headphone out to line-in

[Legend]

I have been asked to do a 400 trip in a cessna aircraft TOMORROW
and to film the trip using my sony camcorder

on previous occassions the built in microphones captures way too much
ambient noise and next to nothing of the intercom and tower
conversations and even placing an extension mic in one side of the
headphones is not satisfactory (noise cancelling circuitry in the
headsets seems to cause interference in the camera)

So in a hurry last time I did a direct connection from the headphone
socket to the line-in knowing that it would be too much of a mismath...
and it was...way too much signal

This time around I would like to get it somewher near perfect but I dont
have any figures on the output of the headphones OR the line-in of the
camera ... and I only have a few hours to get some result.

Can anyone give me a ballpark figure on what value resistor I could use
in the line to cut the signal in half

 

[Mike Harding]

I have been asked to do a 400 trip in a cessna aircraft TOMORROW
and to film the trip using my sony camcorder

on previous occassions the built in microphones captures way too much
ambient noise and next to nothing of the intercom and tower
conversations and even placing an extension mic in one side of the
headphones is not satisfactory (noise cancelling circuitry in the
headsets seems to cause interference in the camera)

So in a hurry last time I did a direct connection from the headphone
socket to the line-in knowing that it would be too much of a mismath...
and it was...way too much signal

This time around I would like to get it somewher near perfect but I dont
have any figures on the output of the headphones OR the line-in of the
camera ... and I only have a few hours to get some result.

Can anyone give me a ballpark figure on what value resistor I could use
in the line to cut the signal in half

To be quite honest with you if you don't know how to
do that calculation yourself there is _no way_ you should
be messing with aircraft electrical systems. Quite apart
from the fact it's illegal and probably voids insurance
and goodness knows what else. I'm actually surprised
the pilot allowed you to do so last time.

Use a mic and run the audio through Goldwave or
another sound editing programme to clean it up afterwards.

Mike Harding

 

[Legend]

To be quite honest with you if you don't know how to
do that calculation yourself there is _no way_ you should
be messing with aircraft electrical systems. Quite apart
from the fact it's illegal and probably voids insurance
and goodness knows what else. I'm actually surprised
the pilot allowed you to do so last time.

Use a mic and run the audio through Goldwave or
another sound editing programme to clean it up afterwards.

Mike Harding

now that I have had the safety lecture!!!!!
you could have saved all those words and just given me a figure....that
is if YOU know how to do the calculations yourself...

I do know how to use ohms law... but as I said previously I dont have
any specs on the output of the headphones or the input of the microphone
socket so I thought that someone who has real experience could just give
me a starting point... from your answer.. I can easily deduce that you
have no experience..and you are just here to look for arguments

it would have been much easier to give me the answer I need if you want
to send me on my way

 

[Russ]

I have been asked to do a 400 trip in a cessna aircraft TOMORROW
and to film the trip using my sony camcorder

on previous occassions the built in microphones captures way too much
ambient noise and next to nothing of the intercom and tower
conversations and even placing an extension mic in one side of the
headphones is not satisfactory (noise cancelling circuitry in the
headsets seems to cause interference in the camera)

So in a hurry last time I did a direct connection from the headphone
socket to the line-in knowing that it would be too much of a mismath...
and it was...way too much signal

This time around I would like to get it somewher near perfect but I dont
have any figures on the output of the headphones OR the line-in of the
camera ... and I only have a few hours to get some result.

Can anyone give me a ballpark figure on what value resistor I could use
in the line to cut the signal in half

The simplest method for going from a high level to a low level is using a
simple voltage divider (voltage divider = 2 resistors). If you want exactly
half the voltage, you'd use 2 x 1K resistors in series across the headphone
output, and run your camcorder line-in across one of the 1K resistors. You
might also put a 300R resistor across the 2 so as to present a decent load
to the headphone output.

Normally, you'd want greater attenuation than half, For example, a more
common drop might be about 14dB, which corresponds to a 5:1 drop, meaning
you could use a 3K9 in series with a 1K, with the line-in connected across
the 1K resistor.

Russ.

 

[Legend]

The simplest method for going from a high level to a low level is using a
simple voltage divider (voltage divider = 2 resistors). If you want exactly
half the voltage, you'd use 2 x 1K resistors in series across the headphone
output, and run your camcorder line-in across one of the 1K resistors. You
might also put a 300R resistor across the 2 so as to present a decent load
to the headphone output.

Normally, you'd want greater attenuation than half, For example, a more
common drop might be about 14dB, which corresponds to a 5:1 drop, meaning
you could use a 3K9 in series with a 1K, with the line-in connected across
the 1K resistor.

Russ.

thanks for this starting point
and thanks for using the NG for what it is intended for
.... helping people sort out their problems
....instead of just a power trip for the hollier than thou's

 

[Mike Harding]

now that I have had the safety lecture!!!!!
you could have saved all those words and just given me a figure....that
is if YOU know how to do the calculations yourself...

I do know how to use ohms law... but as I said previously I dont have
any specs on the output of the headphones or the input of the microphone
socket so I thought that someone who has real experience could just give
me a starting point... from your answer.. I can easily deduce that you
have no experience..and you are just here to look for arguments

Oh just the 30 years or so.

it would have been much easier to give me the answer I need if you want
to send me on my way

What I want to do is to try and discourage you from messing
about with aircraft electrical systems. You may cause problems
with other items in the aircraft and at 10,000 feet you tend to
find your options are limited. You can't just park the thing and
call the RACV. There are a _whole stack_ of safety regs. about
who may work on aircraft and what training they need and that's
for a very good reason.

You'll do what you want to do and that's fine by me but I do
have some knowledge of this area and my advice to you
is don't monkey with the aircraft - I'm sorry if that's not what you
wanted to hear - perhaps you shouldn't have asked.

Mike Harding

 

[GM]

now that I have had the safety lecture!!!!!
you could have saved all those words and just given me a figure....that
is if YOU know how to do the calculations yourself...

I do know how to use ohms law... but as I said previously I dont have
any specs on the output of the headphones or the input of the microphone
socket so I thought that someone who has real experience could just give
me a starting point... from your answer.. I can easily deduce that you
have no experience..and you are just here to look for arguments

it would have been much easier to give me the answer I need if you want
to send me on my way

Legend - You are a clueless idiot.

 

[Phil Allison]

"Legend" <

Can anyone give me a ballpark figure on what value resistor I could use
in the line to cut the signal in half

** Only a "flying" guess - but try 10 kohms.




........... Phil

 

[Legend]

"Legend" <





** Only a "flying" guess - but try 10 kohms.




.......... Phil

thankyou Phil

 

[Legend]

Legend - You are a clueless idiot.

the only clue you teach me is how to abuse
- so you yourself cant know anything of electronics
I am here to learn - you teach nothing

you are the boss and I am nothing - so you are the boss of nothing

 

[Franc Zabkar]

What I want to do is to try and discourage you from messing
about with aircraft electrical systems. You may cause problems
with other items in the aircraft and at 10,000 feet you tend to
find your options are limited.

All he wants to do is to plug an attenuator into the headphone socket.
The worst case scenario is that he'll place a S/C across this output.
As headphone outputs use a series resistor, a S/C would be harmless.
If an aircraft's design can't tolerate a potential *problem* such as
this, then it should be taken out of service immediately.

You can't just park the thing and
call the RACV. There are a _whole stack_ of safety regs. about
who may work on aircraft and what training they need and that's
for a very good reason.

That's what I would have thought, so it came as a shock when I saw the
kind of repair work that came out of an authorised workshop in
Bankstown not long ago. A friend who is an auto-electrician and a
pilot had a faulty landing light (xenon flash?) and traced the fault
to the strobe controller. A repairer at Bankstown charged him $700 to
replace one of the three trigger transistors and did one of the worst
soldering jobs I've ever seen. After installing the controller, this
same landing light still did not work, so the unit went back to the
workshop. The technician set it up on the bench, without a load, and
"demonstrated" that it was faulty. Fortunately my friend was not
stupid, so when he brought it to me to test, we found that it worked
fine, with a load, on my own bench. The actual fault was subsequently
traced to a shorted lamp holder in the aircraft.

Admittedly this is my only experience with aircraft service, but if
this incident is indicative of the quality of work that comes out of
an authorised repairer, then it's no wonder that aircraft fall out of
the sky.

You'll do what you want to do and that's fine by me but I do
have some knowledge of this area and my advice to you
is don't monkey with the aircraft - I'm sorry if that's not what you
wanted to hear - perhaps you shouldn't have asked.

Mike Harding

- Franc Zabkar

 

[Phil Allison]

"Franc Zabkar"

Admittedly this is my only experience with aircraft service, but if
this incident is indicative of the quality of work that comes out of
an authorised repairer, then it's no wonder that aircraft fall out of
the sky.

** I was given the hostie's mic from a Fokker F27 Friendship to fix a few
years back - an original, Dutch, 1960s pushbutton job like you see in
taxis.

Was I supposed to be "authorised " to do that ?

I suppose that mic is considered part of the on board safety gear.



.............. Phil

 

[Mike Harding]

All he wants to do is to plug an attenuator into the headphone socket.
The worst case scenario is that he'll place a S/C across this output.
As headphone outputs use a series resistor, a S/C would be harmless.

You are probably correct. But maybe (for example) his
camcorder is pushing a low level noise signal of a few
MHz out the mic in socket and that signal has now been
connected into the aircraft electronics perhaps causing
degradation in the sensitivity of radio receiving equipment?

Who knows?

And given the OP could not even make an educated
guess at resistor values for this application he really
should not be messing with aircraft systems in any
regard.

Mike Harding

 

[Franc Zabkar]

You are probably correct. But maybe (for example) his
camcorder is pushing a low level noise signal of a few
MHz out the mic in socket and that signal has now been
connected into the aircraft electronics perhaps causing
degradation in the sensitivity of radio receiving equipment?

Who knows?

And given the OP could not even make an educated
guess at resistor values for this application he really
should not be messing with aircraft systems in any
regard.

Mike Harding

Yeah, headphones can be lethal.
http://www.sandpoint.com/off_the_cuff/headphon.htm

http://groups.google.com/[email protected]&output=gplain
http://www.darwinawards.com/darwin/darwin1997-13.html


- Franc Zabkar