Okay here is what I'm trying to do:
I build the audio amplifier based on TDA2003 (Pic attached) which is working fine with my xm-radio.
But here is another thing I'm trying to do. I have a gps unit where I removed speaker and put a headphone jack instead. Now I am trying to connect it to this amplifier and it doesn't work. The thing is that amplifier uses ground as one side for input and gps doesn't have a grounded output. It is about 86KOhm between each output wire and actual ground.
So is there is anyway I can connect a device like that to an amplifier?
My Garmin 495 GPS "*****-in-the-Box" speaker is bridged (push-pull floating). To interface it to a single-ended audio input in my airplane's audio panel, I used a simple audio transformer (off an old modem); floating primary; one side of the secondary is grounded...
That would normally work, but the idiots at Garmin managed to design-in a horrible common-mode noise from the switching power supply into the the GPS's ground lead. If you take the audio single-ended from only one side, the ground-loop contaminates the audio. If you use the transformer, and take the audio differentially, that gets rid of the ground-loop.
The capacitor is in series with one of the wires that connected to the speaker in the GPS unit. The internal wire of the shielded audio cable connects to the capacitor and connects to the top of the volume control of the amplifier.
The ground of the GPS connects through the shield of the shielded audio cable to the ground of the amplifier.
O okay I see now. I tried that - didn't work for me ether. Did it with an audio transformer (thanks MikeMl - would never guess to look at an old pc modem) - working fine.
Thank you guys.
Keep on the good work!