JMP Lead 50 Watt 1975 w/Big M Cabinet

Discussion in 'Member Classifieds' started by fretted friend, Dec 16, 2019.

  1. Relic61

    Relic61 Well-Known Member

    Joined:
    Aug 21, 2013
    Messages:
    490
    Likes Received:
    478
    Location:
    Catskill Mnts
    Well, your Master Volume mod 'could be made to appear' to have used the voltage selector hole. Meaning, the amp could be fitted with a Voltage Selector switch (working or dummy) to give the no 'extra' holes look if & when restored.

    Being I don't see the 2 little screw holes that mounted & held the voltage selector in place that should be left visible.. I'd guess that by 1975 the Voltage Selector was forgone & pre-set for our American market as seen on the back of my 1976 JMP 50 watt Master Volume.

    (1976 50 watt Master Volume rear panel without voltage selector)
    76 back panel.jpg

    (stock JMP photo with voltage selector)
    [​IMG]
    (your amp below)
    [​IMG]

    Now I don't have your amp in front of me & I might be wrong but it appears the pre-amp signal is jumpered over to the rear panel Master Volume mod.

    (Your amp with Master Volume mod wire highlighted)
    upload_2020-3-18_12-6-9.png

    So it's also my guess that your cleanest sound is going to be found keeping the front panel volumes on or below 4 (All my 4 hole 'non-master volume' JMP's start to get power tube driven tones after passing 4 on the Volumes) & then lowering / adjusting the rear panel Master volume to taste.

    The Volume on 4 is usually pretty loud on these old JMP's.
     

    Attached Files:

  2. Sapient

    Sapient Well-Known Member

    Joined:
    Mar 14, 2020
    Messages:
    145
    Likes Received:
    300
    From one newb to another, welcome. Nice amp!

    Ohhh that was a while ago. Welcome anyway?
     
  3. junk notes

    junk notes Well-Known Member

    Joined:
    Dec 10, 2018
    Messages:
    437
    Likes Received:
    402
    There are two on eBay from New York, and another '76 in Illinois craigslist for $100 less, in very good condition.

    edit: Appears ALL original. While the two on eBay have had the speakers replaced.

    (how much for shipping I wonder. Scumback would know. ;-)
     
    Last edited: Mar 20, 2020
  4. Sokool

    Sokool New Member

    Joined:
    Feb 25, 2018
    Messages:
    15
    Likes Received:
    4
    Location:
    Fort Lauderdale, FL
    My '75 Marshall 50 watt JMP MKII needs 12AX7A tubes, but, they range in price from $10 to $200 each... I want what's best for this awesome classic amp... Ideas, because I have none! Which to choose?
    I just bought the 6550's.
     
  5. Matthews Guitars

    Matthews Guitars Well-Known Member

    Joined:
    Aug 17, 2019
    Messages:
    1,422
    Likes Received:
    1,806
    Double tap. See below.
     
  6. Matthews Guitars

    Matthews Guitars Well-Known Member

    Joined:
    Aug 17, 2019
    Messages:
    1,422
    Likes Received:
    1,806
    Just get the Mullard reissues for V1 and V3. For V2, get a JJ 12AX7A. With ONE exception, you don't want to run a Russian made 12AX7 in V2 because the cathode follower circuit it has will cause the tube to fail due to the high voltage applied to the grid. That one Russian exception is the Sovtek 12AX7WB. It's made for the job and it's OK.

    If you want to play around with older tubes, vintage/NOS/tested pulls, whatever, I can't make any recommendations there. Too many variables, too few that I've actually got any experience with.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice