Api Power wedge 114

Does anyone know if its ok to plug a dac,cd transport,or a preamp in one of the iso outputs?
ML 360 dac,380 preamp,and wadia 20 transport.
Of course a tuner also.
It always measures about 4-5 volts more than the other amp outlets at 120 or so.
Even if you start to plug stuff  in the voltage only drops a volt.
Its lower during day when ac grid drops outside.
At night its goes back up.
Will the 125 or 126 volts at night hurt those front end devices?

Or just use the amp outlets which just follows grid voltage 119 day 122 night.

I heard that using isolation transformer for digital and preamp can block noise from amp side.


Update on above.
I forgot to mention if I plug several things in one outlet the volts will go down much lower.
But that defeats the purpose of the isolation!