As I was setting up 4 LDC mics at a time to choose which for vocals and acoustic guitars, yesterday. I noticed this ringing sort of noise that would build up on different mics/channels at different times on the SPLAT tracks playback.
 
It only occurs on the preamp xlr with phantom power on ( I think. I'll do more experiments today) and did not occur on any mics run through my preamps into the 1641 line ins on the back. It also seemed cyclical, but I'll have to pay more attention to how often it repeats.
 
Very strange and disappointing. I think my CAD E100s has issues too, as it's making some constant hash..... oh well. There's a $100.
Anyone have ideas about the ringing? It seems like either the preamps or the phantom power perhaps:?
Michael

Only possibility I can think of is using 4 Mikes requiring Phantom might suck all the juice. But this seems far fetched with the Tascam as it plugs into the wall and should be capable. I've never had this issue myself and have run 4 at a time on drums. But those are smaller mikes. I always use the first 4 inputs and try and group the phantom. That way channels 5-8 are not on phantom. Even though they say it won't hurt them I have always avoided applying phantom to my dynamic mikes if possible... I hate mixers with global phantom.  
So do you have them grouped or do you have other things sharing the groups of 4.  
 
I guess you can try thought the process of elimination.

Thanks JohnnyV . Yeah, the Tascam's never been an issue with 8 mics input, all using phantom in the past....
 
The MA200 has it's own ps and was running through the Warm Audio TB-12 into a 1641 line in in the back. The Kel Song Sparrow, ADK Thor and CAD E100s were grouped to 1-4 on the Tascam xlr ins.
At first I thought the CAD might be the culprit(since it's generating "hash"),  but the ringing/chirping happened on the other mic/channels at different times, regardless. I'm going to try some more "logic tests", to see if I can isolate it/find the source.
 
Michael 

After experimenting I found having the CAD E100s (which is noisy and low output ie not normal/good)on Tascam chan 5 eliminated the noise. So, I'm thinking the CAD being "blown up", caused it, when it was paired with the Kel or Thor on the 1-4 phantom'd group.
The E100s has a self noise of 3.7dbA or thereabouts(which ain't happenin' LOL) and I'll have to send that in for repairs. I don't think there's anything wrong with the Tascam us1641, nor any of my other mics.
Michael

Good news, Mine has been a solid interface since that last driver update Dec 2014. 

Mine too! It's allowed to me have two set ups and not bother selling it yet.
Michael