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Crackling noise coming out the SM7B microphone Condenser Microphones
Old 2nd March 2014
  #1
Gear Nut
 

Crackling noise coming out the SM7B microphone

Hi,

I recently ordered an open-box SM7B (perfect condition), so far so good, except there's some crackling noise coming out of the audio signal.

You can hear a sample of the crackling noise here, it's normalized so you can hear it clearly.

There's only a XLR male to female cable between the microphone and my X2U adapter. My previous microphone AT2035 didn't have this issue and was also connected to the X2U. The suspects here are the XLR cable or the SM7B itself.

RX Denoiser doesn't seem to recognize the crackling as noise so I'm unable to clean the audio like I did with AT2035.

Your thoughts?
Old 2nd March 2014
  #2
The Dropbox link doesn't seem to work.

Have you tried another cable, or at least tried "wiggling" the ends of the one you're using?

Is the output XLR connector block loose or are the pins dirty?

Without hearing the sample it's impossible to guess at the noise. A shorting cable will usually cause the sound to go in and out completely.

Also have you tried "excercising" the roll-off and presence switches (operating them rapidly a few dozen times). The SM7B has no internal connectors (all connections are soldered, so the switches and/or a worn output XLR connector are things to check. The single internal capacitor is only used if the presence switch is activated, and the choke coil is only used if the roll-off switch is closed.

With both switches open, the mic voice coil is connected directly to the output connector, it could not be simpler.

Are you sure that what you're hearing is not just normal mic pre "hiss"? The SM7B is a very low output mic, much lower than a capacitor mic like a AT2035. It requires a much higher gain mic pre and some mc pre built into common, inexpensive do not have a low enough noise floor for a SM7b. Are you running your input gain at a much higher setting than what you were using for the AT2035?
Old 2nd March 2014
  #3
Gear Nut
 

Audio link updated.
Old 2nd March 2014
  #4
Whew! The constant slight background "hiss"is normal, but the periodic "ripping" bursts certainly are not.

Sounds like an intermittent or dirty connection somewhere.
Have you tried a different mic pre channel and do you get the same noise bursts there?

Is the noise there in either position of either of the switches?

If you tap, the mic housing gently, do you hear the same sort of noise burst (as well as the sound of tapping the mic)?
Old 2nd March 2014
  #5
Gear Nut
 

@lotus-7

I've tried changing the roll-off switches, also tightening all the connectors and even with and without Cloudlifter. The crackling persists.

The XLR cable is new and it doesn't have imperfections as far as I know. Yesterday I ordered a new XLR cable Mogami Gold Studio hoping that it will fix or at least decrease this noise.

Please check again the audio link, it's working now.
Old 2nd March 2014
  #6
Gear Nut
 

Quote:
Originally Posted by Lotus 7 View Post
Whew! The constant slight background "hiss"is normal, but the periodic "ripping" bursts certainly are not.

Sounds like an intermittent or dirty connection somewhere.
Have you tried a different mic pre channel and do you get the same noise bursts there?

Is the noise there in either position of either of the switches?

If you tap, the mic housing gently, do you hear the same sort of noise burst (as well as the sound of tapping the mic)?
Yes, with switches on or off the noise persists also tapping or moving the mic won't affect it.

I don't have another preamp to test it. I would love to test it without the XLR cable but the SM7B is too big for the X2U.

My AT2035 doesn't have this problem, yet it doesn't require a cable to fit in.
Old 2nd March 2014
  #7
I did hear it before writing post No.4.
Old 2nd March 2014
  #8
If you run the preamp at the same gain setting as you're using on the SM7, but with the mic disconnected, (Leave the cable plugged into the X2U, but unplug the mic from the far end) do you hear any evidence of the same sort of "burst" noises? Even though you don't hear that noise with the AT2035, the mic pre in the Shure X2U must run at a full 26 dB higher gain setting then with the AT mic for the same audio sensitivity. The noise may be there, but if it's reduced in level by 26 dB, you may not notice it.

One other thought: If the "burst" noise is originating in the mic, adding a CloudLifter should make it much louder (at the same X2U gain setting). If it's originating in the input cable or the X2U itself, adding the CloudLifter should not change the level of the noise bursts.

You do have phantom power turned off when you're using the SM7b without the CloudLifter, right?
Old 2nd March 2014
  #9
Another test to try: Connect tthe mic as follows:

SM7b --> Cloudlifter ---> XLR cable to Shure X2U input ---> USB cable to computer.

Turn on phantom power on the X2U and set the gain high enough that you hear the noise. Turn off phantom power and wait for it to bleed down (30 to 60 seconds). Do not change the X2U thumbwheel "mic gain" dial.

Is there any sign of the noise bursts with PP off? With PP off the Cloudlifter will switch off and isolate the mice from the input.
If the noise stops completely, its not originating in the X2U mic pre circuitry. If it remains, the X2U has problems.
Old 2nd March 2014
  #10
Gear Nut
 

Quote:
Originally Posted by Lotus 7 View Post
If you run the preamp at the same gain setting as you're using on the SM7, but with the mic disconnected, (Leave the cable plugged into the X2U, but unplug the mic from the far end) do you hear any evidence of the same sort of "burst" noises? Even though you don't hear that noise with the AT2035, the mic pre in the Shure X2U must run at a full 26 dB higher gain setting then with the AT mic for the same audio sensitivity. The noise may be there, but if it's reduced in level by 26 dB, you may not notice it.

One other thought: If the "burst" noise is originating in the mic, adding a CloudLifter should make it much louder (at the same X2U gain setting). If it's originating in the input cable or the X2U itself, adding the CloudLifter should not change the level of the noise bursts.

You do have phantom power turned off when you're using the SM7b without the CloudLifter, right?
Jackpot! X2U is the one making the bursting noises. As you mentioned the extra gain makes the noise artifacts even louder. It's a shame that Cloudlifter won't deal with it as good as it does with the hiss level.

It's worth noting that the cable doesn't affect at all the quality of the audio.

Time to buy a new preamp I guess
Old 2nd March 2014
  #11
Gear Nut
 

Quote:
Originally Posted by Lotus 7 View Post
Another test to try: Connect tthe mic as follows:

SM7b --> Cloudlifter ---> XLR cable to Shure X2U input ---> USB cable to computer.

Turn on phantom power on the X2U and set the gain high enough that you hear the noise. Turn off phantom power and wait for it to bleed down (30 to 60 seconds). Do not change the X2U thumbwheel "mic gain" dial.

Is there any sign of the noise bursts with PP off? With PP off the Cloudlifter will switch off and isolate the mice from the input.
If the noise stops completely, its not originating in the X2U mic pre circuitry. If it remains, the X2U has problems.
The SM7B doesn't fit directly into Cloudlifter or X2U, the cable is always required to reach either of those.

Interestingly enough with Phantom Power off the noise bursts are gone.
Old 2nd March 2014
  #12
Quote:
Originally Posted by lonrot View Post
Jackpot! X2U is the one making the bursting noises. As you mentioned the extra gain makes the noise artifacts even louder. It's a shame that Cloudlifter won't deal with it as good as it does with the hiss level.

It's worth noting that the cable doesn't affect at all the quality of the audio.

Time to buy a new preamp I guess
If the cloudlifter increases the noise, it's coming from the mic, not the X2U.
Old 2nd March 2014
  #13
Lives for gear
 
LeeYoo's Avatar
 

I have heard this type of phantom only shotnoise before in not properly made XLR cable.
Rubber jacket not stripped back properly, or bad flux used.
Leo..
Old 2nd March 2014
  #14
Quote:
Originally Posted by lonrot View Post
The SM7B doesn't fit directly into Cloudlifter or X2U, the cable is always required to reach either of those.

Interestingly enough with Phantom Power off the noise bursts are gone.
Again. if there is no noise when the Cloudlifer is cut off (phantom power is OFF) then the noises is not coming from the X2U input circuitry, but is ahead of the Cloudlifter. Both tests indicate that the mic (or the input cable) is the noise source.

The other possibility is that the X2U phantom power supply is generating the noise bursts, but then you would hear them with the AT mic if you turn the gain way up.
Old 2nd March 2014
  #15
Quote:
Originally Posted by LeeYoo View Post
I have heard this type of phantom only shotnoise before in not properly made XLR cable.
Rubber jacket not stripped back properly, or bad flux used.
Leo..
Yes, it still very well may be the cable. Trying another cable is essential.

Running a mic pre at the 60 dB or more gain a SM7B requires means that noise sources in the microvolt range can become audible
Old 2nd March 2014
  #16
Gear Nut
 

Quote:
Originally Posted by Lotus 7 View Post
Again. if there is no noise when the Cloudlifer is cut off (phantom power is OFF) then the noises is not coming from the X2U input circuitry, but is ahead of the Cloudlifter. Both tests indicate that the mic (or the input cable) is the noise source.

The other possibility is that the X2U phantom power supply is generating the noise bursts, but then you would hear them with the AT mic if you turn the gain way up.
The noise bursts are present in every of the following scenarios:

1) SM7B > Cable > Cloudlifter > X2U
2) Cable > Cloudlifter > X2U
3) Cloudlifter > X2U
4) X2U only

The conclusion is that X2U is the one making these noises.

Yet only if Phantom Power is ON.
Old 2nd March 2014
  #17
Gear Nut
 

Quote:
Originally Posted by Lotus 7 View Post
Yes, it still very well may be the cable. Trying another cable is essential.

Running a mic pre at the 60 dB or more gain a SM7B requires means that noise sources in the microvolt range can become audible
After reading these results, getting another cable might "adjust" somehow the signal and fix it?
Old 3rd March 2014
  #18
Quote:
Originally Posted by lonrot View Post
The noise bursts are present in every of the following scenarios:

1) SM7B > Cable > Cloudlifter > X2U
2) Cable > Cloudlifter > X2U
3) Cloudlifter > X2U
4) X2U only

The conclusion is that X2U is the one making these noises.

Yet only if Phantom Power is ON.
Well, that sure sounds like the X2U is the problem. It probably was there all the time but because the gain required when using the AT 2035 was so much lower, the AT 2035's stronger signal masked the noise.

Obviously, it's not the mic if you still have the noise with the mic disconnected.

The Shure X2U has some sort of a DC to DC converter inside (probably a high-frequency inverter/DC multiplier) to provide the +48 Volt phantom power from the +5 Volts available through the USB port. It sounds like the DC/DC converter is creating the noise, or an input coupling capacitor is becoming electrically "leaky" (the coupling caps will have almost no voltage drop stressing them until phantom power is applied), or the input mic-pre IC has developed a noisy input stage.

It really doesn't matter since the issue is in the X2U, and it would likely cost much more to attempt to isolate the exact cause of the noise and fix it.

Looks like you will be in the market for a new interface. Since you now have two mics a 2-channel (or more) device is probably a good idea.
Old 3rd March 2014
  #19
Gear Nut
 

Quote:
Originally Posted by Lotus 7 View Post
Well, that sure sounds like the X2U is the problem. It probably was there all the time but because the gain required when using the AT 2035 was so much lower, the AT 2035's stronger signal masked the noise.

Obviously, it's not the mic if you still have the noise with the mic disconnected.

The Shure X2U has some sort of a DC to DC converter inside (probably a high-frequency inverter/DC multiplier) to provide the +48 Volt phantom power from the +5 Volts available through the USB port. It sounds like the DC/DC converter is creating the noise, or an input coupling capacitor is becoming electrically "leaky" (the coupling caps will have almost no voltage drop stressing them until phantom power is applied), or the input mic-pre IC has developed a noisy input stage.

It really doesn't matter since the issue is in the X2U, and it would likely cost much more to attempt to isolate the exact cause of the noise and fix it.

Looks like you will be in the market for a new interface. Since you now have two mics a 2-channel (or more) device is probably a good idea.
Thanks for all your help! I do voiceovers so one channel is enough, still getting another X2U is too risky, they weren't constructed with the SM7B in mind. Onyx Black Jack might be the next upgrade.
Old 2nd November 2014
  #20
Here for the gear
 

An update that may or may not relate, but I'm having trouble with the X2U and Cubase 6.0.7 on a MB Pro with OS X 10.9.5 and found this thread.

I've used Cubase over 2 years with a Fast Track Ultra, 2CS1000s. a Rode NT2-A, an AKG C214, and various regular and MIDI instruments, gotten the SPDIF channels 7 and 8 working with external A/D and D/A, and everything works fine. I can't recall, but I've had the X2U awhile and may have had it running with Cubase SE several years ago. I'm using OS X 10.9.5 which Shure does not support. I've got the latest firmware in the X2U (I think).

I recently started to set up a "remote" configuration I could lug with me when traveling on business. I was going to bring one of the CS1000s with the X2U and an Akai MPK Mini. I plugged phones into the X2U, set the Mac preferences to use the Shure X2U as both input and output. Selected the Shure as the VST device in Cubase. The result is that the X2U works fine when directly monitoring the mic (X2U Monitor dial set to local, all the way down). X2U Gain and Volume work fine in this mode. I can even get some signal without Phantom Power. As soon as I fire up Cubase, set up the Shure as the ASIO, and dial in some monitor (X2U Monitor dial moved up) it immediately clips to max on the input channel. It also produces horrible, crackling, hissing static either when monitoring through Cubase or just replaying. II tried changing as many settings as possible in Cubase, Mac Sound preferences, and on the X2U and nothing fixed it. I have tried it with all 3 mics, no cable plugged into the X2U, Phantom Power on and off, all combinations of the Cubase and Mac preference setting I could and get the same result.

Early on, I checked it using the time honored component swap troubleshooting by trying it in Garage Band. Of course, it works just fine there!

Seems the likely culprit is the OS X version, even though the X2U works fine with Garage Band, who knows what evil lurks therein? The Shadow SW knows!

So I'm sending out for another in-line XLR to USB converter. Really small is my criteria, several on Amazon. If that doesn't work I may just have to get one of the smaller audio interfaces around that have one or two channels.
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