Soundstream Rubicon 405

The owner of this amp says at lower volumes
This amp plays perfectly fine ..

When you increase the volume the sub channel has issues he says it makes the sub pop and crackle he's tried 3 different Suns and the amp does it to all
3 of them..

I've checked the amp over 3 different times and everything is testing fine ..

Anyone have any ideas what might cause this or where to begin checking ?
 
Only thing that I can see that it's doing is the sub channel has very low output..

So I'm assuming he is turning the volume way up on his car and also the bass boost ..

Im going to clean all switches in this amp to see if I can get the output to increase .. ..

As of right now the gain on the amp is 3/4 of the way up and the head unit is all the way up and the amp barely has any output out of the sub channel
 
Ok if I use the mono inputs to the amp for the sub channel I get very low audio out of the amp ..

If I use channels 1 and 2 as the input to the amp I get more output from
The amp but still not where it should be ..

I'm guessing the the switches are defective..

I cleaned the switches 2 times and rocked them
Back and fourth 30 to 40 times each ..

Should I try cleaning them again or are the most likely defective after 20
Years ?
 
They're likely oxidized. There are two types of switches in those amps. The standard slide switch that cleans relatively easily by working it back and forth. The other switch is a 2-position slide switch that's built like a toggle switch internally. Those are harder to clean by working them because the contacts don't rub together. They simply drop together and there is no cleaning action. Those can be cleaned if carefully disassembled but you can probably buy new switches from J&R.

Before you order, you can jump the terminals that are supposed to be connected in each position to eliminate the switch as the problem.