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Amp question; have I been doing this wrong?

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  • #1

    Amp question; have I been doing this wrong?

    Hi,

    I have a half-stack; 100 watt head, 4 x 12 cabinet. The head has two jacks on the back - 4 ohms and 8 ohms. I've just noticed the cab has a note on it saying "100w/8 ohms. It has an 'IN' jack and an 'OUT' jack.

    Up to now, I've had the amp connected up to the 4 ohm jack on the head, assuming that I'd use the 8 ohm jack if I connected a second cab to the first.

    I'm starting to suspect I've got this the wrong way round; should I actually hook a single cab up to the 8 ohm jack, and use the 4 ohm jack for when I'm using two cabs?

    (I'd assumed that going head -> cab 1 -> cab 2 would see the two cabs in series, so I'd need the higher impedence output for two cabs. The "100W/8ohm" note I've noticed on the cab is what's confused me. If it's an 8 ohms cab, and going head -> cab 1 -> cab 2 puts the cabs in parallel, then the combined impedence of the 2 cabs will be 4 ohms, meaning I need the 8 ohm ouput for one cab, and the 4 ohm output for two cabs.)
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  • #2
    Re: Amp question; have I been doing this wrong?

    If you want to know for sure, use a multi-meter to test the impedance on the cab.

    Other than that, I suspect you might have it backwards.
    || Guitar | Wah | Vibe | Amp ||

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    • #3
      Re: Amp question; have I been doing this wrong?

      My initial guess is that it probably isn't making a difference to the amp since it's sensing an 8 ohm load SOMEWHERE, as the two outputs are probably connected and if you're not plugged into the first one, the second one is where the 8 ohm load is being directed. Again, that's just a guess.
      www.enigmaduo.com

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      • #4
        Re: Amp question; have I been doing this wrong?

        If you have cabs that run on 8 ohms then you use the 8. If you have a cab that works on 4, than use 4. Never cross them or else something might break...
        Its not about love or hate, wrong or right, its about perception. Just do it, say it, feel it. There are no lies... lies are too human. Its so much thought that its none at all. Its no religion, its not defined. Its not even real. Its about being connected to the point that you didnt even know. Its the reassuring peace in pain because it hit you & its over & you felt it. Its the pits of Hell found in Heaven. Its not being connected with a god... we are all god...

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        • #5
          Re: Amp question; have I been doing this wrong?

          You are wrong. Your cab should be connected to the 8 ohm jack, two cabs would run in parallel rather than series and be a 4 ohm load. Using the incorrect jack may make a difference as the 4 ohm jack is probably attached to the 4 ohm tap on your output transformer. Of course this only applies to a tube amp. On a solid state amp, this doesn't matter.
          Originally posted by crusty philtrum
          And that's probably because most people with electric guitars seem more interested in their own performance rather than the effect on the listener ... in fact i don't think many people who own electric guitars even give a poop about the effect on a listener. Which is why many people play electric guitars but very very few of them are actually musicians.

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          • #6
            Re: Amp question; have I been doing this wrong?

            Thanks for all the advice everyone - it looks like I'd got things back to front then

            Originally posted by dystrust
            You are wrong. Your cab should be connected to the 8 ohm jack, two cabs would run in parallel rather than series and be a 4 ohm load. Using the incorrect jack may make a difference as the 4 ohm jack is probably attached to the 4 ohm tap on your output transformer. Of course this only applies to a tube amp. On a solid state amp, this doesn't matter.
            The amp is indeed solid-state. I think I'll plug it in to the 8 ohm jack and have done with it. I only really noticed all this because I was trying to justify a second cab to myself, and I noticed it was an 8 ohm cab I'd got when I looked at the back.

            La Crosse eh? I was over there a few months ago, probably be over again in the next few months.

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            • #7
              Re: Amp question; have I been doing this wrong?

              Drop me a line next time you're in the area. Maybe we can grab a beer or something. I live right across the street from Dave's Guitar Shop if you know where that is.

              On your amp... solid state and tube amps react differently to impedence mismatches. On tube amps this should be avoided if possible as it will cause your output transformer to overheat and it will also severely stress your power tubes. On solid state amps, using an incorrect low impedence may cause the same overheating problems. Using an incorrect high impedence will reduce your output power by a multiple equal to that of the mismatch. For example using an 8 ohm load on the 4 ohm tap would reduce your power to 50W instead of 100W.
              Last edited by dystrust; 05-26-2004, 12:22 PM.
              Originally posted by crusty philtrum
              And that's probably because most people with electric guitars seem more interested in their own performance rather than the effect on the listener ... in fact i don't think many people who own electric guitars even give a poop about the effect on a listener. Which is why many people play electric guitars but very very few of them are actually musicians.

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              • #8
                Re: Amp question; have I been doing this wrong?

                Originally posted by dystrust
                Drop me a line next time you're in the area. Maybe we can grab a beer or something. I live right across the street from Dave's Guitar Shop if you know where that is.
                Sure, no problem, just got to find out when I'll next be over. I actually dropped by Dave's Guitar Shop while I was there, right down the road from the brewery isn't it? That Downtown Brown was my downfall though, couldn't keep away from it

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                • #9
                  Re: Amp question; have I been doing this wrong?

                  I love Downtown Brown, but that's actually made at a different brewery in town. Daves is just south of the City Brewery on 3rd St. I live at 1222 South 4th.
                  Originally posted by crusty philtrum
                  And that's probably because most people with electric guitars seem more interested in their own performance rather than the effect on the listener ... in fact i don't think many people who own electric guitars even give a poop about the effect on a listener. Which is why many people play electric guitars but very very few of them are actually musicians.

                  Comment

                  • #10
                    Re: Amp question; have I been doing this wrong?

                    Originally posted by dystrust
                    I love Downtown Brown, but that's actually made at a different brewery in town. Daves is just south of the City Brewery on 3rd St. I live at 1222 South 4th.
                    Cool, I'll get in touch when I'm due to come over. I'll probably end up in the Holiday Inn, I think it's just down the street from TGI's? Have to see if I can remember my way around when I get there!

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