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RBX JM2 electronics question

Discussion in 'Pickups & Electronics [BG]' started by dkthrone, Jan 7, 2014.

  1. dkthrone


    Feb 9, 2013

    I bought a used RBX JM2 for dirt cheap, and as it turns out some kid had gutted its electronics and left it barely working... anyway, i want to replace the preamp/electronics but choices for a single MM 6 string pickup seem to be very few.

    I found this electronic from Glockenklang:


    My question is if this would work with the stock JM2 pickup? More specific, i am unsure about the 'balance' option of this electronic, which would imply two pickups, right? I simply dont know who to ask, i figured there must be tech-minded people on this forum who would know.

    Or maybe there is a different electronics option i have not yet considered?

    Much appreciated!
  2. tylerwylie


    Jan 5, 2008
    Dunwoody, GA
    FYI Delano and Carvin sell 6 string "MM" style pickups.
  3. ReidK

    ReidK Jst sy n t lsy cmprsn.

    The stock pickup is a Seymour Duncan. If it's working correctly (the previous owner didn't damage it), you'd have a hard time finding a better one.

    You can use just about any preamp/eq system. The balance control is for blending two pickups, but with a single-pickup instrument you can simply remove the balance pot and wire the one pickup directly. That's true of any preamp that has the balance (blend) control before the preamp input, which is almost all of them that I'm aware of (the exceptions are preamps that feature a "buffered blend", and even those will usually be easily modified for a single pickup).

    Glockenlang makes excellent products. Search this forum for that name and you'll find lots of info (and owners who may be willing to answer more questions).

  4. dkthrone


    Feb 9, 2013
    Thanks guys!

    Just about any preamp you say, Reid? Thats good news, gives me more options, as i'm hoping to get a bit more out of a rather dull sounding low B. Right now the bass runs on passive only, with pops and crackles.

    Thanks again!

  5. If only the B string is "dull" sounding, I'd suspect the string itself is the issue there. Unfortunately, many string sets come with low Bs that don't match up with the other strings tonally. And unless the strings themselves sound even, you're going to have a hard time regardless of the preamp you choose because any adjustment you make for the B string will affect other strings as well.

    The SMB-6a is a good pickup. If the current electronics are totally unsalvageable, you could even try connecting it straight to the output jack for now. I'd guess that would actually sound pretty good if you can sort out your low B issue with a different string choice.

    Also, here's a link to the Seymour Duncan MM style preamp which is similar to the stock one on the JM2 (or the same, I'm not sure).

  6. dkthrone


    Feb 9, 2013
    Thanks IronSpatula!

    I see your point about the string itself being the problem... this is a whole other topic but here it goes;

    I've tried three different sets so far, DR, D'addario, GHS. I've kind of given up hope on finding a good low B string. And that is with other basses as well. Maybe my ears are weird, but nowadays, i believe a clear low B on a 34'' scale is very unlikely. I wonder how much money i'll have to spend to find the perfect strings... i'll keep trying.

    I dont know if you've read any reviews on RBX JM2... many have said that the low B leaves something to be desired. other strings sound great to me (and playability of this bass... WOW, best i've played so far) So that is the reason i'm hoping to get a better low B with the necessary preamp change.

    Even Myung changed the preamp with an additional pickup, if i'm not mistaken.

    I dont know how exactly my local technician wired it now, but he said i should get a preamp to get rid of the crackles. And it doesnt even sound that bad, really... its only on the Low B to E that some sterility becomes apparent.

    I'll fix this bass because it's a signature and it plays so great, but for work purposes i'm in the market for a 35''.

  7. Well I haven't yet used them personally, but based on many great sound clips I've heard I'd recommend you check out a balanced set of Circle K strings. Part of the problem with low B strings is that they are frequently lighter tension than the rest of the set and the balanced sets eliminate that. Something with around .140 low B should work quite well. http://circlekstrings.com/store/product2812.html

    I prefer 35" basses as well but on my Fender I get a pretty good low B at 34" with the D'addario XL nickel wound set with a .135 low B. That particular bass also has a pretty flimsy neck and has been pretty problematic with the low B from other sets. The D'addario .135 sounds just as good as the E, at least up to the 5th or 6th fret.

    I've played one or two. I didn't find the low B to be any worse than typical for a 34" bass. YMMV I guess.:)

    This doesn't totally make sense to me. Or at least not as the only option. If you're really running the bass passive and it still crackles, that means there's a short or a faulty component somewhere. Putting a new preamp in may eliminate the noise if the faulty component or connection is removed when the current electronics are replaced. But you should be able to fix whatever is wrong with the passive signal chain and resolve the problem that way for less cost, should you choose to.

    Crackling is actually most common in active basses when the battery is dying IME. If you haven't already, I suggest that you try a fresh battery in your bass and see what happens. It very well may not work but it's a cheap enough thing to do that it might be worth a shot.