Written by 4:23 am Amps • 21 Comments

Why You Need a Variac

Steven Stone reveals one of his essential audio tools, and how he uses it to make things better…


If you had an opportunity to peer into any well-equipped mid-20th
century audiophile’s equipment locker, you would most likely find a variac. And
what is a variac? It is a variable output transformer that permits adjusting AC
voltage from 0 to more than 130 volts.

My own variac is a General Radio Corporation type V10. It’s so
old that it was made before the days of three-prong AC, but still works
perfectly. Actually I have two variacs. The other is built into a Monster Power
AVS 2000
. In the AVS 2000 the variac’s output is controlled by a microprocessor
designed to keep it’s output at a constant 120 Volts. I use it to control the
ac to my projector. Besides keeping the voltage constant it also shields the
projector from spikes and brown-outs.

But who, in the 21st century, really needs a variac?
If you use any tube electronics, older solid-state gear, or have equipment that
goes for more than six months at a time without being turned on, YOU need one.

AR-avs 2000.jpg

I use my variac for several essential tasks. Its primary job is
to save me money. It accomplishes this by preventing me from blowing up gear. I
use my variac to power up anything that I haven’t used in a while. Instead of
flipping the on switch, I attach the component to the variac. I set the Variac
to 0 volts output, turn on the component attached to it, and then I gradually
turn the variac up to 120 volts. By doing this I spare any older or less than
fully-charged capacitors in a component from getting a nasty voltage surge,
which could cause them to fail. By gradually re-forming the capacitor, it can
be restored to a complete level without stress.

I also use my variac
whenever I first power up a piece of tube gear that hasn’t been used for a
while. Again, a gradual voltage increase saves the internal parts from the
shock of going from going from off to on. Also when I re-bias a tube component
I usually put it on the variac to insure a steady, repeatable, AC voltage
during re-biasing.


Another use for a Variac is with an audio component made for
the Japanese marketplace that has been configured for 100 volts rather than 115
or 120 AC. With a Variac you can simply dial back the voltage to 100 volts and
your Japanese-rated component will work just as it did back in Japan. Problem
solved, without going into wire-switching or transformer-swapping.

So, if you don’t already own a variac, you might want to keep
an eye out for one in your EBAY, flea market, and garage sale, travels. They
usually go for short money (because most people don’t know what they are) and
are one of those tools that every serious audiophile needs in their equipment closet.

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