Jvm Knobs & Pots

Discussion in 'Marshall Amps' started by Graham G, Feb 8, 2019.

  1. Graham G

    Graham G Member

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    Sacrilege I expect,but I've just put some different knobs on my recently acquired JVM,so that I can actually see the settings & be able to see to make adjustments when gigging.
    During the specking & then fitting of the knobs,i was surprised at the quality(or rather lack of it)of the pots,cheap through panel pcb mount,plastic shaft,no locking nuts.?
    I believe the JVM(215C)which is british built & not cheap should have better quality components & build quality.
    I'm reluctant to take the Amp head out to look at the quality of the rest of it,not good enough Marshall.
    Of course I could be expecting too much from a £1250 amp & i'm just being a dick :hmm:
     
  2. Adieu

    Adieu Well-Known Member

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    All modern marshalls are cheap PCB builds and have been for quite some time (many decades)
     
  3. Graham G

    Graham G Member

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    I wasn't really complaining about the Control board being PCB,but no excuse for that kind of 50p pot construction.
     
  4. MonstersOfTheMidway

    MonstersOfTheMidway Well-Known Member

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    @OP: If you there are aspects of the amp you don't like, then take it back wherever you bought it or flip it. I don't know why someone would be "reluctant" to take the amp out and look at the "quality of the rest." But hey, it's your money and your decision, so if you feel you've been cheated when comparing what you paid versus what you got, then take it back for refund or exchange (depending on your store's policy), or trade it/sell it. No need for you to keep something that doesn't meet your expectations and satisfaction.

    @everyone else:
    Since 2008 I've been the original owner of what was then a brand new made 2007 JVM410H. I have had no problems with the knobs or pots (actually I've had no problems at all with the amp though I've had to change tubes due to general wear and tear on normal schedule, which reflects more of a "consumables" category than anything indicative of a problem with the amp.

    This whole topic of knobs and build quality has come up in the past. In the past, Santiago has explained the choices for build decisions in regards to the JVM2 and JVM4 series; I'm not gonna repeat his comments and I'm not gonna do any searches, but you can find his comments through a search on either this forum or the JVM forum. From my experience as a long time owner and from Santiago's explanations, I'm fine with their work. Additionally, the JVM series has been in existence for more than 10 years now and yet they keep selling like hotcakes even though the knobs have plastic shafts, no locking nuts (I think someone said newer ones now come with lock nuts but I could be wrong), pcb mounted pots and tube sockets, blah blah blah. True, there are some options owners can take to reinforce and/or further secure the knobs, for example, but in my experience it's not necessary and probably won't help much (see below).

    Final note: nothing is 100% indestructible and/or 100% damage resistant. Give me a vintage amp that's (to borrow a tired cliche on this forum) "built like a tank" and I guarantee I can phuck it up. I'll bend the sh*t out knobs, abuse the phuck out of the inputs/outputs, and torture the power and stand by switches beyond repair. In the end, you'll see that all of that sense of security and quality won't amount to jack sh*t because one big factor always rings true: take care of your sh*t. Again, my 2007 JVM410H is almost 12 years old, and all components are original and in good working condition because I take care of my sh*t, and I suspect that, more than build quality, will make the difference for vintage build quality as as well modern build quality.
     
  5. Graham G

    Graham G Member

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    Hope you enjoyed the rant,i doubt very much you could bend chassis mounted pots,if you think pcb mounted pots with no securing nuts on the fascia is a good practice,feel free to enjoy it.
    The point of forums is to discuss things & voice opinions even incorrect opinions like mine,i have no idea if the subject of these pots has come up before,this is my 1st Marshall & i'm fairly new to the forum,surprisingly I haven't read every single post that's been posted, before I joined.
    I have no idea who Santiago is but if he thinks mounting pots in this cheap amateurish fashion is correct,he must obviously be right :)
     
  6. Moony

    Moony Well-Known Member

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    They are not locked at the chassis, because there is no need for it. In real life I know really noone who has managed to get a pot ripped of the pcb on a JVM. If you can do so, you might be a very special talented guy. :applause:

    And people were also complaining about the plastic shafts of the pots... however a diecast zinc shaft is not more stable. They both will break at some point, if you try to break them. But not in normal use situations.

    The advantage of non-locked pots is simply that you could easily change the front-pcb if needed and replace it with a new unit without doing the hassle with loosening the nuts of 28 knobs on front. FYI, you can buy those JVM spare pcbs (main or front or reverb) and change them, if some part has failed on the original one - maybe at a lower price point than shipping to an amp tech and his time and labour to figure out, what's wrong will cost you. You don't even have to solder anything thanks to the plug connectors.
     
  7. MonstersOfTheMidway

    MonstersOfTheMidway Well-Known Member

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    Thanks for the challenge, and I accept. Send me any amp of your choosing with chassis mounted pots, and I will gladly do my best to bend the shit out of them. Additionally, I also promise to hit them flush so that the shaft gets pushed into the pot, thereby destroying chassis mount, face plate, and the pot itself.

    But my real point of my initial reply remains: if you're unhappy with the components, construction/build, and/or any other aspect of your JVM, instead of creating a thread with your bitching just take it back, sell it, or trade for something else. You could probably get more satisfaction getting rid of your JVM for something more to your standards than coming on here and talking the same old sh*t. I totally subscribe to the idea that not every product will be right for a person, so I encourage you to dump your JVM and go find something that truly makes you happy.

    I don't know if your opinion is "correct" but your initial post certainly continues spreading a misconception that has for the most part been debunked as far as reliability and quality goes. I really don't understand the point of your first post anyways: are you bitching just to bitch, are you bashing an amp to show off your knowledge of circuits, or did you really think you were the first to discover the JVM had plastic pot shafts that were soldered directly to the pcb without any chassis mount? If your first post offered an alternative (such as pictures showing how you made your JVM more to your liking), then I'd see the point.

    I'm trying not to jump all over you because, I like I said, you're not the first to make these comments, but the tone in your writing makes it difficult.

    It's not just the JVM, though, that uses these type of components and construction/build. The new Studio Classic amps use similar components and construction/build (I'm not sure about the Studio Vintage amps do as well, but it wouldn't surprise me if so). A few owners have posted gut shot pics revealing similar internal features. And, like the JVM, the new Studio Classic amps are also made in England. So if the JVM's internals upsets you so much, then future is probably gonna be more of the same.

    Santiago is in reference to Santiago Alvarez. The rest of your comment is amusing, especially since you don't know who is Santiago Alvarez. I only bring up his name because it is extremely relevant to your complaint and his authority and expertise far exceeds mine.
     
    Last edited: Feb 9, 2019
  8. Moony

    Moony Well-Known Member

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    As far as I've seen on those gutshots, in case of the Classic, the pots are probably mounted to the chassis with nuts as there are no scews for the pot-pcb or any plastic clips like on the JVM.
    However, the pots should work either way and I don't think that one lasts longer than the other.
     
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  9. MonstersOfTheMidway

    MonstersOfTheMidway Well-Known Member

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    I couldn't get a good look at the mounting of the pots, but they're similar type to the JVM, and the pots on the Studio Classic are definitely soldered directly to the pcb, like on the JVM. Additionally, the Studio Classic has all tube sockets soldered directly to the the pcb, just like on the JVM.

    To be clear to those reading: I don't find the build/construction on the new Studio Classic or Studio Vintage to be inferior or cheap so long as the build/construction stands up to general wear and tear. On the JVM, the pots, tube sockets, audio jacks, etc., have all stood the test of time in my stock 410H; I see no reason why same the should not be true for the new Studio Classic and Studio Vintage (actually, as far as quality & reliability goes, I expect better from the Studio Vintage and Studio Classic than the JVM (in theory at least) since these new amps should have benefited from any pros and cons learned through the JVM and other previous Marshall amps.
     
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  10. Moony

    Moony Well-Known Member

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    Yes they are. But I think, they are locked with nuts at the front of the panel.

    Yes, but there's nothing wrong with that. The sockets of the power tubes are bolted to the chassis and there are many thick screws around the preamp tubes, which hold the pcb tight in place and avoid bending it.

    Never said anything different.
    The only known problem, the earliest JVMs had, were the fuses of the heaters. But just on 2007s and early 2008s JVMs afaik. Marshall fixed that really fast.
     
  11. santiall

    santiall Well-Known Member

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    that's the way Marshall was building amps since the early 2000s and still is a common way of mounting pcbs with a relatively big amount of pots and many pro-audio brands use it. There are pros and cons but in the case of the JVM wasn't done for cost purposes but for manufacturing reasons.

    In any case, the topic is a bit old as the pot assembly was fixed (pun intended) back in 2007, yes ~12 years ago after ordering a custom made pot with the right dimensions for this product. The 4 channel was released with the modified assembly straight away and, as far as I am aware, the 2 channel sometime after although I don't know the dates or if it has been ever updated.
     
  12. Neil Skene

    Neil Skene Well-Known Member

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    I have one of those amps everyone freaks out about and tells me its going to blow up, JCM 2000 DSL100. I have had it since 2005 or late 2004 can't remember.
    Never been a problem with it (that was the amps fault) and its only on its 3rd set of EL34's which I put in about 2 years ago.
    They look a bit cheap and computery inside but it just keeps on going.
    Don't worry too much about the build quality Im pretty sure it will serve you well, just turn it up and appreciate it with your ears.
    I also believe every one is entitled to an opinion and every post is interesting or boring to someone so, Im not going to go all fanboy on ya, Rock ON!
     
  13. Graham G

    Graham G Member

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    Believe In Monsters.I think you're going completely over the top with the tone of your replies & being way to personal,but if that's the way you respond to threads which you don't like,i suppose that's the way it is.
    To you & the rest of the forum,if my post has offended you,i apologise,i'll make sure I don't say anything that can be construed as critical of Marshall in future,i'll just post about how great red crunch mode is & probably ask about doing the OD2 to OD1 mod,if that's ok:).
     
  14. Moony

    Moony Well-Known Member

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    That's easy:

    Take out the front pcb - that one with the pots, which you don't have to unlock. ;)

    Change R44 from 47k to 33k
    Change C31 from 1500pF (1,5nF) to 1000pF (1nF)
    Change C32 from 1000pF (1nF) to 3300pF(3,3nF)

    Put it back in - done.
     
  15. Graham G

    Graham G Member

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    Cheers,Moony.That's great thanks,what a relief not having to undo all those pot locking nuts.:D
    Is there any advantage of upgrading the already excellent quality caps(if possible):)
     
  16. Graham G

    Graham G Member

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    Thanks,Moony.That's great,what a relief not to have to undo all those Pot locking nuts:D.
    While i'm doing the Mod,is there any advantage to fitting an upgraded cap,although i'm sure they're already top quality:).
    Cheers.
     
  17. Moony

    Moony Well-Known Member

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    If you change the value of the caps, you'll notice a difference for sure.
    If you replace the caps with the same value but use other material, you'll notice a difference, too - but it can vary from subtle to very noticeable. The white and grey film caps are metalized polyester, the red ones are polypropylene.
     
  18. ampmadscientist

    ampmadscientist Well-Known Member

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    Unfortunately, many amps these days are being built with cheap flimsy pots, which break easily, wear out fast and are difficult to clean.
    But you can attach flying leads, and mount good pots. Also the good pots are expensive but worth while for the reliability.

    However the circuit board is easily damaged by inexperienced soldering.
    Which is why you should have a pro do the repairs.

    Caps: good caps such as F&T (filter caps) will make a huge improvement in the sound quality.
    Solen also makes some really nice coupling caps, which are also expensive.
    Changing to good caps will probably make the biggest difference (besides good tubes).
     
  19. Moony

    Moony Well-Known Member

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    The filter caps on the JVM series are just fine - you won't hear a significant difference to F&T - tried that already. If so, then it's due to tolerances of the values.
    I've tried Solen Fast in several amps, don't like them at all for hi-gain applications (if, then only at the PI). More so in Fender style amps.

    In the JVM series I've tried Mallory 150s, SoZo Standard, Orange Drop 225, Cornell Dubilier DME, Vishay MKT368 and Vishay/formerly ERO Roederstein MKT1813.
    I've got extra pcbs for experimenting with different caps and values just for fun. I can tell you, that in this amp, I found the MKT1813 to be the best by far.

    My main JVM has all MKT1813 and for the 470p ceramics those caramel NOS B&C:

    [​IMG]


    But that's not a must have by any means and would cost a fortune to let an amp tech do that.
    If someone could do it by himself, I would recommend the MKT1813s.

    You could also try different tubes, speakers or simply an EQ pedal in the loop to change the sound.
     
    Last edited: Feb 10, 2019
  20. JamesD

    JamesD Active Member

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    The computer-like build of Marshall circuits coming from the Marshall entity is why I now prefer to buy Marshall circuits from other entities who handwire them with quality components, mount the tube sockets to the chassis, etc..

    After all, it’s not the plastic script logo or the legal entity that makes these circuits special - it’s the circuits themselves.

    Would anyone here argue that SRV’s recording of Little Wing is not actually the song ‘Little Wing’ because it’s not Hendrix playing it?

    Likewise, Marshall circuits made outside the Marshall entity are still Marshall circuits.
     
    Last edited: Feb 10, 2019

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