the hifi manufacturer H. H. Scott, who came later), McMurdo Silver, and Zenith, were quite elaborate and could be considered to be precursors of modern hifi systems.

In many cases the ads you may see offering large quantities of radio and TV tubes come from tube stocks that had belonged to retired or deceased radio and TV service people. Typically most of those tubes would mainly be of interest to antique radio collectors, while a relatively small fraction of them would be of the types that are still used in today’s audio components.

-- Al

Examples being the types 45 and 2A3, which were used in high end radios of the early to mid 1930s

I just mentioned those the other day in another thread here. Emission LAB in Czech Republic still produce those 45s and 2A3 and they are probably the best available today. 

Typically most of those tubes would mainly be of interest to antique radio collectors, while a relatively small fraction of them would be of the types that are still used in today’s audio components.

OK. That's what I wanted to know about. 
Thanks for for replies.
I've read that tubes won't be destroyed in a nuclear bomb electromagnetic pulse so there's some comfort in that (and supposedly why they were used in jets), and there's nothing like watching original Twilight Zone episodes on a small screen black and white's warmer...more even harmonics...
A tube is a tube from the simplest diode to the most complex multi element combination tube used in TV's.  Since its first inception in the early 1900's two element diode used to detect radio signals (via Morse code in ships), to the three element Audion (triode) used for signal and sound amplification to the latest tubes manufactured, the theory of tube technology has not changed much. Early radio brought us the triodes WD11's, WD12's and 01A's used in battery sets in the early 1920's.  Later sets used the 80 rectifier and 71A triodes in early AC sets from the late 1920's.  The early 1930's brought us the 2A3 triode output tubes in Stromberg Carlson consoles capable of an amazing 8 watts of power in push pull configuration.  Western Electric brought us the 300B first used in long line telephone amplification and used in early movie theaters amplifiers before Altec. The mid-late 1930's bought out the first power pentode multi element tube (with cathodes enveloping the filament) as the 6L6 (and derivatives 6V6, 6K6) tubes and when used in quad sets could put out 15-18 watts with THD distortion levels less that 2%.  The famous E.H. Scott, McMurdo and Lincoln long wave, standard broadcast and short wave radio receivers (many with thirty tube dual chassis and Jensen or Electrovoice multi array speakers including tweeters)  plus the high end receivers from Zenith (Stratosphere) and Philco were truly near or at high fidelity without being advertised as such.  Early FM on the now defunct 42-50 mHz band also required near high fidelity to bring out the true beauty of noiseless radio.  WW2 brought a stop to FM and early experimental TV but after the war technology and the use of multi element and specialty tubes was needed for both the high frequencies required (up to 300 mHz) in TV tuners and IF circuits.  
The big difference in tubes is in their application.  TV's and high frequencies require a different tubes than those in audio frequencies.  Originally most radios and TV's used tubes with 6 volt filaments powered by a power transformer. Later radios and then TV's used various filament voltages and when used in series would add up to 115 volts AC line voltage to save the expense of a power transformer. An example would be a five tube superhet AM radio (millions made) that used a 35W4, 50C5, and three 12 volt filament tube in series (combined total of 111 volts) so that the filaments could be run directly by 115 volt AC line voltage without the use of an expensive power transformer.  For Hi Fi the first digits indicate the filament voltage (6CA7 6 volt filament, 12AX7 12 volt filament).  
Since most radios and then TV's went solid state in the late 1960's and most of these earlier tube sets are obsolete there is little call for the tubes needed in these sets except for restoration. The most popular tubes are those for early Hi Fi from the 1950's on up and new amps using tubes.  The most popular numbers are the 6CA7 power pentode (Dynaco and others), 12AX7 (dual hi mu triode all), 12AU7 (dual medium mu triode all) 7195 power pentode (Fisher, Scott), KT88, 6550 (all) and others.  
There were literally over 1000 tube types listed in the RCA Receiving Tube catalog of the mid 1960's.  Except for the types needed for Hi Fi they have become obsolete and have little value since most of the sets that required them are no longer around.  
If shopping for replacement tubes try to find NOS RCA, GE, Sylvania, Westinghouse, Raytheon, Tungsol or other American brands.  JAN tubes (Joint Army/Navy) tubes are also of high quality since the specs were often higher than those of the consumer market.  They were made under contract by the above manufacturers mostly GE and Westinghouse.  If you go used make sure that the tube has been check on a good Hickock (not Hitchcock) tube analyzer and get the readouts to make sure that they have at least 85% of their rating when new.  Beware if some on E bay and when you find a good vendor with a high rating, stick with them.  Another good source for used tubes is a local radio/Ham club.  They generally have meetings a few times a year with flea markets and most collectors have overlapping interests which include Hi FI.  I would trust this group the most way over E bay for honesty and reasonable prices. Hopefully this answers your questions about tubes and sorry about getting so wordy.  In response to an earlier answer. I do enjoy watching Twilight Zone, Alfred Hitchcock Presents and Leave it to Beaver episodes on my restored 1948 32 tube DuMont "Meadowbrook" console TV with 12" B/W screen and 12" speaker.

Succinct history lesson on the audio vacuum tube with some good advise thrown in for good measure Steve, well done.
I’ll take all the tubes from the early 40s and early 50s. You guys can fight over the rest of them.
I have never thought the extra $ brought by JAN (military) tubes was justified. A tubes ability to withstand shock and vibration has nothing to do with how this tube will sound. Further many military tubes are the same internally as their civilian counterparts just (supposedly) tested to the shock and vibration standard by the mfgr. for military use. 
Many industrial tubes are just bad, some are very good.
Military Telefunken tubes are oustanding. 
Russian military tubes are better than industrial.  
Dang! I guess I will have to ditch my Hitchcock tube tester and look for a Hickok.