I'm using a lipstick camera hooked up to a camcorder in VCR mode. It has a built in omnidirectional mic that is already converted to the line level so I can just connect it to one of the audio channels on my RCA cable.

What I want to do is use the other channel for a wireless lav mic. So, what would I have to plug the receiver into to so that could plug in into the other audio channel?

Does this make sense? If not, I could probably explain further.

You need a microphone preamp at the least. A mixer if you want more control with both microphone sources.

Microphone preamps range from cheap and awful to awful good and awful expensive.

DSE should have lots of advice on this.

Well, could someone point me to some specific products. I was looking at preamps on B&H and didn't see any with RCA outputs. Basically, all I want is the bare minimum that you need to plug a microphone into the left or right channel of a camcorder or VCR.

Most wireless mic receivers, especially base-station type models already have an unbalanced line-level output connector. On some models this will be a full +4db line-level and may be too hot for the -10db RCA inputs of the VCR. On some models this output is adjustable and you could bring it down accordingly.
Many but not all portable wireless receivers have the ability to output a line-level signal. You'd have to check the specs and possibly get the proper cables or adapters.
Do you already have your wireless or are you still looking for that too?

Here's what I ordered:

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=219454&is=REG

I could always send it back when it gets here and get something else if there's something better for my purposes.

You're in luck. The output of the PR-81 is close to the correct level for the RCA inputs of a VCR. You just need a simple adapter to convert from the male XLR cable that comes with the receiver. Any non-transformer XLR female to RCA female adapter will work because only pin 1 (ground) and pin 2 (signal) on the XLR receiver cable are used. Pin 3 isn't connected because it carries a headphone level signal that's only available on the mini jack adapter cable for this receiver. Don't attempt to connect the mini jack cable to anything but headphones!
A Switchcraft 322 adapter will work correctly for the VCR's input RCA cable. The 322's pin 3 isn't connected, which as i said in this case doesn't matter because the receiver's pin 3 isn't connected to the XLR output either. Other adapters that have all 3 pins wired will also work for the same reason. However the 322 and other adapters will behave differently from each other if you use them with another piece of equipment. If you don't ever use them with anything else, then ignore these details.
The adjustment on the PR-81 only controls the headphone volume on the mini-jack cable. The line-level signal on the XLR connector is fixed. It is however influenced by the transmitter input gain. Set this input gain to get the correct level into your VCR while the presenter speaks with the lav element in position.
If your VCR only has auto level controls for audio, then there will be some fluctuations between silent passages and speaking passages.
If you have any further questions just ask.

Hey, thanks a lot Jay! A camcorder's RCA inputs will work the same as a VCR's right?

Final question: Where do you recommend buying the Switchcraft 322 adapter?

Thanks

How about this, would this work instead of the 322?

For connecting to an RCA cord:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=134182&is=REG

For connecting to an RCA input:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=134178&is=REG

Yes, those adapters should work. Too bad the B&H site doesn't have the correct photo representations available. Since the gender of the XLR side is only the most important aspect of the adapter you'd think they'd have the right picture to go with the description rather than relying on a note that this isn't the right picture.
At any rate you've got the idea. If you want to keep the receiver further away from the recorder, it's best to use an XLR cable rather than a long RCA cable. Even though this is an unbalanced connection no matter what you do, it's usually better to run the longer distance with good mic cables rather than cheap audio hook-up wires. Don't forget that you can also use RCA video cables to carry audio. These are also superior to cheap audio lines.
On some recorders and cameras, there isn't enough space to use the XLR to Male RCA adapter because it's too fat.
Most RCA connectors on cameras do work the same and at the same input levels as those on a VCR. However they also sometimes serve as output connectors too. So don't send audio into the transmitter output. I doubt you'd hurt anything but who knows for sure.
Lastly, on some camera's you can set the RCA connectors to mic level. This would cause severe overload since the PR-81 puts out such a hot signal.

Thanks a lot Jay, if it wasn't for you, I'd have to record the audio separately. I'm still quite ignorant about audio.

You're welcome! Hope it works out. Remember, the key adjustment is the transmitter input gain. You'll need to experiment carefully with this to get a good recording.

Unfortunately, that didn't work. I have no idea why, but the RCA adapter didn't give me any audio. :( It's fine though, because I've found a solution that works just as good anyway.

Do you have any way to test the adapter to see how it's wired? A simple meter will work, you just need to determine which XLR pins go to the RCA connector.
How did you end up solving the problem?
Some other things that could have prevented audio are the PR-81's mute switch isn't labeled or lighted. You have to know the correct position to place it in.
If you're using the RCA inputs on almost all camcorders then you must be in VCR mode rather than camera mode.

Well, I don't have a meter like that. The AKG wireless mic is stereo, would that have something to do with it?

I don't believe your wireless lav is stereo... it's got 3 conductors, but that's because it's balanced, not stereo.

It uses an XLR which carries a mono signal and a copy of the mono signal that is 180 degrees out of phase. I think that you might be using the wrong adapters and are hearing both of these signals and confusing them with stereo. And if you are recombining these sources to make a mono source (as you stated in your other thread) you're probably just cancelling out the bulk of the signal. Go back and make sure you've got the right connections... you'll probably notice a much improved sound quality once you do.

Chris, you're partly correct and partly incorrect. The PR-81 isn't stereo, it's mono but it makes non-standard use of the 3 pin output.
The PR-81 uses an XLR connector but not to carry a balanced signal. Pin 1 is ground. Pin 2 is an unbalanced audio out and Pin 3 is an unbalanced headphone level out. How this is utilized depends on the output cable that's used and any adapters connected to that cable. If you use an AKG cable that has a mini jack, you can get a two-channel mono headphone signal in both sides of the headphones. Again, it's not stereo, it just appears in both left and right with the same signal. You shouldn't be using this output to record from though. It's too hot for the recorder input and the headphone amp needs a minimum amount of impedence from headphones or it can burn out.
The meter I'm talking about is a simple electrical meter available for $10 to $200 that can check the continuity between the female sockets of the XLR adapter and its RCA output. Maybe a friend has one?

interesting... I sit corrected

The AKG receiver comes with a mini jack output as well as a XLR. The male part (I don't know what you call it) is in the stereo shape and when I plug it into my small camcorder, you can hear the mic in both sides of the headphones. My mono shotgun mike only shows up in one channel of my headphones.

It's no big deal. I've decided to use two cameras: one in VCR mode with the lipstick camera and another in camcorder mode with the wireless lav. It's probably better to record that audio separately anyway... plus, I'll have more footage to work with.

That must be a new cable that they didn't have when I got my two systems. It probably uses the Pin 2 output and splits it to both channels of a stereo mini. It's still two channel mono, but it's the proper way to get the signal into a stereo input.
I'd still like to know why the XLR to RCA converter didn't work though.