Note the two trimmer screwdriver slots, surrounded by blue, in the middle of this phase shifter.
Potentiometers are used for most of the controls on pedals and a lot of other electronic equipment as well. A potentiometer (also known as a pot) is defined as a 3-terminal variable resistor in which the resistance is manually varied to control the flow of electrical current. A potentiometer acts as an adjustable voltage divider. Any control on a guitar pedal that has a knob will typically be controlling a potentiometer, or sometimes a rotary switch.
There is a type of potentiometer called a trimmer (also known as a trimpot) that lives inside of some stompboxes. It typically doesn’t have a shaft that sticks up like a regular potentiometer. Trimmers usually have a slot on top for making adjustments with a small screwdriver. They are meant to be set correctly when installed in a device, and mostly never seen or adjusted by the device’s user. Trimmers can be variable resistors, variable capacitors, or trimmable inductors, and they can perform many different types of functions within a circuit.
“I know what an epiphany it can be to unlock that little extra bit of magic out of an already beloved pedal.”
I get a fair amount of questions about trimmers—often: “Is it okay to mess with that?” There are many pedals on the market that have internal trimmers that can be adjusted by users, to tweak to personal taste. It is handy to be able to dial a sound in all the way, almost like fine-tuners on a guitar. Typical user-tweakable micro controls are for modulation speed and/or width, gain, and sensitivity.
Conversely, there are trimmers built into circuits that I would not consider easily user-adjustable. These include things like bias for time-based effects and setting proper voltages so circuits can function as they should. I’ve repaired quite a few analog delays and flangers, for example, that were perfectly functional! The bias had simply drifted out of its sweet spot. Perhaps the user had gotten too curious and decided to tweak those irresistible little trimmers? Or, more often than not, the trimmers had simply drifted a bit away from their set positions over many years of use, not to mention jostling from being transported to and from gigs. A qualified pedal tech has the right meters and test equipment to get those effects dialed right back in. However, bias can be a nightmare to get back to where it needs to be without some expertise. I understand why these folks thought their pedals were broken. A modulation effect that isn’t properly biased can sound absolutely horrible!
Internal timmers, aka trim pots, come in a variety of shapes and sizes. Look for the slots.
It’s only natural to be curious about the guts inside pedals. Trimmers can add so much extra versatility to a device. If you’re ever unsure which ones are okay to tweak, a good rule of thumb is to ask the builder or the company that makes a particular unit which of its trimmers are okay to fiddle with before you twiddle. In some cases, your warranty could be voided if you do adjustments, so it’s always a good idea to check first.
I know from my own playing what an epiphany it can be to unlock that little extra bit of magic from an already beloved pedal, and I enjoy sharing any knowledge that can help guitarists get the sounds that are most pleasing out of their effects. Perhaps that pedal you planned to trade could be transformed into something you really love with a little twist of a trimmer.
A Deeper Dive
I mentioned resistors several times in this column. A resistor is a passive, 2-terminal electrical component that controls electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.
- Does your favorite stomp have an adjustable trimmer? You can find a list of popular guitar pedals that have adjustable trimmers here.
- To read more about voltage dividers, and how a potentiometer works, check this article out.
- And here’s some great information about trimmers, for further exploration.
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Grammy Award-winning artist Warren Haynes is a cornerstone of the American music landscape, lauded as one of the most formidable and prolific guitarists, vocalists, songwriters, and producers of the modern era. Gibson is proud to announce its partnership with Warren Haynes for the release of his first signature guitar, the Gibson Warren Haynes Les Paul Standard. The Warren Haynes Les Paul Standard from Gibson is available worldwide now at the Gibson Garage Nashville and London, at authorized Gibson dealers, and on Gibson.com.
“I’ve always been a Gibson guy—I got hooked on that sound as a teenager and have been playing them ever since,” says Warren Haynes. “Needless to say, I’m honored to be partnering with Gibson to release my Signature Les Paul Standard. Being traditionally a humbucker guy, I’m really loving the hum-free P-90s. It’s a really cool tonal change, and the boost offers even more tonal options. I’m really enjoying playing this guitar on stage and looking forward to using it in the studio. I’m equally psyched that other guitar players will now have the opportunity to own and play one as well.”
Warren Haynes effortlessly cross-pollinates genres and unfurls solos that broil with passion in his distinctive, signature playing style. Renowned and highly regarded for his work in rock, blues, and Americana music through his work with the Allman Brothers Band, as a founding member of Gov’t Mule, the leader of The Warren Haynes Band, a solo artist, and as a session guitarist and sideman for numerous famous friends and groups. As one of music’s most treasured storytellers, Haynes and his artistry have led to thousands of memorable performances and millions of album and track sales. A master of multiple styles and genres, Warren has also shared his expertise with other players via multiple instructional videos. A self-described “Gibson man,” Warren has used several Gibson models throughout the years, including his cherished ’61 ES-335™, among others.
The new Warren Haynes Les Paul Standard is another standout, with features tailored specifically to Warren’s preferences, including a mahogany body with a plain maple cap, a 60s Cherry finish, a mahogany neck with a chunky 50s vintage profile like all of Warren’s favorite Les Pauls, a rosewood fretboard with acrylic trapezoid inlays and 22 medium jumbo frets, a pair of P-90 DC pickups that deliver hum-free performance with all the sonic nuances of traditional P-90 DC pickups, and a 15 dB boost that can be activated via a mini toggle switch. The quick-access battery compartment is mounted into the control cover on the rear, and the guitar will still function, even if the battery dies, by simply flipping the mini toggle switch to the off position.
Bearing the traditional looks and feel of a 50s-era Les Paul coupled with modern features like hum-free P-90 DC pickups and an onboard boost, the Warren Haynes Les Paul Standard bridges modern and traditional and is a great choice for players who, like Warren, want both a traditional appearance and modern functionality in one outstanding guitar.
Last fall, Warren Haynes released his fourth solo album, Million Voices Whisper, via Fantasy Records. Haynes sounds as energetic and focused as ever on the self-produced album, powering through an 11-song set of soulful blues-rock, his first solo collection in nearly a decade. Accompanying Warren on the collection are members of his current all-star band, including John Medeski on keyboards, longtime drummer Terence Higgins (of the Dirty Dozen Brass Band), and Gov’t Mule bassist Kevin Scott. Million Voices Whisper also features guest appearances from his Allman Brothers Band compatriot Derek Trucks, whose unmistakable guitar sound toughs up three tracks on the album that were co-produced with Haynes, and his Last Waltz tour co-stars Lukas Nelson and Jamey Johnson, who are featured on the forceful “Day Of Reckoning.” Joining Haynes in the studio for the first time since the final sunset of the ABB, one of the featured tracks with Trucks on guitar is “Real Real Love,” a song initially co-written with Gregg Allman that Warren finished in Allman’s style and methods as if Gregg were singing it to honor his friend.
Buzzing through the chart-topping album is the question of how to make things better—in love, in life, in the world—led by Haynes’s soaring vocals and the poignancy of his six-string mastery. Million Voices Whisper opens with “These Changes,” a co-write with Trucks, leading into “Go Down Swinging,” co-written with Johnson, which features a horn section and a Van Morrison vibe. Then, there’s the soulful power ballad “Till The Sun Comes Shining Through,” driven by Warren’s impassioned vocals and slide guitar skills. The expressive pipes of touring backup singer Saundra Williams are also heard on multiple tracks, including the lead single “This Life As We Know It,” which reached Top 15 on the Americana singles chart and Top 40 at Triple A radio. Among the four bonus tracks on the deluxe CD version is a new version of the Trucks-Haynes composition “Back Where I Started” featuring Warren on lead vocals and slide guitar and the power trio of Haynes, Nelson, and Johnson covering the CSNY classic “Find The Cost Of Freedom” into an extended version of “Day Of Reckoning.” Million Voices Whisper combines the eloquent musicianship of a triple-threat blues-rocker with the glowing spirit of a vital creative artist at the peak of his powers.
For more information, please visit gibson.com.
Gibson Warren Haynes Les Paul Standard Electric Guitar - '60s Cherry
Gary is not exclusively a destruction machine. Its distortion/overdrive section is a very streamlined take on EarthQuaker’s Gray Channel, a versatile DOD 250-derived double distortion. Like any good circuit of the 250 ilk, Gary’s hard clipping OD/distortion section bites viciously in the high- and high-mid frequencies, supported by a tight, punchy low-mid output. You can play anything from balanced M.O.R. studio crunch to unhinged feedback leads with this side of Gary. But it’s the envelope-triggered pulse-width fuzz—which most of us will hear as a gated fuzz, in many instances—that gives the Gary its werewolf duality. Though practice yields performance patterns that change depending on the instrument and effects you use around the Gary, its fuzz ultimately sputters and collapses into nothingness—especially when you throw a few pitch bends its way. The cut to silence can be jarring, but also compels a player to explore more rhythmic leads and choppy riffs that would sound like sludge with a Big Muff. The Gary’s unpredictable side means it won’t be for everybody, but its ability to span delicioso distortion and riotous splatter fuzz in a single unit is impressive.
EarthQuaker Devices Gary Automatic Pulse Width Modulation Fuzz/Overdrive Pedal
