69 Vs 71

Discussion in 'Let's Talk Vintage' started by boola1, Feb 9, 2018.

  1. boola1

    boola1 Active Member

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    I finally got my new camera (HD!) so I made a video I've wanted to do for a while.. Compare the '69 and '71 JMPs

    Both amps are using cabs from the same year. The 69 cab has a new grill but it's quite dense, like a black basketweave. Both cabs have G12M 75hz pulsonic speakers.

    The playing is a bit ropey, especially at the start, annoyed I f@cked up the Free solo but it's just about publishable!

    You can really hear the difference 2 amps. I hope you like it, it sounds best LOUD!

     
    Last edited: Feb 9, 2018
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  2. liontato

    liontato Well-Known Member

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    I assume the second one is the 71? I love both but like the second one best. Seems to have everything sonically present with lots of harmonic overtones. Love the second amp.
     
  3. boola1

    boola1 Active Member

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    Yes the 71 is second. I've had it for years. It signalled the end of my Marshall tone quest. I only recently got the 69. I had similar feelings at first but for some reason I found myself playing the 69 all the time, preferring the tone. It delivers the goods but you need to be a good player with more finesse and control than I have.

    For bashing out high gain metal, you can't beat the 71, it loves to be running just short of exploding, that's where the tonez are :)

    So maybe the vid is a bit unfair on the 69, a better player could show it's qualities more.
     
    Last edited: Feb 10, 2018
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  4. Pageburst

    Pageburst New Member

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    Great tones boola. The first one, the 69 is a thing of beauty. Woody crunchy it can go from bluesy to classic Marshall crunch. Has that dark hollow ABB quality in moments. The 71 is great too manic, present, lots of overtones and more gain. The gain is not as congealed as the 69 and has an almost jangly biting quality. If you get a chance, I'd love to hear a back n forth with the two amps with you playing the same phrase. But this video certainly demonstrates the strengths of each amp

    Two great amps but I definitely prefer the 69. To me it is The tone. It also is versatile beyond hard rock as you can clearly hear its jtm roots.
     
    Last edited: Feb 10, 2018
  5. liontato

    liontato Well-Known Member

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    Both are incredible. They each have advantages.
     
  6. Trapland

    Trapland Well-Known Member

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    Amazing! I have a 68 and 71. They’re both amazing and sound very different. The 71 screams with a LP or 335. But I love the 68 at any volume, any settings, with any guitar. It definitely needs tighter technique, but the reward is worth it. It’s just mesmerizing.
     
  7. boola1

    boola1 Active Member

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    I'd love to hear your amps if you have any clips?
     
  8. soundboy57

    soundboy57 Well-Known Member

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    What are the model/circuit differences between the amps you all describe?
    Either one should sound alike with the same cathode arrangement, bright caps, coupling caps, tubes, bias, etc.
    Great vid and great tone :)
    I had a 68 and a 71, and the 68 was way prettier and fatter...but it was a bass model. The 71 was kind of a hybrid bass/lead, as far as the circuit, so it was brighter.

    As far as the amps in the video, the 69 will sound better at home or in a 3 piece band, the 71 will cut through better in a two guitar rock band, IME.
     
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  9. boola1

    boola1 Active Member

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    They're both lead models but there are differences as the circuit evolved over time.

    69 from the factory had the NFB connected to the impedance selector but I have wired it to the 8ohm tap.
    71 NFB is factory wired to 4ohm tap.

    69 has .68uf v2a cathode cap
    71 has no v2a cathode cap

    69 has 1202-118 PT (B+ ~445V)
    71 has 1202-164 PT (B+ ~435V)

    69 has 560pf treble cap
    71 has 500pf

    69 probably has 32uf preamp filtering - haven't checked, that is standard for 69
    71 has 50uf
     
    Last edited: Feb 14, 2018
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  10. neikeel

    neikeel Well-Known Member

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    They both sound exactly like they should. I prefer the late 68/early 69 spec.
    You can EQ them to sound quite similar with a bit of twiddling. I think that it is the higher NFB and the cap on v2a that I like.
     
  11. Trapland

    Trapland Well-Known Member

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    Me too. I just moved my 68s NFB from 47k on 4 ohm to 27k on 8 ohm. Big difference but I felt I was burying too much articulation and syrupy flavor behind all that distortion. I might try reducing v1a cap and going back to less NFB, I think I like the breakup and quick cleanup of power tubes from the guitar volume better than the splatter Of the phase inverter.
     
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  12. Durden

    Durden Well-Known Member

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    Gotta love a good 69
     
  13. Trapland

    Trapland Well-Known Member

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    I just revisited this thread as it’s one of my recent favorites. :bump:

    Once again @soundboy57 has nailed my experience. Maybe that’s why I play my 68 so much? It sounds so good for personal practice, and more tonal variety with a 3 piece.

    My 71 cuts better in any band that plays really loud. Also, I wear protection from hard hit cymbals so extra upper mids help.

    I’m doing this from memory, and I have the flu/fever right now so don’t hold me to it.

    Filters are 32 for the 68 and 50 for the 71. The 68 is all orig iron about 380vdc, but the 71 has a 324?PT and makes about 480 on the plates. Someone nuked the PT and STILL left the grid resistors for me to do.

    68 NFB on speaker? 71 on 8 ohm. Changed 68 to 8 ohm right now.

    68 NFB resistor is 27k, 71 is 47k, both have .1 presence.

    The 68 tone stack is 56k/250p? The 71 is 33k/500

    The 68 preamp is 330mf/2.7k shared cathode original. The 71 is 25mf/1.5k shared, maybe not original.

    Neither had a v2a cap. I left the 71 that way. I (gently) added .68 to the 68. Why? Because the preamp is a shared 330mf/2.7k and was muddy as hell. Adding the brite cap and v2a cap made it sound like much more like a lead amp. Without the v2a cap it was a pretty fart machine.

    That’s it...just lightly adding 2 parts (and filling the preamp with NOS Mullards) it made my 68 plexi my dream amp! Adding a basketweave cab didn’t hurt either.

    Thanks for doing y0ur video @boola1 msybe in a couple days if I feel less crumby, I’ll do one.
     
  14. soundboy57

    soundboy57 Well-Known Member

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    They both sound great in the OP video. The 68 is magical :)
     
  15. neikeel

    neikeel Well-Known Member

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    That B+ on your 68 is very low.
    Also either a bass or PA model with that NFB so not really an Apple vs Apple comparison.
    Not to say they might not sound good but boola is comparing two lead spec amps
     
  16. TAZIN

    TAZIN Active Member

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    Do you remember if your '69 has a 2K7 resistor for the cathode of V1b? It should considering the amp is from December 1969, but you never know when it comes to Marshall.
     
  17. neikeel

    neikeel Well-Known Member

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    Trapland's amp is a shared cathode 68 so should be 820R and 250uF on v1a and b.

    We may be getting confused with comparing two pairs of amps of very different specs, worthwhile doing but........
     
    Last edited: Feb 18, 2018 at 1:29 PM
  18. boola1

    boola1 Active Member

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    I haven't checked but 2k7 is standard for 1987s for all years as far as I know. Apart from the dropping resistors the amp is stock so it's almost certainly 2k7.
     
  19. TAZIN

    TAZIN Active Member

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    Actually, the 2K7 is not 'standard' for all model 1987s. The 2K7 started to be phased in around mid August 1969 I believe, so prior amps used the 820 ohm in combination with the 0.68uF cap for V1b.
     
  20. boola1

    boola1 Active Member

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    OK, I'll check it when I get a chance. I think my amp is probably too clean to have 820ohm but we'll see.

    Any idea what the 71 would have in there?
     

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