Marshall 2204 question?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by 110db, May 24, 2004.


  1. 110db

    110db Member

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    Hey guys, I have a 1981 2204 that I recently had serviced, which included new filter caps, screen grid resistors, bias supply caps and new tubes (Ruby Tubes 6550's and 12ax7's). I know these amps aren't considered high gain, but the amp seemed to have hardly any before the servicing, which I thought was just due to age/wear/old tubes. However, after the work was done, it still doesn't seem to have much gain at all. Could there be something else that needs to be replaced that was overlooked? Any help or suggestions would be greatly appreciated.
     
  2. Swarty

    Swarty Member

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    These amps were designed in the mid-'70s, by today's standards they do not have much gain (actually distortion would be more accurate). I see 3 choices; pedals, mods or trade-in. I don't consider tone-sucking attenuators an option, but many do.
     
  3. John Phillips

    John Phillips Member

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    If you're looking for more crunch and distortion at high volume, rather than more gain for low-volume playing, you'd be much better off with EL34s instead of the 6550s. British-market models always came with EL34s, FWIW.

    Unfortunately this would mean rebiasing it again... and it's not within the range of the trimmer either, you need to alter a fixed resistor value.

    Later JCM800 2204s had the two input stages linked in series rather than parallel, which does give quite a bit more gain, but does involve modding the amp - although it's not a big or irreversible mod.
     
  4. Swarty

    Swarty Member

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    I don't believe this timeline is correct. The very first 2204s (circa 1975/76) were different; these were essentialy a 1987 (parallel inputs?) w/ a master volume. I don't think this variety lasted more than a year before they added a gain stage. The setup from this point forward had the low gain input inserted after the first gain stage and remained mostly unchanged (aside from a supressor cap added about 1984) right through the JMP and JCM800 eras.
     
  5. John Phillips

    John Phillips Member

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    I might well be wrong. I thought the parallel-channel 2204s went up to the end of the JMP era, but maybe not.

    You can easily find out which it is - plug a guitar into the High input, and any spare cable or plug into the Low. If you still get guitar coming through, you have parallel channels.
     
  6. Swarty

    Swarty Member

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    Trust me on this one.
     

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