Transistor vs Vacuum tube

Discussion in 'General Electronics Chat' started by tam72f1, Dec 23, 2014.

  1. tam72f1

    Thread Starter New Member

    Aug 19, 2014
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    Hi all!
    I know that Vacuum tube will give a signal that is better than transistor.
    I think you know that but why??
    Can anyone compare structure of them?? Which are main reasons that make tube better than transistor?
    Thank all so much
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Can you explain your assertion that "Vacuum tube will give a signal that is better than transistor", how do you know this?
     
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  3. #12

    Expert

    Nov 30, 2010
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    A jfet acts so much like a vacuum tube that I don't know how you can say a tube is better but...
    Vacuum tubes can handle rather high voltages. Have you ever seen a silicon device that can rectify 30,000 volts for a cathode ray tube supply? Smaller than your fist? For less than $12? Some tubes have multiple, useful, control grids, like the pentagrid converter. One quote from an old guy: "There is nothing you can do with a tube that you can't do with 4 or 5 transistors." The difference is, you don't need 4 or 5 watts to run the heaters on the transistors.

    Then there's the dual gate mosfet, used to replace vacuum tube IF amplifiers in TV's since 1970. Now, that's hard to beat in a vacuum tube design!

    I guess it's the same answer as a lot of other questions. Which is better? It depends on what you need.
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    It is a myth that vacuum tubes are better than transistors.
    Some folks prefer the sound of tube amps but that is subjective.

    The simple reason is that solid state amps will amplify the signal all the way to the power rails and then clip the signal when driven hard.

    On the other hand, tube amps become nonlinear as they go into saturation, a natural compression circuit. The result is a smoother beefy sound when driven hard.

    The bottom line is the two types of amps distort the signal differently when driven to saturation.
     
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  5. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Since the OP doesn't refer to any particular application and then asks a question which would only be valid if his own baseless assertion, that vacuum tubes are better than transistors, is correct; we can only guess. For all we know; he may be referring to vacuum tubes versus transistors when used in computers.
     
    Last edited: Dec 23, 2014
  6. Morvan

    New Member

    Jun 24, 2014
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    Hi. The true reason is that, while transistors, to conduct, they have to produce particles chocks inside its structure, the tube do not. Tubes amplify signal without heat avalanche. That is the real reason. The Semiconductors that comes closer to the old tubes are the ?FET, because they act like electrical keys, without thermal cascade side effect.

    Morvan, User GNU-Linux #433640 (Fedora 21_x64). Be Legal; be Free. Stay GNU-Linux.
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
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    a simple am radio typicaly had 5 tubes, one a rectifier. the same in a modern solid state might have 30 or more transistors, if you count those in IC's. tubes have their place, transistors do to. tubes can be pushed harder, way over their ratings, most solid state quit just above any rating. typicly solid state requires less voltage, but there were tubes designed for 12 volts on their plates too, for use in car radios, but they needed a transistor for the output amplifier stage. as far as tubes sounding better, a properly designed amp will sound good, no mater what it uses.
     
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  8. ramancini8

    Member

    Jul 18, 2012
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    Tubes require a heater supply and solid state doesn't, thus solid state gear is lighter and less expensive. Solid state lends itself to integrated circuits that add more features for very little cost. There is no difference between the sound quality from a tube or solid state amp when operated in the linear range. Try carrying a tube boom box around with you (remember the batteries) and you will quickly appreciate the difference.
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the 6418 tube runs at a filament rating if 1.4 volts dc, at a current of 10 ma. the max plate volts is 24 vdc. developed for hearing aids near the end of tube development. the russians designed tube equipment long after we went solid state, tubes are more radiation tolerant. on the other end of the scale, it is dificult to replace the rca 867 tube, an rf amplifier rated at 183 kw output each.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    The Russians realised before anyone in the West that valves (tubes) were more resilient to EMP from a nuclear detonation.

    Their military aircraft had all the high tech solid state stuff buried deep in the airframe, any thermionics was concentrated nearer the aircraft outer skin - to some extent, it contributed to shielding the solid state stuff mounted deeper.
     
  11. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Some people defend vacuum tubes over transistors when they talk about audio equipment... but as has been mentioned already in this thread, those people are following an urban legend... they say the sound is "warmer" and has more "depth" and stuff like that... when the only thing going on is that the frequency spectrum is different... and that's something that can easily be adjusted with solid state equipment...
    I see the tube vs transistors issue regarding audio amps the same way I see the vinyl record vs digital music... in reality, I consider it just a romantic-nostalgic thing that people simply can't let go of...
     
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