Separate L/R Levels in Stereo file possible with handheld recorders?

[Marcus Rieger]

Hi there,

i cant´t seem to find an answer to that question.

When i record with a camcorder and one XLR mic, i usually record to two channels (left/right). I set the level of one channel lower than the other to have a save track to prevent clipping.

So to make it clear: I just want to use 1 microphone and record 2 channels of it with different levels.

Is that also possible with these recorders?:

1. Zoom H4n
2. Tascam Dr-100
3. Marantz PMD 661

thanks in advance,
Marcus

[Jonathan Bufkin]

I'm pretty sure that all of these recorders will do it but I own a couple of the Dr-100's and I can tell you for sure that it will. You just need to choose a mono source and then you will have independent control over L/R.

[Robert Wiejak]

Zoom H4n - Yes

See: http://www.dvinfo.net/forum/all-thin...e-enables.html

[Marcus Rieger]

thanks,

but I am not sure about the zoom h4n.

The firmware update says:

1. Added the function that recording level of INPUT1 and 2 can be set individually.

So as i understand it: When I use 2 XLR microphones I can set the levels for each Microphone seperately.
But I only want to use 1 microphone and record 2 channels with different levels.

Is that also possible?

[Josh Bass]

I'm a little lost. . . you say choose a MONO source to have separate control of L and R?

I just got a Tascam DR07, has mini plug LINE and MIC ins (one of each). Seems like to get a stereo signal you'd choose stereo, no? That's what the manual says. . .it says mono will give you a mixed signal of all sources on L and R.

I would generally plan on using a mixer with this thing. . .you'd control the levels of the multiple mics with the mixer, no? Set tone and leave it alone after that on the recorder.

[Greg Bellotte]

just wire your mic into both input channels. an xlr y-cord or similar works fine for this...

[Marcus Rieger]

Sorry for the confusion. I will try and explain it better what i usually do when i use my camcorder.

When using my Camcorder (Panasonic HMC150, AVCHD) i plug in my ME66 microphone into the XLR-input labeled "Input 2" and record a stereo signal together with the video on an SD-card.

For channel 1 i select "Input 2" and for channel 2 also "Input 2"
Then i adjust the levels for both channels using the gain knobs for channel 1 and 2.
To prevent clipping i usually set the level for channel 2 a bit lower than for channel 1.

When i ingest the material into FCP for example i have a stereo audio track where one track has a lower level than the other.

So my question was if this is also possible with the above mentioned audio-recorders? Can i use one microphone to record 2 channels and set the level of each channel individually?

Hope i could make things a bit more clear. Thanks for the help!

[Marcus Rieger]

Ok so a xlr y-cord cable could be a solution. Are there any disadvantages when using such a cable. Is the signal still as good as usual?

thanks,
Marcus

[Neil Hurley]

Hi Marcus,
This is a reply I posted a while back to a similar question.It may work for you:

ZoomH4n Menu - Input - Mono Mix On.
Then go back to the main screen and press Rec once to standby.See Mono-000.wav on screen.With your mic connected to input one you should see levels on ch L and ch R. (see Zoom H4n User manual page 072).

Also if your recorder has the most recent firmware update you may be able to set separate levels for ch L and ch R. I am not sure this can be done in Mono Mix mode. If it can then you will be able to set the recording level lower on one channel as has been already mentioned.
I have not used this setup.Make sure to do some test recordings.Good luck.Neil

[Greg Bellotte]

as long as the y is short (1 foot) and wired properly with shielded cable then there should be no degradation of signal.

[Jim Andrada]

I was just wondering if it would work to use the Y cable and put a 10 or 20dB pad one branch of the Y so you didn't have to fool with independent levels in the menu. Just a thought.

[Robert Wiejak]

Originally Posted by Greg Bellotte

as long as the y is short (1 foot) and wired properly with shielded cable then there should be no degradation of signal.

No degradation, but when Y-ing (splitting) the signal you are effectively dividing the signal into two, so your levels will be -6dB at each input (50%).


@Marcus Rieger
I just tried this on my H4n and without Y cable it will not work. As long as you have the “1/2 link” disabled, you can’t “mono mix”.

[Andy Garnett]

On the Zoom H4n you cannot get one input onto both channels with separate levels. I have the latest software and tried to do this a few days ago. If you choose Mono Mix On it will be identical levels and if you turn it off the input will only record to one channel of the Zoom.

[Marcus Rieger]

Ok so it doesnt work with the zoom.

Regarding the Y-cable. If i understand you correctly Robert, the signal will be more silent when using the Y-cable than when not using it. So any preamp noise of the recorder will matter even more, because i have to rise the levels?

thanks guys!

[Greg Miller]

Actually, we need a little math to figure the actual amount of loss. It depends on the actual source impedance of the mic, and the actual input impedance of the recorder.

50 years ago, the answer was a little simpler. Most mics had a source impedance somewhere around 200 ohms. Most recorders had an input impedance somewhere around 200 ohms. If you connected one mic to two inputs, you would be dividing the power from the mic (not the voltage) in half, so the level at a given input would be roughly -3dB lower than it would have been if the mic had been connected to only one input. (Actually it would be slightly lower than that, because you'd now be technically putting more of a load on the mic than it was designed for; that causes some internal losses within the mic.)

Things are different today. We have largely migrated over to a situation where recorder input impedances are typically higher than mic source impedances. For example, the AT4050 source impedance is listed as 100 ohms. The DR-100 mic input impedance is listed as 1.2k ohms per channel.

This is really a nicer system. We have a low impedance source feeding a high impedance load. That's actually similar to our AC power distribution system where a low impedance source (the power transformer) feeds high impedance loads (light bulbs, etc.) So we don't have to worry about exact impedance matching and, therefore, we don't have to worry about power division (as we did in the "old days"). One light bulb does not become half as bright when we plug in a second light bulb.

To do the calculation correctly, you need to consider the mic as a Thevenin generator consisting of a pure voltage source behind a resistance (the mic's source impedance).

OK, let's consider an example with the equipment above, an AT4050 feeding either one or two mic inputs on a DR-100.

For the sake of doing the math, imagine the mic is in a test chamber with a constant tone from a speaker. We adjust the speaker level so the mic is putting out 1.0 volts open circuit... in other words connected only to a very high impedance voltmeter or oscilloscope.

Now let's connect the mic to just one mic input on the DR-100. At that point using the Thevenin equivalent circuit, we've created a voltage divider with a 1.0 volt source voltage, flowing through a voltage divider consisting of a top leg of 100 ohms and a bottom leg of 1200 ohms. The input of the recorder is the junction of the 100 ohm and 1200 ohm resistances. The voltage at this junction is 1.0 * (1200/1300) = 0.923 volts.

Next, let's connect the mic to both mic inputs. At this point the total load impedance is the parallel combination of two 1,200 ohm loads, so it is 600 ohms. We now have a voltage divider with a top leg of 100 ohms and a bottom leg of 600 ohms. (The recorder input is the junction of the 100 ohm and 600 ohm resistances.) The voltage at this junction is 1.0 * (600/700) = 0.857 volts.

Finally, we want to know how much lower the level will be, on a given channel of the DR-100, when the mic feeds both channels, compared to when the mic fed just one channel. dB is a ratio of two quantities, with the ratio expressed in logarithmic units. In this case, one quantity is the input voltage with just one channel fed, the other quantity is the input voltage with both channels fed.

The calculation is straightforward. First we take the ratio of the new (2-channel) signal to the original (1-channel) signal. That ratio is (0.857v)/(0.923v) = a ratio of 0.928. To find how many dB lower the signal has become, take the log of 0.928... the log is 0.032. Then multiply the log by 20, and the result is -0.64dB.

So, happily, we find that when an AT4050 feeds two channels on the DR-100, the level on a given channel is only -0.64dB lower than when that mic feeds one channel. (But the result will be different if the mic's source impedance is different, or if the recorder's load impedance is different.)

Note that this result is very similar to the way your line voltage (measured at the wall outlet) drops only slightly when you plug in a second lighting instrument... because the load impedance of the lighting instrument is much higher than the source impedance of the power transformer out on the pole (including the series resistance of your house wiring).

So, in conclusion: good news! The level will drop very little when you connect the mic to both channels, compared to only one channel.

If you tell me the exact mic and recorder in question, we can look up the source and load impedances, and perform this calculation again for your specific case.