How to headphone jack on bike

Hello everyone,

I have just discovered your forum here while searching for some info so I am a newbie with a problem to solve. It sure looks like this is a great place to ask for this kind of help, lots of very knowlledgeable folks here. If this has already been asked, I apoligize, I tried searching for about a half an hour with no real luck.

What I want to do is put a headphone jack (or some kind of plug for earbud or helmet speakers) on my BMW K1200LT motorcycle. I have removed the rear top case that contained the rear speakers and want to use those leads to connect to the helmet. I know that the stereo jack is only a three conductor plug that uses a common negative. I have been informed that my head unit will be damaged if i share or combine the left and right neg. from the head unit. When using this plug I will most likely fade all the sound to the back speakers from the head unit controls and than adjust the headphone listening level from the head unit as well.

I have recently started learning about electronics so you can let be have it with both barrels with the technical stuff and I will make it my mision to research and understand.

I found a wiring print on another site that holds promise, I just have to understand the last parts function to be comfortable with it. This is what that print says to do....put the left and right spkr leads in series with an 56 ohm 2 watt resistor and connect to the plug (this part I understand). Do not use the left and right neg spkr leads at all but instead run a ground wire from the plug to chassis ground in series with a 16v 220 uF polarized capacitor connecting to pos side first than to ground. Its the function of the capacitor in this circuit that I have not yet learned enough about to understand what it is doing. You see I haven't studied the audio electronics yet and really don't know what type of current, voltage or power etc. will be flowing into the capacitor at that point in the circuit. I know caps won't let dc current thru at all and will slow the flow of ac.

Any help or advise you folks can offer will be much appreciated. I thank you for taking the time to read this.

Pat

hi,

the above wiring should work....the resistors limit the power to the headphones for each channel, the capacitor provides dc isolation so as not to damage the radio itself, but still allow an ac(audio) ground for the headphones.  you may want to experiment with the value (larger) for the capacitor....should give more low end as value increases.  hope this helps.

mark

Thanks for the info Ween.

When you say dc isolation, you are referring to dc that could flow from chassis thru the neg back to the head unit and cause damage?

Thank you

Pat

thanks Ween,

Why does the capacitor have to be polarized for use in this circuit? I understand why some capacitors have to be polarized so they function (electrolytic & tantulum). Just wondering.

I ordered and recieved the parts just before I got your advice about playing with the value of the cap. I have never done any soldering yet and am still not sure how I will build this circuit yet (learn to solder  ). Do you have any tips. Is there an easy way to be able to swap out and try different caps.

Thank you for your time,

Pat

shouldn't matter about the capacitor being polarized, although a polarized one of a larger value is easier to find.  just wire the circuit up temporarily and experiment with the values

mark

hook the negative lead of the capacitor to ground.  use the positive lead as the common for the headphones.  i maybe dating myself but the circuit being made as described above is a floating ground adapter.  used to be needed on old booster eq/amps before the circuitry was designed in them

mark

thanks mark

It will be a couple of weeks till I get time for this project, I will post here again and let you know how (or if) it worked. Hope it don't blow up.

Thanks for your time

Pat

Hi folks,

Well its been more than a couple of weeks but I finaly got around to doing this project.

I am disapointed in the results. The sound just isn't right, you can't hear the vocals well at all on most songs. I inserted a second capacitor of the same size in paralel with the first and that did'nt seem to have any effect. As a test I reconnected the factory speakers and they sounded alright so the problem must be caused by the above circuit.

Every thing is hooked together temperarly right now using posi-lock connectors.

Does anyone know what I could do to get better audio out of this set up?

Thank you for your time,

Pat