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GA-9 speaker out help


joebor1776

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Hi,

New member here. I was recently given a ~1957 Gibson GA-9 combo (2 6v6s, 1 12ax7, 10 watts, 10" Jensen speaker). It is an 8-ohm amp, apparently. It sounds really great as it is, but I wanted to see how it would sound through my 2-12 cab that is loaded with 2 WGS Green Beret speakers (25 watts each). So, I wired up a simple speaker-out jack in the amp. I sort of guessed at which lead was negative and positive (they both looked the same--I assumed the one on the left was positive). It still sounds correct and great when the internal speaker is connected, but when I connect the extension cabinet (by itself, no internal speaker), and put any sort of volume through it, I get some nasty farting distortion. The cabinet is 2 8-ohm speakers wired in series for 16 ohms, so I know there's a slight impedance mismatch, but I wouldn't think it would sound this bad. The cabinet sounds great with my Marshall DSL40c and my AC15. Does anyone have any ideas about what I might be doing wrong? I have very basic soldering skills, but I'm sure my joints are OK.

 

Thanks!

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  • 3 weeks later...

Hi,

New member here. I was recently given a ~1957 Gibson GA-9 combo (2 6v6s, 1 12ax7, 10 watts, 10" Jensen speaker). It is an 8-ohm amp, apparently. It sounds really great as it is, but I wanted to see how it would sound through my 2-12 cab that is loaded with 2 WGS Green Beret speakers (25 watts each). So, I wired up a simple speaker-out jack in the amp. I sort of guessed at which lead was negative and positive (they both looked the same--I assumed the one on the left was positive). It still sounds correct and great when the internal speaker is connected, but when I connect the extension cabinet (by itself, no internal speaker), and put any sort of volume through it, I get some nasty farting distortion. The cabinet is 2 8-ohm speakers wired in series for 16 ohms, so I know there's a slight impedance mismatch, but I wouldn't think it would sound this bad. The cabinet sounds great with my Marshall DSL40c and my AC15. Does anyone have any ideas about what I might be doing wrong? I have very basic soldering skills, but I'm sure my joints are OK.

 

Thanks!

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Chances are 99.5% that you have not wired the new output jack correctly. Amps like this are very tolerant of impedance mismatch and will not produce that kind of distortion when just mismatched. It sounds more like a short, which happens frequently when jacks are not properly wired (not really that hard to do!)

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