The charts below shows the effect of 120 volts into the 105v-115v tap of
a power transformer.
The first chart shows the voltages as they are without the variac attached.
The second chart shows the voltages as they are with the variac installed
and set at 110v out.
I recommend setting the heater voltage to 6v-6.3v and you should be in the
right range for the amp.
