Similar White Noise Issue

WaydeRich

New member
Hi all

I know similar posts have been made, however I also know that environment can play a part in causing this issue. In that context I will outline my setup / environment.

I'm running a Macbook Pro with an external HDD attached via USB. I'm running Logic Pro X. I have an AKAI EIE Pro Audio Interface. I have a standard mic lead, and a Samson C1 (not USB) and a Studio Projects B3 Condenser Microphone.

I record in my lounge room, approx 5 x 4 metres. All doors shut, and covered with blankets and other soft items. One glass window. And I use one of the "MIC Thingy's" - essentially a piece of sound proofing foam that sits behind the mic. And of course a pop filter.

I have switched mic's (both are in excellent condition, and 1 is only a couple months old). I have switched mic leads, tried 2 other USB interfaces. And I have even run it all through my old PC Laptop, using Cool Edit Pro.

My brother believes it's "white noise". From reading up on white noise, it's apparently generally caused by over amplification of the source. Now as best as I have been able to ascertain, Logic does not have input levels in the software. (Correct me if I am wrong). But all my reading and searching implies that input levels are controlled by the audio interface. I have set the gain to 12 o'clock on dial (so essentially only half way). The white noise can be heard through monitors and headphones. It lessens if you turn the gain back, however going less than half, the input from the MIC seems to only hit around -20dB. That being said, if you take the gain knob right down, you can still hear the white noise.

I have no issues when recording DI, such as guitars/bass. And if I use a Dynamic MIC, again the issue isn't there. It only is present once the phantom power is switched on.

After typing this all out, I'm errring towards the over sensitivity of the condenser MIC's picking up noise in my environment which is either not noticed, or inaudible to my ears.

Anyone have any thoughts??
 
It is white noise, but for all practical purposes, it's just hiss. There are a few useful clues in your post. You mention there is no hiss when you use a dynamic, with phantom off - this removes the possibility that the hiss is generated in the audio interface pre-amp. In fairness, they all his when the gain is cranked up to some degree, but this kind of generated hiss goes up and down with the gain control on ANY type of mic. If the problem comes with the phantom power then you have two possibilities, the microphone probably being faulty (easily proven by connecting to to somebody else's interface) or that the power supply in the Akai is in some way faulty - rare, but possible. Often, it's a combination of circumstances. First thing to do is connect a dynamic and then turn on the phantom power. If the hiss suddenly appears, then it's being generated in the power supply in the preamp/interface. If when connecting the dynamic and applying phantom no hiss appears, then the problem looks like the microphone. Some condensers draw too much current - more than the phantom spec allows for, and what can happen is that the mic attempts to take too much, the power supply cannot provide it and the 48V drops down to a lower level that the supply can manage. Now many mics are happy with phantom voltages of perhaps 5V right up to over 50, but some are not. The lower voltage causes the preamps to hiss in the mic.

You need to borrow another condenser mic to use as comparison. Sometimes it's just an unhappy accident that an interface might be current limited but your only mic a heavy demand one.

Do the check with the dynamic with phantom on, and see if the hiss suddenly starts. If it does, then the interface is simply faulty - and you can look to getting that sorted. If it doesn't hiss with the dynamic, look to your condenser, and try another different one and check again for hiss. Sometimes mics can just be faulty. Rare, but it happens.
 
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