'68 Plexi vs. '69 Plexi

Discussion in 'Amps and Cabs' started by AK1, Feb 28, 2006.

  1. AK1

    AK1 Member

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    There are slight differences on the circuit boards. Anybody knows how that translates into sonics ?
    I'm looking at two 50w Plexis right now, trying to decide which one to get...
    thanks for the help fellow vintage snobs.
     
  2. Playloudd308

    Playloudd308 Supporting Member

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    One tip PLAY THEM FIRST... the late 60's plexi's were really inconsistant and one sounds WAY different from one another. Get which ever one sounds better because they all sound a bit different
     
  3. AK1

    AK1 Member

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    I know what you mean, I live in Hawai'i though, no can try bra...
    but I've had a '68 before, so I've got some point of reference.
    And you're right, no same model, same day of production point to point amp will sound the same. Even new production, like the Komets, I've tried
    a couple...
     
  4. Playloudd308

    Playloudd308 Supporting Member

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    yes, in general they are amazing amps but there are some bad lemmons out there. But if you live in hawaii and theres no way around it, you could always sell if you didnt like it. And if you decide to get it... Congrats!
     
  5. sws1

    sws1 Member

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    68 varied wildly. BY 69, they were starting to get more standardized. In general, the 69 is most likely a bit brighter. But not necessarily. Sometime in 68, they reached the circuit that was used in 69. So it all depends on when your 68 was built, and what stuff was lying around.
     
  6. riverastoasters

    riverastoasters Member

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    They can sound like night and day. Play 'em. It's the only true way to know.
     
  7. riverastoasters

    riverastoasters Member

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    If you can't try them, can you get someone you know close to them to try them?
     
  8. 908SSP

    908SSP Supporting Member

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    If your looking at all original condition and price is right just buy it you wont ever loose anything on it. It has ever been modded and the price is right then you can make it sound just like you want with very little changes. I played my early 68 tonight for a couple of hours and it sounds wonderful. Very warm and rich deep bass, nice crunch, alto leads loads of sustain just a joy. Is the 69 your looking at a Plexi or a metal panel? Same goes for it either way. If you have done your research and gotten lots of pictures and the price is right the only thing you have to worry about is shipping.
     
  9. Roe

    Roe Member

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    I believe amps from 68 often have more filtering than amps from 69.
     
  10. Fretmaster

    Fretmaster Member

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    buy both....try em....keep which ever one is best to your ear and sell the other. chances of losing $$ on either of those amps is slim.
     
  11. AK1

    AK1 Member

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  12. smilefan

    smilefan Member

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    Another thing to consider. Since you cant try them,
    is it possible to find out,
    as specifically as possible what tubes are in them?
    There is a wealth of tube knowledge on this board,
    the Weber VST board, Mike from KCA (Bluestrat),
    that could round out your picture of what to expect
    from the amps.

    I once sat down with my old tech and A/B'ed a
    variety of NOS tubes into a SF Bassman that he
    "blueprinted" for me. All the tubes were American
    NOS. RCA, GE, Sylvania, etc. Each set of tubes changed
    the tone and response of the amp to the point where I wouldn't
    have known it was the same amp.

    Also, if one has a set of NOS Mullards, and the other
    has a set of new JJ's, that would certainly help you
    make your decision.
     
  13. bjm007

    bjm007 Member

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    Not sure about the 50's but the 100 watters are just the opposite of that...

    In '68 for example they had 100uF caps on the mains and 32uF on the screens, and all the caps were inside except for one.

    In '69 they upped the screen filtering to 100uF (just like the mains) and put the caps up on top.

    '68 was also a transitional year for the shared vs split cathode. Early '68's were most likely shared while later in the year they started doing more split. The'69's are split.

    In general, the earlier in '68 you go, it's gonna be a little looser on the low end because the screen filtering is less. Also the shared cathode design has a slightly different gain structure. (Somewhat less...)

    By the time you get to '69, you had more screen filtering so (in theory) it's going to be tighter and the shared cathode is going to change the gain structure somewhat.

    The V1/V2 Lead Channel coupling cap also changed in '69 to a .0022uF (from a .022uF in '68) which is going to strip off more lows, giving the tone a little more of a treble character.

    They also changed the bright cap in '69 from a 100pF to like a 4,700pF. That makes the '69's sound really ice picky when you back off the volume, but it's easy to change if you wanna swap it back to 100pF......

    As the other guy said, since you're in Hawaii (like me) just buy it and try it out for a while. You can always sell it if you don't like it... They tend to hold their value pretty well...
     
  14. AK1

    AK1 Member

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    that's great info, mahalo braddah.
     
  15. that_brianm_guy

    that_brianm_guy Gold Supporting Member

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    I've owned a marshall RI and a clone.. I prefer the sound of .022 to the .0022, and I remove the bright cap altogether.

    I also change the presence cap to a .068.

    That removes the icepikiness, and smooths the presence quite nicely....

    If you want to talk Marshall circuits, check out http://www.metroamp.com/forum/ - that's the place to be...
     
  16. Gordon

    Gordon Silver Supporting Member

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    The only thing that I haven't seen mentioned yet is the difference in tone circuits. The '68 used a much more bass oriented tone circuit, ie. a 56K slope resistor and a 250pf treble cap. The '69 used a more guitar oriented tone circuit, ie. 33k slope rx and 500pf treble cap. What does all that mean to the sound? The '68 will generally have a smoother, more musical sound (that's my personal way of describing it), the 69 more aggressive and mean sounding for lack a better term. The 68 will require you to throw away a buch of bass in order not to be too muddy. I mean like turning the bass knob down below 2. It will also have a low-end emphasis and will not get louder as you play higher notes. The 69 has a greater emphasis on the high notes and can sound weak on the low notes untill you really crank it. It will sing better on the high notes though. It's a matter of how and what you play as to which will be the perfect fit.

    Good luck and have fun, they're both great amps.

    Gordon
     
  17. awangotango

    awangotango Member

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    that last post was a cool way of describing the differneces. The 68 has more of an early billy gibbons feel which is loose and fat and brown. The 69 will have more of a 'harder' tone with a faster response. It's only a couple components change from each other though. So no worries, a soldering iron can remove the bright cap and maybe change a filter cap or two, connect the pins on V1 or disonnect (split/shared) and it's the same amp. That's the great thing about the pre 73 amps, any guitar player can dick around inside and dial it in to his preference. 68-73 amps can all be made to sound like one end of the sepctrum or the other in about 15 mins. soldering time.
     
  18. bjm007

    bjm007 Member

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    Ain't that the truth... :AOK

    It's nice to be able to actually work on something as complicated as an amplifier and be able to dial it in YOURSELF... That's cooll... I haven't had this much fun working on my amps in years... :dude
     
  19. AK1

    AK1 Member

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    damn, I'm gonna print this **** out for my reference.Thanks for the education.
    I might even dust of my soldering iron.
    Looks like I'm going for the '68, just because it's priced more realisticly.
     
  20. awangotango

    awangotango Member

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    if you really want an education. head on over to the 'plexipalace' forum and search old posts. That's where one can really learn 'what is what'. There's really no mystical magic going on inside old marshall's. Depending on the style of music you play, there is a stock marshall circuit that will fit like a glove and there's also plenty of gain as well, without mods. I personally am into rev. billy G, nuge, angus, EVH, etc and find the 68 circuit to be real cool. I replace the bright cap with a 470k resistor, use a .68uf cap bypassing V2a for more raunch (stock at various times 67-72) and a .68uf presence cap (beefs up mid with cool presence) and can get all the tones mentioned above depending on how i set the vol. and tone, all at a reasonable volume, (because of the 470k resistor -parkhead mod, over at plexi palace). The new 'heritage' celestion G12M 20 watters, and a vanzandt trubucker pickup help me get "there" as well. That's all it takes, no pedals, fancy mods, expensive les paul's, vintage greenbacks, mystical PAF's etc.
     

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