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Fake Parallel Trick?

Discussion in 'Amps and Cabs [BG]' started by glasser_cannon, Mar 7, 2016.


  1. I saw a forum on here a while ago that explained this perfectly, but now I can't find it. There's was a video on this forum that explained how you could take a speaker cable, cut it, and solder the end to create a dummy cable. Basically it acted as a dead end so that you could trick an 8 ohm cab into a parallel circuit, making it 4 ohms.

    I recently picked up a 70's Fender Bassman 50 head that only runs in 4 ohms, so I really want to find this video to make sure what I'm talking about is true, before I either blow out my cab or kill this awesome head. Has anyone ever tried this or have any information on it that could be helpful?
     
  2. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
    Use any cabinet that is 4 ohms or greater. Amps don't work only against a fixed load.

    Never put a dead short on the output of your amp. The idea of this cable is stupid, misguided and potentially dangerous to your equipment. Let it go.
     
    Duder, Munjibunga, Fat Steve and 3 others like this.
  3. There is no way to trick electrons.
     
  4. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    This thing.

    It does not exist.
     
  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    It's fakerware.
     
  6. NWF Bassist

    NWF Bassist

    Aug 1, 2004
    Killakee
    LIES!!!!
     
  7. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    You're talking about monkeying with the output transformer tap arrangement on a tube amp. If you have the right tap available for an 8 ohm cab just wire the amp that way. It won't automagically make an 4ohm ohm cab out of an 8 ohm one though.
     
  8. The only amp I can see using this trick is the B15. The internal driver is 8Ω and “sees” the 8Ω tap on the OPT. When you plug into the external speaker jack, a switch operates changing the OPT tap to 16Ω and runs the external load in series with the internal driver. If you replace the internal driver with a 16Ω unit using a shorted plug in the external jack will allow for correct matching. 4Ω does not belong in the equation.
     
    spaz21387 likes this.
  9. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    You mean shorted plug, no? I like your version better though...
     
  10. Charlie I fixed it already!!! Yeah I think I like it better too! :D
     
  11. T_Bone_TL

    T_Bone_TL

    Jan 10, 2013
    NW Mass/SW VT
    You could make 2 4 ohm cabs into an 8 ohm load you could drive if your amp couldn't drive 2 ohm with a trick cable. The other direction would only "work" (uselessly, as you'd be wasting all the "extra" power) if you put a high-power 8 ohm resistor on the end of it - much quieter than, and probably more expensive than, a second cab. Since the point is (or should be) to make sound, use a second cab, which will actually make sound. That's all the "trick" you need - put a cab on the end of the cable, trick done.
     
    Last edited: Mar 7, 2016
  12. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Think you mean a series speaker cable that would make two 8ohm cabs 16ohm, which is sometimes useful, instead of the parallel that would make them 4 ohm that is the default way of having amp to speaker jacks set up.
     
    BassCliff likes this.
  13. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
    Maybe I'm grumpy because of the rain, but knock it off, guys!
    The OP stated that he has a '70s Fender Bassman 50. Here is a picture of the rear panel of said amp.
    fender-bassman-50-silverface-125322.jpg

    As clearly indicated on the label, the amp is not to be used with a speaker load less than 4 ohms. Any single cab or combination of cabs that provides a load of 4 ohms or greater will work fine. No trick or magic involved. Here's a simple guide to understand how to execute the wiring: Wiring Diagrams | Eminence Speaker

    Putting a shorted cable on this amp will damage it. Putting a shorted cable on any amp will probably damage it.
    Let's not add any more misguided information to the thread, however well intentioned.
     
    BassCliff likes this.
  14. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    You have it backwards. It's a tube amp, so you can use a 4 ohm or lower load. You can short it. As a matter of fact the output jack is wired so that if nothing's plugged in it does short the output. What hurts tubes is a high impedance load. SS amps have a minimum load, and can be damaged if the output is shorted.
    +1.
     
  15. Bro you are most definitely grumpy. I don’t see anything condescending or insulting in the posts in this thread. The OP asked a question and we tried to answer it.

    I owned two of those amps and there is no way that any cable “trick” will convert an 8Ω cabinet into a 4Ω one. I ran my last one into a 16Ω Marshall cabinet for gig after gig without a problem. It’s not ideal by any means but the amp will not explode pushing an 8Ω cabinet and 50 watts isn’t going to damage the cabinet either. I never did like the Bassman in the first place yet I ended up with the last one in a trade.
     
    BurningSkies likes this.
  16. Further, OP never run the amp without a load connected. Rick is correct in his statement that the Speaker jack shorts the output. This will save the amp from an infinite load but will cause the output tubes, 6L6GC, to wear faster.
     
  17. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    If'n I'm going to be blamed for something no one actually said...I'll say it.

    Totally make a shorting speaker cable. I think it will have the best of outcomes. Don't forget to make a video when you do it... you know, to prove this works to us.
     
    Fat Steve likes this.
  18. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
    The idea of a dead short on the output runs contrary to my electronics schooling, tube or SS. Willing to be educated, but it seems like it would be rather fundamental.
     
  19. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics

    Start here, in the output transformer section: http://www.geofex.com/tubeampfaq/tubefaq.htm#transformers

    A dead short is quite preferable to an open circuit in this particular case.
     
  20. abarson

    abarson

    Nov 6, 2003
    Santa Cruz

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