Want to record Skype calls for your podcast interviews? This is how you do it.
Below is a complete photo walkthrough of the mix-minus setup demonstrated in this video.
Recording a Skype conversation or any other VOIP program on your computer using professional (XLR) microphones with the ability to mix in other sounds all without having the person on Skype get a feedback loop of their own voice, requires you to setup a mix-minus via your audio mixer.
The basic concept of a mix-minus is inputting multiple sources of audio into an audio mixer (your microphone, sound FX, Skype, etc.) then sending that audio back out to Skype, minus (a.k.a. without) the Skype callers voice thus preventing a feedback loop.
To do this you need a mixer with at least one auxiliary send channel. This is a dedicated output on your mixer that allows you to select which audio sources coming into the mixer get sent back out through the aux send channel.
In this video I’m using the auxiliary B (post-fader) to send my microphone and a soundboard (Bossjock app) with sound effects back to Skype. If your mixer has both pre and post aux faders, you can use either one. Don’t get too confused between the two but here’s some explanation of the differences between the two.
Post-fader simply means that the aux send passes through the main channel fader before getting sent out of the auxiliary channel. In this case, you must turn up both the Aux B send fader and the corresponding channels main volume fader in order for Skype to hear the audio. If we were using aux A (pre-fader) then the main channel fader would have no effect on our audio leaving the mixer via the aux send for each channel we are sending audio out of the aux A output.
Why would you choose a pre fader over a post fader and vice versa? If you were recording your mix to an audio recorder, as seen in this video, I could use aux A (pre-fader) to send audio to Skype without being affected by each channel’s main fader so that I could use different audio levels to go to Skype than I’m sending to the recording.
Using aux B (post-fader) would allow me to easily control what level of audio Skype gets by simply adjusting the main channel fader.
In this video the setup is as follows (see the links below for a list of gear used including the best cables*)
- My microphone (Heil PR40) is plugged into channel 1 via XLR cable.
- My iPhone is plugged into channel 5/6 via a stereo 3.5mm to Y cable (1/4″ left and right) for sending sound FX into the mixer.
- My computer (Skype) is plugged into channel 7/8 coming from my computer’s headphone output using another stereo 3.5mm to Y cable.
- The mixer is sending audio to the computer (Skype) via Aux B using a 1/4″ to 3.5mm stereo cable.
To achieve the mix-minus setup, the aux B fader on my microphone’s channel as well as my iPhone’s channel is turned up (set your fader at whatever level is good for Skype. I like my Skype audio meter (can be viewed in Skype’s audio settings) to register about 70 to 75%).
The aux B fader on my computer’s channel (7/8) is left in the off position or turned all the way down so that no audio is going out of the aux send. This is the minus part of your mix-minus. All the audio in the mix is going out to Skype through the aux sends, minus the Skype caller’s audio on 7/8. If we had this aux send turned up then the person on Skype would hear their own voice back because we would be sending it back to them after it came into the mixer.
In this video’s setup, each channel that we are sending audio out of the aux B must also have its main channel fader turned up as well or else the audio won’t leave through the aux because we are using a post-fader as explained above.
It’s much more complex sounding that it really is. Take your time and go through each step repeating as necessary. Skype has a test calling service (echo123) that will allow you to place a test call just as if you had an interviewee on the line. Add this to your contact list and use this to test your setup as often as you need.
Step by Step Mix-Minus Walkthrough with Photos
****KEY – Red Arrows = cable, Yellow Box = mixer input, Blue Box = Mixer Controls****
Step 1 – Mixer Requirements and Cabling
For a proper mix-minus setup you’ll need a mixer with an “Auxiliary (Aux) Send” (yellow box in image). This channel allows you to choose which individual channels get sent out of your mixer (blue boxes in image). For a mix-minus, I’ll be sending all of my audio in the mix, minus the channel that has Skype on it.
The yellow box in this first image (above) shows you where the AUX SENDS are located on my particular mixer. You see that this mixer has two (A (pre), B (post)). Your mixer needs at least one auxiliary send in order to properly setup a mix-minus. The more aux channels you have the more separate instances of Skype you can include in your mix.
It’s important to note that many mixers label the auxiliary send channel differently. For example, my Mackie ProFX12 labels them as Mon (monitor) Send and FX Send. Depending on what mixer you are using, they could be called something else but a quick check at the specs should tell you how many aux sends your mixer or the one you plan to buy has.
In the blue box you see the controls for the aux send channels for each individual channel on this mixer. This is where you will set the amount of volume that comes out of the aux send channel for each channel on your mixer including sending NO audio (level all the way down/off) on the channel that has Skype coming into the mixer.
Remember, this is called a mix-minus because you are sending the “mix” of all the audio coming into the mixer back out to Skype, “minus” the Skype audio.
This prevents the person on Skype from hearing their own voice back causing a feedback loop.
Cabling – Mike Phillips (@McPhillips) wrote an excellent article on choosing the best cables for setting up a mix-minus with your computer. The cables recommended by Mike can be seen in the following images.
The cables you see in the video above are fine but as Mike points out, anytime you use a adapter (i.e. 1/8″ to 1/4″) you create another point of potential failure. I’ve never had any issue with the cabling you see in the video but why not start with the best option and take Mike’s (expert) advice when it comes to selecting the proper cables.
Cables you’ll see in this walkthrough
Step 2 – Plug in the Microphone(s) and Get Initial Levels
Here you see I’ve plugged in my microphone (Heil PR40) to channel 1 using an XLR cable. I’ve turned the gain knob (first blue box below the mic input on the mixer) to its center position and the fader for channel 1 (lowest blue box on channel 1) to the center as well. I’ve also turned the fader for the “Main Mix” (blue box on far right, bottom) to the middle position. This knob controls the overall level of all the audio that is feeding into the mixer.
These levels are just an initial setting to make sure I’m getting audio from the microphone into the mixer. Simply talk into the microphone to see if you are registering levels on your mixer’s LED audio meter.
If you have more than one microphone, repeat this step as outlined above. You can see on this mixer I can plug in three more XLR microphones.
Step 3 Plug in Aux Send Cable to Mixer and Computer Input
The next step is to take a cable out of your mixer’s auxiliary send channel and plug that into your computer. This will be how Skype will receive the audio coming from your mixer.
In the picture above you see the red arrow points to the type of cable you want to use. Referring to Mike’s article on cabling for a mix-minus it’s important to note:
Most Internet broadcasters and podcasters are (or should be) using an auxiliary send on the mixer to send a mix-minus feed to Skype. That feed is mono. Most desktop and USB computer sound cards have stereo inputs. Skype really only looks at the left channel for its input, but some cheap, no-name sound cards may actually get the channels reversed internally. Therefore, it’s a good idea to feed to audio from the aux send on the mixer to both the left and right channels of the computer sound card.
A good solution is to use the Hosa CMP-105 cable, pictured here. The CMP-105 has a 1/8 inch TRS plug on one end and a ¼ inch TS plug on the other. The tip of the ¼ inch plug is connected to the tip and ring of the 1/8 inch TRS plug. The ¼ inch mono plug connects to the mixer’s aux out jack, and the 1/8 inch plug connects to the computer sound card. Even though Skype is mono and only sees the left channel of the audio input, the CMP-105 causes audio to appear on both the left and right inputs of the computer sound card.
In this setup, I’m using the aux B or post fader on the mixer to send audio to the computer. You can use either pre or post fader depending on your own preference. For another explanation of pre vs post faders see the end of the video starting at 9:20.
Next you’ll notice that the input to the computer is being handed by a device called an “iMic” made by Griffin. This is an analog to digital converter which takes the 3.5mm input (seen here plugged into the “in”) and converts it to a digital signal which is taken into the computer via USB.
If your computer doesn’t have a 3.5mm microphone input (e.g. Apple Macbook Pro models later than 2011) then you’ll need a device like this to input your audio to the computer from the mixer. When you setup your Skype audio preferences, you’ll want to select this device as your “microphone input.”
Step 4 – Plug the (Skype) Computer into the Mixer
Step 5 (optional) – Plug in a Soundboard or Additional Audio to the Mixer
If you have another source of audio such as a soundboard with music and effects, listener feedback, or any audio from another computer/device, then you can use one of your remaining open channels to bring in those sounds. In the picture above you see I’ve inputed an iPhone using a CMP-159 ?” stereo to ¼” dual mono cable. I’m using one of my remaining stereo channels because the app I’m using as a soundboard (Bossjock for iOS) will be bringing in stereo audio such as music and sound FX. If you are bringing in a mono source such as voice, you can use one of your remaining mono inputs (1/4″ plugs below the XLR inputs) and only plug the left channel ¼” mono plug (gray lead labeled “Tip”) into the mixer.
You can see I once again set an initial level (blue box on channel 5/6) to confirm I’m receiving audio from the iPhone.
Step 6 Plug in an Audio Recorder to the Mixer
Finally, we get to the final step in this setup which is plugging in an audio recorder so we can record our Skype call/podcast. Check the “alternative setups” section below to see how you would wire this setup if you wanted to record into your computer.
If you do chose to record into a computer, I still strongly suggest getting an audio recorder to record into as a backup. There are also other ways to handle recording a backup by using other software.
But having an additional hardware device can save your recording if your computer crashes. It can be really painful to be 20, 30, 60 minutes into an interview only to lose it because your software decided to crash.
In the picture above I’m using a 1/8″ stereo plug to dual RCA and outputting the mixer’s audio through the “Tape Out” output. This will capture a recording of all the audio going into your mixer including the person on Skype.
Record to separate channels
If you have a mixer that has either a FireWire or USB2.0 or higher output, you can record all the channels your mixer provides on separate tracks inside audio recording software that supports it. However, most mixers do not have these types of connections. When you only have a stereo mix out of your mixer how do you record audio on separate channels? Panning.
It’s important to understand that because you don’t have FireWire or USB2.0, you can only achieve two separate channels. However for many podcasters this will be enough because it’s just you (the interviewer) and Skype (the interviewee).
You’ll notice in the image above that channel 1 and channel 7/8 have their “pan” knobs turned all the way left and right respectively. Because you are sending a stereo mix (2 channels on a single track) to your audio recording software, you can create two separate channels with the left side of the stereo track containing audio that you panned to the left and the right side containing all the audio you panned to the right.
For example, in the above image, my microphone on channel one will be on the left side of the stereo track and the Skype caller on channel 7/8 will be on the right side of the stereo track. The resulting audio file will look something like this:
Once you begin to edit your audio, you can break apart this stereo track creating two separate mono tracks each containing only the audio that was placed on each track as a result of using the pan knobs. Now I have much more control over my audio in the editing process because the persons voice on Skype is not mixed with my own.
Some examples of what this allows you to do in the edit:
- Apply different effects to each audio track – Each person’s voice will be different from the other. When adding effects such as EQ, Compression, Gates, Denoisers, etc. you’ll want each person to have their own unique recipe of effects. By having yourself on one track and you Skype caller on the other, you can handle how each track is processed separately.
- Remove unwanted sounds – Your interviewee might cough while you’re talking and you’ll want to remove that. Having them on their own track will allow you to remove any part of their audio without affecting your own. If you recorded a stereo mix with panning your two channels, that cough could not be removed without also removing your own audio.
- Creating cleaner audio – My audio editing workflow consists of removing the parts of an audio track where there is no talking. For example, if I’m asking a question and the interviewee is just listening, I remove that part of their audio. This also removes the noise floor (hiss) from their track thus making the overall mix cleaner. There are other ways to accomplish this such as inserting silence or using noise gates but for me this is the most effective workflow.
- Fix crosstalk – If your guest speaks at the same time as you are speaking it can cause both or one of the person’s audio to get lost in the crosstalk. This always seems to be the case just as someone has made their most important point. Having each person on their own track allows you to shift the two pieces of audio on the timeline thus allowing each person to be heard. This is an incredibility powerful tool to have as an editor.
Recording into the same computer that’s running Skype
If you want or need to record your audio into the same computer you are using for Skype, you’ll need to run another audio feed out of your mixer and into another input on your computer for your recording software.
For example, you can take the Main Mix out of the mixer and input that into your computer (using a separate sound card explained/input on your computer) and use that feed to record into software that is on the same computer as Skype. This feed will contain all the audio including the Skype callers voice.
The key to this setup is that you have a second sound card. You need this because each piece of software you use (Skype, recording software, etc.) will need to have its own input.
If you are using only one sound card, both Skype and your recording software will only have one option to get its audio from and as we learned in this tutorial, the aux send will not contain the voice of the person on Skype. Your recording software of course needs to have an input with all voices. This would be the main mix out of your mixer.
If your mixer has USB output then the mixer becomes your second sound card and you can simply tell your recording software to get its input from the USB mixer. Skype would then still get its audio from the input on your computer that contains your aux send output from the mixer.
Other alternatives to getting a second sound card would be iMic that I mentioned above, and audio interface or another sound card that you install into your computer.
Recording with two computers
Another way to handle the recording of your Skype interviews using a mix-minus setup is to use two computers.
Having two computers allows you to dedicate one computer (can be a much older computer) to just running Skype. This allows all of the computers resources to be dedicated to Skype which may help improve your Skype connection and thus quality.
But primarily, using two computers allows you to send your aux send into the Skype computers input and the main mix from your mixer into another computer for recording the interview. This is another way around not having two sound cards in a single computer.
CABLING (for best results, use these cables)
- Hosa Technology Neutrik XLR Elite Microphone Cable – 10′
- (2) Stereo Mini (3.5mm) Male to 2 Mono 1/4″ Male Insert Y-Cable – 3′ (1 each for input of computer and iPhone to the mixer)
- 3.5mm TRS to Dual RCA Pro Stereo Breakout Cable-3′ (for output to audio recorder)
- Stereo Mini Male to Stereo 1/4″ Mono Male Cable – 5′ (for outputting Aux send audio from mixer to computer)
*Gear used to make this video:
- Canon 60D
- Canon Normal EF 50mm f/1.4 USM
- Transcend SD card 16 and 32GB UHS1 Class 10
- Manfrotto 701 HDV Tripod
- Rode VideoMic Pro
- F&V LED Ring Light
- Sigma 30mm 1.4
- Heil PR40 microphone
- Bossjock App for iOS (recording and soundboard app)
- Alesis USB 2.0 mixer (this replaced the discontinued Firewire version I’m using in this tutorial)
- The stand holding the mixer is actually for laptops but works well with this form factor
- Griffin Technology iMic USB Audio Interface (for use if you don’t have a 3.5mm input into your computer)
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