XLR Mic Only Showing on One Channel

I’m using the Focusrite Scarlett 2i4 audio interface along with a Shure SM7B for recording.

The problem I’m having is that the Scarlett 2i4 has two channels, and I sometimes record things with someone else using two mics, so I have my Windows audio settings to “2 channel.” However, when I go into Audacity and record in Stereo, there’s only audio on one channel. When I have both mics turned on, there’s audio on both channels, one mic per channel (one on left, one on right).

Is there a way in Audacity (or Windows even) to have both mics distributed evenly across both channels? I hope this is making sense. I attached a screenshot of the audio settings and what the track looks like when I record within Audacity.

Thanks in advance for any help, and if you need any additional information, please let me know.

If you want to record one microphone, distributed across both left and right, use input 1 of the Scarlett 2i4 and set Audacity to record “1 channel (mono)”.

If you want to record two microphones simultaneously and have each microphone across both left and right, then this requires two steps:

  1. Record into Audacity as “2 channels (stereo)”
  2. Split the recorded (stereo) track into two mono tracks (see: Split Stereo to Mono)

In post production, it’s Tracks > Mix > Mix Stereo down to Mono.

Then, if you’re sure the performers are going to be split left and right, Effect > Amplify: Amplification: 6dB > Enter.

USB interfaces are not mixers and you can’t arbitrarily assign or fade microphones.

You can buy a mixer with USB interface or a straight analog mixer and plug that into your existing 2i4. Switch the 2i4 inputs to “Line.”

Sometimes the driver software included with the interface will allow you to play tricks with the channels. Consult your instructions.

I went the analog mixer route and my computer has stereo analog inputs. The mixer will fade multiple microphones to the “middle” and I can tell Audacity to capture stereo or mono. If you try to play tricks with the channels in the computer or the Audacity channel assignments, you could get 50% clipping problems like this.


If you want to record one microphone, distributed across both left and right, use input 1 of the Scarlett 2i4 and set Audacity to record “1 channel (mono)”.

I’m pretty sure that gives the 50% clipping problem. Audacity thinks it’s trying to mix stereo down to mono. The Scarlett doesn’t produce a mono bitstream—that I know of.

Someone will correct me.

I recommend either the Scarlett Solo for mono microphones or the full mixer. It’s rough to stop in the middle between those two.


Yes you can do that, but once they are mixed they cannot be un-mixed. Better to keep them as separate mono tracks until ready to export, so they can then be adjusted / processed / edited separately if necessary.

Okay, so some of this stuff went over my head, and some of it didn’t. I’m not necessary new to audio and video production, but I am a little out of my depth with my complicated technical specifics. So I’m going to provide a bunch of details and pictures to make sure we’re on the same page. I thought the Scarlett 2i4 was USB, but only because it connects via Firewire to a USB port. This is an image of the current physical setup:
As you can see, I do have two XLR mics regularly plugged in, which is why I also have this as my default Windows settings:
As someone mentioned, my main microphone is in input 1, and this is the different in wavelengths when I record in Stereo vs. Mono in Audacity:
Stereo v Mono.PNG
The top is Stereo and the bottom is Mono. As you can see, the bottom looks significantly…thinner? Less robust? And both are only heard on the single side.

Ideally, I don’t want to have to remove a microphone and reset the mixer every time I’m only using the single mic, so I was wondering if there was a switch or setting to toggle to get “stereo” sound from a single mic. Still hoping I’m making sense. Thanks for all the help so far!

The setting in Windows should be “2 channels”. This allows the computer to correctly access both channel 1 and channel 2 of the Scarlett 2i4 .

When recording one microphone with the Scarlett 2i4 and Audacity,

  • the microphone must be plugged into input 1 of the Scarlett 2i4,
  • Audacity must be set to record “1 channel (mono)” in the device toolbar.

Where does the 6dB gain reduction come from if you do this dance wrong?


I think it’s a driver issue.
If you consider the signal chain:
Hardware → Drivers → Software

When the number of channels matches in Hardware and Drivers and Software, then there is a straightforward mapping of either:
Hardware (mono) → Drivers (mono) → Software (mono)
|Hardware (channel 1) → Drivers (channel 1) → Software (channel 1)
|Hardware (channel 2) → Drivers (channel 2) → Software (channel 2)

If the number of hardware channels does not match the number of channels requested by the software, then the Drivers have to work out how best to distribute the data.

If the drivers are set for 1 channel (mono) and the hardware device has two channels, then one possible design for the drivers is to halve the amplitude of each hardware channel, and sum the result. In this case, if only one hardware input channel is used, then the sum is “(half of channel 1) + (half of nothing)”.

The difference between “Mix down to one channel for recording” and “Select the first channel of many for recording.”

The decision appears to be in Audacity because switching between services in Audacity seems to give the volume change.

This is why I recommend single channel interfaces such as the Scarlett Solo and the Behringer UM2 and UMC22. Everything is expecting one single microphone and performance through the whole chain.

But what happens when the services don’t match? One scenario has the system straight mixing the two microphones into one channel in Audacity. That’s dangerous because what happens when the two microphones are listening to the exact same performance. The volume doubles and that can cause permanent overload and sound damage.

No problem, we reduce the volume of each microphone by half, so when they add up and double, everything comes out even. What’s what you have. What doesn’t work so well is each microphone appears half volume.

Somewhere, we have to convince the system to completely ignore all microphones past 1 and treat that single microphone as single channel. And that’s where the hand-holding between the device, the drivers and Audacity has to be addressed. That’s the blank look we’re giving each other.

6dB on the bouncing sound meters works out to half on the blue sound waves. You see your waves went from peaking at about 50% (normal) to peaking more like 25%. Nothing is ever that simple, however, you will probably find that the overload point isn’t 100% any more. That got moved down, too. This is where you get distortion at 50%.

Once we get this sorted, you will usually not get two blue sound waves. You will get one single mono wave which will play to both speakers. See where it says “Mono?”
Screen Shot 2018-04-29 at 7.23.41.png
You sure you don’t want to invest in a single channel interface?


Oh, I’m not positive I don’t. The problem is I DO use both microphones a good amount of the time. Sometimes I record with someone else. Sometimes I record alone. That’s where the issue is presenting itself, it seems…what does someone do when sometimes they use one channel and sometimes they need two?

Leave the settings in the Windows Sound Control Panel for recording “2 channels (stereo)”, and in the device toolbar, select “1 channel (mono)” when using only channel 1 of the device, or “2 channels (stereo)” when using both channels of the device.

So, about that. I’m not sure if I mentioned it (I thought I had), but even when I use both mics, one shows up on the left channel and the other on the right when I select stereo in Audacity, which is very odd. It seems more difficult that it should be to just have one or both mics come through both channels.

That’s precisely what is supposed to happen. That’s what a “stereo” recording is.

If you want two mono recordings (one from each mic), then the procedure is:

  1. Record as 2 channel (stereo)
  2. Split the stereo track into 2 mono tracks (see: http://manual.audacityteam.org/man/splitting_and_joining_stereo_tracks.html)

That and these interfaces Are Not Mixers. You can’t arbitrarily assign microphones to channels and manage channel behavior unless the writer of the driver software made it that way. A plain interface shovels microphone one down channel one, and microphone two down channel two. If you capture stereo, that’s the way it’s going to appear.

What you’re supposed to do is connect a real sound mixer to the interface. Then you can assign microphones, centering, reverse, mono, two-track mono, adjust levels and all the other mixer tricks.



Any recommendation on hardware that interfaces with a PC that would work better? Preferably something in the consumer/prosumer budget?

I appreciate all the help and I’m definitely learning things here!

No reason to not stick with the Scarlett 2i4. As Koz wrote, you can use a mixer before the interface, but there’s really no need unless you are using more than 2 mics at the same time. Once you have split the stereo recording into two mono tracks (which is just a couple of clicks), you can adjust the levels and the pan positions (if required) in Audacity.

A stereo track is really just two mono tracks stuck together, with the upper track panned hard left and the lower track panned hard right. By splitting the stereo track into two mono tracks, you can act on each of the tracks separately and mix them in any way that you want to.

If you pre-mix the tracks before recording, then you are pretty much stuck with whatever mix you created when recording - adjusting the mix later is severely limited. This is why professional studios will usually record each instrument onto separate tracks, and mix later.