# Bad Amp RCA Input



## AndyFL777 (Dec 19, 2013)

Hello everyone:

I'm doing an amp install (Rockford Fosgate P300) in MONO to a single sub and have a few concerns. 

The amp was given to me and it seems the Left RCA Input is bad. When I connect either one of the RCA cables to the *Right Input *the amp sounds normal, but when the Left Input is connected, there is no sound output at all. The fact that either RCA works fine on the Right Input make me to the believe both RCA connections' are good. I'm using the RCA pre-out connections from the speaker wire outputs, in other words, a clean, un-amped signal.

Being I'm running this in MONO, Am I missing a lot of sound output by not being able to have both RCA connected to the L/R Inputs? Is my sound output 50% less being only the Right Input works?

Kindly appreciate everyone's input and/or responses.


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## Bloodyjames (Dec 7, 2013)

Well their could be many reasons why that particular channel doesn't work. It doesn't exactly have to concern the RCA's. The channel could be blown. You would have to open up the amplifier if possible (note it may void warranty) and see if their are any leaks or burns on the board.


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## Jepalan (Jun 27, 2013)

You *may* be losing power. Some monoblock amps are just two-channel amps that are bridged internally.

If yours is a true monoblock, then the input jacks just go to a mono summing circuit and there is no harm in just using one input. You can check if your amp is putting out full power using a volt-meter. 

Does it sound good? Does it get loud with gains properly adjusted? No harm in just running one jack otherwise.

It is not uncommon for an RCA input jack solder connection to crack loose from the PCB. This can be a pretty easy fix if you are comfortably with a micro tip soldering iron. Open it up and take a look where the RCA solders to the PCB - wiggle it a bit and see if a leg is loose.


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