Jump to content

Small diaphragm condenser mics causing interference/noise


PMitch

Recommended Posts

I recently bought a matched pair of Lewitt 040 small diaphragm condenser mics and sent them back because they created a huge amount of noise and were unusable for recording (acoustic guitar). I then bought a pair of Rode M5s but exactly the same problem occurs, so it can't be the microphones - it must be something in Logic Pro, my iMac or the audio interface (Focusrite Clarett 2Pre). There is repetitive noise, similar to morse code, and a lot of crackling, and, bizarrely, it gets much worse when I move my mouse on my iMac. I am connecting the mics to a Focusrite Clarett 2Pre, which is connected by USB to my iMac. I should stress that there is absolutely no problem when I use any other kind of mic - my Rode NT1-A large diaphragm condenser mic is almost silent when played through exactly the same set-up with the same gain level, and so is my Shure SM58 dynamic mic. Sample rates for Focusrite and Logic Pro are both 44.1. I would be very grateful for any help on this.
Link to comment
Share on other sites

Thanks for the reply. The 'Morse code' is different to cell phone interference. Hard to explain! I haven't got a wired mouse to hand but that's a good suggestion. The crackling is definitely audible in the recording. I've just tried it through my old Focusrite Scarlett 2i2 interface and the interference/crackling is not as loud but it's still there. It's so odd that it doesn't happen at all with large diaphragm condenser mics...
Link to comment
Share on other sites

I've realised it must be an issue with the Focusrite Clarett 2Pre audio interface or the XLR cables. I have disconnected it from my iMac (and obviously from Logic too) and the noises still continue, even with the phantom power turned off, with two of the XLR cables but not the third. However, when I connect the third cable to the microphone, the noise reappears (though not if I connect it - or either of the other two cables - to the large diaphragm condenser mic or a dynamic mic). I realise this is a Logic forum and this is clearly not a Logic issue, but if you or anyone else can throw some light on this incredibly confusing situation, I'd be very grateful!
Link to comment
Share on other sites

How can you hear the noises if you've disconnected the interface?

 

The interface was connected to my iMac by a USB cable. I disconnected that but the interface has its own external power source so I was able to hear the noises through headphones connected to the interface.

Link to comment
Share on other sites

How old is your Clarett 2Pre? My Focusrite 18i6 worked fine until one day noise started happening...turns out that the power supply on the interface was failing, and eventually quit entirely.

I wound up finding the noise problem occurred when completely disconnected from a computer as well.

 

3 year warranty, so probably worth contacting Focusrite.

 

It looks like the external PSU is a simple 12v DC 1.5 amp, center-positive wall wart. Hunting the web a bit shows a compatible power supply available, new, for less than $30 US - that's probably a less-cost attempt to fix than getting the unit checked out by Focusrite...

Link to comment
Share on other sites

How old is your Clarett 2Pre? My Focusrite 18i6 worked fine until one day noise started happening...turns out that the power supply on the interface was failing, and eventually quit entirely.

I wound up finding the noise problem occurred when completely disconnected from a computer as well.

 

3 year warranty, so probably worth contacting Focusrite.

 

It looks like the external PSU is a simple 12v DC 1.5 amp, center-positive wall wart. Hunting the web a bit shows a compatible power supply available, new, for less than $30 US - that's probably a less-cost attempt to fix than getting the unit checked out by Focusrite...

 

Thanks for your reply. The Focusrite is only 6 months old. I seem to have partially solved the problem, though. I moved the Focusrite into another room, connected the mic and the noises disappeared. So I can only assume that the XLR cables are picking up some interference in my 'studio' room, though my iMac is the only piece of electrical hardware in that room, which is a bit baffling, as I can't imagine that is causing the interference. The thing that doesn't quite make sense is that there is no interference when I connect my Rode NT1-A (large diaphragm mic) with exactly the same XLR cable, only when I connect my Rode M5 (small diaphragm mic) and the Lewitt 040 (small diaphragm).

Link to comment
Share on other sites

I would get in touch with Rode, since one of their mics works OK and the other deosn't. Perhaps they can suggest something.

 

That 2 of the cables pick up noise even with no mic connected is troublesome. If you then connect those cables to your NT1-A the noise stops?

 

You moved the Focusrite into another room...so it's no longer plugged into the same AC outlet. Do you have a long AC extension cord? Plug it into the AC outlet you were using in the intial room, then plug the Focusrite into the other end but keep it in the other room. If noise returns, it's a grounding issue with the power supply, although why only two mikes are affected would still still a mystery to me.

 

Good luck.

Link to comment
Share on other sites

Thank you to everyone who has replied to my post and offered suggestions and help - I really appreciate it. I have, in fact, 'solved' the problem. After a lengthy process of elimination I have realised that the noises come from the XLR cables picking up interference from my wifi booster, which is in the same room. I have never noticed this before because it does not happen with the large diaphragm Rode NT1-A, just the small diaphragm condenser mics. Why this is the case remains a complete mystery but at least I can record interference-free with the wifi booster turned off.
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...