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Using combo as extension cabinet

Discussion in 'Amps and Cabs [BG]' started by kasbrey, Apr 1, 2015.

  1. kasbrey


    Aug 23, 2002
    York UK
    I have a Markbass Minimark 2x6" combo which has an extension jack socket. I would like to use a separate amp head to power my Markbass 4x6 cabinet but connect the Minimark as an extension cabinet only (if necessary to use the combo amp section as backup in case of head failure).
    Would there be a problem connecting the head up via the extension cab out jack considering the combo's amp is not isolated (although not powered)?
    I must confess to having tried this already (seemed ok) but I am now concerned that it may cause damage to either the speakers or the combo's amp.

  2. Most combos wire the speaker to the amp internally. Connecting another amp to the extension output would fry the amp. I don't know how you got away with that.
  3. anderbass


    Dec 20, 2005
    Phoenix. Az.
    I agree with Downunder, you got lucky. Don't try that again unless you mod your combo to disconnect its speakers from its amp section.

    I've done this type of mod to my combos by simply installing male & female speaker plugs in the wiring in-between it's amp section and speakers. Then, I can choose to simply leave them plugged in together to use my combo like normal. or unplug them to have the options of either using my combo as a cab, or using my combos amp-section to power other cabs. It works fine, just make sure you maintain the same (speaker wire) polarity, and also follow the minimum ohm recommendations, same as you would when using any other amp and cabs.

    Here's a pic of a combo I modded. I didn't wanna drill any holes, so I just mounted my 1/4" female jack with a simple homemade bracket. My female jack is wired to the the combos amp section. The male jack goes to the combos speaker, It has an extra long wire so I can just plug it into another amp when using my combo as a cab:


    Attached Files:

  4. kasbrey


    Aug 23, 2002
    York UK
    I'd only tried it at low volume so I got away with it !

    I've taken it somewhere to have a new jack socket fitted that will disconnect the amp from the speakers if used.

    Thanks for the advice.
    anderbass and S-Bigbottom like this.
  5. If doing it that way be absolutely fastidious about everything being fully powered off before connecting or disconnecting.

    I still don't know how you got away with it. Afaik giving an amp a look at the back end of another amp it's like a gay porno. Even if the sound is off you can't escape.
  6. kasbrey


    Aug 23, 2002
    York UK
    Haha - I really should have known better. Maybe it shows how resilient Markbass gear is.

    Btw I never unplug speaker jacks without turning amps off.
  7. Has nothing to do with the brand or engineering and everything to do with luck. Considering the cost and wait times on MarkBass repair parts, VERY lucky.
  8. kasbrey


    Aug 23, 2002
    York UK
    It may be different in the UK as we have different distributors but in the 10 years that I've had Markbass amps and cabs I only had one failure, after about 3 years of having my LM2 the power section stopped working. I didn't have to pay anything to have it repaired as it was deemed to be a known component flaw on the very first batch of LM2's.
    I realise it isn't the same experience in the US.
    B-string likes this.

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