Using a Variac like this old Staco model allows you to vary the level of AC voltage coming through. Most Variac users prefer to keep the voltage around 110 to 115.
As a lifelong musician, I’ve had to find a way of surviving on the cheap. After over a quarter century in the biz, I went from qualifying for government cheese to a solid taxpayer, yet I still can’t help but economize whenever possible.
Years of Rig Rundowns combined with basic gear envy had me hankering for a power conditioner/voltage regulator for ages. I didn’t pull the trigger until now, because it felt a bit like buying the $3 bottle of water when you’re standing next to a drinking fountain. Sure, the expensive option is probably better, but free is free.
At a session last week, I was the only player (other than the drummer) plugging my gear straight into the wall at the studio. The deep shame burned an indelible “I” for “incompetent” on my fragile heart. Still stinking of ineptitude, I made a solemn vow then and there that I would never again feed my beloved amps unconditioned power and risk damaging their tube-y goodness. But first, some research.
In an interview with Popular Mechanics, Van Halen told how he discovered and used Variacs—initially a trade name for a brand of variable auto-transformer, but now used generically—to produce the tone that was in his head. In the article “How Eddie Van Halen Hacks a Guitar,” he explains:
“I’d bought another Marshall amp, and I had no idea that it was actually a European model. I plugged it in, and I'm waiting for it to warm up and thinking, I got ripped off here, there’s no sound coming out! Pissed off, I came back an hour later to give it another shot. I’d left the amp on the whole time. I didn’t know it was set on 220, so when I turn my guitar on it sounds like a full-blown Marshall, all the way up, except really, really quiet. That was when I realized there was something going on with the voltage ... so I went down to a place in Pasadena and asked if there was some kind of industrial-size variable transformer that would let me adjust voltage, and they introduced me to the Variac. It's just a huge light dimmer. I plugged it into the amp and controlled the voltage from that. That became my volume knob. I would set the voltage depending on the size of the room we were playing, getting all that feedback at any volume.”
Once I knew what I needed, I did the usual predatory gear hunting. Regrettably, the models that had everything I wanted cost more than I was comfortable spending. So, I focused on industrial Variacs. I bought an old Staco 3PN1010 Variac on eBay for $64 (including shipping). This thing is built like a battleship and retails for a whopping $750. It will last longer than I will.
Here’s the rub: The Staco has a dial that lets you control what percentage of the electrical current you want, but there’s no voltage readout to know how many volts you’re getting. And that’s important, because if you accidentally turn the wall voltage up, you could fry your amp. So you have to use it with a separate voltmeter. I didn’t want to constantly be shoving voltmeter leads into outlets for testing, so, for a mere $8.99, I bought a voltage measuring monitor that gives me a clear blue digital readout in real time. I also bought a 3-way, T-shaped adapter ($3.33, thank you, Amazon Prime). Now I have a flat-screen digital read in the center plug telling me voltage, plus two open outlets for my amps.
Grand total: $76.32
I’ve been using blackface Fender amps since I was 15. Back then, the standard AC voltage was 110. Now the outlets in my home run between 124 and 125, which explains why my old amps would sound great in one venue then bad in the next. Now, every amp I have sounds way better with sweet natural compression and less noise and heat. I can use bigger amps for smaller gigs and just crank down the Variac to a modest 80 percent to get the sound I’m after in any room.
Now, when you turn the AC voltage down, you’re turning the filament voltage down as well. The tubes need to be heated to at least 6V AC or it will cause cathode stripping. That’s what the 6 in 6L6/6V6 means. You can do it and it will sound great, but everything sounds great on the edge of blowing up. Play it safe and keep that voltage around 110 to 115 and your tubes are going to last longer.
People told me for years that power really makes a difference, but I was too cheap to do anything about it. Now that I have, I’m kicking myself for not doing it earlier. But Variacs may not be for you: Low power works well with vintage-style amps, but digital gear likes a clean 120. Regardless, it’s worth exploring. You can take control of your power but you don’t have to spend a fortune to get there.