Firebox - low rumble when turning on phantom power

R

Russtopher

New member
Ok - Presonus Firebox, powered both off of FW and also the wall wart (tried it both ways to see if that was the issue). Whenever I plug in condenser mics and hit the phantom power switch, I get this nasty low rumbling noise that occasionally pops. It's loud enough that meters in both Cubase and Reaper pick it up. It sucks. Originally I thought it was a bad cheap Nady condenser, but today I plugged in an MXL 990 - same problem. I tried both front inputs, different cables, etc. Does this sound like something's wrong with the box? Plugging in dynamic mics is fine, no issues with noise or rumble. Just condenser mics when I plug in and hit the 48v button. Problem happens on both my desktop and my laptop.

Anyone else hear of this, or have this happen?

TIA!!!
 
Here I am, answering one of my own posts again. Sheesh, I gotta stop doing that :rolleyes:

I did some Googling this morning and it looks like the rumbling I've been hearing may be due to moisture on the capsules of the condensers. I've kept them in bags/bases but down in my basement where I run a couple of dehumidifiers due to the high moisture down there. I'll try drying them out using the lightbulb method and see if that solves the issues with the rumbling...
 
mshilarious said:
Maybe, but if not, try a different cable. If dry mics and different cables don't help, it's a problem with the phantom power supply.
Click to expand...

I tried 4 different cables yesterday, same problem with each unfortunately. I noticed that my Nady mic was doing it a while back on and off, but yesterday my MXL started to do it as well. I realized that I had left the MXL on it's stand for a few nights accidentally after Googling the issue this morning. That made me think if it was the phantom power on the Firebox, then perhaps the problem was with the mics since it was one, and now both later on.

Thanks for the tips, if the "lightbulb drying" method doesn't work, it's on to Presonus and seeing if I can dig out my receipt for the unit....
 
One of my MXL 603s' was doing that this weekend. I put it in a ziplock bag with a couple of dessicant packets and, by the next morning, it was good as new.
 
Yup, it was the moisture. I got a mondo jumbo-sized dessicant packet from work (we get daily shipments of large electronic devices) and put the CM90 and the MXL 990 in a quart-sized ziplock back with it. 4 hours later, good as new.
 
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