Help MSHilarious! or ? mic hummmmmmm

[tmix]

Hey guys! have a small problem I hope you have an answer for.

I have recently bought some EV n/d 406 or 408s (i cant remember).

They are the dynamic mics that are egg shaped and are suspended on a yolk of sorts.
They sound excellent except for the fact there is a verrrryyyy slight hum reminicent of a single coil guitar pickup.

As soon as you touch the mic the hum sound disappears and is wonderful. Problem is... it is hard to play drums and touch the mics at the same time...

Is it some sort of ground issue within the mics? All three exhibit the same noise.
I am wondering what the fix is?

Thanks!

Tom

[mshilarious]

The 468, maybe? I don't know much about it, but I would guess you are getting induced noise, maybe from the cable from the capsule to body. That shouldn't be the case if it is a shielded cable, but I dunno what else to guess. But the noise has to come from somewhere, so you might look around your house for noise sources--flourescent lights, dimmer switches, electric heaters, etc., and see if turning something off helps.

Another thing that confuses me is the mic's self-noise spec of 14dBA. A dynamic mic shouldn't have self-noise; there is a bit of thermal noise but that should be way less than 14dBA. Like 40dB less Unless they knew the mic was suspectible to interference, and put the self-noise spec in to CTA Compare this to the specs for the RE20, where there is no self-noise spec (typical for a dynamic mic), but they show "hum pickup level" at -130dBm.

Sorry, just wild guesses from these quarters . . .

[TheHunter]

Is your system grounded? Most of this common problem is fix by running a ground wire.

[tmix]

As far as I know all things in our system are grounded except the rolling racks dont have a direct ground.

The funny thing is no other mic dynamic or otherwise has this problem, and I have a pretty huge selection from different manufacturers.

It may be what MS suspects... inherent in the mic or design of the mic.

hmmmm

I may try opening the mic body up and see if there is a good connection from the capsule wire to the mic body or xlr connector.

Thanks!

[mshilarious]

Originally Posted by tmix

As far as I know all things in our system are grounded except the rolling racks dont have a direct ground.

The funny thing is no other mic dynamic or otherwise has this problem, and I have a pretty huge selection from different manufacturers.

It may be what MS suspects... inherent in the mic or design of the mic.

hmmmm

I may try opening the mic body up and see if there is a good connection from the capsule wire to the mic body or xlr connector.

Thanks!

You know, looking at the mic again, it could be a simple shielding problem. If the mic capsule is totally surrounded by steel mesh, it is only partially shielded, something like 30% or so. Try an experiment; find something metal to surround the grille, and connect it to the case, and see if the problem goes away.

[tmix]

Good Idea.

I'll try an aluminum can first. I have a test lead with some alligator clips on it to make the jumper.

If I can't find a way to make them quieter, I'll have to off them on EBAYor something.

Shame though... They basically sound really nice.. better than a sm57.

[boingoman]

Make sure to give the connectors a good cleaning in addition to whatever resoldering you do. I have four I use all the time, the only time I have had a hum problem turned out to be a tired XLR connector.

[tmix]

Originally Posted by boingoman

Make sure to give the connectors a good cleaning in addition to whatever resoldering you do. I have four I use all the time, the only time I have had a hum problem turned out to be a tired XLR connector.

COOL!

That would be really excellent if that is all the problem is.

[big country]

a dimmer light switch can also make noise

is it just those mics that make noise?
and other mics sound fine...

[tmix]

Originally Posted by big country

a dimmer light switch can also make noise

is it just those mics that make noise?
and other mics sound fine...

It is just those (3) mics out of the 30 some odd mics I have.

I dont have fluorecent lights , dimmers, or the like, but the last place I used them was in my old studio which was in my garage, so just maybe something was putting off something evil near by. I have not tried them since I moved into my new studio which is a stand alone structure.

I'll experiment with them and see if the problem still exists.