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? about my JCM 800's mod....

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  • ? about my JCM 800's mod....

    This is a vage or general question but here goes..... My early 80's JCM 800 2204 50 watt model head has an added pretube circuit..... I have been told that this extra circuit is most likely the source of the extra noise and hum that the amp has... It's been checked over by a tech, but he is not the best tech... What type of MOD circuit is this.... what do they do besides add another tube for more gain?.... what else may go with this extra tube inside.....?

  • #2
    Re: ? about my JCM 800's mod....

    Sounds like it's just an additional gain stage, pretty common mod. But yeah, with more gain stages, you get more noise. Have the filter caps been changed?

    MJ
    EMB Audio Remote and Pedal Wahs: www.facebook.com/EMBaudio

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    • #3
      Re: ? about my JCM 800's mod....

      Originally posted by Monty-Jay
      Sounds like it's just an additional gain stage, pretty common mod. But yeah, with more gain stages, you get more noise. Have the filter caps been changed?

      MJ
      Ya the tech that the store uses that i bought this used and abused head from changed some filter caps but not all, also replaced the power tubes, and added some sheilding to something... That quieted things down a bit but i still need to take it to a better tech.... He did this work for free because i complained about the noise

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      • #4
        Re: ? about my JCM 800's mod....

        Typically mods are a little noisier, but you have a very common mod. However, it shouldn't be so noisy that you can't use it. Where do you live, perhaps we can point you to a good tech in your area. Otherwise, there are a couple of techs we all know that do great work. You'de need to ship it to one of them, but they would make it right.
        My Sound Clips

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        • #5
          Re: ? about my JCM 800's mod....

          Originally posted by Jeff_H
          Typically mods are a little noisier, but you have a very common mod. However, it shouldn't be so noisy that you can't use it. Where do you live, perhaps we can point you to a good tech in your area. Otherwise, there are a couple of techs we all know that do great work. You'de need to ship it to one of them, but they would make it right.
          I'm a 1/2 drive away from Toronto.... There is a great tech i know of in Toronto that works out of his house... i need to take this head to him.... in this area he is the tube amp guy to see... A lot of vintage dealers and Canadian artists use him..

          As soon as i throw the standby switch it sounds like i have a single coil guitar and and fuzz pedal on... And that is with my volume off on my guitar.... or even when i do not have a guitar cable plugged in the amps imput... the noise/hum is always there.... my 5150 is dead quiet compaired to my 800 head... I knew it was a fixer upper when i bought it...

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          • #6
            Re: ? about my JCM 800's mod....

            It just sounds like with a cap replacement and some other tweaks/shielding it can be made right. It will probably never be DEAD quiet, but it can get close.

            If you have a tech with a reputation like you say, then it's worth every penny to take it to him. Give him carte blanche and say do what you need to do, make it right. It probably won't cost what you think to get it done, and you'll be much happier. The tone will kill you.

            I had my 2205 modded to be Fender BF on the clean channel, and Plexi/2204 on the drive channel, just to get some of what you already have. Your 2204 will sound FANTASTIC when you get the noise issue taken care of....there is nothing like it cranked and smokin.
            My Sound Clips

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            • #7
              Re: ? about my JCM 800's mod....

              Originally posted by Jeff_H
              It just sounds like with a cap replacement and some other tweaks/shielding it can be made right. It will probably never be DEAD quiet, but it can get close.

              If you have a tech with a reputation like you say, then it's worth every penny to take it to him. Give him carte blanche and say do what you need to do, make it right. It probably won't cost what you think to get it done, and you'll be much happier. The tone will kill you.

              I had my 2205 modded to be Fender BF on the clean channel, and Plexi/2204 on the drive channel, just to get some of what you already have. Your 2204 will sound FANTASTIC when you get the noise issue taken care of....there is nothing like it cranked and smokin.
              The tech i am going to take it to wants to remove the extra gain mod, add some sort of Tone Mod..... he says that his Tone mod greatly helps in making these early Canadian Marshalls sound their best.... Plus the tone mod can be reversed easily he says if i don't like it.... i have to get this thing too him soon..... he is in an out of the way place for me but i think it'll be worth the drive!

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              • #8
                Re: ? about my JCM 800's mod....

                It will definately be worth the drive. Theory and knowledge on how to get Marshalls to sound their best have come a long way. Amazing things can now be done to them WITHOUT adding tubes or diode clipping. I have no doubt that a good tech can achieve this for you.

                Can't wait to hear how you like it.
                My Sound Clips

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