A little problem miking my amp

[KendallC]

So in my praise band I use a Vox Valvetronix VT30 amp with my Les Paul with a DigiTech RP300 and BOSS DS-1. Yes, I know my rig is small. Okay. I use a Shure SM57 to mic it.

Here is the thing. My amp has to turned down a little low. It's not that quiet and the mic is turned up to where it rightly should be. Not to sound conceited but I kinda know what I'm doing except I'm having this one problem. The amp is close the the main(s) speakers (I don't have a choice). So that means the microphone is close to the speaker as well. The speaker is pretty high off the ground. About 7 feet? And the microphone, amp are on the ground, of course. The problem is that I'm getting this hum coming out of the mains at some times.

The microphone is not EQ-d at all from the board and my amp is set accordingly how I want my sound. Any ideas why I get that hum and sometimes hiss?

[loudboy]

Do different patches on your FX unit have differing amounts of gain?

If so, they could be causing hum in the amp, which is amplified thru the PA.

The next time you notice the hum, turn the volume all the way down on your amp and see if it goes away.

If it does, it's the amp.

If it does not, it's something in the PA.

If that's the case, track it down and get rid of it.

[cruisemates]

Hums usually come from high impedance cables picking up RF (radio frequency) static. A guitar cable, with its shield, acts like an antenna. Things to try to get rid of hum inlcude shorter, better shielded cables between your guitar and amp, and also separating cables. A bad one would be if your guitar cable ran alongside the very high wattage speaker cable go to that mains speaker.

Also - turn yourself (holding your guitar) on an axis (face N, S, E W) one direction at a time and see if the hum goes away. Often it does.

[KendallC]

Thanks guys! I appreciate the feedback!