YJM100 Boost (calling on the techs, please)

Discussion in 'Marshall Amps' started by crossroadsnyc, Mar 7, 2021.

  1. crossroadsnyc

    crossroadsnyc Senior Moderator Staff Member

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    Here's my question:

    The YJM100 has a built in boost, can you tell me anything about the placement of the boost w/in the amp? I'm not a tech, so while I'd like to share a schematic, there are so many things that come up in a search, that I'm not sure what to share. I suppose I'm curious as to the placement of the boost w/in the amp in comparison to using an external boost. An external boost makes sense to me, but when it's inside the amp, I'm not sure exactly what's going on.
     
  2. ricksdisconnected

    ricksdisconnected Well-Known Member

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    in for the education.
     
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  3. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    I think it's 1st thing, but, I bet Santiago knows exactly what's up, w/o looking... @santiall
     
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  4. santiall

    santiall Well-Known Member

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    20210307_232638.jpg There you go, straight from the handbook
     
  5. crossroadsnyc

    crossroadsnyc Senior Moderator Staff Member

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    Thanks (my manual is tucked away, and I didn't even think to dig it out). This might be a dumb question, but does having the boost built into the amp react any different than having it out in front on your pedalboard? For example, when in front of the amp, you might be going through several patch cables, several other pedals, and then of course the long lead taking you into the front of your amp/FX loop, whereas having it built into the amp, you eliminate all of that.

    The reason I ask is because I can't figure out whether it's the particular boost built in that I like so much, or whether there might be a technical explanation as to why it works so well. There's just a naturalness to the boost that feels so much a part of the amp, and I don't get that with any other boosts (not only w/this amp, but others through the years). It's more like a natural extension of the amp if that makes any sense.

    One final question ... there's a lot of speculation as to which boost the YJM boost was modeled after (I've read everything from the YJM308 to an old school grey box DOD250) ... are you at liberty to say one way or another? If it turns out that the placement of the boost is irrelevant, it'd be nice to find out which boost it's modeled after so as to maybe pick one up for other amps (I really like it).

    Thanks again!
     
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  6. ufguy73

    ufguy73 Active Member

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    i don’t remember exactly (and it wasn’t even the YJM but another amp that had a particular style of boost built-in that sounded better than very similar boost out front) but i spoke to an amp builder once about this concept and I thought he was saying something about the boost circuit running at higher voltage when integrated into the amp or something...

    maybe something like that is in play for the YJM too?
     
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  7. marshallmellowed

    marshallmellowed Well-Known Member

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    All subjective, of course, but I never noticed anything special about the YJM boost. It was OK, but nothing I hadn't heard before. Clean design, as it was built-in, but a bit limiting, as you only had control of the "Drive" level.
     
  8. bigbadorange

    bigbadorange Well-Known Member

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    Just for the record Im with you on something going on. I rolled dozens of other overdrives, and happen to have several 4 holers. None sound as good as the YJM with its built in boost. And its interesting as without the built in boost, it DOES pretty much sound like any other four holer. There IS something more going on.
     
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  9. santiall

    santiall Well-Known Member

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    it is YJM308 powered at 9V.
    If shouldn't make much difference having it inside or outside when engaged but when using an external pedal, if the effect is OFF, it'll depend a lot on your cables or whether you have anything buffering your guitar signal before the overdrive
     
  10. crossroadsnyc

    crossroadsnyc Senior Moderator Staff Member

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    Thanks, dude ... this has been on my mind for a while now, so it's nice to have a better understanding. It looks like I'm just a fan of the YJM308!
     
  11. crossroadsnyc

    crossroadsnyc Senior Moderator Staff Member

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    Yeah, a tone control would be nice, but manipulating the EQ works just great for me, so it's not a deal breaker by any stretch.
     
  12. crossroadsnyc

    crossroadsnyc Senior Moderator Staff Member

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    Sounds like the secret is the YJM308 :hmm:

    I'm totally going to have to get one now and do a comparison.
     
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  13. santiall

    santiall Well-Known Member

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    have fun!
     
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  14. Gene Ballzz

    Gene Ballzz Well-Known Member

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    I'm gonna make a guess here and bet that the "on board" boost has had the impedance and levels more closely matched to the circuitry of the amp, as opposed to having it be a "one size fits all" approach to operate in front of any amp!
    Again, Just A Guess?
    Gene
     

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