MXL990 Microphone problem

daniellumertz · 10-02-2020, 09:46 PM

So, not reaper related, but don't know really where to find some help....

I have two MXL 990, I haven’t used them in some months now, decided to use this week and one of them start to have an very different sound, very strange, even with the same cables, same input gain in the interface, same input etc etc, one is very strange. I wonder what it might be, I will send an recordings of the two. I havent used them in a while, but I always keep them in the case, so they don’t get dust. This is the first time it happen, they used to be equal.

Is there some frequent problem it might happen? They never fell or anything like that....

Bad MXL 990
https://drive.google.com/file/d/1bKX...ew?usp=sharing
Good MXL 990 https://drive.google.com/file/d/1ysF...ew?usp=sharing

It is very clear when seeing the waveforms

Thx people

ps: ohhh, I posted in the wrong part of the forum, can some mod send it to the right one ?

cyrano · 10-04-2020, 04:31 AM

How long have you had these?

A first guess would be a cap went sour in one of them. You could see it as an occasion to "upgrade" the bad one?

I'll see if I can dig up a reliable schematic. Since these are popular mics for modding, something should show up.

daniellumertz · 10-04-2020, 11:04 AM

Hmmm my guess it could be some damp problem , but this is strange as I always keep it in the box, and my room does not have much moisture.

When you say cap is the capacitor? I could switch it ... is there some thing that this problem could be related to it to be sure it is prob the problem?

thx very much for the answer .

tspring · 10-05-2020, 03:34 AM

A bad capacitor is possible. The mic contains a circuit board with numerous compoments, any of which could be out of specification. Excessive moisture is not necessary for a failure, but it accelerates age related failure of some types of capacitors. Electrolytic capacitors will eventually fail even in a dry environment. The shift in frequency spectrum of microphone self noise suggests a problem in the circuit. If the mic has been dropped, stretching or tearing of the capsule membrane is a possibile cause for loss of high frequency response although I am not sure that such damage would cause the downward shift in the self noise spectrum evident in your soundclip. There is not much that you can do if this has happened.

T

ivansc · 10-05-2020, 05:23 AM

For what it is worth, I have a rode valve mic & have always kept it in its case with a silica gel sachet in the case to make sure any moisture is absorbed. Just putting it in the case wont absorb any moisture in there.

Listening to the difference between the two mics on your recording, it does seem to me that this is either because of damp or dust or something on the capsule, although on that particular mic you are not talking top-of-the-lie performance regardless, so this really could be as simple as degradation of the two mics at different levels. FWIW the noise on the "good" one seems to be far more errati than on the bad one, even if the overall level is lower.

But depending on how old the mics are, it could well be capacitor-related. electrolytics are cheap unless you need high voltage ones as used in valve amplifiers.

cyrano · 10-05-2020, 07:10 PM

The impedance around the input of the circuit is so high, even a little dirt can do strange things to the sound.

Even mediocre pcbs can contain enough humidity to ruin a recording. One mic I dealt with years ago had an earworm in it...

Open it up, clean very thoroughly with pure IPA (Isopropyl alcohol).

Dark Fader · 10-05-2020, 11:02 PM

Yeah, don't use India Pale Ale!

jpanderson80 · 10-06-2020, 08:09 AM

I agree: capsule or possibly a circuit component issue. You may be able to look at the capsule and see an issue.

IPA... LOL That one got me!

poetnprophet · 10-06-2020, 09:43 AM

I have a custom 990 by MJE, have had for a few years. At one point, I started getting this static type of noise, I would jiggle the cable, tried other cables, preamps, all kinds of things, then it would go away or something but it happened like every day. I can't open your google files right now so I can't hear what's happening with yours.

But, one day I unscrewed the basket/grille and just poked inside, made sure everything was snug etc, then put back together. The noise went away. Maybe I got lucky, but just something to point out. Never had that happen with any other mic before.

jrk · 10-06-2020, 09:57 AM

Quote:

Originally Posted by poetnprophet

just poked inside, made sure everything was snug etc, then put back together. The noise went away. Maybe I got lucky, but just something to point out. Never had that happen with any other mic before.

I've had cars like that.

daniellumertz · 10-06-2020, 04:07 PM

Hi people thanks for the response ! I open it up, see the capsule and eletronics, by my eye everything was 100% I leave it out of the box for some days and the noise kinda lower a bit but still there, almost sure it is an damp problem... I Think I will try to clan the capsule with IPA. It is my favorite beer maybe it likes too xD.

Thxxx

cyrano · 10-07-2020, 01:27 AM

Go easy on the capsule, if you've never done it before.

Clean the board and components and, most importantly, the wire from the capsule to the board.

Dark Fader · 10-07-2020, 04:47 AM

Could be dust bunnies!

ivansc · 10-08-2020, 12:53 AM

If it is just damp, putting a silica gel bag in with it should sort you out in a day. It certainly did in my case, where I had used a perforated disk pop shiled instead of my usual nylon cloth one. The mic started spitting popping & distorting after I had recorded about three or four songs & the studio engineer THEN told me that the perforated metal pop shields let a fair bit of moisture through if the singer is up pretty close!

I was shitting bricks, as my beloved vocal mic is a Rode Classic Mk1, which became unobtainable several years ago... fortunately a night with a gel sachet cured it all.