Noise Floor

By “power hum,” I mean it sounds like interference coming from the wall socket. Wall power.

I analyzed the tones in the hum and I think it’s safe to say you’re recording in the US. British power noises have different tones.

Now we’re flying blind. It’s good to know the environment and the connections.

I had one hum problem which turned out to be the sound mixer brick that plugs into the wall. It hums if I get the microphone too close.


It’s an ST55 FET Condenser microphone and I have it going through an A R T professional Mic preamp. See attached Pic (I hope). I don’t know what buttons to push on it. I’m guessing that it’s the problem though. ‘Normal’ ???

You’re working today I see. Good for me, maybe not so good for you. :slight_smile:

You’re working today I see.

The forum elves are volunteers. The joke is we do this stuff between bouts of Real Life. That’s one reason for the absences and holes in the response.

I’ll look up your equipment and see what’s going on. I don’t expect the system to behave like this. Is it new?

Buying previously owned audio equipment doesn’t bother me because I have sound analyzers and tools to take something apart and fix it. Home users could run into problems.


Okay, I see what you mean. I have a power strip and everything is pretty bunched in together. I’m also using a laptop. Does that matter? The problem doesn’t occur with the other mic, right? So must be the connections on this mic and preamp - or the plug? Thanks SO much for your help. ACX told me there was an electronic hum but I had no idea where to even start.

Do you have an actual XLR-3 cable between the mic and preamp?

What is the model number of the ART? They make a bunch of different ones.


0598? I don’t see any other number on there. I can give you the serial number. 127-15769.

Yes, I do have that cable running to the mic. Those three grey buttons that can be pushed in or out - do I push any of them in? They’re all out right now.

I need to go back and look. Yes I know where they’re supposed to go. In a minute

How is the ART connected to the computer?


Amazing that you can here if the hum is U.S. or U.K. I live in North San Diego, California.

Three prong on the ART and USB to the computer…

Amazing that you can here if the hum is U.S. or U.K.

Not that amazing. US power reverses direction 60 times a second and the UK does it 50. Interference tends to follow multiples, so hum and buzz in the US tends to 120-240-360, etc. Analyze > Plot Spectrum will draw me a tone pitch map.

Three prong on the ART and USB to the computer…

That’s dangerous. The only interface I know configured that way wouldn’t do this job right. Model numbers? Any other information? Getting your voice into the computer seems like it should be a snap … and it’s not.


Can you hear the hum? I’m guessing from your responses, no.

How are you listening? Not having quality speakers or headphones works fine until something goes wrong. Then you have to actually hear the performance in good quality.

Can you record one test with the computer on batteries and the computer wall power brick disconnected?

We posted ACX testing and audiobook mastering techniques and tools. When we get this solved, I’ll show you what we’re doing.


I switched out the cable to the mic - had another one handy. No change. I’m thinking about taking the preamp to guitar center, maybe get a different power supply to the mic? I don’t even know where this one came from. I’ll look at it again one more time after I get back from the gym.

get a different power supply to the mic?

Wait. What?

You can’t leave things out like this. We need to build your system in our imagination since we can’t see you in real life.

Do you have a little Phantom Power brick between the microphone and the ART? You shouldn’t need that. The ART should be supplying power to the microphone.

I’m having trouble keeping up.

We don’t know anything about the adapter between the ART and the computer, either. Any of these things can cause problems since the sound is analog the whole way.

Any time you plug more than one thing into the wall, you have the possibility of hum problems. Sometimes they can be rough to find.

More when I get back home.


You should have your Microphone plugged in with one single 3-pin XLR cable directly to the back of the ART. The Middle button on the Art, P-Power+48v should be pressed. No other adapters or odd cables. No other buttons.

As near as I can tell from the instructions, the microphone has no lights to tell you what’s going on, so that’s as far as that goes.
Also as far as I can tell, the ART has no place to put headphones, so wer’e flying a little blind.

Then it goes through the Mystery Adapter into the USB socket on the laptop.

That should work right now. Does it? Do you still have the hum?

If you do, unplug the computer from the wall power and try it again. Run on battery. Even if the hum doesn’t go away, did it change?

I reeelly want to know more about the thing between the ART and the computer. Does it plug into the wall?


I misspoke about the power supply. Sorry. The ART connects directly to the computer. I was interchanging the name (ART/Power supply). The ART has three connectors in the back. One to the electrical outlet (a power strip), one to the microphone 3-pin XLR cable, and one with a USB connector on one end with a 3-pin connector plugging into the ART. I pulled out the plug and it was much worse. I can only gauge the noise by the green lights that flash in Audacity. It seems better now. Here’s another sample. Did switching out the cable work? I don’t get much volume though.

Hi Koz,

I just went to Guitar center for a different reason, but talked to someone there about my hum problem. He recommended an Ebtech hum elimination device:

What do you think of that idea?


Hope I’m not inundating you here. You’ve really taught me a lot and I thank you for your valuable time and knowledge.

I just discovered that the ART is two pronged. The Yeti is a 3 prong plug going into a 3 plug outlet. Not so the ART. Damn! I’ll bet that’s it! I should have checked that first.

One to the electrical outlet (a power strip)

By way of a little power supply brick? There’s 100v coming out of the wall and the ART takes 9 Volts. There has to be a ‘thing’ between those two.

USB connector on one end with a 3-pin connector plugging into the ART.

That’s the thing I need to know about, If you wanted to buy another one what would you do? Web page? Part number? Those are not normal and they cause troubles.

I pulled out the plug and it was much worse.

You ran the computer on batteries and the hum got worse? That means there’s a wiring or connection error somewhere. That is very not normal.

I don’t get much volume though.

We should stick with one problem.

So you’re looking for information on the doobly-do between the ART and the computer.


Chances are good the power isolator (hum bucker) is going to do the same thing as pulling the computer plug out.


You took a bus from Toronto to San Diego?

The hum is still there.