
Just say no to cheaters!
Catching an unintended buzz with your two-amp set up? Here's why, and what to do about it.
Ground loops are all around us. They exist almost everywhere electrical circuits are connected. Most go completely unnoticed, but your guitar rig has dozens (maybe hundreds, depending on the sharpness of your pencil), and, when provoked, they can cause or contribute to all sorts of bad behaviors. Fixing a ground loop in your pedalboard rig incorrectly can be hazardous to your health.
"Ground" is an electrical concept that indicates a reference point from which all voltage potentials in a circuit are measured. Ground serves as voltage-zero for a circuit, and when drawn on a schematic, is a platonic ideal that pins everything connected to it at that zero potential, whether it's sinking 1 mA or 1000 A. The real world is not as kind.
A ground loop is created whenever two electrical circuits that theoretically have the same ground potential have a non-zero potential between them in practice. While there are several means of creating ground loops and driving noise in them, let's give a concrete example you've likely encountered before. Begin with two guitar amps, each connected to power via a 3-prong (grounded) cable. Each amp has one path to ground and is content to sit there and amplify with as little noise as its design and manufacture allows. Each amp's input jack is referenced to its local ground, and each preamp amplifies the difference between your guitar and that local ground. If you connect those amps together with a guitar cable to your board (via a passive Y-cable or a second input jack), you are creating a new path for ground currents via the shield of the guitar cable.
A safer and more effective solution is an isolation transformer at the input of your guitar amp.
This would be no problem at all in a world with superconducting bullet trains, electric car batteries, and guitar cables, but we live in a world where the relative conductivities of guitar instrument and power cables are less than super. As those wayward currents travel from one amp to the other, they develop a potential on the shield conductor of the cable that is different from the local amp's ground. This potential is essentially a new signal on top of ground that is made possible by the ground loop. Instead of the first preamp amplifying the difference between your guitar and the local zero volts ground level, the preamp tube is amplifying the difference between your guitar and the ground loop potential. Because the predominant currents in your guitar amp are related to rectifying the 50/60 Hz mains voltage, the ground loop is predominantly 50/60 Hz and related harmonics. So, presto, a hum is born.
Now, each amp has two paths to ground: one through its own power cable to electrical ground and another via the guitar cable to the second amp and its power cable to electrical ground. All the ground currents inside the first amp are seeking ground as best they can, and while most of that current would prefer to ride the wide and well-conducting highway that is the local power cable, a few may venture out on less-traveled paths, through your guitar cable and into the second amp, finding ground via the second amp's power cable.
What can be done? You will find guitar rigs where one of the amps has what we affectionately call a "cheater" on its power cable. This adapter is intended to adapt modern, grounded power cables to older, ungrounded outlets, but is often misused in guitar rigs. They are usually placed there by misanthropic club FOH engineers trying to fix a hum problem by breaking the ground reference for the amp. By breaking this ground, you can break the ground loop, but you also break its safety ground. Should some of those tube-driving 500V electrons touch the amp's chassis, they may not immediately blow a fuse and instead seek ground wherever they can find it—with some traveling down the guitar cable to the second amp and some traveling down the guitar cable, through the board, to the instrument, through the bridge, through the strings, and into whatever guitar player is unfortunate enough to be playing "Brown Eyed Girl" that evening.
A safer and more effective solution is an isolation transformer at the input of your guitar amp. The transformer can transmit your guitar signal without a ground connection, while maintaining the safety ground of the amplifier through its power cable. This will keep ground currents where they should be and keep them from developing into hums and buzzes in your backline. Isolation transformers, like the Ebtech Hum Eliminator and the Lehle P-Split, can be found for $100 to $180. Please, don't ever use a cheater. Your nervous system and Van Morrison fans will thank you.
- Bass Bench: Chasing Grounding Gremlins - Premier Guitar ›
- Tone Tips: Keep It Quiet, Part 2 - Premier Guitar ›
- Got Noise Issues? It Could Be Your Pedalboard's Power Supply ... ›
Do you overuse vibrato? Could you survive without it?
Vibrato is a powerful tool, but it should be used intentionally. Different players have different styles—B.B. King’s shake, Clapton’s subtle touch—but the key is control. Tom Butwin suggests a few exercises to build awareness, tone, and touch.
The goal? Find a balance—don’t overdo it, but don’t avoid it completely. Try it out and see how it changes your playing!
The author dials in one of his 20-watt Sonzera amps, with an extension cabinet.
Knowing how guitar amplifiers were developed and have evolved is important to understanding why they sound the way they do when you’re plugged in.
Let’s talk about guitar amp history. I think it’s important for guitar players to have a general overview of amplifiers, so the sound makes more sense when they plug in. As far as I can figure out, guitar amps originally came from radios—although I’ve never had the opportunity to interview the inventors of the original amps. Early tube amps looked like radio boxes, and once there was an AM signal, it needed to be amplified through a speaker so you could hear it. I’m reasonably certain that other people know more about this than I do.
For me, the story of guitar amps picks up with early Fenders and Marshalls. If you look at the schematics, amplifier input, and tone control layout of an early tweed Fender Bassman, it’s clear that’s where the original Marshall JTM45 amps came from. Also, I’ve heard secondhand that the early Marshall cabinets were 8x12s, and the roadies requested that Marshall cut them in half so they became 4x12s. Similarly, 8x10 SVT cabinets were cut in half to make the now-industry-standard 4x10 bass cabinets. Our amp designer Doug Sewell and I understand that, for the early Fender amps we love, the design directed the guitar signal into half a tube, into a tone stack, into another half a tube, and the reverb would join it with another half a tube, and then there would be a phase splitter and output tubes and a transformer. (All 12AX7 tubes are really two tubes in one, so when I say a half-tube, I’m saying we’re using only the first half.) The tone stack and layout of these amps is an industry standard and have a beautiful, clean way of removing low midrange to clear up the sound of the guitar. I believe all but the first Marshalls came from a high-powered tweed Twin preamp (which was a 80-watt combo amp) and a Bassman power amp. The schematic was a little different. It was one half-tube into a full-tube cathode follower, into a more midrange-y tone stack, into the phase splitter and power tubes and output transformer. Both of these circuits have different kinds of sounds. What’s interesting is Marshall kept modifying their amps for less bass, more high midrange and treble, and more gain. In addition, master volume controls started being added by Fender and Marshall around 1976. The goal was to give more gain at less volume. Understanding these circuits has been a lifelong event for Doug and me.
Then, another designer came along by the name of Alexander Dumble. He modified the tone stack in Fender amps so you could get more bass and a different kind of midrange. Then, after the preamp, he put in a distortion circuit in a switchable in and out “loop.” In this arrangement, the distortion was like putting a distortion pedal in a loop after the tone controls. In a Fender amp, most of the distortion comes from the output section, so turning the tone controls changes the sound of the guitar, not the distortion. In a Marshall, the distortion comes before the tone controls, so when you turn the tone controls, the distortion changes. The way these amps compress and add harmonics as you turn up the gain is the game. All of these designs have real merit and are the basis of our modern tube–and then modeling—amplifiers.
Everything in these amps makes a difference. The circuits, the capacitor values and types, the resistor values and types, the power and output transformers, and the power supplies—including all those capacitor values and capacitor manufacturers.
I give you this truncated, general history to let you know that the amp business is just as complicated as the guitar business. I didn’t even mention the speakers or speaker cabinets and the artform behind those. But what’s most important is: When you plug into the amp, do you like it? And how much do you like it? Most guitar players have not played through a real Dumble or even a real blackface Deluxe Reverb or a 1966 Marshall plexi head. In a way, you’re trusting the amp designers to understand all the highly complex variations from this history, and then make a product that you love playing through. It’s daunting, but I love it. There is a complicated, deep, and rich history that has influenced and shaped how amps are made today.
Lenny Kravitz’s lead-guitar maestro shares how his scorching hit solo came together.
Hold onto your hats—Shred With Shifty is back! This time, Chris Shiflett sits down with fellow west coaster Craig Ross, who calls in from Madrid equipped with a lawsuit-era Ibanez 2393. The two buddies kick things off commiserating over an increasingly common tragedy for guitarists: losing precious gear in natural disasters. The takeaway? Don’t leave your gear in storage! Take it on the road!
Ross started out in the Los Angeles band Broken Homes, influenced by Chuck Berry, Buddy Holly, and the Beatles, but his big break came when he auditioned for Lenny Kravitz. Kravitz phoned him up the next day to tell him to be at rehearsal that evening. In 1993, they cut one of their biggest hits ever, “Are You Gonna Go My Way?” Ross explains that it came together from a loose, improvisatory jam in the studio—testament to the magic that can be found off-leash during studio time.
Ross recalls his rig for recording the solo, which consisted of just two items: Kravitz’s goldtop Les Paul and a tiny Gibson combo. (No fuzz or drive pedals, sorry Chris.) As Ross remembers, he was going for a Cream-era Clapton sound with the solo, which jumps between pentatonic and pentatonic major scales.
Tune in to learn how he frets and plays the song’s blistering lead bits, plus learn about what amps Ross is leaning on these days.
If you’re able to help, here are some charities aimed at assisting musicians affected by the fires in L.A:
https://guitarcenterfoundation.org
https://www.cciarts.org/relief.html
https://www.musiciansfoundation.org
https://fireaidla.org
https://www.musicares.org
https://www.sweetrelief.org
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Producer: Jason Shadrick
Executive Producers: Brady Sadler and Jake Brennan for Double Elvis
Engineering Support by Matt Tahaney and Matt Beaudion
Video Editor: Addison Sauvan
Graphic Design: Megan Pralle
Special thanks to Chris Peterson, Greg Nacron, and the entire Volume.com crew.
Tobias bass guitars, beloved by bass players for nearly half a century, are back with the all-new Tobias Original Collection.
Built for unrivaled articulation, low-end punch, and exceptional ergonomics, the all-new Tobias Original Collection comprises an array of six four and five-string bass models all offered in both right and left-handed orientations. The Tobias range features Classic, Killer B, and Growler models, and each is equipped with high-quality hardware from Babicz and Gotoh, active electronics from Bartolini, and the iconic Tobias asymmetrical neck design. Crafted from the finest tonewoods, Tobias Original Collection bass guitars are now available worldwide on Gibson.com, at the Gibson Garage locations, and at authorized Gibson dealers.
The bass world has been clamoring for the return of the authentic, high-end Tobias basses, and now, Tobias has returned. Combining the look and tone of the finest exotic tonewoods, such as quilted maple, royal paulownia, purpleheart, sapele, walnut, ebony, and wenge, with the feel of the famous Tobias Asym asymmetrical neck and the eye-catching shapes of the perfectly balanced contoured bodies, Tobias basses are attractive in look and exceptional in playing feel. However, their sonic versatility is what makes them so well suited to the needs of modern bassists. The superior tone from the exotic hardwoods, premium hardware, and active Bartolini® pickups and preamps results in basses with the tonal flexibility that today’s players require. Don’t settle for less than a bass that delivers everything you want and need –the look, the feel, and the sound, Tobias.
“I’m thrilled to release Tobias basses, emphasizing the use of exotic woods, ergonomics, and authenticity to the original Tobias basses,” says Aljon Go, Product Development Manager for Tobias, Epiphone, and Kramer. “This revival is a dream come true, blending modern craftsmanship with the timeless essence of Tobias.”
“It’s amazing to see this icon of the bass world return,” adds Andrew Ladner, Brand Manager for Epiphone and Kramer. “These models are truly a bass player’s bass, and true to the DNA that makes Tobias world-class—the ace up the sleeve of bass players around the globe since 1978. Today’s players can find that unique voice and feel that only Tobias can offer.”
For more information, please visit gibson.com.