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Fixed the problem, but how did it happen?

Discussion in 'Amps and Cabs [BG]' started by basscooker, Oct 6, 2013.


  1. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    I needed to run a series connection for two 4 ohm cabs to show my amp 8 ohms. I noticed that only one cab would play. Switched the ends plugged into each cab and the same thing. Cable tested fine. As it turns out, the 1/4" plug on one of the ends needs to be ALMOST all the way in or it won't work, so problem solved, but now I have a question that's bothering me:

    Being a series cable, how did only one cab work at all? Shouldn't it have been an "all or nothing" deal?
     
  2. Remus_Redbone

    Remus_Redbone

    Dec 27, 2010
    Western AR
    If you have tip and ring shorted, the series path is continuous just one speaker will work. A partially plugged-in 1/4 jack can short tip & ring.
     
  3. megafiddle

    megafiddle

    May 25, 2011
    Sounds like the plug on the silent cabinet was being shorted by the jack somehow.
    So the cab looked like a zero ohm speaker in series with the working cab.

    Can you describe the cable wiring and jack functions?

    ...
     
  4. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    Only one speaker worked UNTIL I did this, now both work. It isn't exactly "partially" plugged in, Just putting a 1/16" or so thick piece of foam between the plug and the jack makes the whole system work. I can't figure out how either speaker was working if one of them didn't.
     
  5. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Do you have a TRS jack where it shouldn't be?
     
  6. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    Sure. The speaker jacks are wired just like they should be, as 4 ohm cabs. I took a speaker cable and interrupted the (-) wire, inserting the (+) from another cable to the end closer to the speaker end of the plug, and the (-) to the end closer to the amp plug.

    amp+ to spk+ / spk- to spk+ / spk- to amp-
     
  7. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    I didn't consider this, but both jacks should be mono. They're the long sleeve jacks, like for thick panels with no jackplate, or for guitars. It doesn't matter which cab I use, whichever one gets this one specific plug, i have to use the little foam "shim" to make it work. I just can't figure out how either worked if one didn't.
     
  8. Remus_Redbone

    Remus_Redbone

    Dec 27, 2010
    Western AR
    Didn't catch the details. If both speakers work with one cable end partly unseated, and both cable ends did the same thing in the same cabinet jack, then that cabinet jack is messed up (jacked up?). It's properly touching tip & ring when the cable is partly unseated and shorting tip & ring when the cable end is fully seated.

    If the problem is following one cable end, you have some kind of non standard cable plug or a tip, ring, sleeve stereo plug, or your series cable isn't assembled correctly.
     
  9. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    You're almost caught up ;)

    Both cabinet inputs work fine, and the cable tests fine. It's just that one of the plugs on the cable only works when I do the "shimming". It's more of a nagging feeling that I can't understand how I got ANY sound before I figured it out.
     
  10. megafiddle

    megafiddle

    May 25, 2011
    Just a guess, but I would say that the tip of that one particular plug is
    not engaging the tip contact in either of the jacks properly.

    What may be happening is that the plug tip is pushing the contact forward,
    forcing it against the jack sleeve (which is also the shield). The tip contact
    and plug contact is now shorted to the shield, bypassing the speaker and
    completing the cable connection at the same time.

    Seating the plug back a little bit prevents the tip contact from touching the
    jack sleeve.

    If you compare the bad plug to a working plug, I suspect the length will look ok.

    Does the plug tip look any different, though?

    ...
     
  11. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    I think you edited this in while I was typing, but you may have nailed it---- upon closer scrutiny, it does seem that the suspect plug is the teeniest bit longer than the other. It is from a cable I had marked as "wonky" and wasn't using anymore. It always tested fine, but was regularly being proven to be the problem when things weren't working. I always figured there was a break in the cable, and didn't even think it could have been that the plug shaft was too long....that's a new one for me. But it still doesn't satisfy my initial bewilderment.

    seriescablecabends.

    It's really not very evident in the pic, but the one on the left has a shaft that's maybe 1/16 or less longer than the neutrik one on the right.

    seriescableconnection-1.

    here's the connection: yes they're soldered! they're just taped over. The white wire is the uninterrupted (+) from the "wonky" cable. The neutrik end is the one I inserted in the (-) side of this cable. Interestingly enough, the side of the "wonky" cable that plugs into the amp output has a shaft that is the same length as the plug that gave me trouble, and works fine with the amp's connections.
     
  12. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    I'll take that! DING DING DING. must be this. It IS actually longer, see the post above! good catch, it was killing me why, but this must be it! thanks. Like I said in the OP, problem solved, but MAN it was killing me that I couldn't figure out how I was getting sound at all!
    So, wow i was running my amp at 4 ohms there, huh? well it still works, so....
     
  13. megafiddle

    megafiddle

    May 25, 2011
    Sure is. The sleeve on that plug looks like it actually extends to the point where the tip begins on the good plug.

    Don't give me too much credit though. I was expecting a tip that was out of spec, not the length.

    The bad plug wasn't failing to make contact. That would have prevented both cabinets from working.
    The bad plug was being shorted inside the jack. The short provided the series connection between tip and shield.

    Normally the cabinet would have been making that series connection. But in this case a direct connection (the short)
    was in series instead. So the working cabinet was still receiving a signal through the short in the "problem" cabinet.

    Also, because of the short, that speaker was receiving none of the signal. The signal path was into the jack and right
    back out again, bypassing the speaker altogether.

    ...