Alpha 8100 Operating Manual page 23


Low Voltage vs. Current Draw
If either of the two low voltage taps is used, be aware that the amplifier is normally shipped
fused with 20A/250V fuses. You may want to consider replacing these with 25A/250V "slo-blo"
fuses for very low line voltages (less than 100 volts). If you do, be aware that the higher current
at the lower voltage will significantly warm the power cord for the amplifier. The cord (as well
as fuse holders and some internal connectors) are operating near their maximum ratings due
to the current demand at lower voltages. Be sure that the AC cord is not coiled too tightly or
placed where normal air flow is restricted because the cord could overheat. If other equipment is
drawing current from the same circuit as the Alpha 8100, then the considerations in section 4.2.3
should be taken into account.
High Voltage and Tube Life
At the high end (sometimes encountered when using poorly regulated generators) the plate
voltage and tube heater voltage may be too high. If voltages above 250 volts are applied for any
length of time, the lifetime of the tubes may be reduced. If this is your situation, the first line of
defense is to contact your utility company and ask if they can reduce your line voltage. If this is
not possible, you may want to consider placing your own step-down transformer in line between
the AC outlet and the amplifier. If this is necessary, a transformer with at least 4-kVA rating is
required, due to the nature of the current waveform in the primary. Another choice for voltage
control, a ferro-resonant voltage regulator, is an expensive solution, but is a good way to stabilize
primary voltage.
Note: If you intend to operate the amplifier on any of the 90 - 130V settings, the two lower 2
amp fuses on the rear panel will have to be changed to 5 amp to allow for the increased in-rush
current.
ALPHA 8100 OPERATING MANUAL
www.alpharadioproducts.com