Weird condenser mic issue

[foxAsteria]

Heya, I was hoping someone might know why my AT2020 is being weird. It usually works fine, but a while into a recording session, the signal will often grow very faint and build up a quiet hiss. Hoping there's some way to fix it without having to replace it. The funny thing is that it seems to happen faster when mounted on a stand. Could it be picking up some interference from my screen or monitors or so? I can't seem to duplicated it manually; kinda random. I've tried different mixer channels, cables, etc.

[Tod]

Originally Posted by foxAsteria

Heya, I was hoping someone might know why my AT2020 is being weird. It usually works fine, but a while into a recording session, the signal will often grow very faint and build up a quiet hiss. Hoping there's some way to fix it without having to replace it. The funny thing is that it seems to happen faster when mounted on a stand. Could it be picking up some interference from my screen or monitors or so? I can't seem to duplicated it manually; kinda random. I've tried different mixer channels, cables, etc.

They will have capacitors, resisters, diodes, and other active parts in the mic that can go bad. They are usually pretty hard to work on and fix.

Also, check your 48volt supply using other condensers if you have them.

[foxAsteria]

I was afraid of that. Thanks. All other condensers are fine in the same situations.

[Tod]

Originally Posted by foxAsteria

I was afraid of that. Thanks. All other condensers are fine in the same situations.

Yeah, I have an AKG 451 that is bad and I know what the problem is, I actually got the capsule open and determined that it was a diode, but trying to get the tiny little circuit board out to fix it was beyond my ability. I need to send it to AKG for the tune of $100 or more.

[foxAsteria]

Hmm, maybe it is my phantom power? I have an MXL990 that's doing the same thing if the input source is not consistently loud. My NT1A doesn't do it though... The phantom power is coming from a mackie onyx mixer. Have to test with another interface... Boy that will be loads shittier if it turns out to be the mixer.

[Tod]

Originally Posted by foxAsteria

Hmm, maybe it is my phantom power? I have an MXL990 that's doing the same thing if the input source is not consistently loud. My NT1A doesn't do it though... The phantom power is coming from a mackie onyx mixer. Have to test with another interface... Boy that will be loads shittier if it turns out to be the mixer.

Do you have any compressors, limiters, on the track?

[foxAsteria]

No, I'm just listening to the direct signal via phones.

[Tod]

Originally Posted by foxAsteria

No, I'm just listening to the direct signal via phones.

How about your Mackie board, could you inadvertently have a compressor/limiter on that.

Heh heh, if it's all of a sudden happening with a couple of mics but not others, then it becomes a mystery.

Take a very close look at your input to output structure, both with your mixer and Reaper, make sure it correlates in a way that you can rule it out.

EDIT: Okay if you're hearing it in the earphones from the Mackie, then it probably has nothing to do with Reaper.

The thing is, if two microphones go bad at the same time, that would be unusual. However, I've never had a 48 volt power supply go bad either, and that's over 45 years, but I could have been lucky. Consequently, I wouldn't know what to expect if it did go bad.

[cyrano]

Originally Posted by foxAsteria

Hmm, maybe it is my phantom power? I have an MXL990 that's doing the same thing if the input source is not consistently loud. My NT1A doesn't do it though... The phantom power is coming from a mackie onyx mixer. Have to test with another interface... Boy that will be loads shittier if it turns out to be the mixer.

The AT2020 isn't very power hungry, but the MXL is, in my experience.

I suppose you have tried another cable? Another channel?

Too much resistance in a cable can produce problems like this. But the small switches on the Mackie onyx also can develop resistance. Usually, rocking them a bit cures it. Otherwise, gently drip in a few drops of alcohol and repeat the rocking.

Do you have a DMM (digital multi meter) to check power on the mixer? The PSU could be dying. To test, unplug Firewire. Measure with one wire of the DMM to pin 2 and the other wire to pin 1. After that, check pin 3 and 1. You should see 48 VDC or even a bit more.

[Tod]

Originally Posted by cyrano

The AT2020 isn't very power hungry, but the MXL is, in my experience.

I suppose you have tried another cable? Another channel?

Too much resistance in a cable can produce problems like this. But the small switches on the Mackie onyx also can develop resistance. Usually, rocking them a bit cures it. Otherwise, gently drip in a few drops of alcohol and repeat the rocking.

Do you have a DMM (digital multi meter) to check power on the mixer? The PSU could be dying. To test, unplug Firewire. Measure with one wire of the DMM to pin 2 and the other wire to pin 1. After that, check pin 3 and 1. You should see 48 VDC or even a bit more.

Yeah.

[foxAsteria]

No effects on the board. I'm getting the same issue with another interface, so it's definitely the mics. Could my interface be slowly frying my mics for some reason? That's 2 down in the last couple months, so now I've only got one reliable condenser.

[Tod]

Originally Posted by foxAsteria

No effects on the board. I'm getting the same issue with another interface, so it's definitely the mics. Could my interface be slowly frying my mics for some reason? That's 2 down in the last couple months, so now I've only got one reliable condenser.

I'd say check the pins like Cyrano suggests. Also check for any AC, I don't know what that would do because I've never had a problem with my phantom powering.

You should get 48 volts or there abouts, they are usually 9 volt to as much as 52 volt. I would think it would take significantly more than 52 volts to do the damage.

[foxAsteria]

Yea, I have to get a new multimeter. I'd rather get some new mics first though...

[dmoss74]

just a thought. have you been careful to plug in the mics with the phantom power off? and conversely making sure the power is off, before unplugging them? and did you try the suggestion of trying another channel on your mixer?

it seems odd that two mics would go bad simultaneously, but i guess it's possible.

[Pet]

Originally Posted by dmoss74

just a thought. have you been careful to plug in the mics with the phantom power off? and conversely making sure the power is off, before unplugging them?

Very good advice, I want to add that often the phantom power needs a pretty long period of time to completely shut down. I noticed (most with Mackie-Mixers) that it can take up to a minute.

Good luck, I hope nothing is damaged...

[foxAsteria]

Yea I make a habit of having the phantom power off when (un)plugging cables, but of course I've forgotten on occasion. Other people could have made the mistake as well. It's just odd, the way it comes and goes.

[cyrano]

The AT2020 is an electret. The MXL is a "classic" condenser, eg it needs polarization voltage. The AT2020 should be fairly immune to phantom trouble, imho.

If both are not old and go bad in a short period of time, I'm thinking humidity...

What part of the tropics are you in?

Humidity is the natural enemy of every condenser mic (except Senn MKH's, maybe). And loss of level and hiss sound "humidity" to me.

If there was AC on the phantom line, you'd certainly hear that, unless it was HF. But you'd still "feel" HF, as it would disturb compressors and sound funny if the signal is strong.

EDIT: Your other interface isn't an AKAI Pro, by any chance? I would suspect that interface to eat some mics, as the phantom power circuit is very badly designed.

[foxAsteria]

It's very dry in Colorado, but they were in a band space for a year, but they both seemed fine for months after I got them out of there. They're both probably 10 years old. Other interface is a Firebox. I think they were using another Presonus mixer in the band space.

Well generally I was just wondering if this was any kind of known issue encountered with condensers. The MXL goes silent, briefly at frequent intervals if trying to record something like vocal, seems to work fine on something louder like drums. The AT2020 goes all "dim and fuzzy" for longer at longer intervals and doesn't really care about the source. But they both started having problems just recently.

[cyrano]

The MXL could have a loose diaphragm. If it touches the backplate, the polarization voltage is short circuited (and a hole in the diaphragm could be the result).

Replace capsule with something better?

These are great bases for U47 or U87 mods:

http://microphone-parts.com/pages/mxl-990-mods

There are more affordable parts than the RK47.

The AT2020 could be simply a defective electret capsule. These tend to age and loose their "permanent" polarization. There's no easy fix, but you could also replace the capsule. Hard to open, though. Very hard glue on the screws, SMD parts...

[foxAsteria]

Gee, what? A U87 clone for $300? Maybe this is a good thing...kinda wish I hadn't just bought a $400 DI, now. Thanks, Cyrano, for the great tips.

[Greedy]

Are you near Denver? Music go round in Aurora has a used 2020 for sale $59.99. Maybe not the solution you want, but if you like the mic... Also see them pop up on CL fairly regularly.