Technical/Safety question - 2 amps, 1 speaker- Advice please...

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BeexterBeexter Frets: 597
I have 2 valve amp heads and a 1x12 cab fitted with a single 12"  8 ohm speaker. The connection panel on the back of the cab has 2 jack sockets and you can plug into either.

Now I know that you shouldn't turn a valve amp on unless it's connected to a speaker but can I connect both amp heads ( one to each jack socket) to the cab if only one amp is on?

i would only ever use 1 amp at a time, just leaving the other one connected for convenience.

Is this safe?

If so, would the "unused" amp need to be completely off or could it be in standby?

I'd welcome advice from those with much greater knowledge than me!

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Comments

  • ICBMICBM Frets: 71956
    No, it's not safe. The jacks on the cab are in parallel so you're effectively connecting the outputs of both amps together via the cab.

    Do not ever connect two amplifier outputs together, even if one is turned off. There is a good chance of damaging at least one of them.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • DJH83004DJH83004 Frets: 196
    IC beat me to, but you are effectively putting both output tx secondaries in parallel, so the amp in use is essentially driving the speaker plus secondary winding of the other amp (including inducing back emf into the primary).
    all in all not good news for either amp :o





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  • BeexterBeexter Frets: 597
    Thanks guys. Saved me making an expensive mistake!

    What then, would be the purpose of the 2nd socket on the cab - connecting another cab I guess?

     I assume connecting another 8 ohm speaker would then result in a 4 ohm load if it's a parallel socket?
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  • ICBMICBM Frets: 71956
    Beexter said:

    What then, would be the purpose of the 2nd socket on the cab - connecting another cab I guess?

     I assume connecting another 8 ohm speaker would then result in a 4 ohm load if it's a parallel socket?
    Yes, exactly. I also find it useful to have a spare socket on a cab - they do occasionally get damaged if the cable gets tripped over or someone forgets to unplug it before carrying the head away :). If you break the only socket on the cab at a gig, you're a bit stuck...

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

    0reaction image LOL 0reaction image Wow! 1reaction image Wisdom
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