Microphone buzz help (details in post)

[Icantthinkofaname]

I have a 3U Audio CM1 that buzzes only when the headbasket is a bit "off axis". I know the headbasket usually doesn't move when the mic is assembled, but for whatever reason my CM1's headbasket does shift a bit. When facing left (probably misaligned) there is a buzz when I touch the mic. When facing right the mic works without issue. I also can't open the mic as I should be able to because the bottom nut doesn't rotate. Maybe it was twisted too tightly and the threading was stripped, I don't know. Now the solution would be "Don't turn the mic's headbasket to face left" and that's a good idea. But there's always a chance of doing it accidentally when putting the mic in a shock mount (like on of those spider ones where you have to tighten the bottom) or clip holder. I have a couple questions about this issue so please help me out if you know the answers.

The first is what would cause the headbasket to shift when the mic is assembled? I'm guessing a screw is loose or the notch in the mic body isn't straight or is the wrong size.

The second is this: My theory is that the headbasket shifting is also shifting the capsule mount, turning the caspule and possibly pulling on the ground wire. Could the ground wire shifting cause the buzzing assuming it's a grounding issue? If this is not the issue please give me an idea of what issues can be caused by a shifting headbasket. I'm pretty sure it is being caused by the headbasket as since I've turned it left and right several times and buzzing only occurs when the headbasket is turned to the left.

The third question is if anyone has opened one of these mics with a really hard to turn nut how/were you able to open up the mic?

Now this mic is under warranty and I have contacted Guosheng about the issue. I'm planning to send the mic in for servicing if shipping won't be ridiculously expensive. But please play along and answer my questions on the off chance shipping is astronomical or I get charged or have to pay a ridiculous COD from a private service like UPS or FedEx.

 

[Bo Deadly]

Maybe the basket isn't making proper contact with the body and so it's loosing it's shielding properties. Does the buzz go away when you touch it or press on it? Try connecting a bit of jumper wire between the shell and the body to see if it has an effect.

 

[Icantthinkofaname]

Maybe the basket isn't making proper contact with the body and so it's loosing it's shielding properties. Does the buzz go away when you touch it or press on it? Try connecting a bit of jumper wire between the shell and the body to see if it has an effect.

The buzz only happens when the mic or aluminum shockmount is touched and the headbasket is "turned" to the left (more like nudged as it doesn't visibly move).

I can't get the mic open so I can't attach anything to the inside if that's what you mean. I'll also need to pick up some jumper wire since I'm sure it's different from the jumper leads on a multimeter. Honestly I'm a bit confused since looking jumper wire up on Amazon is giving me the wire you use to connect stuff to a board like the Raspberry Pi.

I'm actually planning on selling the mic, otherwise I wouldn't care about the buzz so much since it only seems to happen under certain conditions.

 

[Bo Deadly]

I can't get the mic open so I can't attach anything to the inside if that's what you mean.

No, I meant just for diagnostic purposes. It really should not buzz when you touch it. It sounds like it could be a grounding issue. If it buzzes only when you move a part, that sounds like perhaps something is loosing contact because metal parts are not secured properly. You might be able to verify that with a simple piece of wire used to assert that the basket is grounded properly. If the problem goes away, then you know it's a construction issue and you can focus your efforts on that.

 

[Icantthinkofaname]

No, I meant just for diagnostic purposes. It really should not buzz when you touch it. It sounds like it could be a grounding issue. If it buzzes only when you move a part, that sounds like perhaps something is loosing contact because metal parts are not secured properly. You might be able to verify that with a simple piece of wire used to assert that the basket is grounded properly. If the problem goes away, then you know it's a construction issue and you can focus your efforts on that.

Yeah Guosheng said it's most likely a grounding issue. It's really only happening when the headbasket is turned slightly to the left which I assume is a misaligned position. I know it shouldn't buzz and I'm pretty sure it only happens when the headbasket is misaligned and the mic is in a metal shock mount.

So if I touch wire to the microphone and it buzzes it suggests that something isn't grounded properly? Would any old piece of wire do, or should I buy a specific kind? Would touching the mic with the leads from a multimeter reveal anything?

 

[Bo Deadly]

So if I touch wire to the microphone and it buzzes it suggests that something isn't grounded properly? Would any old piece of wire do, or should I buy a specific kind? Would touching the mic with the leads from a multimeter reveal anything?

No, if it stops buzzing, then that would suggest a grounding issue. Think about it - if it's not grounded, it's not shielding the capsule and thus you get buzzing. If you then solidly ground the basket by taking any old piece of wire and connecting the basket to the body and the buzzing stops, that would be meaningful. But it has to be a solid connection. I have a few wires that have alligator clips on the end. That is the sort of thing that would be ideal because you need something that makes good contact. In fact, it could be rather difficult to get the wire to really make good contact because of oxidation, paint, plating and such. You need something with teeth.

Incidentally, the way you open a LDC mic is to unscrew the base. But I'm not familiar with 3U audio so I don't know for sure what you need to do in your case.

 

[Icantthinkofaname]

No, if it stops buzzing, then that would suggest a grounding issue. Think about it - if it's not grounded, it's not shielding the capsule and thus you get buzzing. If you then solidly ground the basket by taking any old piece of wire and connecting the basket to the body and the buzzing stops, that would be meaningful. But it has to be a solid connection. I have a few wires that have alligator clips on the end. That is the sort of thing that would be ideal because you need something that makes good contact. In fact, it could be rather difficult to get the wire to really make good contact because of oxidation, paint, plating and such. You need something with teeth.

Incidentally, the way you open a LDC mic is to unscrew the base. But I'm not familiar with 3U audio so I don't know for sure what you need to do in your case.

It should come apart the usual way I believe. Initially I was told that I should be able to turn the base to tighten it, but it's actually so tight that I can't tighten or loosen it. It may be that way by design as me pointing out that it wouldn't budge didn't get a response.

Now this doesn't bother me personally because I know to control the problem, but if I try to sell the mic it'll become a problem. I can't imagine the resale value is very good already because 3U Audio doesn't seem to be that well known outside of Gearslutz, this site, and homerecording.com.

 

[Icantthinkofaname]

The issue is solves now. So I didn't think about wearing rubber gloves while trying to tighten or loosen the base. It just had to be tightened more.