Originally Posted by parapaul
If it's just from one speaker it's almost 100% down to the wiring.
I'd then take the door card off and check all the wiring to and from the problem speaker, make sure all your connections are as good as you thought.
Few things to consider:
1- Swap the RCA bullets. Red (R) RCA bullet to L amp input and L RCA bullent to R amp. If the noise goes to Right speaker, than problems is somewhere b/w HU output and amp input.
2- If the outcome of step one is negative, i.e noise is still in the same speaker, then problem is somewhere b/w output of amp and car wirings.
Follow what Paul said.
3- If you cannot troubleshoot it from the above, then switch the mids to channel 3/4 and subs to channel 1/2 and see if noise disappears.
4- Also check your left tweeter if none of above helps you.
On a side note, do you think your gains are correct for L7 mids?