Splitting One Mic to Two XLR's? at DVinfo.net

Bill Binder · January 13th, 2006, 10:50 AM

I probably have this wrong in some way, but I'm betting someone here can help me out. I've read (somewhere, but now I can't remember) about people taking a mic input, splitting it somehow into two XLRs. Then using a MixPre or something equivalent, running the levels on one of the two inputs a little hotter than the other while feeding both into the L-R channels of the camera. The idea is that I only have a single mono source anyway, and this offers the potential to running the signal as hot as possible while still having a back at a lower level on the other channel just in case. Now I know I could use the limiter on the MixPre if I wanted, but let's ignore that for the sake of discussion. Is this possible? Or do people use two mics when they do this? I'm confused how this could even be possible...

Chris Barcellos · January 13th, 2006, 12:08 PM

While I don't have it here with, On my BeachTek adapter, I switch to mono, with a one Mic input, and I think it sends signal out to both left and right sides separately. As I recall, I am also able to dial the level for each side up and down. That would seem to do what you are looking to do.

Chris Barcellos

Seth Bloombaum · January 13th, 2006, 02:50 PM

Some camcorders have switching for this function, eg. Sony PD150, 170, Z1.

(almost) Any external mixer (including mixpre) can do this as well:

1 mic - the split happens in the mixer. You need to cable up both mixer outputs to the camcorder.

Send 0db tone from mixer to camcorder - set channel 1 on cam to -12db, set ch. 2 to... -24db. (or other, probably somewhere between -18 and -30)
Microphone into input 1 of mixer.
Pan mic to center (feeds mixer outputs equally).
Run mic peaks up to 0 on the mixer.

This accomplishes a recording in which Ch. 2 is 12db lower than Ch. 1.

Although, as mentioned above by the OP, a good mixer such as the mixpre also has a limiter circuit that can also be used to tame unexpected peaks.

Be aware that passive "mic splitters" which can be found from pro audio retailers do not pass phantom power.

Jay Massengill · January 13th, 2006, 03:13 PM

As mentioned, it depends on the camera and the device that's hooked to the camera for the best procedure on how to do this. So there are some variables involved, but it's almost always possible to achieve this setup if desired.
In addition though, I'll re-emphasis that it isn't just the recording levels and meters on the camera that you have to be concerned with. If you have the camera's recording levels and meters offset from each other to have two different strengths on your tape, but you're feeding the camera with the same strength signal, it's still possible to overload the input. If that happens, even your "safe" channel will still distort even though your recording level doesn't hit digital zero.
If you're sending the camera a signal that's close to the capacity of your input sensitivity setting (Mic, MicAtt, or Line), then you may want to send two different signal levels to the camera for an even greater margin of safety instead of setting two different levels on the camera. Again, it depends on your circumstances.
In the example from the OP using a MixPre, you'd have to use either a splitter on the input or an attenuator on the output to send two different signal levels out from that mixer since the pan controls are L/C/R only. You could always set the limiter controls differently if you were using a splitter on the input, but that's a tricky adjustment and I like to keep my limiters matched. In addition, the limiters affect each input signal, they aren't directly tied to the output. So if you used a single mic, no splitter and no external attenuator, and wanted to send two different levels to the camera, the limiter controls would not achieve that. You'd have to rely on different level settings on the camera and be aware of overloading the input.

January 13th, 2006, 10:50 AM	#1
Bill Binder Major Player Join Date: Jun 2005 Location: San Francisco Posts: 542	Splitting One Mic to Two XLR's? I probably have this wrong in some way, but I'm betting someone here can help me out. I've read (somewhere, but now I can't remember) about people taking a mic input, splitting it somehow into two XLRs. Then using a MixPre or something equivalent, running the levels on one of the two inputs a little hotter than the other while feeding both into the L-R channels of the camera. The idea is that I only have a single mono source anyway, and this offers the potential to running the signal as hot as possible while still having a back at a lower level on the other channel just in case. Now I know I could use the limiter on the MixPre if I wanted, but let's ignore that for the sake of discussion. Is this possible? Or do people use two mics when they do this? I'm confused how this could even be possible...

January 13th, 2006, 12:08 PM	#2
Chris Barcellos Inner Circle Join Date: Nov 2005 Location: Elk Grove CA Posts: 6,838	BeachTek Adapter Work ?? While I don't have it here with, On my BeachTek adapter, I switch to mono, with a one Mic input, and I think it sends signal out to both left and right sides separately. As I recall, I am also able to dial the level for each side up and down. That would seem to do what you are looking to do. Chris Barcellos

January 13th, 2006, 02:50 PM	#3
Seth Bloombaum Inner Circle Join Date: Sep 2003 Location: Portland, Oregon Posts: 3,420	Some camcorders have switching for this function, eg. Sony PD150, 170, Z1. (almost) Any external mixer (including mixpre) can do this as well: 1 mic - the split happens in the mixer. You need to cable up both mixer outputs to the camcorder. Send 0db tone from mixer to camcorder - set channel 1 on cam to -12db, set ch. 2 to... -24db. (or other, probably somewhere between -18 and -30) Microphone into input 1 of mixer. Pan mic to center (feeds mixer outputs equally). Run mic peaks up to 0 on the mixer. This accomplishes a recording in which Ch. 2 is 12db lower than Ch. 1. Although, as mentioned above by the OP, a good mixer such as the mixpre also has a limiter circuit that can also be used to tame unexpected peaks. Be aware that passive "mic splitters" which can be found from pro audio retailers do not pass phantom power.

January 13th, 2006, 03:13 PM	#4
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	As mentioned, it depends on the camera and the device that's hooked to the camera for the best procedure on how to do this. So there are some variables involved, but it's almost always possible to achieve this setup if desired. In addition though, I'll re-emphasis that it isn't just the recording levels and meters on the camera that you have to be concerned with. If you have the camera's recording levels and meters offset from each other to have two different strengths on your tape, but you're feeding the camera with the same strength signal, it's still possible to overload the input. If that happens, even your "safe" channel will still distort even though your recording level doesn't hit digital zero. If you're sending the camera a signal that's close to the capacity of your input sensitivity setting (Mic, MicAtt, or Line), then you may want to send two different signal levels to the camera for an even greater margin of safety instead of setting two different levels on the camera. Again, it depends on your circumstances. In the example from the OP using a MixPre, you'd have to use either a splitter on the input or an attenuator on the output to send two different signal levels out from that mixer since the pan controls are L/C/R only. You could always set the limiter controls differently if you were using a splitter on the input, but that's a tricky adjustment and I like to keep my limiters matched. In addition, the limiters affect each input signal, they aren't directly tied to the output. So if you used a single mic, no splitter and no external attenuator, and wanted to send two different levels to the camera, the limiter controls would not achieve that. You'd have to rely on different level settings on the camera and be aware of overloading the input.