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Amp gone wrong


whisky182

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:D as most of you will know, i have recently bought a Marshall MG412A to use as an extention cab of my Marshall MG30DFX, (i went through all the trouble of putting an switch jack out and everything)

now, the problem is, it isn't as loud as i hoped it would be, (infact it sounds the same as it did before i put the extension cab on!) :D

B) is this normal, was i hoping for too much, or is it just some crap wireing or something!

thanks for any help given! :D

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It's a good idea to check the wiring as rob suggests... but let me ask, what's the impedence of the speaker in your MG30DFX vs. the impedence of the new 4x12 cabinet? If, for example, the internal speaker is 4 ohms and the new 4x12 is 8 ohms, you only have 15 watts going into your cabinet.

If this is the case and the wiring checks out ok, then this is the way it should be... but I'm surprised that it sounds the same. You should have a "bigger" sound (more low end, etc.) with the new cabinet.

Oh, I just noticed you said "extension cab." I hope you followed our past advise and wired the switched jack to allow an either/or operation of the internal and extension cab (not both at the same time.)

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It's a good idea to check the wiring as rob suggests... but let me ask, what's the impedence of the speaker in your MG30DFX vs. the impedence of the new 4x12 cabinet? If, for example, the internal speaker is 4 ohms and the new 4x12 is 8 ohms, you only have 15 watts going into your cabinet.

If this is the case and the wiring checks out ok, then this is the way it should be... but I'm surprised that it sounds the same. You should have a "bigger" sound (more low end, etc.) with the new cabinet.

Oh, I just noticed you said "extension cab." I hope you followed our past advise and wired the switched jack to allow an either/or operation of the internal and extension cab (not both at the same time.)

Why either/or???

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um the power of the amp i'm running the cab off is 30watts, 8ohms,

the can is 120 watts, 8 ohms,

the wiring is decent and i don't think it is worth getting them "checked over" becuse they are both fairly new (the amp's a year old, and the cab is 1 week old!)

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Why either/or???

A 8 ohm internal speaker wired in parallel with an external 8 ohm cab, yields 4 ohm total... I didn't want whisky182 to risk burning out his amp.

Edit: I should add that it's probably best to keep the impedance load the same. This is especially true when using a tube amp. Solid state amps are more forgiving B) but you don't want to go crazy like wiring up a 2 ohm cab when it's expecting 8 ohms :D.

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um the power of the amp i'm running the cab off is 30watts, 8ohms,

the can is 120 watts, 8 ohms,

the wiring is decent and i don't think it is worth getting them "checked over" becuse they are both fairly new (the amp's a year old, and the cab is 1 week old!)

If that's the case and everything is ok then you were "hoping for too much"... sorry B). I'm still surprised that a single 10" speaker sounds the same as a 4x12 cab. :D:D

Edit: Oh, wait by "checked over" we meant the wiring you did for the switched jack, not any internal wiring done at the factory. You do the "checking over."

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Edit: I should add that it's probably best to keep the impedance load the same. This is especially true when using a tube amp. Solid state amps are more forgiving B) but you don't want to go crazy like wiring up a 2 ohm cab when it's expecting 8 ohms :D.

Actually Mesa's manuals explain in great detail (my nomad has 60 page manual) how to mismatch cabs, and recomend it in some situations. Pull up one of mesa's manuals and check it out. I dont know if it would apply in a solid state situation.

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if i am not mistaken the mg30 is a close backed single 10",which accounts for the similar sound.

open backed acctually! :D

run it through a power amp

how expencive are these?!, if they are over £200 then i may as well just buy the Marshall MG100HDFX to use as a head for it!

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