Noise in condenser mics

I don''t know if this is relevant or not, but I had a noise problem my CAD E-100 a while back.  I contacted them about it.  Turns out the noise was present because the mic had not been used in a very long time and the internal battery needed to be more fully charged.  I left the mic plugged into my preamp overnight and this fixed the problem.

don't forget to check cables as well....
long shot, but more than once i've trouble-shot issues, only to find out it was
the G'Dam cable!!

LOL

If the phantom voltage were low or very noisy, that could account for the noise -- some mics might deal with dirty phantom power better than others. However, I think you can eliminate phantom power as the culprit because when you bypassed the preamp and went straight into the interface your phantom power source also changed.

The mic cable would be my #1 suspect, the first thing to test.

Second suspect would be some external RF noise source, then the interface itself.

Behringer make a great little cable tester. (CT 100) In fact it is something you all should own. It is a must. It does not cost much and tests all cables for wiring etc. It also has a wiggle test where you plug your cables in and wiggle the ends while observing the LED's.  A multimeter will not show a tiny break (for a very short time)  in a cable it may show it still in continuity. But the Behringer will detect if a cable break ocurrs for even for a very very short amount of time.  Many cables when first plugged in pass the wiring test but fail the wiggle test.

The Behringer also will show if phantom power is working and also has a built in oscillator which can be very useful especially at a live gig. It also displays how cables are wired correctly or incorrectly. This can be an issue especially when cannon to jack cables are wired. (there are two ways of wiring this balanced to unbalanced connection, one is more correct than the other)

Most people can't solder to save themselves and if you have made cables yourself you really need something like this to test them before using them. At a live gig I test every cannon to cannon cable before I even setup. Usually I find at least 10 to 20% are faulty! (I have mine with me of course just in case)

  Bitfiliper

   thank you so much for the input but ive tried all you mention.
Ive got an old pre with a 24volt phantam power. dont use it
but I like understanding and knowing. Learning is cool too.

  I want to thank you all so very much for your input.
I have read all your remarks over and over seeing if some
kind of "something I'm missing" might click in my mind.

  Bitflipper.

of course you know I'm a thinker and hopefully
my brain won't explode. I've been electrician all my life
and have troubleshooted thousands of electrical/electronic
problems.

 Very often I have to use this "why does this happen"
"what made it happen" mindset. It bugs me to no end to
not know "why".

  I'm glad you mention how different mics behave differently
to a given situation (or phantom power). 3 different
pres and different phantom powers are all doing the
same thing. And 3 different mics are too.
 
Mike.

  The caps subject really has my attention. They went from
noise to a bit more crackling sounds as I hooked up the
mics and let them sit. "leaky caps?" But until I have some
sort of a "narrowed down to this" thing I'm still stuck.

   I haven't yet but I guess it's time to get out the
digital multi meter and see if I can at least find something.
Had this been only one mic or one pre I would have
done that first.

  Jeff

  I really do need to get a tester like you mention just
because I do need one. The meters "aren't fast enough"
subject is "sort of" true. An analog meter of course is
slower but given a certain situation they are better
suited for "a given situation"

  digital meters of course are faster and some faster
than others. Could a digital meter do what this tester
can do? yes (if it's fast enough).

 So your point is valid and well taken and I am going to
get one of those so thanks again for the mention.
I just wanted to point out that all meters are not
created equal. 

  thank you all again and hopefully I can come back
with some explanation after I do some testing.
I just thought surely someone would know
"the problem is such and such" and "this is why"

  Its like my older brother for example he's a great
auto mechanic. I drove to his garage one day.
he was standing outside the garage as I drove up.
I pulled up and stopped/ turn off the engine.

  Before I said a word he said "you've got a cracked
distributor cap"  I said "how did you know that?
He said "because the way the engine runs"
I opened the hood/ pulled off the distributor cap
and "that was it!"  

  So I just thought maybe someone could narrow
"my situation" a bit from experience.

   thanks everyone