What Makes The JCM800 Magic?

Discussion in 'Marshall Amps' started by Brad O'Dell, Aug 25, 2019.

  1. john hammond

    john hammond Well-Known Member

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    this is interesting..i wonder what do they do with them after? is it like cars...do they destroy them or do they end up in peoples closets somewhere.
     
  2. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    No man. a reference standard is a specific series all of which are built and adhere to the original.
    Its the expensive stuff. Everything is measured to it's standard.
    A reference standard lives on forever.
     
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  3. Nik Henville

    Nik Henville Well-Known Member

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    .
    .
    .

    Talking about tone is like dancing about architecture...
    ...we get the idea, but have no clue as to what it means.
    .
    .
    .
    :hippie::pirate::uk:
     
  4. Kelia

    Kelia Well-Known Member

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    Heard this quote not long ago in a movie but don't remember which one !
     
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  5. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    That type of quote rings back to the medieval times and the dance actually had a name, safety dance.
     
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  6. Nik Henville

    Nik Henville Well-Known Member

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    Most credit Martin Mull with it, from 1979, though variations exist back to the very early 1900's (like... 1918?) and are credited to innumerable folk... for which I thank Alan P Scott at: http://www.pacifier.com/~ascott/they/tamildaa.htm
     
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  7. Relic61

    Relic61 Well-Known Member

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    [​IMG]

    Hey Brad, that's a joke. I hope you get it &, I hope you can laugh at it.

    Honestly though, these 2 amps are so vastly different & made up of so many different parts (more than in common) in so many ways that to think changing a choke or cap value or transformer or whatever simply is ignoring or overlooking that fact.

    Lets just look once more at the internals of a JCM model. These pics are of a 1983 JCM 100 watt lead amp
    [​IMG]

    And we might as well look at the top too..

    [​IMG]

    Then look back upon the inside of your MA that you posted..

    [​IMG]

    (and one you didn't post)
    [​IMG]

    And its comparable top side..

    [​IMG]

    It's just as plain to the eye to see the serious amount off differences here as it was to your own ears to hear the differences when you played these amps yourself...

    And we haven't even touched on the schematic electronic design differences!!! But just looking at the two should be an indication that it is going to take way more than changing a part or 2, or 3, or more.

    I will simply put it like this,.. The beauty of a great JCM is the sum of all it's parts & engineering coming together to work beautifully as one amazing amplifier. In direct comparison, the MA was designed & made as affordably (I didnt dare say cheaply) as possible!

    While your quest is a noble one sir, please don't get mad when people have a negative reaction to your notion of this quest being possible or financially feasible or even worth the time or effort. It's a natural reaction in this type of situation & premise.

    But, even if you did come up with something 'close', are you really going to be comfortable changing the intended design & then relying on a modded MA to withstand gigging touring road use & abuse? How much is reliability & peace of mind worth in that situation Brad?

    And while some will always opt for the adventure of turning this..

    [​IMG]

    and this..

    [​IMG]

    into this...

    [​IMG]
    (not the there's anything wrong with that..)

    there will always be those that balk at the idea & scoff at those who try such things.

    Now my best advice as a gigging musician for over 40+ years now.. spend the damn money you need to spend to have good reliable equipment that gives you the sound you want & love so you feel great & can truly feel happy when you're playing on stage in front of people! You know inside it's worth every penny when you have that going for you on stage.

    There's nothing like sounding good & feeling good because you're sounding good! It's infectious! Infectious because those feelings are being conveyed through the music you'll be making. Yes, your happiness will be communicated through your music & touching the people you're playing for. This is an important job. Treat it that way, do it well & enjoy the multitudes of rewards. The cost for not doing so could be higher in more ways than one.

    Recognize, appreciate & treat that gift & responsibility accordingly.
     
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  8. Brad O'Dell

    Brad O'Dell Member

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    As stated in the original post, I own an 80s model JCM800. I just dont want to gig with it.

    This thread was not ever supposed to be a "What is your opinion of the Marshall MA100H?" thread, however, those who have nothing to offer but opinions did not hold back doing so. (With or without experience with the amp.)

    This was supposed to be a technical thread about what makes the JCM800's gain channel so good, and what can be changed in the MA100H to better replicate that.

    There have many helpful posts in this forum regarding increasing the power to the tone stack and reducing the negative input, you just have to find them among this threads dilution.

    When it comes to changing parts in the MA, I do not feel like new tubes were a waste of money or the $20 in pots to perform the mods. I also do not feel that these mods threaten reliability, as other members have done them to other Marshall amps such as DSLs and JVMs without problems.

    To answer your question, the biggest difference I see between the MA and 800 is Chinese tubes, and the amount of soldered wire use vs circuit board use. I also see how much technology has reduced the size of components like capacitors. It would be the same difference one would see if you opened any old electronic device and compared it to ones from today.



    Looks like the other difference between the 800 and MA is Marshall decided to keep the MA's tubes on soldered wire and moved the pots to a printed board, where as the 800 pots are wired.
     
    Last edited: Sep 2, 2019
  9. Relic61

    Relic61 Well-Known Member

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    Then look at the simplicity of the 800 schematic. That's what makes it so good. Look at the components too! Note the direct design & use of the extra gain stage of a 12ax7 tube fro pre-amp drive as well as all various values from voltages to capacitor usage for tone. The MA hardly resembles a JCM yet you want it to sound & behave like on doing a couple magic changes. Meh.. maybe you can improve a thing or two to get close but... hey man, if it interests you then rock on right?!

    Of course things look different today but as I'm trying to make apparent, these just aren't the same amplifiers.

    Here's you MA100 pre-amp
    [​IMG]

    Here's a JCM pre-amp.
    upload_2019-9-2_7-4-46.png

    You really need to get back to the simplicity & electronic values of that circuit to achieve the JCM fidelity of sound & its tonal sonic reproduction.

    You can't run your guitar signal through that MA100 circuitry & expect to it have the JCM's organic qualities & purity of sound.

    For some reason, you are being hard pressed to see this And in reality who TF am I to discourage you from going on your adventure & learning all you can so I say.. enjoy yourself, learn all you can & don't let discouragement get in the way.

    If I wanted to achieve this I would replicate the JCM's pre-amp & use what you say is a decent sounding amp section when run clean. but doing that to an MA just seems.. well I'm not going to sound discouraging so.. ya.. rock on
     
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  10. Brad O'Dell

    Brad O'Dell Member

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    2210a.jpg 2210b.jpg


    Great post!

    Keep in mind that I am looking for a "Stunt double" to stand in for my JCM when I play less than optimal gigs. I used the MA, because it was what I had, not because I specifically went out and sourced it as the replacement. IMO it is already a suitable stunt double, I just want it to be better in the gain channel. I feel like I am on the way to achieving that.

    https://www.google.com/search?q=stu...g7LkAhVMmeAKHeyxAOQQ_AUIESgB&biw=1366&bih=654
     
    Last edited: Sep 2, 2019
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  11. john hammond

    john hammond Well-Known Member

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    turning an MA into more of a jcm800..hmm

    - you'll need voltage doubling
    - you'll need to make sure they have the same amount of gain stages.
    the more gain stages,the less dynamic punch.
    - the iron can be smaller on the MA,but the sound will be smaller.
    - the eq will need to be in the same place( before 2nd gain stage? ..wherever they are)
    -filtration will have to be sort of the same values( part of voltage doubling conversion)

    -v2b on a jcm800 is an impedance buffer, and what i consider a signature tone shaping feature on jcm800 and plexi amps....if the MA100 has no impedance buffer = not gonna sound right.


    the last point alone is enough to forget about it,not gonna happen.
     
    Last edited: Sep 2, 2019
  12. Brad O'Dell

    Brad O'Dell Member

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    [​IMG]

    Me: I am thinking that a haircut will make the stunt double look more like the original.
    You: You will need to reshape his scull, nose, and jaw.
    Ampeq: Chris Pratt sucks.
    Most of this forum: Get Patrick Wilson to be the stunt double.

    Me in 2 weeks:
    haircut.jpg
     
    Last edited: Sep 2, 2019
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  13. plexilespaul

    plexilespaul Well-Known Member

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    modern amps are built more like a pc. the more i look at the inside of them the more I understand why you can't really get great tones out of them.
     
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  14. sonicexplorer

    sonicexplorer New Member

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    I didn't read through all 10 pages of this discussion, but will share something that is almost always overlooked in these kinds of debates....

    The same exact circuit and parts can sound vastly different, not just because of tolerances, but simply depending on differences in circuit board layout and wiring paths. This is completely not intuitive and sounds crazy, but indeed true. I've ran into this a number of times first hand when trying to duplicate amps or alter an existing amp. There are electronic and physics theories behind why this occurs. Just suffice to say it is something to at least be very aware of.

    Sonic
     
  15. Musicmaniac

    Musicmaniac Member

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    Couldn't have said it any better! :dude:
     
  16. Chris-in-LA

    Chris-in-LA Well-Known Member

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    I’ve read the whole thread, OP has mentioned the “gain channel“ on his jcm800 and most here seem to assume he’s talking about a 2203 but I believe he’s talking about a 2210. Does that make a difference?
     
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  17. Brad O'Dell

    Brad O'Dell Member

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    1984 100w JCM800 2210
     
  18. Relic61

    Relic61 Well-Known Member

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    Why thank you.. Thank you very much..

    [​IMG]

    [​IMG]
     
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  19. Brad O'Dell

    Brad O'Dell Member

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    Did the negative input mod. (The knob is beside the standby switch.)
    -WOW- Thanks for the help, fellas!
    Now I need a sticker that says "Fat" on one side and "Thin" on the other with a scale from 1-10 knob.jpg back.jpg
     
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  20. Cadorman

    Cadorman Well-Known Member Premium Member

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    Interesting how changing the value affects the drive isn't it.
     

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