Headset audio to personal earphones
 

I know this has been discussed before but I am a bit puzzled at why some personal earphones work with my 1/4in mono to 3.5mm stereo jack and others do not. I have a set of Bose QC20s that work great with this arrangement but I have a couple of pairs of JBL and Sony earbuds that don't work with the latter only working if you turn the volume on the audio control panel to max.

I fly a 777 if it helps.

Thanks :ok:

I am guessing that there is an incompatibility with the 3.5mm jack and some earbuds.

I presume you have a lead that goes from a male 1/4" jack to a female 3.5mm socket? And you are plugging your earbuds into the 3.5mm female socket?

Some earbuds have volume controls or microphones, and these use a modified 3.5mm jack. A normal stereo jack has a tip contact and two ring contacts along the pin separated by insulating rings. Jacks with built-in volume controls or mics have a tip contact and three contact rings along the pin.

What might be happening is that the normal stereo 3.5mm socket on your lead is shorting out one or more of the rings on the earbud plug. Your are only hearing anything via the signal "finding" an alternative path through the impedance of the mic or volume control or other circuitry.

If I am right, you will need to solder a four contact 3.5mm female socket onto your adapter lead, and connect to the audio connections, leaving the fourth control connection unconnected.

Alternatively, it could be an impedance problem. This is the 'resistance' of the headphones, as seen by the amplifier. If you plug in phones/ buds of too low an impedance, the audio amplifiers feeding the socket might not be able to supply enough current to operate the buds - hence your very low sound level. See if you can look up what the impedance of your buds is, anything at or above 600 Ohms should be OK. Anything lower than that might be your problem.

I don't have the Ohms symbol on my keypad, but it looks a bit like a horseshoe with the open end at the bottom.

I don't have the Ohms symbol on my keypad, but it looks a bit like a horseshoe with the open end at the bottom.

The character is the Greek upper case omega - Ω.

Some useful techniques for the PC (the Mac, no doubt, has equivalents) to access the extended character set:

(a) find the character map program (absolutely essential if you need to use the extended character set routinely). Windows\system32\charmap on my current system but in a similar spot on earlier versions - make a desktop link to the program so that you have it neatly to hand forever and a day. I use it very frequently and, if you don't, then you are denying yourself a great feature of your computer. Find the appropriate character, copy and then paste it. Nothing to remember and absolutely easy peasy.

(b) learn a bunch of alt codes which do the same thing via the numeric keypad (the hard way).

(c) learn a bunch of unicodes - ditto

(d) use one of the net equivalents to (a), eg https://unicode-table.com/en/

In respect of the OP's concern, do be careful about design considerations and what your patch cable might be doing to the system .... suggest you talk to your tech services electrical engineering folk before you make up such things for use on the line.

I have read tales of charmap's causing problems - none ever in my experience of the program over many years but I note the concern for what it may be worth.

Thanks for printing the Ohms symbol John :ok: So the OP is looking for impedances of 600Ω or higher for their phones/buds to be compatible.

I know where the extra characters are on a PC, and I also know some alt codes, (e.g. for fractions etc), but haven't found them on my iPad yet.

Can't help with the iPad, unfortunately ...

However, Mr Google appears to provide some guidance links such as How to Type Special Characters and Symbols on iPhone or iPad (igeeksblog.com)

Thanks for the replies. I am indeed connecting the earphones to the 3.5mm female socket port of a 1/4" mono to stereo jack. I thought there was perhaps an incompatibility issue with the mic that comes with the earphones that are designed for handsfree phone use but the Bose earbuds have the same, so I discounted that. I wonder if it is perhaps impedance related?