i understand all that, i have used 4k7 as i need at least 1.4v at the output as I am passing the signal thru a bridge rectifier to get a DC output (as the line current is AC). If i reduce this value, my output voltage quickly falls to zero.
What about if i scrap the bridge and go for a precises ac-dc converter using two op-amps? i have a circuit that will convert whatever the ac voltage, but to a dc, so no need for the 1.4v offset?
But will this rectifiy my problem? I may well still get the hum?