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Two heads-one cab

Discussion in 'Amps and Cabs [BG]' started by Youngspanion, Feb 21, 2013.

  1. Youngspanion

    Youngspanion Supporting Member

    Jun 16, 2003
    Staten Island, NY
    I've got a gig coming up Saturday and I want to bring my new Rumble 350 Head along with my LMII. Is it possible to connect one cab to both heads. This way when I want to change heads, all I have to do is shut one off and turn the other on.. Sounds like its a good Idea but I've got a feeling I might burn something out.

  2. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    This is a very dangerous proposition unless the cab in question has multiple loudspeakers wired in isolation, one or more to each amplifier
    Don't do it or your rig will be the wrong sort of smoking.:bassist:
  3. vbchaos


    Sep 5, 2011
    Groningen, The Netherlands
    Uncompensated endorsing user: fEARful

    No really, DON'T!!! I mean it!! Attaching 2 amps to one cabinet will eventually blow something, even if only one amp is powered and the other is shut off.
    AFAIK both heads are SS heads so, what I would do is:
    Both heads get one speaker cable, but only one is connected. When I would want to switch - turn off the current amp, disconnect the speaker, connect the other head, and turn on... Question of seconds!!!

    There are load-switches for what you try to do
  4. rubbadubdub


    May 8, 2012
    This is a very bad idea. You would have to have a switch in your speaker lead and with the amount of power running through it you don't want something momentarily shorting out the connection. It's bad for several technical reasons. Also you will run into issues regarding impedance and power handling.
    If your combo isn't powerful or loud enough for the gig you would be better off getting an extension cab and adding this to your combo (or maybe using it with the second amp). That is assuming your combo has such an extension speaker socket?
    If you want the pre amp facilities from both amps then you could take a line out from your second amp (from that amps pre amp NOT it's speaker out leaving the power stage doing nothing and not connected) and run that into an effects return or line in jack on the rumble. Again that is if your amps have such facilities.
    I'm not sure why you want to run two amps together? If it's for more power or volume, forget it. On the other hand if it's for better tone then it may be worth the trouble of dragging both around and bypassing one pre amp with another. I am not familiar with either of your amps unfortunately but running two amplifier speaker outputs into one speaker in the way you describe is likely to end in tears and a blown speaker and probably blown output transistors in both amps.
    It may be worth running the preamp output from the second amp into the active input on the combo so that you have two preamps running in series. You would have to be careful with the gain but it may give you more eq possibilities.
    Basically, combining or mixing line or instrument levels is worth a try. Never plug a speaker output into a line level and dont try 'mixing' speaker outputs into one speaker.
    There is an exception to this called 'bridge mode' which is worth googling but not worth attempting with the speaker and amps you have currently.
    If in doubt do nowt is my advice.

    I hope this hasn't confused you?
  5. rubbadubdub


    May 8, 2012
    I just reread your post and noticed that you have a rumble head rather than a combo. The same advice still applies though. It may mean that you have more options for running one pre amp into the other?
  6. mystic38


    Dec 4, 2012
    Mystic CT
    you will kill one, the other, or both amplifiers if you connect their outputs together.

  7. Youngspanion

    Youngspanion Supporting Member

    Jun 16, 2003
    Staten Island, NY
    Thanks. Thats what I thought. Still glad I asked.:cool:
  8. DWBass

    DWBass The Funkfather Supporting Member

    Even though one amp is off, it's still a dangerous proposition. Just leave the second head unplugged from the speaker. Make sure to remove the cable and turn off the other amp before connecting the second amp. But never have them both plugged in at the same time.

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