View Full Version : sound mixer question


Joe999
03-03-2008, 01:38 PM
I am playing with a new toy, a "DV Promix 3 Portable Audio Mixer". It seems pretty clear on how to use it, except for one thing. The output XLR connectors have a switch that can be set to 40, 10, 0; these relate to dB levels to send to the camcorder audio XLR inputs. I am not sure which to select, could use some help.

Here is the web page showing my Canon XH-A1 audio specifications
http://www.usa.canon.com/app/html/HDV/XHA1/audio.shtml

This is from the quick start guide of the sound mixer, regarding the connectors to take mixer XLR output to the xha1 input: "The output XLRs can be set either to -40dB (microphone level), -10dB (consumer line level), or 0dB (line level). This level must match the input level of your camera. See your camera's owner's manual
for the proper selection."

oakstreetphotovideo
03-03-2008, 03:16 PM
You can select line or mic level on your camera with a tiny switch above the input ports. I'd suggest using "-40" on your mixer and mic level on the camera unless your audio mixer has a cleaner, higher quality pre-amp than the camera ... which is possible, but not likely. The other reason to use line levels is for long transmission lines. By amplifying the signal at the mixer and sending the higher voltage to the camera (with "line" selected on the camera and "0" on the mixer), you'll have a better signal to noise ratio on your inputs ... again, assuming the mixer has a high quality pre-amp.

Joe999
03-03-2008, 03:20 PM
You lost me. First I thought you are saying -40 on mixer and mic level on camera, then I think you are saying 0 on mixer and line level on camera. ???

You can select line or mic level on your camera with a tiny switch above the input ports. I'd suggest using "-40" on your mixer and mic level on the camera unless your audio mixer has a cleaner, higher quality pre-amp than the camera ... which is possible, but not likely. The other reason to use line levels is for long transmission lines. By amplifying the signal at the mixer and sending the higher voltage to the camera (with "line" selected on the camera and "0" on the mixer), you'll have a better signal to noise ratio on your inputs ... again, assuming the mixer has a high quality pre-amp.

oakstreetphotovideo
03-04-2008, 08:17 AM
Depends on length of transmission line from mixer to camera. My first recommendation of -40 and mic level was based on the unfounded assumption that the Canon has a cleaner pre-amplifier, so we just skip pre-amplification in the mixer.

The second, contradictory recommendation was to deal with noise that may result from a longer transmission line between the mixer and the camera. Essentially, the noise level will be relatively constant if the transmission line stays the same and the cable is not moved. What you care about, as the signal reaches the camera is the signal to noise ratio. You can improve the signal to noise ratio by sending a louder (higher voltage) signal from the mixer to the amplifier, which, given a constant noise level, will cause the signal to be stronger than the electrical noise picked up by the wire. Balanced audio wiring isn't very susceptible to noise, so my first recommendation would be the likely best choice.

To reiterate, the 1st recommendation was based on an assumption. I haven't detected any amplifier noise coming from my Canon's pre-amp, so I'm pretty sure it is higher quality than many pre-amps.