Recording 2 things at once/muting channels

Special Interest Groups Recording Techniques
1

Hey I have 2 questions:

  1. Is it possible to be able to record a mic AND music from your computer/any sound from your computer at the same time? Or is there any equvilent that is possible?

  2. Is is possible to mute one channel during recording? Like if I was recording a mic, could I slide a dial over to the right to mute the left channel LIVE? I know i could wait until afterward, seperate the stereo clip into 2 mono clips, and mute the parts from there, but is it possible to do it live while recording?

Thanks!

2

I would have posted this on the Windows section of the forum because the answer changes a lot depending on the machine.

Let’s assume Windows.

You can set the Windows sound panels to record from all the inputs at the same time. Microphone, Line-In, CD, etc. This can cause problems if you leave some of the controls active by accident.

“How come the radio is in the background of my voice recording? I can’t hear anything in the room with me.”

This can also be dangerous because I think it’s the Mix control will record the output of the sound card. That can cause feedback and howling, but that’s the one you need open to record internet radio shows.

<<<Is is possible to mute one channel during recording?>>>

You can try it, but I believe the controls are locked out during recording. If they do work, you may get audio distortion at the points you changed the settings. Give it a shot.

Koz

3

okay thanks but can you tell me exactly how I would record whatever sound comes out of the computer AND my microphone. I was messing around with the “What U Hear” setting, but usually what happens is the computer noises sound great, but then the microphone sounds hollow, quiet, and just bad. So is there a better way to record both and still have good sound quality?

4

I got pieces. I know that if you try to record your microphone and What-You-Hear at the same time, you will get a really odd sounding microphone.

You may get a push from the wiki page.

http://audacityteam.org/wiki/index.php?title=Mixer_Toolbar_Issues#Using_the_Control_Panel

Koz

5

melloyellow,

Unless you have a sound card that can record from 3 analog inputs at once, you’re out of luck.

At this point, your best bet is to use Audacity to record the video sounds, and then go back and record your mic signal while listening to the original recording.

6

This is an old thread but I’m interested in the answer to the question "How do I mute one channel during recording. Koz says “You can try it, but I believe the controls are locked out during recording.” - but he doesn’t say which controls!! I have Version 2.0.3 under Windows. I’ve hinted everywhere for a controls to nute a channel during recording but I can’t find one anywhere. It would certainly be a useful facility.

7

What are you specifically trying to do? What is your input, is it mono or stereo and what are you trying to remove from the input that cannot be removed after the recording?

If your stereo input has a balance control in the Windows control panel for sound or in your sound device’s own control panel, you can turn the balance control fully one way or the other, or if there are separate left and right sliders, turn one of the sliders fully down.

Many computers’ built in sound devices cannot change the balance these days.

If you want step-by-step to find the Windows controls, please say exactly what version of Windows you are using.

Audacity cannot mute one channel of a stereo recording while recording, but such a feature is under discussion as part of a “recording profiles” feature. See https://forum.audacityteam.org/t/wip-enhancing-multichannel-fix-single-channel-recording/28626/1 for a special Audacity build for Windows you can download or a patch you can try if you are able to build Audacity from source code.

Following the steps in that topic, add these profiles to audacity.cfg:

[AudioIO/RecordProfile1]
MaxRecordChannels=2
Name=Left muted
Channel1=0
ChannelName1=Left muted
ChannelType1=Stereo
Channel2=2
[AudioIO/RecordProfile2]
MaxRecordChannels=1
Name=Right muted
Channel1=1
ChannelName1=Right muted
ChannelType1=Stereo
Channel2=0

Then restart Audacity and select the profile you want from Device Toolbar.


Gale

8

Hi Gale
thanks for the reply.
I will explain my problem. I am an actor and I learn my part by recording all my lines on one channel and everyone else’s on the other. I can then play back the recording either with both channels playing or, with “my” channel muted, listening to the other lines and reciting mine. I have a small switch which allows me to switch a microphone quickly between the left channel, the right channel, or in the middle for both. For many years I used a cheap cassette recorder, but that has now died, and I also no longer have a cassette player in the car, so I use CDs or MP3s. However I cannot record the sound on my computer or my laptop as neither seems to support a dual channel mic input. I thought this was because both my desktop and laptop are quite old, but I am now in the process of buying a new laptop andI am having enormous problems finding one that will support stereo recording. (My neighbour has a Dell which has an IDC chipset and drivers and works great, but all the ones in the shops, and also the newer DELLs, seem to have Conextant/Realtek sound systems which for some reason do not support stereo. I have been driving the guys in PC World nuts by trying out all their laptops with my switched mic and a VU Meter app).
I have also hunted high and low for a (reasonably priced) USB sound card which will do what I want, but that is also proving elusive.
If I cannot get hold of suitable hardware then the other solution is to do it in software - hence my query. I need to be able to switch quickly and easily from one channel to the other (and to both would be nice too). Ideally this should be a single keypress ( say cursor left, cursor right and middle, or three of the function keys). I might be able to live with a single button click for each channel, but it can’t be any more complex than that as I have to read the lines from the script and switch the channel back and forth as I go.
If you or anyone else on this forum have any suggestions, hardware or software, that I could try I would much appreciate it. I cannot believe that in this technological age I am having such a problem with what ought to be such a simple job.
Dave

9

Have you looked in the Windows control panel or the sound device’s control panel? What version of Windows? I think a button rather than a slider is unlikely, but it is worth a look.

Almost all mic inputs are mono. Does your laptop have a line-in, which would be stereo (blue)? Does your mic that you plug in to the computer have two rings on its plug for stereo, or only one for mono?

How about rip your CD to WAV then import the WAV into Audacity (or import the MP3) then Tracks > Stereo Track to Mono. Set Transport > Overdub (on/off) to on (checked). Set Audacity to record in mono in Device Toolbar. Click the red Record button to record your lines while listening to the others’ lines.

Now you have two mono tracks, all the lines from the CD on one track and your lines on the track below. Before we go into the neatest shortcuts to play one track or the other, does this sound like it helps you? That is does the CD or MP3 have only others’ lines, or have we got to get your lines removed from the upper track?


Gale

10

I cannot believe that in this technological age I am having such a problem with what ought to be such a simple job.

“We can put a man on the moon…”

Sorry, but neither of us can quite gather what you were doing with your cassette machine. We get the actors on “right” and your responses on “left,” but after that it got foggy. I’m gathering it’s foggy for the people helping you with your shopping trips, too. You may have fallen in love with an oddity of your cassette machine that 's not possible to easily replicate in a computer.

Single microphones in a computer are almost always mono and not associated with "left’ and “right.” So that’s the first shortcoming right there. Audacity tends to not edit in real time. You can’t change filters or effects while you’re playing the show. Yes, it’s very awkward and real time effects is a popular Feature Request.

However, that’s not to say we can’t help you.

Audacity has a feature called Overdubbing. It has its own set of instructions and it’s a little involved, but people use it all the time to build an orchestra one instrument at a time. First you record the guitar. Then you play the guitar recording and add the drums. Then you play both of those and add the xylophone. etc.

Using this technique, you can play the actors in full stereo into your headphones and record your responses to a separate track. Then you can play both of those into your headphones and switch either one off and on, in real time, as you wish. That part does work.

Having the performers flip and flop back and forth left and right is actually harder than doing it this way which uses commonly available parts. You can even record a third pass and fourth and turn each one on and off into your headphones.

The individual tracks top to bottom might be:

Actors
Me, first pass – sucks.
Me, second pass. Better, fluffed a line.
Me, third pass. Could use more interp.
Me, etc. etc. etc.

All the performances are available to both ears all the time. No left and right switching (Headphones Required).

There is one oddity to doing this and I’ll get technical after I find out if this might be useful to you.

Koz

11

I have a couple of this USB sound card http://www.amazon.co.uk/External-Stereo-Surround-optical-digital/dp/B003VWII3A

It has stereo microphone input in the form of two mono jacks. I sometimes use it with two mono microphones and sometimes
with a stereo microphone through a stereo female to 2x mono male adapter.

The same basic interface is sold under a lot of different names, google for “USB SoundBox 7.1”.
Here’s two examples from Amazon:

http://www.amazon.com/Sewell-USB-SoundBox-Sound-Card/dp/B004Y0ERRO

And another one from Skinflint in the UK:

http://skinflint.co.uk/delock-usb-sound-box-7-1-61803-a488206.html

–
Ragnar

12

Many thanks for taking an interest. I don’t think you’ve quite understood what I do. I’ve grabbed a bit from a play called “Soemone to Watch Ovber Me”. It goes like this:
Michael: “Why am I chained to a wall?”
Adam: “You’ve been taken hostage”
Michael: “Kidnapped?”
Edward: “Yes”
Adam: “My name’s Adam Canning. I’m an American”
Edward: “Edward Sheridan. Irish”
Michael: “I’m an Englishman”
Edward: “Of course you are”.
Now, I plaed Edwatd, so | would switch the mic to the right channel, read Michael’s line, then Adam’s line (with an American accent!), then Michael’s next line, then switch to the left channel and read Edward’s line, and so on until I have a recording of the entire play. To start with a listen to it normally, hearing all the voices. Then as I learn the part I mute the left channel and listen to Micheal and Adam, and speak Edward’s lines in the gaps. If I forget a line I can back up, unmute the left channel, and listen to it.
My mic has a steio 3.5mm jack - ie. Three connection (collar, band and tip - is that the correct terminology). I don’t think there was anything particularly special about my cassette recorder. As I say, laptops with the right sound chips do it no problem.
I could overdub it, that would be a solution. However it would mean going through the whole play twice, and if it’s a large part in a long play it can be fairly time consuming so I’d rather find a way to just to it once if possible.
I have thought of using a mic preamp and using the line in (although why the line-in should be stereo and the mic-in is not is also a mystery, as on most laptops they are the same socket), however I am also usnable to find a pre-amp tha woeks. I have an SP-24B (Maplin’s best) but it produces nothing but a lot of hum, I have no idea why. I thought it was because it didn’t provide the voltage needed for a condensor mic, but it’s the same with my dynamic mic.
I need to find some way of doing thism even if I have to buy a cassette recorder on ebay!. Many thanks to all respondants. I shall look at the h/w suggestions in detail when I have more time, and all furtehr suggestions are still welcome.
Dave

13

Oh, I should have also mentioned that I don’t play this stuff back on the computer. Once I’ve recorded it I put it on a CD so I can learn lines in the car (using the balance control as a channel mute), or just with a little portable CD player.
Dave

14

why the line-in should be stereo and the mic-in is not is also a mystery, as on most laptops they are the same socket

No, no, no, no.
Most Windows laptops do not have Stereo Line-In. They have Mono Mic-In only.

1000×660 65.3 KB

They are designed for communications like this.

1000×721 42.8 KB

Some unusual Windows laptops computers do have all three connectors (blue for Line-In) and some odd laptops have one connector that can switch between Stereo Line-In and Mic-In. Those latter laptops, it has been our experience don’t work particularly well.

Yes, perfectly correct that Mic-In and Line-In use the same connector with the same number of rings, but they do very different jobs. Stereo Line-In from front to back is Left Sound, Right Sound, and Protective Shield. The Microphone connector, front to back is Very Tiny Microphone Signal, Laptop Battery to run the microphone and Protective Shield. No you can’t cross them.

http://www.kozco.com/tech/audioconnectors/audioconnectors.html
Scroll down through the whole thing.

Edward: “Oh, John…”

Yes, that’s clearer. You’re recording the show with “your” part on a special track so you can turn it on and off as needed. It’s just that I can’t think of a good way to do it in real time with a computer – without a mixing board. With a small mixing desk featuring a panning control, this is a piece of cake. The attached is one of the controls of a small Peavey PV6 sound mixer. The knob in the middle “Pan” will place a microphone in the middle, left, right, or wherever you want it in the show.

http://www.sweetwater.com/store/detail/PV6USB?utm_source=Google&utm_medium=PPC&utm_campaign=none&gclid=CIWYx53aj7YCFaFxQgodSTsA_g

I’m sure there are smaller ones, but I happen to know how to run this one. You still need a microphone, but it will accept almost any analog microphone and it will supply 48v Phantom Power, too.

Koz
Screen shot 2013-03-21 at 11.31.29 PM.png

15

Further to Koz’s reply.

If you have a separate line-in port then the mic port must almost certainly be mono.

Have you looked in the Windows Control Panel and checked if you have a balance control, as I suggested before? Older versions of Windows just might have such. You still have not said what version of Windows you are on.

Does the CD or MP3 you record from already have some voices to right and some to left?

Here are the only solutions I can see in Audacity, either the recording profiles I mentioned before or changing the track you are recording in. Both mean physically stopping and restarting recording but could be automated down to a single keyboard shortcut using automation software.

Using Recording Profiles it would be five steps to change channel while recording (each action has a keyboard shortcut):

  1. Stop Recording
  2. Open Input Channels dialogue
  3. Down Arrow to change to Right muted or Up Arrow to change to Left muted
  4. ENTER
  5. Append Record (to the end of the track where you last stopped)

In practice of course you would use AutoHotKey to make a single keyboard shortcut that switched to right muted and another to switch to left muted.

Or perhaps easier to co-ordinate:

  1. Tracks > Add New > Stereo Track
  2. In the Track Name (Audio Track), Split Stereo to Mono
  3. Set Audacity to record in mono
  4. Click in the upper track to select it, then SHIFT + R to Append Record to the upper track only
  5. SPACE to Stop
  6. Click in the lower track to select it, then SHIFT + R to Append Record to the lower track only
  7. And so on repeating the last three steps …

You can change SHIFT + R to R or something more convenient in Keyboard Preferences.


Gale

16

A great play Dave - my favourite quote is the line from the Irishman (Stephen Rea in the original London production):

“I can sum up this situation in just two words: ridiculous ridiculous.”

WC
17

Koz:
Many thanks for explaining the ring connections on a mic jack. I didn’t know that and it explains a lot. How does this work with a dynamic mic? I need to look at the jack on mine, I can’t remember (I’m in the office), but I would guess it has just the one ring and shield, in which case the phantom voltage is either going to connect to the mic itself, which could damage it, or to the shield which would effectively short out whatever is supplying the voltage (the laptop’s PS???), neither of which sound very healthy!!
Thanks for the suggested sweetwater mixer but it really is overkill for what I want to do. I’d like to find something simpler (and cheaper) if I possibly can. A simple mic preamp into the line-in would suffice, and I still don’t know why I can’t find one that works.
“Most Windows laptops do not have Stereo Line-In”. Actually a lot of the ones I tried (eg the Dells I mentioned) did - when you plug something into the socket you get a dialog up asking “are you using mic-in or line-in?” or words to that effect.

Gale:
Also thanks.
I’m currently on XP (laptop and desktop), but I need to get a new PC and I decided to buy just a laptop as the modern ones will do all I want without shelling out for a desktop as well. The new one will, of course, be ghastly Windows 8 (I think I missed the boat on 7 but I’ll be installing a start menu replacer pretty quick!)
"Does the CD or MP3 you record from already have some voices to right and some to left? ".
I think I’ve still not quite explained it properly. I don’t record from a CD or MP3, I just record my own voice on the two channels. I then copy the whole show to a CD (or MP3) to play in the car/train etc.
I’ll certainly have a look at using the profiles and something like AutoHotKey to automate them. I’ll keep looking at hardware options too. If all else fails I’ll just have to write my own recording program (oh, I should have said, I’m only an actor when the sun goes down. During daylight hours I’m a freelance C++/C# developer)

WaxCylinder:
Yes it’s a great play. We did it in a small and very intimate 70-seater in-the-round theatre and it was very powerful indeed. One of my favourite roles.

Many thanks to all, and if you think people will be interested I’ll keep you up to date with my progress.

Dave

18

Whoa - hang on guys. I’ve been thinking through Koz’s explanation of the three connections on the 3.5mm mic jack and it still doesn’t make sense.
First off, a condensor mic works by applying a voltage (the “phantom” voltage) across the plates of a capacitor. The sound waves then vibrate one of the plates, causing fluctuations that are detected as tiny currents by the sound device, in this case the sound card. So surely the connector that the voltage is applied to must be the SAME one that the signal is picked up on, not a different one (feel free to get technical, I have a degree in electronics).
Secondly, my little switch box (which was originally designed for use with a dynamic mic) simply connects the tip, ring and collar of one jack (socket) to the tip ring and collar of another jack (plug), and then disconnects the tips if pushed one way and disconnects the rings if pushed the other way. If it really were the case that the signal is on the tip and the phantom voltage on the ring, then this could never ever work. If the tips were switched out there woul be no signal at all, and if the phantom voltage on the rings were switched out, well, then there would also be no signal at all. And yet it works fine on both of my neighbour’s Dells and on several PCs (apparently the ones with IDC sound chipsets) at my local PC World shop.
I’m sorry to worry at this like a demented Labrador, but I am determined to get to the bottom of it.

19

We could do with more of those! If you are ever interested in compiling Audacity and offering some code, please feel free to look here Missing features - Audacity Support and then consider signing up on the audacity-devel mailing list.

Thanks


Gale

20

(the “phantom” voltage)

That’s the polarizing voltage. Phantom has to do with the voltage delivery method.

causing fluctuations that are detected as tiny currents by the sound device, in this case the sound card.

That’s greatly simplified, but condenser elements create variations in voltage, not current. They work by voltage variation as the spacing between the plates vary. This signal has no horsepower at all and will not go down a cable or do any useful work – like the static charge on your comb – so there has to be an amplifier in there somewhere.

Electret Condenser Microphones have a permanent static charge on very tiny plates inside the microphone head. The signal is very delicate with no horsepower. You send computer 5 volts up the “ring” connection to run a tiny amplifier which then jams the beefier sound signal down the Tip connection. That’s not phantom power because there are dedicated wires to do everything.

Scene shifts to a “grown up” condenser microphone like the AKG 414.

http://www.sweetwater.com/store/detail/C414XLII/

That one uses a three-wire XLR cable.

This one uses real 48 volt phantom power. The mixer or recorder sends 48 volts up the cable to run the microphone (and the condenser plates) using all three wires but the microphone sends the show down only two using the third as a passive shield. Each is a phantom to the other. The 48 volt system can’t see the sound and the sound system can’t see the 48 volts even though they’re using the same wires. The sound goes down differentially between 2 and 3 and the 48 volts comes up single ended on 2 and 3 versus 1.

Scene shifts to an SM58 or other dynamic microphone.

http://www.sweetwater.com/store/detail/SM58/

Theory has it you can plug a plain, passive SM58 into a 48 volt phantom sound system with no problems or damage, but I probably wouldn’t because if someone disconnects or changes the microphone with everything running, there could be a brief time during the plugging or unplugging when the 48 volts is applied to the wrong place causing damage.


The 5 volts on the ring of the “computer microphone” connector isn’t pure, robust 5 volts from the power system inside the computer. It’s buffered and protected so you could connect it to ground or other wires without causing a fire, but if you cross it with the sound wires, you can create a very powerful crack or pop sound in the system. You do not want to be in your high quality headphones or standing in front of the speakers during those events. You may be Rock Concert Deaf for a while after that.

A dynamic microphone uses a floating sound element inside the metal covering connected to pins 2 and 3. Full stop. There is usually no connection between the sound element and the outer shield. In order to hear this microphone in a computer system, you have to connect (conventionally) pin 2 to the tip of the 1/8" and pin 3 to the shield. The ring connection isn’t used at all.

That’s how this is wired.

This series of adapter has been working for decades, originally with unbalance news gathering tape machines.

You can mess this up and it will still seem to work, just not as well. There is a very common series of adapter that just goes 2-tip, 3-ring and 1-shield. This is an extraordinarily bad idea because it pushes the dynamic sound element up to 5 volts (both wires) and puts 5 volts on the tip connection and into the sound card. It also fails to provide a ground for the sound element to work against leading to a greatly degraded signal, but it will probably still work a little. It probably would have been better if it just failed rather than limping along.

Koz