wire for measuring audio voltage signal

[shanmei]

I need to measure the audio signal/voltage from the phone.

The audio jack node A is connected to phone.
Node D is short to oscilloscope to measure voltage.

Can the node B and C are connected together? I just want to get the audio signal.

Or any other adapter or wire that I can use to directly connect the phone audio interface with the oscilloscope?

Thanks.

 

[BradtheRad]

Your red cable appears to have a banana plug. It is not likely to fit into the 1/8 inch phone jack. Even if it does it will be difficult to make good contact with the small tab inside which carries a signal. The banana portion must not touch the ground ring.

You need a total of two wires connected between your scope and the device: (a) signal-carrying wire, and (b) ground (return) wire.

Are you certain the adapter cable carries audio from the phone? Is it a portable phone? (If it is a landline then you need to beware of 50 or 60V on the wires.)

 

[Relayer]

Hello shanmei,
Looks like you're going to use an Video/Audio plug to connect to your phone. You need to identify the correct output socket to measure the audio on a CRO.
You will also need to connect to ground on your scope.
Here's a link to pin outs on an Audio/Video plug. Look at the last column, as this pertains to mobile phones:
**broken link removed**
I hope the above helps.
Regards,
Relayer

 

[shanmei]

Are you certain the adapter cable carries audio from the phone? Is it a portable phone? (If it is a landline then you need to beware of 50 or 60V on the wires.)[/QUOTE]

Yes, I checked that.

The adapter cable does NOT split out the left audio, right audio & microphone, and only duplicates them. That is not I want. I just want to split the three signals.

It is a cellphone. Thanks.

 

[Relayer]

The adapter cable does NOT split out the left audio, right audio & microphone, and only duplicates them.

Are you referring to the adapter in your picture? If so, the three sockets DO have their respective signals split. i.e. Right, Left and Microphone.
Next you wrote:

That is not I want. I just want to split the three signals.

As I've already stated, that adapter will separate each signal.
In your original post:

Can the node B and C are connected together?

No. You're just looping the wire back on itself.

If you're wanting to measure the right channel for example, you first need to identify which socket is the right channel output. You need to get a plug to suit the socket, then connect your CRO probe and ground to the back end of the connector.

If I'm still not correct, then you need to explain exactly what you want done.
Regards,
Relayer

 

[Mattylad]

Take your cable (or get another that's a bit longer) chop the socket end off and bare the wires.
Check for continuity to see which one goes to which pin on the 3.5mm plug.

Fit a BNC plug to the pair that give you the audio you need, if you want left and right then you will need to add a BNC per side.

Time to get the soldering iron, offcuts of wire and some solder out of the draw and make an adapter.

You may need to add capacitors for isolation and\or a resistor for loading.

 

[shanmei]

Thanks, Relayer.

Now I know that for the adapter on the left figure, the three sockets have their own left, right and microphone signals.

- - - Updated - - -

Mattylad, thanks for the detained explanation.

 

[c_mitra]

Now I know that for the adapter on the left figure, the three sockets have their own left, right and microphone signals..

I believe that the female adapters (on the left figure) are phono jacks and they carry the common ground with them. If you use a phono jack, you will connect to both one common ground and the respective signal (l, r or m).

I do not think you will have to do any butchery.