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Help with PA and Acoustic/Electric guitar


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I recently bought a new Yamaha powered mixer (EMX512) for an acoustic rock group I'm starting. I've just used the thing at home so far, and have a question someone might be able to answer.

 

Each channel has a line/mic switch. If I plug my guitar (Yamaha apx7a) into a channel with the switch set to 'mic' and the channel gain at 1/4 up, the guitar is loud and clear -but I can just hear a slight distortion through the speakers (Peavey SP 15).

 

If I put the switch to 'line', same channel gain, the signal drops to almost nothing. You have to crank the gain to 3/4 just to hear the guitar.

 

Microphones sound great through this PA (switch set to mic), so I don't think the speakers are a problem.

 

Do I need to buy some kind of DI box to use this PA? I'm used to running my guitar directly through the house Mackie powered head at open mic, and didn't notice if there was a line/mic switch -but whatever it has, I plug in my guitar and it sounds great.

 

thanks in advance, for any help!

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The mic /line switch reduces the sensitivity of the input. If the guitar sounds distorted with the switch in the mic position, you are likely overdriving the input. Switching the input to line will reduce the likelyhood of overloading the input, but you will need to turn up the channel gain to make up for the reduced sensitivity. Theres nothing wrong with operating the channel gain at 3/4 .

If you can't get the guitar load enough, try increasing the master volume and backing off on your mic channels.

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IIRC the APX7a is an acoustic with active electronics right? You should be ok going into the line, but you *might* get better results using a DI. A cheap (price not quality - you CAN get quality DIs cheap!) passive unit should do the trick.

 

AS

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With a DI, this user would be using 1/4" cord out of the guitar andninto the DI, and then an XLR cord out of the DI, and into the input on the mixer, and could then again set the input switch to "mic" correct?

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Originally posted by Rbts

With a DI, this user would be using 1/4" cord out of the guitar andninto the DI, and then an XLR cord out of the DI, and into the input on the mixer, and could then again set the input switch to "mic" correct?

 

 

Yeah, but don't get hung up on whether the input is set to mic or line. It really doesn't matter. A DI will really only help you if you have a cord more than 20 feet long going to the board or if you have a ground loop you need to remove. We plug acousti guitars direct to the mixer all the time when we mix on stage. Mixer is set to line. Works great. Just dial in the preamp gain properly and don't worry about it.

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Yeah, but don't get hung up on whether the input is set to mic or line. It really doesn't matter.

 

 

Nothing could be further from the truth. Mic/line switching is about level and impedence matching. As the original poster has already learned, there is a huge difference.

 

Get yourself a decent DI for your guitar (which connects XLR to a MIC input) and you'll be fine.

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Originally posted by where02190



Nothing could be further from the truth. Mic/line switching is about level and impedence matching. As the original poster has already learned, there is a huge difference.


Get yourself a decent DI for your guitar (which connects XLR to a MIC input) and you'll be fine.

I'm going to side with G on this one.

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OMG

 

If you are plugging the guitar directly into the board, using 1/4" cords... then use the "line" setting.

 

If you are using a DI, and going from the 1/4" cord to an XLR (out of the DI), then use the "mic" setting.

 

Either will work.

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Originally posted by Rbts

OMG


If you are plugging the guitar directly into the board, using 1/4" cords... then use the "line" setting.


If you are using a DI, and going from the 1/4" cord to an XLR (out of the DI), then use the "mic" setting.


Either will work.

 

 

Yup that pretty much covers it, except I will add that if you need a cable longer than 15-20 feet to get from guitar to board, you'll want to use a DI. Unbalanced instrument lines become very suseptable to noise and interference, and basically become big antennas past about 18 feet, and suffer some fairly severe high end loss as well. Using a DI and a short cable from guitar to DI will yield a better quality signal and a lower s/n ratio.

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