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1959SLP vs 2203 What Lies at the Heart?

Discussion in 'Marshall Amps' started by NewReligion, Oct 15, 2010.

  1. NewReligion

    NewReligion Well-Known Member VIP Member

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    My question to all is other than the obvious cosmetic differences, what are the changes to the circuit that separates the 2203 from the 1959SLP. Would it in fact be easy to mod a 1959 into a 2203 or a 2203 into a 1959?

    I can hear the sonic differences but am very curious as to what lies at the heart of the matter. Feel free to remark on any aspect of these two models or their 50 watt little brothers.

    David :cheers:

    WWW.MySpace.com/DavidCHopkins
     
  2. kingswebe

    kingswebe New Member

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    Two major differences as a starting point;

    1) The 1959SLP has no Master Volume, while the 2203 does. So gain preamp gain structure is different between the two.

    2) the 1959SLP has 4 inputs. Many of the 1959SLP enthusiasts' preference for this amp is based on jumpering two of the inputs to together so you end up getting the sound of two separate channels playing simulatenously. I forget which two inputs are the most commonly "jumpered" together.

    Because of this, I think it would be pretty challenging to mod a 2203 to do what a 1959SLP does/sounds like. And conversely, probably much easier to get a 1959slp to sound like a 2203 - and probably not by mods even, but by placing the right overdrive pedal in front of the 1959slp.
     
  3. NewReligion

    NewReligion Well-Known Member VIP Member

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    Thank you sir. Yes I was aware of the Master Volume and 4 input as I do own a Plexi Re-Issue. :)

    I recently had a 2203X modded and it now sounds like the greatest hot rodded Plexi I have ever heard, just smooth saturation full of harmonics. This is the reason that I asked about the circuit. I suspect that the two circuits must be quite close in relation to each other.

    Thanks again for the input.

    David :cheers:
     
  4. kingswebe

    kingswebe New Member

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    Sorry about that.

    Would you mind sharing what particular mod you had done on your 2203X? I am actually currently trying to set up my JCM 800 to sound closer to a 1959slp myself. Your recent mod sounds very interesting...
     
  5. ynot

    ynot New Member

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    When I was going to MI another student that lived in my apt complex had a JCM 800 that was modded so the gain became the high volume,the volume became the low volume & there was no longer a gain control.I was pretty young at the time & didn't know much about Marshalls (this was in '89 & I was only 18, :eek:) but in retrospect it sure seems as though he was trying to turn it into a plexi.How successful that attempt was IDK.Someone like Wilder may be able to tell you if one can or can't be modded into the other though.
     
  6. MKB

    MKB Well-Known Member

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    A few more additional differences are: the 2203 has an additional stage of treble boost, and an additional input gain stage. The voltage gain half of V2 has its cathode resistor set for lower gain than in a 1959 as well.

    The pre phase inverter master volume in the 2203 is important as it will set the mix of overdrive between the preamp and phase inverter. In the 1959, the preamp is always wide open and the first stage to distort is the phase inverter, where you have to have the master cranked fairly high in a 2203 for the PI to distort.

    It would not be terribly difficult to convert a 2203 into a 1959 type circuit, or vice versa. Just a handful of parts would be needed in any case. A hardwired version would be significantly easier to change over than a PCB, however.
     
  7. SoloDallas

    SoloDallas Well-Known Member

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    Thanks for that. I am evaluating in fact the differences between a 1976 JMP Super Lead and a 1979 JMP Master Lead. The Master Leads sounds more aggressive and "nasal", if that makes sense.
     
  8. NewReligion

    NewReligion Well-Known Member VIP Member

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    I agree with the EQ nasal comment. Though both are fantastic products.

    David :dude:
     
  9. Wilder Amplification

    Wilder Amplification New Member

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    Circuitry-wise, both amps are identical from V2 to the speaker jack with the exception of the pre-phase inverter master on the 2203/2204. The difference is in how the front end is configured.

    On a 1987/1959 each 1/2 of V1 is its own channel. One 1/2 is the Normal channel while the other 1/2 is the Bright channel. The outputs of the two channels are passively "mixed" together right after their respective volume pots.

    On a 2203/2204 both 1/2s of V1 are cascaded (i.e. 1 gain stage output feeds the input of the next gain stage). There is a breaking point between them at the Low input jack. On the High input jack your signal is going through both halves of V1 whereas on the Low input jack your signal only goes through 1/2 of V1.

    Other than that all else is the same.
     
  10. NewReligion

    NewReligion Well-Known Member VIP Member

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    Thank you Jon. Then the amps are more closely related than I had actually suspected. Being a tone chaser, it is comforting to know my ears were not deceiving me. Personally the way my 2203 is now after JV and Major helped me out is a huge improvement IMO. It is to that end that I say (full well knowing I will be drawing Fire, lol.) it seems that Marshall could have taken a little more time in their haste to develope the 2203/2204 with more gain as they did but with "smoother" and improved sonic results. It is not my intention to insult the circuit of the stock 2203 but rather there are obvious improvements that should/could have been made.

    Thanks again Jon.

    David :cheers:
     
  11. D-Max

    D-Max Member

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    Hi NewReligion,

    What do you mean with 1959SLP?

    Marshall used this designation for the first time when they did the 3rd re-issue of the 100W non-master volume amp with the classic style head box in '93.
    The 1959 has always been part of the JCM800 range in the JCM800 style head cab.
    The first reissue of the "plexi"NMV was in in '88, the 1959S amps, going back the 60's/early 70's head cab style.
    The 2nd reissue was the 1959X amp in '91.

    Where the comparison is made that from V2 up everything is the same, this applies for metal-panel amps era and further on (and so for the JCM800 era until Marshall went to horizontal input jacks) having these specs:
    - 6 filter cans on top
    - feedback on 4 ohm tap with 100K NFB
    - presence circuit using a 100nF in series with the 22K or 25K presence pot
    - 680nF bypass cap removed again from the cathode resistor of V2a
    This would mean metal panel NMV amps from let's say... '70 or '71 and up? Not sure about the exact year when the 0.68nF cap was omitted.

    Before that the Super Lead spec varied throughout the entire amp:
    - different powersupply filtering topologies (cap values, 1 or 2 bridge rectifiers, etc)
    - feedback loop: different feedback resistor values and different taps on the OT
    - presence circuit was different - 5K presence pot with 100nF (some 680nF) cap at the wiper to ground
    - early bright channel used a 22nF coupling cap into the bright channel volume pot, the later ones used 2.2nF.
    - the earliest plexi's even had 100nF PI output coupling caps, a shared cathode circuit on V1 and different tone stack component values on the slope resistor and treble cap.
    When going even earlier, there also a number of differences.

    If you are comfortable with reading schematics, here are both preamps in the same schematic: http://www.drtube.com/schematics/marshall/jcm800pr.gif

    The 2203 is basically cascading both 1959 channels after each other with some changes and moving one pot after the tone stack to become the master volume.

    Look on the followin page for a Marshall board layout that has a switchable 1959 bright/2203 preamp (with courtesy of SDM): Misc Mods and Info
     
  12. NewReligion

    NewReligion Well-Known Member VIP Member

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    Thank you D-Max. That was very informative and more of what I was interested in finding. Between you and Jon Wilder I would think everything should be made clear.

    Thanks again and welcome to the Forum Sir.

    David

    David C. Hopkins on MySpace Music - Free Streaming MP3s, Pictures & Music Downloads
     
  13. D-Max

    D-Max Member

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    Jump on over to the Metroamp or Vintage Amps forums once in a while.
    Cool stuff on 60's and 70's Marshall amps over there.
     
  14. Frankie

    Frankie Well-Known Member

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    There's not too terribly much different between the two. Both power sections are the same, the differences are, as mentioned above, the preamp. The 1959 has two channels with a single gain stage. Jumpering them gives you two gain stages in parallel. A JCM 800 takes both of those channels and cascades the gain stages, so you get gain squared. Both will absolutely blow your face off they're so loud.
     
  15. SoloDallas

    SoloDallas Well-Known Member

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    I noticed - while playing both examples today (a 1976 JMP SL and a 1979 JMP Master Lead) that rolling off the volume on the guitar(s) has a different effect. Cleans "better" on the Super Lead; doesn't clean well on the MV.
     
  16. Frankie

    Frankie Well-Known Member

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    That's because of the double gain stages. Plug into the low input on the MV amp and crank up the master. It'll be real similar to the Super Lead.
     
  17. SoloDallas

    SoloDallas Well-Known Member

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    HA. Thanks for that trick :)
     
  18. Frankie

    Frankie Well-Known Member

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    Nobody ever uses that damn low input on a JCM 800. It drops one of the triodes out of the preamp, so it's essentially a single gain stage amp like a 4 holer.
     

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