Cockpit audio for recording

gprellwitz

Touchdown! Greaser!
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Grant Prellwitz
What equipment do I need to hook up the audio of the intercom to a video camera or a tape recorder in a plane? Can I use a cell phone interface, perhaps with another adapter between them?
 
gprellwitz said:
What equipment do I need to hook up the audio of the intercom to a video camera or a tape recorder in a plane? Can I use a cell phone interface, perhaps with another adapter between them?

I discovered that the "ears" part of a headset is the same as on a computer - provided you get the plug to match. A transformer or resistor (1000 ohm? Lance?) in series would get it down to line level input for a tape recorder or video camera.
 
What Mike said-

It is easiest if you happen to have an extra headset plug (i.e., have 4 seats with plugs, fewer than four people plugged in).

For isolation's sake, I'd prefer to use a transformer for coupling, have never run the numbers to determine values. I bet someone has, though (Jesse?).
 
mikea said:
I discovered that the "ears" part of a headset is the same as on a computer - provided you get the plug to match. A transformer or resistor (1000 ohm? Lance?) in series would get it down to line level input for a tape recorder or video camera.
SCCutler said:
What Mike said-

It is easiest if you happen to have an extra headset plug (i.e., have 4 seats with plugs, fewer than four people plugged in).

For isolation's sake, I'd prefer to use a transformer for coupling, have never run the numbers to determine values. I bet someone has, though(Jesse?).
Well, since I (almost) never have as many butts in the seats as I have seats, I usually have an extra set of plugs.:)

Being a software guy, I just naturally resist all this Ohms talk. And I won't touch this while coupling. :rofl: Ahh, juvenile electrical humor!

But seriously, I gather that I need to have comparable values on the headset output and the microphone/aux input, as well as making sure that the plugs are physically compatible. I'm not sure I understand a transformer here, as I usually think of that as switching AC to DC, and I didn't think we would be doing anything like that here.

Does anyone have suggestions on what part to order from Radio Shack? I really know no EE stuff at all, and don't think I could read a circuit diagram on a bet. OTOH, I knew where to turn for the answers!
 
gprellwitz said:
I'm not sure I understand a transformer here, as I usually think of that as switching AC to DC

A transformer doesn't actually switch between AC and DC.

A transformer changes the levels, for instance, the transformer outside your house converting the thousands of volts from the power line to the 120 volts you use in your house.

Now, for instance, DC to AC is done by an inverter. It's just that we're used to low-voltage DC (ie 12V in a car) and 120V AC, so the inverter also incorporates a transformer. If you were converting 12VDC to 12VAC, you wouldn't necessarily need one.

Now, to get back on the thread topic - The other "trick" I've seen used is to get one of those portable intercoms that has in and out minijacks. 1/8" male to 1/8" male cables are very easy to find, and all of the other necessary electronics are built in to the intercom.
 
gprellwitz said:
I'm not sure I understand a transformer here, as I usually think of that as switching AC to DC, and I didn't think we would be doing anything like that here.

You've got 1/3rd of the part right. Everyone calls those little power supplies transformers. As stated by Kent, the transformer changes the voltage levels (120V AC to 12V AC) then a few diodes / rectifier makes the change to DC and a capacitor will help smooth out the voltage level.

Are the headset levels that much higher than line-out levels? We're not driving big speakers here. :)
 
AirBaker said:
Are the headset levels that much higher than line-out levels? We're not driving big speakers here. :)

Yes, they are amplified.
If you get a 1/4" (for the headset end) to 1/8" jack (or whatever your tape recorder/video recorder input thingy is) and fitz around with the volume, you should be able to get a decent sound quality happening.
You will probably have to turn down the volume of the comm a bit to get a signal into the recording device with out distortion.
If you're using a high end recording/video device, it should have some sort of attenuation on the input that would achieve the same result.
One of these days, I'm going to try and record something in an airplane, and I will post something here for ya'll.

DW
 
lancefisher said:
Here's a $5 part from Radio Shack that will probalby do the job when coupled with a 1/4" to 1/8" mono adapter. That's assuming all you have on the recorder is mic in. If you have line in, it will probably take the headphone signal directly without attenuation.

http://www.radioshack.com/product/index.jsp?productId=2103841&cp=&kw=line+level&parentPage=search

Lance,
I used this exact setup in my A/C. While it did record the audio from the intercom and radio's it did greatly reduce the volume to the headsets while connected. It may have to do with the junk intercom in my plane. It is a Sigtronics that I have hated ever since I bought the A/C. The volume has to be turned all the way up to be able to hear. It has all of Sigtronics mods and still sux. I have a Garmin GMA-340 laying here to put in it when time permits. Hopefully that will solve all the problems.
Don
 
lancefisher said:
Here's a $5 part from Radio Shack that will probalby do the job when coupled with a 1/4" to 1/8" mono adapter. That's assuming all you have on the recorder is mic in. If you have line in, it will probably take the headphone signal directly without attenuation.

http://www.radioshack.com/product/index.jsp?productId=2103841&cp=&kw=line+level&parentPage=search
I just ordered a digital recorder (same one that a pilot friend has) and a pilot friend [same one as I just mentioned] of mine told me how he does his setup. I already had a 1/4" to 1/8" stereo-to-stereo adapter and a 1/8" to 1/8" stereo cable, which will go into my digital recorder. I have to go test it out the next time I go fly and report back! I bought a digital recorder which allows silence [pauses] to be automatically not recorded, so it *should* record only when it senses audio. All I'll have to do is plug it into the back seat audio out in the 172 or if I fly the 152, get a 1/4" Y-splitter and run that from the audio-out IC jack to the headset and recorder.

Does anyone know if stereo-to-stereo adapter and cable will work, or do I need a mono? I figured since I had the stereo, I'd give it a try, but I don't think it will make a difference. Answers? Opinions?

Thanks,
Jason
 
lancefisher said:
Here's a $5 part from Radio Shack that will probalby do the job when coupled with a 1/4" to 1/8" mono adapter. That's assuming all you have on the recorder is mic in. If you have line in, it will probably take the headphone signal directly without attenuation.

http://www.radioshack.com/product/index.jsp?productId=2103841&cp=&kw=line+level&parentPage=search


Gee, Lance, you let me down. That's how I would have solved the problem back when I was an 8 year old electronics nerd. The attenuator is a resistor, right?

Anyway, an audio transformer is what I meant. That will match impedences but would be hard to come by if you weren't buying 1000 of them.
 
HPNPilot1200 said:
I just ordered a digital recorder (same one that a pilot friend has) and a pilot friend [same one as I just mentioned] of mine told me how he does his setup. I already had a 1/4" to 1/8" stereo-to-stereo adapter and a 1/8" to 1/8" stereo cable, which will go into my digital recorder. I have to go test it out the next time I go fly and report back! I bought a digital recorder which allows silence [pauses] to be automatically not recorded, so it *should* record only when it senses audio. All I'll have to do is plug it into the back seat audio out in the 172 or if I fly the 152, get a 1/4" Y-splitter and run that from the audio-out IC jack to the headset and recorder.

Does anyone know if stereo-to-stereo adapter and cable will work, or do I need a mono? I figured since I had the stereo, I'd give it a try, but I don't think it will make a difference. Answers? Opinions?

Thanks,
Jason

The stereo cable should work. The worse case is you'll only hear the source on one side. You can get a mono-stereo adapter from Radio Shack. One will do ya.

Jann's dad was a musician who we can guess would go to Radio Shack whenver he had to connect anything. He had quite a collection of adapters I inherited. In spite of that, I had to go myself to get an adapter not too long ago.
 
mikea said:
Gee, Lance, you let me down. That's how I would have solved the problem back when I was an 8 year old electronics nerd. The attenuator is a resistor, right?

Anyway, an audio transformer is what I meant. That will match impedences but would be hard to come by if you weren't buying 1000 of them.

I assume the cable has a voltage divider (pair of resistors). No transformer is needed as long as the recorder is battery powered, otherwise a transformer would provide some isolation and prevent ground loops. Impedance matching is generally not an issue as the mic input will likely be a high impedance which will work fine with a low impedance source like an intercom.
 
Hmmm. I just got a cell phone adapter to plug into the intercom for calling flight service from the ground. I'm wondering if it might be easier to chain off that. It does have a bettery for, I presume, amplicifation. (It's the Sporty's model, and I generally fly the new 172S's.)
 
HPNPilot1200 said:
I just ordered a digital recorder (same one that a pilot friend has) and a pilot friend [same one as I just mentioned] of mine told me how he does his setup. I already had a 1/4" to 1/8" stereo-to-stereo adapter and a 1/8" to 1/8" stereo cable, which will go into my digital recorder. I have to go test it out the next time I go fly and report back! I bought a digital recorder which allows silence [pauses] to be automatically not recorded, so it *should* record only when it senses audio. All I'll have to do is plug it into the back seat audio out in the 172 or if I fly the 152, get a 1/4" Y-splitter and run that from the audio-out IC jack to the headset and recorder.

Does anyone know if stereo-to-stereo adapter and cable will work, or do I need a mono? I figured since I had the stereo, I'd give it a try, but I don't think it will make a difference. Answers? Opinions?

Thanks,
Jason
If your recorder has a "line in" connection a direct link should work fine. If it's a "mic" input, chances are the headphone signal will be too high a voltage and the sound will be severely distorted. That's what the attenuator cable I posted earlier should fix.

As to stereo vs mono issue, a stereo cable will work best in most cases. If your intercom is stereo and the recorder is stereo (not likely unless it's meant for recording music or is a camcorder) then you definitely want a stereo connection. If the intercom is stereo but the recorder is mono a stereo cable will probably prevent the loss of audio to one side of any headsets on the same output (some intercoms provide separate outputs for each headset and some don't). If the intercom is mono and the recorder is stereo, a stereo cable will deliver sound to only one channel on the recorder, and you'd need a stereo to mono adapter to do any better. If eveything is mono, the stereo cable should still work as well as a mono cable which would be fine also. The cable I posted is mono AFaIK.

Another (mono) choice would be an inductive pickup as sold to record telephone conversations. They usually have a suction cup on one end and if you stuck that onto a headset plugged into the intercom, you should be able to connect it to the mic input on a recorder and get good audio.
 
Last edited:
Don Jones said:
Lance,
I used this exact setup in my A/C. While it did record the audio from the intercom and radio's it did greatly reduce the volume to the headsets while connected. It may have to do with the junk intercom in my plane. It is a Sigtronics that I have hated ever since I bought the A/C. The volume has to be turned all the way up to be able to hear. It has all of Sigtronics mods and still sux. I have a Garmin GMA-340 laying here to put in it when time permits. Hopefully that will solve all the problems.
Don

Some of the Sigtronics intercoms connect their audio output to the aircraft radio's output through a resistor and with that setup you have all sorts of problems with things like this and using headsets with different impedances. To get around the problem I think a headphone booster amp (available from RS for a about $30) would solve the problem (as would installing a decent intercom). You'd connect the booster to the headset jack and then use the attenuator cable from the booster output to the recorder's mic input.
 
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