Mixing line and mic source into a camera

[Pete Cofrancesco]

When using a beachtek like pre-amp, what should the switch going into the camera be set at line or mic? I looked at the manual and it doesn't say.

http://www.dvinfo.net/conf/showthread.php?t=73413

[Sharyn Ferrick]

Which beachtek are you using? the 4 6 or 10?

Typically what you want to do is to take the line level and pad it down to mic level, usually this is somewhere between 30 and 50 db. What you are going to run into is that the output of the sound board might not be something that you can control and also might be set more for the level to the amps then the level you need, SO If you are handy with building stuff http://www.tkk.fi/Misc/Electronics/c...ne_to_mic.html

OR you could look at buying
http://www.taiaudio.com/catalog/prod...roducts_id=944

there is another option that you could look at that is usually used for a mic but you could use it with the line level expecially if you don't need the full 40-50 db reduction

http://www.frontendaudio.com/Product...oductCode=7178

A small mixer is of course the other option, but these are some suggestions for pretty much using what you have

Sharyn

[Guy Bruner]

For most unbalanced, 3.5mm mic jacks, you should use MIC, not LINE, for the output.

[Pete Cofrancesco]

Sharyn thx, I think I know what i did wrong:

I set the camera to line and tried to use the pre amp to increase the mic source to line level, which it couldn't do.

Next time I'll set the camera to mic, and ask the sound booth guy to lower the line to match the mic. I might get one of the inline device incase they can't lower the line level enough.

[Steve House]

Originally Posted by Pete Cofran

Sharyn thx, I think I know what i did wrong:

I set the camera to line and tried to use the pre amp to increase the mic source to line level, which it couldn't do.

Next time I'll set the camera to mic, and ask the sound booth guy to lower the line to match the mic. I might get one of the inline device incase they can't lower the line level enough.

Pete - AFAIK the only Beachtek that puts out a line level signal is the DXA-10. Is that the one you have? All the others put out a mic level signal. The mic/line switch sets up the input sensitivity comning into the Beach, not its output to the camera. Line level inputs are padded down to mic level outputs.

[Pete Cofrancesco]

Originally Posted by Steve House

Pete - AFAIK the only Beachtek that puts out a line level signal is the DXA-10. Is that the one you have? All the others put out a mic level signal. The mic/line switch sets up the input sensitivity comning into the Beach, not its output to the camera. Line level inputs are padded down to mic level outputs.

Its like a beachtek but made by signvideo

http://www.signvideo.com/xlr-pro_xlr...udio-mixer.htm

[Steve House]

Originally Posted by Pete Cofran

Its like a beachtek but made by signvideo

http://www.signvideo.com/xlr-pro_xlr...udio-mixer.htm

As I read the specs, if you input a line level signal it's dropped 54 db to mic level. and the "gain" controls further pad that on down even lower if you need it. Too bad they don't seem to have more detailed specs online.

[A. J. deLange]

It's pretty clear that this device is primarily a balun - not a mixer (though it looks as if you can sum the two channels passively). It is intended to take whatever signal you give it in balanced form, mike or line, and convert it to unbalanced for input to an unbalanced camera input. If the input is mic level set the switch to the adapter "mic" position and the switch on the camera to "mic". The gadget's "gain" control allows the mic level to be attenuated if needed. In the full CW position the level to the camera is the level from the mic (less small unavoidable losses). By turning this knob CCW the gain can be reduced as needed thus eliminating the need for an external pad or the use of ATT settings in the camera (if it has them) in hot situations.

If the input is line level then you have three options. 1. Leave the camera set for "mic" input and select "line" position on the converter. A pad (approximately 54 dB) will be inserted in the signal path and the level presented to the camera will be mic level which can be trimmed with the pot. 2. Set the camera for "line" and the converter for "mic". No pad will be inserted and the line level input will be passed directly to the camera. The pot can be used for trim. 3. Set the camera for "mic" and the converter for "mic". No pad will be inserted and the line level will come booming through 50 or more dB too hot. Use the pot to attenuate the signal to mic level.

Option 3 is clearly not such a good idea and in Option 1 you take line level and reduce it to mic level this necessitating the use of the preamp in the camera. The signal has already been through a preamp (that's how it got to be line level in the first place) and has been subject to the distortions produced by that preamp. In running it through the camera's preamp it gets distorted further and as camera preamps are not often the greatest this may degrade the signal noticeably. In Option 2 the line level gets converted to unbalanced and is passed straight throuh to the camera whose preamps are not used thus limiting distortion to that in the preamps which fed the board from which the line level signal was taken. That's the option I'd choose.

[Steve House]

A.J.

Sign posts a spec that says the maximum input level in the "mic" position is 880mv. That's in the vicinity of +1dBu and the soundboard's output is likely to exceed that, especially on peaks. Since this is a passive device it might not be an issue but I'd want to test it first just to make sure there're no surprises - isn't it possible to drive a transformer into distortion by saturating its core with higher level signals that it's designed for?

[A. J. deLange]

Steve,

Yes, indeed it is possible to saturate the core of a transformer. If that happened it would probably cause worse distortion than going through the second preamp. Whether that would happen or not would depend on several things (like the input impedance of the camera) but they must have put that spec on there for a reason. Good call!

A.J.

[Pete Cofrancesco]

Originally Posted by A. J. deLange

2. Set the camera for "line" and the converter for "mic". No pad will be inserted and the line level input will be passed directly to the camera. The pot can be used for trim. ...

In Option 2 the line level gets converted to unbalanced and is passed straight throuh to the camera whose preamps are not used thus limiting distortion to that in the preamps which fed the board from which the line level signal was taken. That's the option I'd choose.

I tried this but it doesn't work. When the camera is set for "line" and the converter for "mic", the microphone source signal is too weak. Seems like this device doesn't do much amplification. The other way around camera set to mic and the converter set to line the line source was too noisy and distorted. But maybe the line source was too hot for the converter to attenuate and I had to tell the sound booth guy to turn it down.

[Steve House]

Originally Posted by Pete Cofran

... Seems like this device doesn't do much amplification. The other way around camera set to mic and the converter set to line the line source was too noisy and distorted. But maybe the line source was too hot for the converter to attenuate and I had to tell the sound booth guy to turn it down.

This device doesn't do ANY amplification - it's strictly a passive device. The "gain" setting is really an attenuation setting and is all in negative numbers - it ranges from "unity gain," meaning the signal is the same out as it is coming in, down to to "minus infinity," meaning the signal is completely attentuated.

Does your camera have line level inputs you could use? You haven't mentioned what your camera is, would be a help to know.

[A. J. deLange]

Originally Posted by Pete Cofran

I tried this but it doesn't work. When the camera is set for "line" and the converter for "mic", the microphone source signal is too weak. Seems like this device doesn't do much amplification. The other way around camera set to mic and the converter set to line the line source was too noisy and distorted. But maybe the line source was too hot for the converter to attenuate and I had to tell the sound booth guy to turn it down.

It doesn't do any amplification at all. It is a passive device: no batteries, no external power connection. If the board output is too low for your camera's line input then this approach can't be used. Just be sure that the "gain" control is all the way to the right (approximately unity gain) before abandoning this approach (and watch out for distortion if you can get it to work). The other way round you should be able to lower the level by using the knob on the converter.

[Pete Cofrancesco]

Originally Posted by Steve House

Does your camera have line level inputs you could use? You haven't mentioned what your camera is, would be a help to know.

its the vx2000 which has one mic jack with a line/mic switch. i need to find someone who has experience with mixing line and mic source.

[Steve House]

Originally Posted by Pete Cofran

its the vx2000 which has one mic jack with a line/mic switch. i need to find someone who has experience with mixing line and mic source.

If you need to actually mix a line level feed from a sound board with other mic level sources and send the resulting mix to your camera, you really need to be looking at an actual ENG/EFP field mixer rather than a simple XLR to miniplug attenuating adapter such as the Sign device you have. Shure, PSC, Wendt, Sound Devices are a few brands to consider at various price points. How many mics do you plan to have in use at a given time and is the feed from the soundboard mono or stereo? That'll determine how many channels you need to be looking at.