Can you build a 100% stock EL34 1987 Marshall with a tube rectifier?

Discussion in 'Amps and Cabs' started by soldano16, Sep 24, 2008.

  1. soldano16

    soldano16 Member

    Messages:
    2,348
    Joined:
    Oct 7, 2004
    Location:
    British Columbia
    Just curious if it can be done or if something would need to be changed to handle a 50 watt amp with a tube rectifier.
     
  2. Groovey Records

    Groovey Records Member

    Messages:
    3,146
    Joined:
    Nov 19, 2007
    Location:
    Jackson Heights Birthplace of Johnny Thunders
    yes but then its not stock

    The new TopHat EmplexadorTR is Tube Rectified. The Kits From Metropollis amp are excellent Marshall omages and they offer that option.

    I prefer the tube rectified platform it's more plesing to my ear and I enjoy the feel from the TR
     
  3. QRSS

    QRSS brutalist

    Messages:
    7,620
    Joined:
    Dec 11, 2006
    Location:
    nolita
  4. SatelliteAmps

    SatelliteAmps Member

    Messages:
    6,185
    Joined:
    Oct 19, 2007
    Location:
    Normal Heights, Calif
    The big issue is making sure the power transformer has a 5v tap on it.

    You could build one, or have one built and it would be considered stock, but not what most people think of when they talk about 1987 models. Or even better would be to find a vintage 1967 one.
     
  5. MBreinin

    MBreinin Supporting Member

    Messages:
    3,844
    Joined:
    Nov 29, 2006
    Location:
    New Orleans, Booziana
    There is an Emplexador with a tube rectifier? Wow, that has to be cool!!
     
  6. dewman

    dewman Gold Supporting Member

    Messages:
    5,750
    Joined:
    Nov 23, 2005
    Location:
    NC
    Germino Lead 55 LV is fairly close and an amazing take on the real thing. Its a late 60s plexi circuit in 50ish watts with tube rectifier. You can get it with a SS rectifier switch as well or run a plug in when you're feeling the need to send it to the next level. This amp sounds phenomenal. I sold a 1987X early year reissue and a Bluesbreaker reissue to get a Lead 55 LV and it sounded WAY better than the reissues, even though the bluesbreaker was modded with Mercury Magnetic trannies, sozo caps and NOS glass.

    I've gone the other way, adding a SS rectifier to a tube amp and it is WAY easier than the reverse...
     
  7. ChickenLover

    ChickenLover Member

    Messages:
    1,696
    Joined:
    Sep 7, 2006
    Location:
    Florida
    Just be careful with how you wire the SB switch and how much capacitance at the power supply first node. There are limits to how much capactance you can have and IIRC the 1987 circuit exceeds it slightly (check the GZ34 datasheet but I think it's 80uF max for the first node and I think the 1987 has 100uF there). The old GZ34s could probably take more abuse than new production so even if the early Marshalls exceeded it they could probably get away with it.

    Look into the Tube Rectifier issues with some of the reissue Voxes...for ideas on what NOT to do.

    Also, if you do use a tube rectifier then it's probably gonna be easier on the rectifier tube to NOT use the standby switch...just let the GZ34 bring the whole amp up slowly. Obv this doesn't apply if you use a tube rectifier with a directly-heated cathode (GZ34s have an indirectly-heated cathode...that's why they come on slowly).
     
  8. 908SSP

    908SSP Supporting Member

    Messages:
    5,801
    Joined:
    Jun 22, 2004
    Location:
    Michigan
    It's is called a JTM50 and Marshall built them.
     
  9. Roe

    Roe Member

    Messages:
    6,953
    Joined:
    Jul 12, 2005
    Location:
    tromsoe, norway
    most of these amps are from 1967 and are called jtm50. some of the first jmp50s had gz34s as well. I've also seen a later marshall 50w with original tube rectifier. it no problem to build a jtm or jmp50. I recommend metro's jtm45 kit but with marstran jtm50 trannies (128 OT)
     
  10. SatelliteAmps

    SatelliteAmps Member

    Messages:
    6,185
    Joined:
    Oct 19, 2007
    Location:
    Normal Heights, Calif
    Later ones would have to have had their power trannies changed, as there is no 5v filament tap.
     
  11. Roe

    Roe Member

    Messages:
    6,953
    Joined:
    Jul 12, 2005
    Location:
    tromsoe, norway
    I recommend the 118 pt and the 128 (or 139) OT from marstran. use a metro jtm45kit but replace the mixer resistors with 470Ks and up the filtering to 32 overall (or even 32+32 for the mains). also, use 1k resistors instead of the 470s on v4 and v5
     

Share This Page