Battery Drain Since New Install-Mercedes 300D

I have a 1983 Mercedes 300D, and after having a new head unit and powered sub installed, I'm getting a significant battery drain (1.5 amps).

Unplugging the head unit and unhooking the sub from the battery did not resolve the problem.

Pulling the fuse associated with both the radio and power antenna normalizes the power drain.

Does this make any sense? Some people have suggested that the installers may have "tapped in" to the antenna wire to wire the sub, and that the antenna wire is always hot, even when the power is off.

Any suggestions? I'm at a loss, and want to have some ideas before I start pulling wires to isolate the source.

Thanks in advance for your input!

if you had someone install it ask them what they did, there is a good chance that they may know.

They claim there's nothing related to the stereo, especially since leaving amp/sub and head unit unplugged doesn't solve the problem.

Sounds like something is staying on.

is the amp in you powered sub where you can see it to figure out if it is staying on? if it is there should be a indicator light that tells you when its powered up.

I dont know about you, but I wouldnt be tracking down a drain. The car would be back where the install happened. If you didnt have the problem before it was put in, they would finding out what is left on. But something is staying on.