Gain and Hum - Mic, Mixer or Incompetence Problem?

[wombatzoner]

I'm not sure if this is a mic, mixer, or cable problem, and since I'm new and can't rule out simple ignorance, I'm posting this here.

I'm just getting started with recording. Some friends and I want to do some 'radio theater' style productions, and I'm the poor schmuck who volunteered to assemble and operate the recording equipment. I've got the mixer connected, the software installed and have made a few recordings.

So far so good. Unfortunately, I'm having a heck of a time with this really annoying hum on the mics, and I'm not sure what to do to fix it.

Equipment:
Mixer: Alesis Multimix 12 Firewire
Mics: Two Shure SM58 and one SM63 mics (all three are connected the the 3-pin XLR jacks on the mixer with 25' XLR cables)
Software: Cubase LE on a Mac

Material: The bulk of what we're planning on recording is spoken voice only for the most part, as well as some in-studio (okay, in-basement) sound effects.

First Question: In order to get the level LEDs on the mixer to even approach 0, I have to turn the gain dial for each microphone channel 3/4 of the way or more to maximum. If I don't do this, the recordings are way too quiet in Cubase. I understand mics do need to be pre-amped to be heard clearly, but is it normal to have to turn the gain up so much?

Second Question: When the gain is turned up, there is a hum or a buzz on the channels the SM58 mics are on. I can turn the gain down to where it's not noticeable, but at that point not even the lowest LED on the level meter will light up. I did some more testing (with the computer off and disconnected to eliminate that as a suspect) and determined I get the hum on any channel an SM58 is connected to, even if the switch on the handle of the mic is turned off so it's not picking up an air-duct or the furnace or other sound in the environment. I can plug the SM63 in, no hum. Plug either SM58 into that cable (and leave all controls in the same position) and as soon as the pins make contact, I get the hum. Any idea what is causing hum and what I can do to stop it?

This has me kind of stumped at this point, since I don't know if I need to get new mics, a different brand of mic, or some other gizmo to between the mixer and the mics. Any advice anyone has would be appreciated.

 

[tmix]

The shure 63 is a dynamic mic like the 58? I can't remember.

Anyway, the firsrt thing is to eliminate the cables being the issue.
Since the one mic gets no hum try all three cables on that mic.

If the cables are not the issue, and it seems you have the gain up about the same on all three, it could be that the 58s are picking up some kind of RF frequencies due to lighting, dimmers and such.... or... they have both been dropped.

It is not real unusual to have to crank the gain about 1/2 to 3/4 to use dynamic mics from a distance. Condensor mics have a hotter output, they might work better for you if you have access to the and your mixer has phantom power.

Otherwise you are going to have to figure a way to get the mics closer like hiding it in some props or disguising it to look like a hand held ice cream cone or something.

 

[cusebassman]

The shure 63 is a dynamic mic like the 58? I can't remember.

Anyway, the firsrt thing is to eliminate the cables being the issue.
Since the one mic gets no hum try all three cables on that mic.

If the cables are not the issue, and it seems you have the gain up about the same on all three, it could be that the 58s are picking up some kind of RF frequencies due to lighting, dimmers and such.... or... they have both been dropped.

It is not real unusual to have to crank the gain about 1/2 to 3/4 to use dynamic mics from a distance. Condensor mics have a hotter output, they might work better for you if you have access to the and your mixer has phantom power.

Otherwise you are going to have to figure a way to get the mics closer like hiding it in some props or disguising it to look like a hand held ice cream cone or something.

I generally prefer my ice cream cones mounted with a shockmount

As for the poster's problem, I have a sneaking suspicion that the preamps in your mixer are simply too noisy at the level you are setting them at. Like the guy above said, either get those mics closer to the source, or try out some condenser mics, as they usually require less gain supplied by the preamp to get the same output.

 

[wombatzoner]

The shure 63 is a dynamic mic like the 58? I can't remember.

According to Shure the SM63 is dynamic, yes.

Anyway, the firsrt thing is to eliminate the cables being the issue.
Since the one mic gets no hum try all three cables on that mic.

Checked that this evening. No hum on the SM63, regardless of cable.

If the cables are not the issue, and it seems you have the gain up about the same on all three, it could be that the 58s are picking up some kind of RF frequencies due to lighting, dimmers and such.... or... they have both been dropped.

If it's RF noise, I can't find the source. The lights in the basement are incandescent, the dimmer controlled lights are off, and the nearest operating piece of electronics is a PC upstairs at this point. I even left my cell-phone across the room.

It is not real unusual to have to crank the gain about 1/2 to 3/4 to use dynamic mics from a distance. Condensor mics have a hotter output, they might work better for you if you have access to the and your mixer has phantom power.

Otherwise you are going to have to figure a way to get the mics closer like hiding it in some props or disguising it to look like a hand held ice cream cone or something.

As for the poster's problem, I have a sneaking suspicion that the preamps in your mixer are simply too noisy at the level you are setting them at. Like the guy above said, either get those mics closer to the source, or try out some condenser mics, as they usually require less gain supplied by the preamp to get the same output.

Just to clarify, it's radio theater, not stage theater, so mercifully I just have to keep them from bumping into the mic stands. I seem to be able to get decent levels with no noise the SM63 gain cranked about 3/4 of the way, so at this point, I'm guessing I have two turkey SM58s.

Next stop, calling Shure I guess.

 

[wombatzoner]

Just a quick follow up. According to Shure, both mics are counterfeits. I guess this will teach me to be a little more cautious about where I get my gear in the future.