OKAY
Well, I diagnosed the preamp noise. It is not the left channel of my FF800 (i.e, input 1 L) that is responsible for the noise. It is the first preamp in my SCA rack, which is coincidentally closest to the power transformer of the SCA rack! Transformer induced cyclical hum it is.
However, this has only solved a problem I don't know about. I need to try to figure out the larger issue.
Well, I diagnosed the preamp noise. It is not the left channel of my FF800 (i.e, input 1 L) that is responsible for the noise. It is the first preamp in my SCA rack, which is coincidentally closest to the power transformer of the SCA rack! Transformer induced cyclical hum it is.
However, this has only solved a problem I don't know about. I need to try to figure out the larger issue.