EL34 tubes - which one?

Discussion in 'Amps and Cabs' started by pete12string, Mar 16, 2015.

  1. pete12string

    pete12string Supporting Member

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    I'm thinking of replacing the tubes in my Fargen Micro Plex. Right now it has a JJ EL34 and a Sovtek 12AX7. It sounds okay with these but I've never replaced the tubes - they're probably about 2 years old.

    I want low noise, reliable tubes.
    Based on the information I see on The Tube Store:
    For the 12AX7 I was looking at a Svetlana 12AX7
    For the EL34 I was looking at a Tung-Sol EL34B (are these the Tung-Sol reissues?) or Svetlana EL34

    I can use EL34/KT66/KT77/6550/6L6/5881/6V6 with no re-biasing. Any opinions or advice? :dunno
     
  2. BluntForceTrauma

    BluntForceTrauma Member

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  3. dehughes

    dehughes Member

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    EL34BSTR, no question. IMHO, YMMV, IME, etc...
     
  4. lang.murphy

    lang.murphy Member

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    Siemens... a bit more pricey than others, but you only have to buy one, and they are stellar.

    Gold Lion KT77's are pretty sweet too...
     
  5. microphonefolk

    microphonefolk Member

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    Hi Pete, I have been servicing tube amplifiers since the 60's. I use to do warranty work for Marshall, Traynor and Ampeg in Vancouver during the 70's and we used Sovtek EL34 tube which are made in Russia.

    I use Sovtek 6072a tubes in all our microphones and we find them very reliable.

    However, if the MicroPlex can work with a single EL34, 6550, 5881, 6L6 or 6V6 then it cannot have a plate voltage higher than 400v to accommodate the 6V6.

    I saw some Chinese made EL34 tubes that sell new for $12 and they would probably work well in the PLEXI as they are not running the EL34 very hard in a 6V6 circuit. My guess is the have no more than 350v on the plate of the tube.

    If the amp has a good biasing circuit then it would be pretty cool as you could get between 4-9 watts between different tube types I imagine. Being class "A" you can run 20db into the on-set of distortion before it get "too" nasty sounding.

    We use all class "A" circuits in our microphones because of that reason.

    A high grade EL34 can be run with 800 volts on the plate. My friend Peter Traynor ran a pair of EL34 tubes in his Bassmate ampliier circuit at 600 volts and I measured the output at 90 watts RMS {FULLY DISTORTED). However, to do this you had to take pin 1 and place it at the bias potential down at -38v.

    The Plexi circuit will have strapped pin 1 of the socket to pin 8 so the EL34 will work like all the other tubes.


    The 6V6 will distort first, then the 6L6 then the 5881 then the EL34 and 6550.

    If you swap the Sovtek 12AX7 for a 6072a it will be cleaner and a bit quieter in the front end. The first tube is the one with the most gain and it must be the quietest.

    Tubes have an average life of around 5000 hours. So, If you have had the amp for 2 years it would have to be played 24/7 for 100 days each year before the tube would reach the end of their life.

    It "sounds" like the perfect amp for the Studio.

    Cheers, Dave Thomas
    www.aamicrophones.com


     
  6. FourT6and2

    FourT6and2 Member

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    For EL34s, I like the Electro Harmonix, RFT/Siemens, original/NOS Tesla (not JJ), and the Ruby EL34 BHT or BSTR should do really well too.
     
  7. Blue Strat

    Blue Strat Member

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    For economy minded (new production), Ruby EL34BSTR. For high quality, NOS Tesla or NOS Siemens. The Svetlana 12AX7 is a good modern 12AX7.
     
  8. tech21nyc

    tech21nyc Member

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    Hey Mike, do you know what the difference is between the Ruby EL34BSTR and the EL34 BHT in terms of sound. I read the BHT takes more voltage but was wondering if they sound any different.
     
  9. sleewell

    sleewell Member

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    tung sols are good too.
     
  10. big mike

    big mike Moderator - EL34 Emeritas Staff Member

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    Yeah I like the tungsols, as well as the new sensor svetlana's for new production.

    JJ's are good too.
     
  11. broken_sound

    broken_sound Silver Supporting Member

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    I've always been partial to RFT 34's, but for the price, you really can't go wrong with the new mullards or winged c's.

    Is your only criteria reliability?
     
  12. pete12string

    pete12string Supporting Member

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    Low noise is a big one. Don't want mud either.
     
  13. broken_sound

    broken_sound Silver Supporting Member

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    If you want a reliable, clear, low noise 34, you might want to look into a big bottle 6CA7. Had a pair of EH 6CA7s in an old Marshall that lasted me years without any degradation.
     
  14. Blue Strat

    Blue Strat Member

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    I haven't compared them. Sorry.
     
  15. Echoplexi

    Echoplexi Silver Supporting Member

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    I'm running 6ca7s right now. I love them, clear big tone that can take a pounding.
     

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