Help Me Please? Bad ART MP Preamp or mic? Need opinions, mic stopped functioning correctly

Hi all- I'm not all that hardware savvy and hoping someone could suggest what might be happening here..
 
I have an MXL 990 Condenser mic that is being powered by an ART MP Tube Preamp. I'm running this to a Toneport UX1 through XLR, to the XLR input.
 
It had been working flawlessly for a good couple of months. Two weeks ago, I tried using the same setup having not changed anything and noticed the audio sounded a little different. The quality was not nearly as good and the volume seemed lower. I didn't think much of it until I went to use it again two nights ago. This time the volume was super low and distored and was acompanied by a TON of noise. It went from tolerable two weeks ago to just flat out horrible.
 
Initially, I thought this was the monitoring software that the Toneport comes with so I reinstalled it.. updated Toneport drivers to the latest.. still sounds awful. I tried changing the settings on the preamp to no avail. I plugged in another mic to it- this one was a handheld dynamic mic. The volume was still super low but less distortion.. there the amount of noise was still just as bad.
 
Is this likely a problem w/ the preamp or the mic? I am at work at the moment but was going to try to hook the preamp out to a PA to see if I get the same noise. Thanks in advance!

Thanks for the response.. I'm using Sonar X1. I should've been clearer in my original post..

The UX1 has a proprietary "zero-latency" software that I use for monitoring. This runs standalone outside of a DAW. Listening to the input outside of SONAR gives the same results.

I don't think it's software related since I've reinstalled the said monitoring software and have updated the interface drivers. I'm guessing it's some hardware issue- just wondering if it's the mic or the preamp?    

fireberd


The MXL 990 requires phantom power (48 VDC).  Is the 48 VDC switch pushed on (if I remember correctly on the ART MP Preamp) ?  If that was accidentally turned off the mic won't work.
 
Another possibility is the 12AX7 tube or the external "wall wart" power supply for the ART.

Thanks for the response, fireberd. The 48 VDC switch is definitely on.
 
When you say another possibility, are you suggesting that either the tube or the adapter is bad? TIA.
 
 

I'm an ex amp tech and the first thing I would suspect is the 12AX7.   May not be, but replacing the 12AX7 would be the first thing I would do.   If you have a 12AT7 or 12AU7 available you can try that just to see.  They will work, just have lower amplification than a 12AX7. 

Thanks guys- Istopped at the music shop on the way home for a replacement tube- sure enough, that was it! Working again now!

You too!

They are the "starved plate" and more or less just a "buffer amp" to provide a little tube sound/warmth.   There are a lot of "tube" units around like that.  I have a Presonus dual Blue Tube preamp and that is basically what that is, although a NOS RCA 12AX7 made a positive difference over the stock Chinese tube.  I used to have a TubeWorks (MosValve) "realtube" rack type guitar preamp.  The 12AX7 in it was basically the same thing.