Shure sm58 through Marshall AVT150X

by Andy

I've just received my Shure sm58 and i assumed i would have enough volume from my 150-Watt ValveState guitar amp. But it turns out that the only way for me to get substantial volume from it is to funnel the sound to the microphone using my hand, and the turn the amp up higher than i've EVER dared to when using a guitar through it, which is so high there's audible noise which has no relevance to the position of the microphone. I would have thought a 150-Watt guitar amp would be enough, but does it sound like there's something wrong with the microphone/cable, or do you always need a PA loudspeaker? Can anyone help?

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Nov 27, 2009
You just need to add a mike mixer
by: Andrew Campbell

You just need an inexpensive microphone mixer to amplify the 1 to 2 mV output from your SM58 mike up to the 100 mV or so required by the Marshall AVT150X. The signal output from your electric guitar or an electro-acoustic guitar is derived from your vigourous plucking and/or strumming of up to six metal strings whereas the output signal from your SM58 mike is derived from your voice sound waves passing over a very small moving coil transducer in the mike. Just try singing close to your guitar strings with the amp gain turned up high to see just how weak the voice is as a signal source!

For your immediate requirements a 2 channel mono mike mixer will probably suffice and it need not be expensive. It should have 2 XLR mike inputs, some EQ (tone controls) and either gain or volume (or both) on each channel. It will connect your mike to one of the jack inputs on the Marshall. You will also need an XLR to XLR mike cable to connect your SM58 mike to the mixer and another suitable cable between the mixer output and any jack input on the Marshall. Your local friendly guitar store staff will advise you on how to set up the levels for best results but DO REMEMBER that to keep feedback (aka howl around) under control you, with your mike on a stand, facing you directly must stand or sit BEHIND the closed back of the Marshall Amp i.e. with the Marshall Amp cabinet loudspeaker firing at the audience. Good luck and let us know how you get on.

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