Microphone to Amp connection: Static!! - AVS Forum
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post #1 of 10 Old 01-16-2009, 03:53 PM - Thread Starter
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Hi Everyone,

I recently bought a small 12-watt amp to play around with. I have a Shure mic that i'm trying to use with the amp, and therefore purchased an XLR (f) to 1/4" (m) cable to be able to plug it into the amp.

The problem is that there is an enormous amount of static and sensitivity about the connection. For example, gently tapping on the XLR <-> 1/4" cable produces a much louder output on the amp than anything sent through the microphone. I also have to turn the Gain almost all the way up and push the overdrive button off to be able to transmit sound to the amp via the mic.

Does anyone know what the issue is? Is the XLR to 1/4" cable the problem? It is essentially this cable:

Thanks for your help!
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post #2 of 10 Old 01-16-2009, 03:54 PM
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What type of mic is it?
What type of input are you using on the amp?

The difference in connector suggests this is not a good match despite the adapter cable.

Kal Rubinson

"Music in the Round"
Senior Contributing Editor, Stereophile
http://www.stereophile.com/category/music-round

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post #3 of 10 Old 01-16-2009, 04:25 PM - Thread Starter
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Sorry, I meant to state that it is XLR to 1/4" (not 3.5mm). I corrected the original post.

I'm not exactly sure which model of mic, but it looks similar to this one: http://www.shure.com/ProAudio/Produc...588SDX_content

And there is only one input on the amp. And it's a 1/4" input.

Thanks!
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post #4 of 10 Old 01-16-2009, 05:18 PM
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Are you sure that you have the correct 1/4in connector. XLR connectors and most mics use 3 wires/pins. The connect in the photo has only 2 wires/pins.
Also mic cables and guitar cables that they sell at music stores, are designed to not make noise when moved. Cables designed to connect two pieces of equipment don't normally get moved much.
Also #2. If the mic is expecting phantom power and not getting it, that will be a problem.
Also #3. If the amp is providing phantom power, but the mic does not need it, that could be a problem.

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post #5 of 10 Old 01-16-2009, 05:55 PM - Thread Starter
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Thanks for the reply.

Both my mic and the cable have the standard 3-pin XLR connection. I'm not sure how you see "2 wires/pins" in the photo above; I am not sure where you see that.

I bought the adapter cable at Fry's Electronics. It is probably not high quality.

Can you tell me how I can figure out if I my mic needs phantom power and if my amp provides it?

The amp is small (12-watt) and looks like it is from the 70s (PRIME amplification):



I'll post mic model/specs when I get home.

Another hint: when I tried using a PC microphone with a 3.5mm - 1/4" adapter, I was barely getting any signal from the mic through the amp. The only time it worked at all is when I put my mouth directly on the mic and made a low-pitched humming/breathing vibration noise and I could still barely hear it.

Thx.
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post #6 of 10 Old 01-16-2009, 06:27 PM
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The 1/4in connector in the picture is a 2 conductor connector (tip & sleeve) not a 3 conductor connector (tip, ring & sleeve).

Kevin
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post #7 of 10 Old 01-16-2009, 11:43 PM
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I'm guessing the biggest problem is that the microphone puts out a much lower signal level than the amp needs to make decent output.

Dunno if the mic needs phantom power, but I can all but guarantee that amp doesn't provide it.

Just because there is a knob doesn't mean you should turn it.
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post #8 of 10 Old 01-17-2009, 12:36 AM
 
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The mic you linked to is a dynamic mic that doesn't need phantom power. That mic also has a hi/lo impedance switch for use with "guitar" amp high impedance inputs.
The cable you have has a 3 conductor connector on one and and a two conductor connector on the other.It probably ties xlr pin 3 to ground.
A PC mic is an unbalanced "electric condensor mic", it requires a 5VDC bias voltage.
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post #9 of 10 Old 01-17-2009, 01:57 AM - Thread Starter
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Thanks everyone for the help!

It turns out I have this mic (http://www.shure.com/ProAudio/Produc...5SD-LC_content) and I needed a high impedence transformer. I bought it at the local guitar shop and the sound is now excellent.

However, I now need an extension cord for the mic. Since the transformer is XLR female to 1/4" male, I can either get an XLR extension or 1/4" extension. Does anyone know what advantages one has over the other?
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post #10 of 10 Old 01-17-2009, 08:26 AM
 
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The XLR is balanced, the 1/4" is not.
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