Adcom car amplifiers question

[azvrt]

Adcom car amps have RCA shorting plugs which must be used according to the manual. It is stressed multiple times in the manual. It does not say why.
Would anyone know why, and more importantly, what could happen when powered on without them ?

I powered on a GFA-4302 earlier today but I might have done so without one of the two plugs, can't remember for sure. Could I have caused damaged ? It seemed to be playing music fine.

Hopefully someone can set my mind at ease, I'm really afraid I might have caused damage ?

 

[Perry Babin]

The amp is designed for balanced inputs. Without signal on the negative RCA, the amp may not have the right gain or may not be able to prevent ignition noise (guessing at possible issues). Installing the jumper in the negative RCA is like switching a SS amp from balanced to unbalanced.

 

[azvrt]

Thanks.

So no harm done if I accidentally did use it without shorting plugs earlier today ?

 

[Perry Babin]

Not as far as I know. You can make shorting plugs. Cut an RCA cable, strip it and twist the center conductor and shield together. If you have male RCA connectors, solder the shield directly to the center conductor.

 

[azvrt]

Yes this amp misses one, so the former owner made an extra one himself. As I first thought these plugs were just to cover the unused inputs, I removed the ugly looking self-made plug. I think I tested the amp with the plug removed. Later I saw the plug had the center shorted with the shield, and contacted the former owner that's when I learnt they weer not plugs just to cover unused inputs but shorting plugs.

As long as I did not do any damage, that makes me happy.
Any idea whether these plugs can still be obtained from Adcom. I heard they quit all support on car audio products ? I am also missing a couple of screws for the speaker terminals.