Music Input

I have a Guardian iPad mini mount which I am trying to connect with my PS PAR200A intercom. The wiring diagrams are kept on-line at Guardian's site. The power side of thing is fine, but there is nothing concerning the audio - which SHOULD be simple.

The intercom (PAR200A) expects audio left, audio right and audio lo. The supplied Guardian cable has a 3.5mm music jack which fits the iPad headphone socket. It has audio left, audio right, ground and mic - this should be the configuration from the jack tip inward. The 2 audio channels are fine (red and white). Ring 3 doesn't seem to be connected to anything. Ring 4 is connected to purple with 6.7k resistor. The final wire (black) gives 6.7k across the purple wire but nothing on anything else. I can't even work out a wiring that exhibits these parameters!! I have also found a note on the PAR200A diagram saying NOT to connect Audio lo to ground as it is a differential music input. Well that's fine because neither of the "spare" wires is grounded - but where DO I connect Audio Lo?

Any of you avionics gurus throw any light on this.....

This might help:




Audio "LO" is identified as "GROUND" on the plugs.

Thanks. I had that. I just couldn't make out the wires vs the rings ........

I think I have it sorted. I found that the third ring is, in fact, attached to a green wire (must have been going mad last night). I had assumed that ground would be black . Anyway, I now have 3 wires connected to the tip and the middle 2 rings. The base I don't need as (for iPad) that is mic. So I believe I connect those to Audio L, Audio R and Audio Lo

Now I know why I have had my harnesses made by professionals before

As gill mentioned audio Lo and ground are both grounds. However, it is important that the connection from the Ground ring only goes to the music device and is NOT also attached to the mounts ground plane. This is what PSE was warning about. That audio lo, while technically a ground, needs to be isolated from the general airframe ground, lest you get noise and static due to that differential design. This is just like your headset jacks, where you use plastic or fiber washers to keep the grounds isolated.

Larry

Understand that, thanks.

Now back to the crimper ...................