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When I flew to Oshkosh two years ago, my friend Peter brought with him a cockpit voice recorded audio cable made by NFlightcam which connected inline with the headset cable, and had a pigtail wire which you could connect to your phone to record audio. I looked at buying one, but it was somewhere around $40 (http://www.amazon.com/Nflightcam-Smartp ... B00HQMLFWC) which seemed to be excessive considering all it consisted of were a could of cheap connectors and some resistors. So I reverse engineered the cable, ordered the connectors and resistors off of EBay from China and for under $10 made my own version.


This is the basic schematic of the cable. The parts list is simply the following:

(1) Male 1/4" Stereo Plug
(1) Female 1/4" Stereo Jack
(1) 3.5mm (1/8") TRRS Cable - 6'
(1) 1.8 kOhm Resistor
(1) 62 kOhm Resistor

I was able to squeeze all of the resistors into the male jack, although it was a tight fit.


The Tip and Ground are the only contacts used for the microphone, however, you do need to pass the RING signal to the female jack for the headset to work.


The TRRS 3.5mm jack only needs the first two contacts used for the audio.

Cool project! Would this work with a GoPro? Or is it just for iPhone?

Bruce,

The signal voltage levels this circuit outputs is definitely compatible with a GoPro, you will just need use a stereo 3-conductor 3.5mm plug wired slightly differently, and a 3.5mm <-> USB Mini connector similar to the following:


(Ebay http://www.ebay.com/itm/Mini-USB-3-5mm- ... SwnDxUkoPE - $1.39 shipped from HK)

12/2022 update (above ebay link is no longer valid)
https://www.amazon.com/ASHATA-Camera-Ad ... B07YWVPRFK

Thank you SO much for posting this - I have been looking at the NightFlight audio recording cable and suspected it was
pretty basic (apart from the price!) I have their propellor filter on my GoPro and had to modify it to make it fit...

I have ordered the parts to make one, but had a sudden thought - my headset jacks are different sizes (David Clark 13.4)
and if I remember correctly the mic jack is not a quarter of an inch (6.35mm in the UK) but smaller?? (which being a non-standard
size I suspect will be impossible to obtain!)

I have ordered a 6.35 male/female stereo cable and plan to unscrew the socket and attach a cable, terminated with the
3.5mm four ring jack plug (which I actually had several of already)

You do clearly state 6.35mm - I guess what is being recorded is what is fed back to the earcups? Hence using the larger jack?

I am asking because I am planning to also make an adaptor to record the audio directly on my GoPro Hero 3+ ultimately (I have also
ordered some right angle USB mini plugs with this in mind)

Best wishes from the south west of the UK

Chris (EuroFOX, G-EFOX)

Hi Chris,

First and foremost, welcome to Rivetbangers!

I don't think you need to be concerned with the mic jack, as the mic audio is fed back through the headphones via the intercom. You only need the 1/4" plug and jack.

I haven't used this with the GoPro yet (I have the GoPro mounted on the tail of my airplane), but I record the audio through my phone's mic jack all of the time successfully.

Thanks very much - I'll give it a go and let you know how I get on

Regards

Chris

I have finally got around to this - and success

The only thing I might change it to connect left and right audio together, as with one side not connected there was a little bit of noise on that channel, but otherwise the quality was excellent

I would post a short sample but can't see any way to include attachments??

This will enhance my videos considerably, once again thank you so much

Chris

Hi
Thanks for this very interesting schematic. It is very expensive to buy such cable in Europe so I will be happy to built my own one. However I am not so skilled in electronic and wonder if the values of the resistors you put will be compatible if I use a voice recorder with a 2 kohms mic input line and an headset David clarck H10 13.

Thanks for your reply,

JB

Could anyone please upload the pics again? seems to be down....
Great job bullojm1, thank you very much for sharing this

Regards!

Thank u!!

Hi everyone
First of all happy Xmas Eve for averyone.
I have trouble with this diagram, I´ve made the cable but still can´t get it to work on a Moto X Gen4
Don´t know where the problem is, already check the wiring, but it´s like the cell won´t detect the external mic. (Already checked with a motorola wired headset and the mic works perfect)
Thank you in advance!
Regards

Thank you SO much for posting this - I have been looking at the NightFlight audio recording cable and suspected it was
pretty basic (apart from the price!) I have their propellor filter on my GoPro and had to modify it to make it fit...

I have ordered the parts to make one, but had a sudden thought - my headset jacks are different sizes (David Clark 13.4)
and if I remember correctly the mic jack is not a quarter of an inch (6.35mm in the UK) but smaller?? (which being a non-standard
size I suspect will be impossible to obtain!)

I have ordered a 6.35 male/female stereo cable and plan to unscrew the socket and attach a cable, terminated with the
3.5mm four ring jack plug (which I actually had several of already)