Aww Crap...that 68 Plexi Is At My House. Help Me Decide.

Discussion in 'Let's Talk Vintage' started by Trapland, May 12, 2017.

  1. Trapland

    Trapland Well-Known Member

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    So 9 months ago a 1968 50 watt JMP organ model turned up in my favorite shop. While I was "deciding" it went away, believed to be sold. It's VERY nice, not flawless, but pretty straight with some roughed up corners.

    When it went away I was sad. So I did the only logical thing and bought a tweed 59 Super-Amp AND a clean 71 small box. After the lightest tweeking of the 71 head, with you guys help, it's pretty much magical. Really, it so good I HAVE to have a guitar hanging below my belt line.

    And the Super sounds as good as any tweed I've heard, better than most. It's only 34 lbs, loud enough for most bands without being obnoxious, and works perfectly with original circuitry. It has silly amounts of gain and distortion, yet a twist of a knob and it's Fender clean. YET it does NOT sound like a Marshall lead amp.

    Now the 68 is back, and I am test driving it at home. It sounds more like a tweed Fender than a Marshall lead amp. At the least I would have to add 2 capacitors and tweak the NFB to suit my tastes.

    Because I just dropped bank on the Tweed and 71 Small-box, I would pretty much have to trade the Tweed Super. It's a good amp and rare, but so is the plexi, and I have several other Fenders and Marshalls, but no real deal plexi OR tweeds.

    Question: Knowing I would have to trade a similar valued Tweed, would you trade?

    [​IMG]

    (I know the logo is aftermarket.)
     
  2. neikeel

    neikeel Well-Known Member

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    Have you tried 'lead' plexi settings?
    Presence 6, Bass 2, Mids 8-9, Treble 7-8, Volume 1 in top jack at 8 (unused vol 2 on 4-5., plugged into an early 4x12 with original coned Celestions and a good Les Paul, then decide.

    I must say if the 68 sounded right (modding it to lead spec properly is much more than 2 caps) at those settings then I would keep it and the Super and sell the 71:)
     
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  3. Trapland

    Trapland Well-Known Member

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    I have tried every setting, including the unused volume half way up (I read your posts, lol). Even with the bass on 1, it's flubby and it needs to be over 8 volume with full presence to get any real crunch. But I'm not too worried about that, I know I can tune it up with very minimal changes, maybe even just tubes. I wouldn't need to mod it to lead spec properly, just a little closer.

    Keep both the Super and Plexi? It's probably not an option before this 68 plexi is no longer being offered to me. Crap!

    Just to pretty up this thread, here's some photos. I posted these last year.

    [​IMG]

    [​IMG]
    [​IMG]
     
  4. Trapland

    Trapland Well-Known Member

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    Some things I may trade for the plexi....

    [​IMG]
    2015 es-175 59 reissue
    [​IMG]
    1971 Model 1985 4 hole PA head. Just got it and it sounds amazing.
    [​IMG]
    Pretty clean 1966 Jaguar. Daphne Blue. All original inc case. Sounds amazing with barely any fret wear.

    [​IMG]
    The 1959 tweed Super. Or maybe the 1976 explorer with the fattest neck ever yet weighs 7 lbs.


    I'm not really playing the Super or the Explorer but I like them. I have no special feelings for the Jaguar. I like the 1985 pa and the es-175.

    I really like all of my Les Paul's. I suppose I could always trade some money too, but it would be nice to make a dent in the trade with a major piece. The Super? The Explorer? The Jaguar plus something?
     
  5. neikeel

    neikeel Well-Known Member

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    Looks pretty clean and original, although by adding a mixer bypass cap to channel 2 you would find some of the zing will have been lost from channel 1, if it is an organ model it should have a 100pF cap on channel 1 pot which also adds a little.
    Looks like it had a master volume mod at some stage (replaced wire to wiper lug of treble pot with a blue piece and the grey RS cap is a NOS replacement - so I would not feel guilty about replacing it with a 25uF for better guitar tones).
    With very minor tidying definite collectorbility, but it should sound good too. That is where the problems start as it may need a cap job to restore its tightness but then you lose value, daft isn't it! Well worth testing them in situ for function with a scope (or doing a tube review/replacement) before shotgunning the parts.
     
  6. boola1

    boola1 Member

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    You want to trade all that stuff, including an amp that you love the sound of, for one that you don't really like the sound and need to mod.

    Go for it!
     
    Last edited: May 13, 2017
  7. London John

    London John Active Member

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    If you're thinking of moving the 175 or the Super.....PM me, I'll give you better than trade-in money (depending on the year of the 175, but been looking for a PAF blonde for ever).
     
  8. neikeel

    neikeel Well-Known Member

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    Does Mrs LJ know?;)
     
  9. Trapland

    Trapland Well-Known Member

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    ALL that stuff? Lol, no. Some of it probably. In the end I'll still have plenty of amps and guitars, but hopefully a new vintage plexi.

    There are plenty of metal panel amps still to own. In my area, actual plexis are pretty scarce.
     
  10. JLBIII

    JLBIII Active Member

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    Maybe my eyes are getting old but the blue Jag looks like a Mustang
     
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  11. Trapland

    Trapland Well-Known Member

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    Oops. Of course it is. Shows how little I know about Fender guitars. :). I'll confess I'm much more of a Les Paul through a Marshall guy.
     
  12. ampmadscientist

    ampmadscientist Well-Known Member

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    In your bathtub.
    The Marshall is way too loud.
    Plexi must be CRANKED to get a good sound....so your logic is flawed.

    For most people, the Fender is a better choice. It's the realistic choice.
     
  13. sct13

    sct13 Active Member

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    I own a 68 Plexi....

    I love it, I also have a 77' 2203 another amazing amp....I also built a JTM 45 and a 69 Superlead and while they are excellent sounding, I still prefer the 68' It has something that the others don't have...

    Regarding volume....I know many look down on attenuators, but if ratting the wife's glass wear, scaring the complete hell out of the cats, or completely ruining your fish's day....then they are worth it...

    would prefer to play on 11 all day but it just isn't practical. get a good attenuator. the sweet spot on the 68 is volume 6.
     
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  14. ampmadscientist

    ampmadscientist Well-Known Member

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    In your bathtub.
    Well, you could say that Plexi is standard to which all others are compared....
    but Plexi was made for stadiums.
    And so, the big challenge is always to get a "cranked" Plexi sound...at a lower loudness.
     
  15. TubeStack

    TubeStack Well-Known Member

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  16. Trapland

    Trapland Well-Known Member

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    Well it's been a week or so. After some negotiation that 68 is mine. I traded a near mint vintage 66 mustang and 76 Explorer LE. I feel I did well, and the shop sell guitars much easier than amps so it probably a win-win.

    I now believe this amp was a #1986 with an added part, to make it half way to an organ model. Or it's an organ model without the bright cap, not sure.

    I'll try to remember to post more photos. It's not the cleanest example, but it's mine. Because it's got some roughed up corners I think I can gig this amp without worry about damage. Much like my guitars, amps that I don't or shouldn't play soon end up on the trading block. I want to at least use this one as my #2.

    Regarding sound. This amp is pretty bass-y and it flubs out easily. I will definitely need more treble and less bass. It's wearing all Mullard 12ax7 and a pair of x2f EL34. I'll try different tubes and store the Mullard EL34 for safekeeping.

    It has a 500pf across BOTH mixer resistors. No bright cap. .022 on v1a and b couplers. No screen grid resistors.

    Now a new dilemma. What is the absolute MINIMUM I can mod this amp to brighten and gain it up without devaluing? I don't HAVE to play it, I have plenty of Marshalls. But if I can just add a bright cap, and maybe bypass v1a without a big devaluation, I'll go for it. My #1985 50 watt PA sounds amazing and it's pretty close to this. I only added a cap to the first mixer to make it perfect.

    I have yet to measure voltages. The overall distortion character and general tone is good, and it's very quiet. I just need more upper mids and treble OR less bass and s bit more gain.

    Thoughts?
     
  17. Trapland

    Trapland Well-Known Member

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    @neikeel You once said that having a cap across both mixer resistors would lose some zing. What do you mean by zing and how much?

    Also do you know what the 100pf cap from an organ model #1989 should look like?
     
  18. neikeel

    neikeel Well-Known Member

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    Early amps used a red tubular ceramic. Later ones a Murata ceramic disc 100pf.
    The 470pf or 500pf mixer will make the lead channel a bit brighter in the typical mid volume settings. It also makes other channel a bit fuller too
     
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  19. Trapland

    Trapland Well-Known Member

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    Thank you. I have 500pf on BOTH mixers. Do you know what the effect will be on channel 1 if I lift the cap on channel 2? I solder well, but want to keep it to a barest minimum on this amp. I admit I don't understand why the channels interact when using just one input. Something to do with loading through the shared cathode maybe?
     

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