I’ve got my Podcast studio set up and I am hearing what sounds like a loud fan in the room. There is no fan or HVAC and the room is about 10x6 feet and acoustically treated. I have a Shure SM7B Mic. A Fet Head Inline Pre-amp. Running through a ProFX8 V2 Mixer. All of this is connected by USB to my HP Laptop Windows 10. Using Audacity to record.
I’ve tried everything that I can think of including doing some googling but nothing has solved the problem. Even unplugging the mic doesn’t help. You can still hear the “Fan”. I’ve tried adjusting volumes controls, gain etc. My headphones are plugged into the mixer. If I plug into the computer there is a good amount of latency that makes it unusable.
The only thing that gets rid of it is turning off the Phantom Power. I know this mic doesn’t need it but when I turn it off the mic doesn’t pick up anything. I’ve even tried moving cords to make sure the XLR wasn’t picking anything up. I tried moving the laptop away and out of the room. I’m assuming it’s the mixer but I don’t know where to begin with it. All this equipment was purchased new by me. Any help or advice would be appreciated.
That means it’s coming from the FetHead or the preamp in the mixer. All active electronics generate SOME noise. Amplification stages tend to generate the most, or whatever is generated is amplified.
But the FetHead needs power. And that implies that the FetHead is to blame. If you take-out the FetHead you should get something, but it will be about 30dB quieter. Your mixer MAY have enough gain without it. But my GUESS is that the FetHead is quieter so it’s probably better to get the gain from it.
Most audio interfaces are “marginal” with dynamic mics but most mixers have more gain.
And low digital levels are not a problem. Pros often record at around -12 or -18dB, leaving plenty of extra headroom. But you may need more analog signal for monitoring, etc.
And… when you amplify digitally, of course you are amplifying any analog or acoustic noise along with the signal so when you compare, make sure you are listening at the same volume.
A stronger signal will give you a better signal-to-noise ratio. That means speaking/singing relatively close to the mic with a strong-confident voice.
You can also try some “careful” noise reduction or noise gating. But sometimes “the cure is worse than the disease”, especially if the noise is bad. These are things you just have to experiment with.
…Noise is pretty-much the “last remaining problem”. With home recording acoustic noise is usually the biggest issue (the lack of a soundproof studio). Pro electronics might be a little quieter but there is some very-good affordable equipment.
I just tried taking out the FetHead and that did reduce the noise substantially but it is still fairly prominent. But without it my voice is barely audible even with volumes and gains turned up. Phantom power only helps a little without the fethead. I’m begining to think this may not be a good mixer for my set-up, or at least my limited ablilites as an “audio engineer.”
Is this close? This is what it sounds like when the data signal in the USB cable leaks into the analog sound. This can be a finger pointing exercise. The computer goes: “Carefully filtering, cleaning, and preparing the USB five volts is expensive. We’ll just do a quickey job and hope the microphone can handle it.”
The microphone is going: "Boy, I hope the computer did a good job of cleaning that 5 volts because that’s really expensive and we didn’t do it.
So now you have slightly dirty five volts running the hyper-sensive preamp in the interface. I bet it goes away or changes if you change computers.
We used to recommend a wall-powered USB hub in the USB line with only one thing connected to it. The five volts is coming from the wall power, not the computer. We stopped doing that when people started finding USB hubs with city power noises on the five volts.
Oh, there’s another one. How long are your USB cables? They should be heavy and short. Like 4 to 6 feet. Some production outfits arrive with 8 or 10 foot long USB cables. That’s begging for trouble.
That’s the Home Microphone Syndrome. If we make a microphone with common volumes and characteristics, the home user is likely to overload it by accident—which sounds terrible—and send it back. If we make a quiet microphone, the home user will assume it’s their fault and keep it. No contest.
There’s a Phantom Power thing, too. Phantom power is called that because it runs up the microphone cable to run the microphone at the same time that the microphone is sending your voice back down. The two are phantoms to each other. Everybody knows phantom voltage is supposed to be 48 volts because that’s the lowest voltage they could get vacuum tubes to work in 1939. I’m not kidding.
That’s a real problem because of modern electronics, so it’s been shrinking and there is now, I believe a common standard of 12 volts. There is another standard of “Phantom Power—Really—And You Just Have To Believe Us.”
That voltage is directly running the super sensitive electronics, so you can’t mess with it too much before causing problems.
The phantom power should have zero effect with your SM7B, unless something “funny” is going-on with your mixer and the gain is changing.
Condenser mics have a “head amp” inside and that amp needs power. Dynamic mics don’t have any active electronics.
There are some tube condenser mics still in-use (and still made) and they come with their own special power supply.
Not in this case. He’s using a Shure SM7B. It does have low output because it’s a dynamic mic. I see it in a lot of “pro” podcasts. From what I recall, it has about the same sensitivity as an SM57/58.
Oh, right. Missed that. However this is still not a bad place for a microphone booster. The SM7B has a rated output of about -58 or so. Many home mixers have a powerful microphone production boost that zooms all the way up to 40dB. If you use the anti-pop wind sock on the microphone, your natural voice may not even show up on the Audacity meters and indicators.
But yes, if you send phantom power from the mixer up to the booster, it will not go through to the SM-7B, so that part is cool. What’s not cool is a phantom power with data noise on it. That will go —zoop— right into your show
I don’t think we actually got the poster to confirm that my sample is the noise he has. Frying Mosquitoes. In a blast from the past, we do have a Frying Mosquitoes pre-built filter.
The USB is 4’. (someone asked. ) By the way, thank for all the replies! As for the sound demo. Yeah it sounds some what like that but louder. I think the description of a fan nearby is the best one I can come up with. I have even removed the laptop from the room just make sure it wasn’t picking up anything from it.
OK, so that’s probably not it. Did we get posts out of order? Two messages up I posted a tool we designed to get rid of USB whine errors like that. Depending on how successful that is, you may not need to fix anything, although the system is broken.
Mosquito-Killer carefully removes all or most (it’s a setting) of the musical tones that make up that whine. It can do this because USB service data is pretty much standard. The default (8 mosquitoes) usually does it, but be clear it is removing some tones from the performance.
I came up with the screaming mosquitoes name. We couldn’t think of a good name, either. And we are assuming that’s what it is. If it’s not, Mosquito Killer won’t do anything.
It does have low output because it’s a dynamic mic. I see it in a lot of “pro” podcasts. From what I recall, it has about the same sensitivity as an SM57/58.