I need to get my mixer into the mic jack to my Cannon HV40. When i plug the f/f to m 1/8" adaptor in, it cuts the signal, when I plug my mixer adaptors (xlr f - 1/8" male mono) in I just get a loud buzz. Any thoughts, Thanks........Shaun

Your camera audio input would be stereo mic level, are you using a stereo plug wired in the correct way? ( you mentioned a mono plug, this is possibly shorting out the camera input)
The output of the mixer is line or mic level, balanced or unbalanced? (what pin sonnections on the XLR-F are you using)
Is the cable between mixer and camera wired as mono or stereo?
Is the cable shielded correctly?
Are you running both the camera and mixer on mains or is one or both on battery power?
Is there any fluro lights, electric motors, TV or computer screens nearby?

Any one or more of the above can give you problems of some sort either a buzz, hum or whistle.

Your camera audio input would be stereo mic level, are you using a stereo plug wired in the correct way? ( you mentioned a mono plug, this is possibly shorting out the camera input)
The output of the mixer is line or mic level, balanced or unbalanced? (what pin sonnections on the XLR-F are you using)
Is the cable between mixer and camera wired as mono or stereo?
Is the cable shielded correctly?
Is the cable shielded correctly?
Is there any fluro lights, electric motors, TV or computer screens nearby?

Any one or more of the above can give you problems of some sort either a buzz, hum or whistle.

Lets see if I can answer these
1 Your camera audio input would be stereo mic level, are you using a stereo plug wired in the correct way?
Im using a f/f 1/8" adaptor going into the cam
2 you mentioned a mono plug, this is possibly shorting out the camera input)
Its an adaptor that is xlr f tp 1/8th mono plug.. that goes from mixer to adaptor (Im thinking its grounding out some how)
3 The output of the mixer is line or mic level, balanced or unbalanced? (what pin sonnections on the XLR-F are you using)
Both outs on mixer are balanced I assume as I use the same set with my big cam with only xlrs, left channel is factory set to line level, the right side is switchable and set at line. Dont know which pins are being used. I assume all 3
4 Is the cable between mixer and camera wired as mono or stereo
Out of mixer is a l and r output, with a l and r f xlr coming out with an 1/8" mono male end these 2 cables go into the 1/8" adaptor which goes stereo into cam
5 Is the cable shielded correctly
Its a Hosa cable... I hope it is but can only assume
6 Is the cable shielded correctly
Both on electric
7 Is there any fluro lights, electric motors, TV or computer screens nearby
No Flour, no motors LCD TV but not close enough to cause any interferrence
When you plug the adaptor into the cam, it cuts the audio. When you plug the mics into the cam whether they are connected to the mixer or not I get a huge Ground sounding buzz....Im thinking its a pin assingment issue

Disregard....Problem Solved.... Thanks!!!!