JCM 800 ,JCM 900, SL-X ,AMP MODIFICATION

Discussion in 'The Workbench' started by Exotic, Nov 30, 2019.

  1. Exotic

    Exotic Active Member

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    i just ordered jcm 900 4500 high gain dual reverb from ebay ,mostly because my jcm 800 2210 is in the shop ,and i have become a tone chaser and want to compare them ,but i'm wondering if maybe i should have gotten the sl-x . does anyone know some differences in these 3 amps? as far as crunch . and does anyone know how do they modify marshalls so they become crunchier ?

    https://www.ebay.com/itm/Marshall-J...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
     
  2. South Park

    South Park Well-Known Member

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    I prefer the jcm 800 the right amount of gain and tone . Easy to mod easy to repair . Old Skool
     
  3. Crikey

    Crikey Well-Known Member

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    I run my 800 2210 with my 4100dr and it freakin rocks.
     
  4. Crikey

    Crikey Well-Known Member

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    Both 800 and 900 have their own qualities.
     
  5. Exotic

    Exotic Active Member

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    both heads at once?
    do u think it's worth it to add another preamp tube for more gain ?
    costs alot doesn't it?
     
  6. Exotic

    Exotic Active Member

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    is this only for older amps ? or can it be done to jcm 900's also ?
     
  7. Exotic

    Exotic Active Member

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    so the jmc 900's get more gain from diodes ? can u remove the diodes and add a preamp tube for more gain ,how much does it cost?
     
  8. South Park

    South Park Well-Known Member

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    The diodes are for clipping the signal no gain . Adding tubes is not something you want to take on . Just add pedals and call it good
     
  9. Crikey

    Crikey Well-Known Member

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    I run AB and A or B. It is a fat freakin sound. For my ears I see no need for another gain tube. Both the 2210 and 900 have more than enough IMO.
     
  10. Exotic

    Exotic Active Member

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    whats the deal with the ohm switch on a jcm 900 ? how do u use it to avoid blowing up ur amp and can u run a stack ,can u run 2 cabs 8 ohms each? seems to be different than on the jcm 800's
     
  11. Exotic

    Exotic Active Member

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    and if the amp is on low power setting(25 watts) does it change the impedence? when u take out 2 tubes on a jcm 800 2210 (100 watt amp)it cuts the impedence in half .
     
  12. RLW59

    RLW59 Well-Known Member

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    4500 head is 8 or 16 ohms. You can use one 16 ohm cab, or one 8 ohm cab, or two 16 ohm cabs.

    The confusing label is because the combo versions switch from 4 to 8 ohms.

    The combos and heads have the same output transformer which has 4, 8, and 16 ohm taps -- it's just a matter of which two wires are connected to the switch. So you could rewire it to switch between 4 and 8 like the combo if you want to use two 8 ohm cabs ( two 8 ohm cabs is a 4 ohm total load).

    Edit: if you want to run two 8 ohm cabs but don't want to mod the amp, you could use a series junction box or a series cable to connect the cabs in series for a total load of 16 ohms.
     
    Last edited: Dec 1, 2019
  13. RLW59

    RLW59 Well-Known Member

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    The power setting switches between normal pentode mode and triode mode.

    Both output tubes operate in both modes -- it doesn't turn either of them "off". So impedance is the same in both power settings.
     
    Last edited: Dec 1, 2019
  14. RLW59

    RLW59 Well-Known Member

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    delete
     
    Last edited: Dec 1, 2019
  15. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    do u think it's worth it to add another preamp tube for more gain ?

    No

    so the jmc 900's get more gain from diodes ?

    No
     
  16. tschrama

    tschrama Well-Known Member

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  17. Ufoscorpion

    Ufoscorpion Well-Known Member

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    Why not just get a JVM ?
     
  18. Ken Underwood

    Ken Underwood Well-Known Member VIP Member

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    I rest my bloody case, amptechsovernight.com
     
  19. BftGibson

    BftGibson Well-Known Member

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    Good amp. Just get the volume up.
     
  20. Exotic

    Exotic Active Member

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    THIS ALL SOUNDS PRETTY GOOD ,i can get a cab link .
    i can try out the 25 watt mode see how that go's .
    wondering if the diode clipping is going to get along with my mxr 6 band graphic eq ,and a mxr phase 90 and a cry baby wah . should sound great with my speakers ,jbl d120f's , evh speaker , greenback reissue , g12t-75's , marshall vintage ,and avt speakers .
     

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