JCM 800 2205 info needed

Discussion in 'Marshall Amps' started by hunter008, Nov 30, 2020.

  1. hunter008

    hunter008 New Member

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    Hi, I was wondering if someone could help me with some info about this amp.
    It has been explained to me that they changed a circuit at one point. After the initial production.
    That made it a lot better. Could you guys tell me what serial numbers correspond to that change? I've been wanting one of these amps for some time now. And I want to get the correct one when I finally pull the trigger. I usually only see them for sale online so I may not get to test it or pull a tube to check it in person before purchasing.
    Thanks in advance.
     
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  2. South Park

    South Park Well-Known Member

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    From the reviews it looks like a problem with conductive circuit beards . Bias drift and Chanel bleed over if you are going to get one make sure you can get a good circuit board . Cant say if Marshall fixed it with better circuit boards
     
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  3. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    1987 is when the channel bleed was fixed, also a bit more gain. The purpose of V1 and V2 preamp tubes was reversed in the new versions. V2 runs the boost channel in early design, clean channel in later ones.
     
  4. Gunner64

    Gunner64 Emotional Support Animal Gold Supporting Member

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    Never had a 2205 with bias drift..they do have some channel bleed. Mine was an 87, and did have some bleed. Idk if they ever totally elimi ated it. I used mine like a one channel amp anyway so I didn't care. And as was mentioned about 86- 87 on up they got hotter.
     
  5. hunter008

    hunter008 New Member

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    And what serial numbers would indicate a 1987?
     
  6. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    Oh I was under the impression the bleed was actually fixed at that point. My mistake! I know it got much better after that stage.
     
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  7. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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  8. hunter008

    hunter008 New Member

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  9. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    No probs! Would be a fun amp!
     
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  10. headcrash

    headcrash Well-Known Member

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    Apart from the channel bleeding, there were genuine different versions of the split channel amps, and I have yet to find out, when exactly Marshall switched from the old to the new design. My guess ist, it was around '86.

    The older ones had a rather untypical topology for the gain channel, with the tone stack in between the gain stages, resp after the first one, IIRC. Topology-wise this is similar to the Boogie Mark series amps. Using the tone stack you will be able to fine tune the distortion sound. However, it is not the typical Marshall topology, and like the Mark series amps, which are said to be dialed in difficultly, it can lead to unpleasant results. Turn up tha bass i.o. to have a sound with thundering low end? Won't work, with higher levels of distortion, you will end up in a muddy mess. You would most likely turn down the bass to get a tight distortion. And loose much of your low end, of course. This is why the Mark series amps mostly have the graphic EQ to compensate for.
    I think I remember an interview with Marshall's amp designer back then, Steve Grindrod, mentioning, he was advised to develop an answer to a "certain amplifier which was popular at the time", which might be a hint for the similarities in design with the Boogies.

    However, Marshall might have understood mid 80s, that Marshall players want a classic Marshall sound, and revised the circuit to a more classic topology with the tone stack of the gain channel after the gain stages.

    By the way, both versions achieve a certain level of their distortion through diode clipping circuits.
     
  11. Gain Man

    Gain Man Active Member

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    Mine is from 1984 (serial number begins with S) and it has the newer type circuit. Since I am not the first owner of this amp, I would not know for sure, if maybe a previous owner changed the circuit board or something.

    However, since they switched to the newer circuit, it has been modified a couple of times until production ended.

    Side note:
    If you get your hands on one and want to find out, if it uses the old or the newer circuit, pull out the second preamp tube (V2). If the Boost Channel still works and the Normal Channel is silent, then it is the newer circuit. If the Boost Channel (or both - I don't remember) is silent, then it is the older type circuit.

    As far as channel bleeding goes, you might hear a clean sound in the background, when playing on the Boost Channel, but only with the Normal Channel's volume on 10 and the Boost Channel volume very low. The question is, why would you even do that?
    Maybe the problem is worse on other amps than mine - this is probably not talked about for no reason.
     
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  12. Sapient

    Sapient   Silver Supporting Member Platinum Supporting Member

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    I've got the '88 and to be honest it sounds pretty much like a Crate from the same era.

    No, that is not good. :(
     
  13. Gunner64

    Gunner64 Emotional Support Animal Gold Supporting Member

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    Then somethings wrong with it
     
  14. CROWEMAG

    CROWEMAG Well-Known Member

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    Get that thing serviced. Something is wrong.
     
  15. scozz

    scozz Well-Known Member Gold Supporting Member

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    :shock:
     
  16. lonewolfsx

    lonewolfsx Well-Known Member

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    I've seen the 1987 year thrown around a lot but I have an 85 ("T" serial number) and it's the newer circuit revision. Just food for thought.

    I've played an 82 and really disliked it. It didn't have as much gain and I felt it was a bit thinner. Of course, it may have need repairs or who knows what. I didn't know shit about amps when I tried it compared to now.
    I loved my 85 right off the bat in the store, took it home and checked the circuit, new version. There's hardly any channel bleed, I can coax it into bleeding ever so slightly if I set the "normal" channel volume to 10 - but you would probably never use the amp set like that, the normal channel is insanely loud, much louder than the boost channel.
    I actually kind of like the tonal variation with the normal channel set to 10 and playing the boost channel. It's so subtle but it adds a tiny bit of thickness - it's almost like blending channels on a jumpered plexi. Considering the circuit isn't too far off of that idea I'm not surprised. Obviously not as noticeable or drastic of a change as on a real plexi.

    My advice, go try one out and if you like it, get it. Take it home and pop out the V2 tube. If your boost channel stays exactly the same, it's the new circuit. Enjoy. If not, you still got an amp you liked. I didn't like my 82 but I know people who would like it (I'm a high gain fan so it wasn't enough oomph for me).

    @Headcrasher nailed it btw. The early circuit tonestack location is the biggest reason they sound so different. I have a Mesa Mark IV and it's that same topology, the recommended method for that amp is to max the treble, set mids to taste (usually around 5-6) and bass real low, like 3 or 4, but both mids and bass controls do almost nothing on that amp compared to what you might be used to. Bass set any higher and it sounds like actual garbage, IMHO, for high gain tones at least. So you use the graphic EQ to make up for it by raising up the lower frequencies way after the gain stages, so they stay tight. There's a reason why Mesa Mark's without the graphic EQ are so much cheaper than the ones that have it.
    I'd say with an EQ in the fx loop the early circuit could probably sound pretty great. Max the treble, or all of the tone controls, roll the bass off until it loses the flub, then use the EQ to tame the highs and add back in some thickness.

    Still, I'd say, hunt down the newer revision circuit if you can. Neither circuit is exactly the traditional Marshall sound but it's closer. The late 2205 is my favorite Marshall actually.

    Now a question in case someone in the know sees this, I've seen a few posts but nothing concrete saying there was a 3rd circuit revision, minor stuff like more gain or a slightly different voicing, in either '89 or '90 right before the Mk III's came out. Is that just a complete rumor or is there any truth to it? I can't find a schematic anywhere but I don't have access to the service manuals or anything Marshall might have hidden away in their library.

    Edit: Somehow I missed it, Gain Man already covered most of what I said in his post. My bad. Also, '84 and the later circuit? That's got to be one of the earliest ones! From what I understand, it isn't an easy change to change from the old to new circuits.
     
  17. lonewolfsx

    lonewolfsx Well-Known Member

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    I'll take it off your hands if you just can't stand it... :naughty:
     
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  18. Sapient

    Sapient   Silver Supporting Member Platinum Supporting Member

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    According to your signature, you'll have to fight with @Drinkingdeath01 over it. :p
     
    Last edited: Dec 1, 2020
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  19. Sapient

    Sapient   Silver Supporting Member Platinum Supporting Member

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    Wow, I'm surprised by your posts. I thought this (especially being a diode clipper) was kinda frowned on in its sound. I thought the 2210 got all the glory as it does sound fantastic. I've never heard a stock YouTube vid where the 2205 actually sounded good ...but there are a few mods that sound great.

    I removed the diode clipping from mine this summer to try to "salvage" the sound and now it sounds like a "tube ..transistor amp". :scratch: I thought it would shed the very very compressed, 0 dynamic range sound and feel for some serious tube dynamics. It's like half horrible now ..really weird. It's been sitting on my bench in the basement abandoned since August. My JVM410HJS heads have really had me completely forgetting about it ..quite well.

    I'll try a few more things with it (already tried LED clipping too) to see what happens but I'm not very optimistic.

    I expected more to be on-board. :shrug:
     
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  20. hunter008

    hunter008 New Member

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    Now damn. Why didn't I think of that...
     

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