Distortion issue

egproductions

egproductions

Veteran
Having an issue with distortion that I'm hoping will be obvious to some here.

I'm feeding my camera audio into a house amplification system. For a few reasons, for now I have to do it using my headphone out. There are two ways into the house amplification:

1. Wireless lav transmitter pack. This option seems to work and sound fine but I would like to avoid wireless and having to deal with batteries.

2. Plugging into an xlr faceplate on their wall that is labled "microphone".

The issue is, when I plug in the audio from the camera to the XLR wall input, the audio sounds distored. My only guess is that there is a phantom power running through the wall and it's causing issue with my output from the headphone out. I plugged in an SM58 into the wall and it sounds fine.
 
The issue is that you are feeding a signal that is way too hot for the input. If it's labeled "Microphone", it is expecting a signal somewhere in the -60 to -40dB range. The output of your headphone (if you are using the FS7 listed in your signature) is -16dB. So you need to either find a way to use a different output that will send at "Mic level", or if you use your headphone output see if you can input into a "Line Level" input on the house mixer.

Have fun!
 
No the answer is you are sending a headphone level signal to a mic in. That is probably a few thousand time more than it wants. Also you are feeding a "stereo" signal into a balanced input.

You need an adapter, or two. First if you actually have a stereo signal you want to send you will need two mic ins. You will need to split the headphone signal into Left and Right. And you will need to lower the level a LOT. You can get a stereo phono jack to two mono phono jack splitters, or two RCA jacks. Then you need a balancing transformer for each and an attenuator. There is probably a ready built box that does it all and would be a little less clunky. Knocking the signal by 45dB or so should be enough if you keep the headphone level low.
 
A Direct Inject (D.I.) input box would be best for this, and outputs balanced mic level. Many have attenuation options built in. The Rolls DB25 and DB25B is affordable, rugged and works well. As Scott stated, a stereo TRS headphone output may need an adapter to get both L&R channels or it could short out feeding a 1/4" TS jack which most DIs have.
 
Thank you, I didn't realize that headphone out was considered line level, i figured it was closer to mic. I can add attenuation/pad to bring it down. There are two mic inputs on the wall so I could split the stereo if needed, truth is I only need 1 of the channels.

Thank you!
 
egproductions said:
Thank you, I didn't realize that headphone out was considered line level, i figured it was closer to mic. I can add attenuation/pad to bring it down. There are two mic inputs on the wall so I could split the stereo if needed, truth is I only need 1 of the channels.

Thank you!
Click to expand...

Actually headphones are small speakers, so the headphone out is more like a weak speaker connection than a line out. A line out is still a pretty small signal and is looking for quite a bit of impedance (essentially resistance) as in 10K Ohms or so, where a headphone out is an actual amplifier out looking for 8 ohms to maybe 32 ohms. So in terms of power it's more like Mic is to Line what Line is to headphone. That is very rough but it's ball park and will remind you of what the relative levels are.
 
Noiz2 said:
Actually headphones are small speakers, so the headphone out is more like a weak speaker connection than a line out. A line out is still a pretty small signal and is looking for quite a bit of impedance (essentially resistance) as in 10K Ohms or so, where a headphone out is an actual amplifier out looking for 8 ohms to maybe 32 ohms. So in terms of power it's more like Mic is to Line what Line is to headphone. That is very rough but it's ball park and will remind you of what the relative levels are.
Click to expand...

As Noiz2 pointed out, you are probably also running into a bad impedance mismatch that will give noise problems. Again, it helps to use a transformer like the ProAV box.
 
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