FP11 line preamp self noise

Date Updated: March 2, 2018 FAQ #533
I've recently purchased a pair of the Shure FP11 mic line preamps. I've noticed self noise (hiss, static) added to the mix. Currently, I am running a pair of condenser mics through the FP11's into a Sony DAT deck. I have troubleshot the cables, equipment, etc. and have found that this interference is coming from the FP11. Any ideas of ways to remedy this problem?

Being an older design, the FP11 would need to be completely redesigned to lower its self noise. Sound Devices is a company that sells a low noise preamp, like the FP11. The model is MP-1.