How do I connect a mic on a dvr? I have a dvr with an rca input for the microphone. Do I need a special mic? Does it have to be amplified?

Any *dynamic* mic should work without an amp, although you may find an amp is required depending on the sound level you're trying to record. Avoid condenser mics, as they need to be powered, which most often means using a battery - last thing you need is to be replacing a mic battery every few months.

If you are using a "regular" microphone then you may need to get an inexpensive DJ mixer to plug the mic into, and to allow it to be the preamplifier that the mic needs, and then plug the output of the mixer in to the dvr.

You can use this as it has a preamplifier built in as do most cameras with built in mics
http://www.eclipsecctv.com/ECL-MIC_microphone.html


http://www.amazon.com/gp/product/B000972KQG

How about this one?

http://www.grant-security.com/product.p ... 339&page=1

Or this one?
http://www.allelectronics.com/make-a-st ... ONE/1.html

If I remember correct DVR Audio In (Input) is at Line Level
Meaning dynamic mic will need Amp
Line level is usually between -10 to +4 dbm in strength
while MIC levels are normally -60 dbm.

^Yeah, good point, that input is likely line-level; the only mic that would drive it directly would be an old-style carbon or crystal mic (along with terrible sound quality).

I know I'm going to hear about recommending anything from these guys, but this one actually works very well. http://www.supercircuits.com/Microphones/PA3 .. or you could go with the Louroe stuff, at ten times the price.

There's always your friendly neighborhood Radio Shack...

I vote this one!!!!
http://members.cox.net/n4jk/d104.htm

A thing of beauty.

Use condenser microphones with built in phantom power supply and preamp...don't use dynamic mic, because they are usually directional with short range, used in PA. Condenser are better for human voice on longer range and are far more sensitive. If price is not an issue, use AKG. Or, if it is, use cheep electrec ones with DIY electronics.

Perhaps this one has merit?
http://www.louroe.com/mics.asp?model=amic

Oh, yes, I like it's dome style housing, almost as a fire alarm detector!