When you use the AC adapter (where you say the noise goes away), is the AC Adapter plugging into the AC Adapter power jack on the empeg, and are you plugging it into a wall socket to get its power in that case?
I have tried going through the sled wiring I have rigged up as well as the power jack with similar but not identical results. The noise is slightly quieter with the power jack even with the sled outputs still connected. If I switch to on board RCAs, the noise gets quieter but this is just due to gain differences. When on AC, the power is always from the Empeg adapter to either of these two connections.
And when you use the 12v cig lighter source, is it connecting to the car dock continous power wire (which IIRC is yellow)?
That is correct. The ignition sense is also connected to +12 volts to keep everything running.
I wonder what would happen if you got a 2.5mm connector and wired the power source from the 12v cig lighter powere into the AC Adapter jack. In other words: Same power source, but, different jack on the player. Wonder if the noise would go away then or if the noise stays.
See my answer above. The noise stays.
My theory is that the noise occurs because of a ground loop between your portable amp and the empeg when they are both powered and grounded from the same spot. The reason it goes away when you use the AC adapter is that it's powered and grounded from a completely different place than the audio amp in that case.
There does seem to be something to your theory, but seeing as how wiring the Empeg as intended produces the noise, it begs the question as to what changes can be made? I just tried connecting a digital recorder to the output while on DC, there was no noise. A couple of the units I have are making this noise in what is said to be a professional install but I unfortunately do not have access to them, just my makeshift test setup.
Thanks again Tony!
Stu
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