
Photo 1
Want to reduce the power in an amp with four output tubes? Here’s how to do it right.
Hi Amp Man,
I’ve heard of people pulling one of the two output tubes to reduce the power in a dual-power tube amp. Does this affect the amp’s reliability? Also, if the technique is okay, can you use it on quad output amps like a Fender Twin? And which tubes would you pull? Thanks!
David Lemnah
Hi David,
It seems there’s no shortage of players who want to drop the output power of their amplifier. Some may want to drive their amp’s output stage hard to achieve output-tube distortion, while others may simply find their amp has too much power to even use as a clean platform. Sometimes an amp just sounds better, even when playing it clean, if the output tubes are working a bit harder. This will cause the current flow to increase past the idle current, especially in standard-biased class A/B amps. In my opinion, this makes for a better sounding output tube. Whatever your reason, there is a right way and a wrong way to remove output tubes.
Photo 2
But first, in a standard amplifier with only two output tubes, it’s never okay to remove one output tube. While this would certainly reduce the output power of the amp, two things will happen: It will unbalance the primary side load the tubes place on the transformer, and it will leave one side of the primary completely unloaded. The latter could create excessively high voltage in the winding, and thus cause arcing and transformer damage. Bottom line: Do not remove one output tube in a two-output tube amp. There may be exceptions, such as a single-ended output amp with multiple output tubes in parallel, but I’m sure these are few and far between.
Now, in an amp with four output tubes it is possible to remove two of them, but you need to know which two to remove. Typically amps with a quartet of output tubes have what’s known as a push-pull output stage. (This also applies to amps with dual output tubes.) This basically means that each half of the output stage amplifies one half of the audio signal.
Sometimes an amp just sounds better, even when playing it clean, if the output tubes are working a bit harder.
If two of the output tubes are removed from the same side of the output stage, half of the signal will not be amplified and the sound will be extremely distorted. This will also cause the same issues as removing one tube in a dual-tube amp, so let’s make sure the correct output tubes are removed!
You have a few options: remove the two outside tubes (Photo 1), remove the two inside tubes (Photo 2), remove the first and third (Photo 3), or remove the second and fourth (Photo 4). I prefer any of the last three methods, because each provides a bit more cooling area between the tubes.
Photo 3
After removing the two output tubes, there’s another step that is theoretically necessary, and you should take it if possible. This is to change the output impedance selection to reduce the speaker load by half. For example, if you are running your amp into a 16-ohm load, reduce the impedance selector to 8-ohm. For an 8-ohm load, reduce the impedance selector to 4.
This is more important in Marshall-style amps, as their output transformer design seems to be, or at least is perceived to be, a bit more finicky and vulnerable. Impedance reduction is not an option in amps without impedance selectors, such as early Fender amps, but they seem to be pretty stable and not significantly impacted by this mismatch. In fact, certain amps—such as the Mesa/Boogie Mark Series—feature a “half power” switch that electrically disconnects two output tubes from the output stage with no impedance adjustment and no ill effects.
Photo 4
This tube-removal technique works best in amps that are fixed biased, as opposed to cathode biased. Also, some amps have their output tubes physically arranged in asymmetrical patterns, so consult with the amp manufacturer if possible before removing any tubes. As far as the amp’s reliability, other than the aspects we already addressed, if you occasionally use the amp with all tubes and occasionally with two, consider alternating the tubes you pull so they all wear evenly.
One more point: There are other ways to reduce the volume level of an amp. One is by simply inserting an attenuation device between the amplifier and speaker. THD, Weber, Soldano, Tube Amp Doctor, and other companies make such devices and they function quite well. Another option is to have your tech install a “pentode/triode” switch. This changes the wiring of the output tubes, converting them to a “faux” triode operation. This reduces the amp’s output by approximately 40 percent, which is on par with removing two output tubes.
WARNING: All tube amplifiers contain lethal voltages. The most dangerous voltages are stored in electrolytic capacitors, even after the amp has been unplugged from the wall. Before you touch anything inside the amp chassis, it’s imperative that these capacitors are discharged. If you are unsure of this procedure, consult your local amp tech.
[Updated 12/30/21]
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Growing up in Australia, guitarist Jedd Hughes tells us he dreamed of playing in Vince Gill’s band as far back as elementary school. Now, he lives in Nashville and stands next to the man himself on stage night after night. We’ve invited Jedd to join us on this episode of 100 Guitarists to talk about just what makes Vince’s playing so special.
Jedd tells us how his dream came true and how he first started playing with Vince. We dig deep into how everybody’s favorite country guitarist raises the bar every time he picks up the guitar, how he gets his amazing clean tone, and we take time to appreciate all aspects of his solos—including how he builds them and how he plays such clean bends. As for why his concerts are so long? “He loves to play.”
In our current listening segment, we’re covering the Black Crowes and Jimmy Page’s Live at the Greek box set and a live recording from Burlington, Vermont’s Breathwork.
This episode is sponsored by EMG Pickups.
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!
An ode, and historical snapshot, to the tone-bar played, many-stringed thing in the room, and its place in the national musical firmament.
Blues, jazz, rock, country, bluegrass, rap.… When it comes to inventing musical genres, the U.S. totally nailed it. But how about inventing instruments?
Googling “American musical instruments” yields three.
• Banjo, which is erroneously listed since Africa is its continent of origin.
• Benjamin Franklin’s Glass Armonica, which was 37 glass bowls mounted horizontally on an iron spindle that was turned by means of a foot pedal. Sound was produced by touching the rims of the bowls with water-moistened fingers. The instrument’s popularity did not last due to the inability to amplify the volume combined with rumors that using the instrument caused both musicians and their listeners to go mad.
• Calliope, which was patented in 1855 by Joshua Stoddard. Often the size of a truck, it produces sound by sending steam through large locomotive-style whistles. Calliopes have no volume or tone control and can be heard for miles.
But Google left out the pedal steel. While there may not be a historical consensus, I was talking to fellow pedal-steel player Dave Maniscalco, and we share the theory that pedal steel is the most American instrument.
Think about it. The United States started as a DIY, let’s-try-anything country. Our culture encourages the endless pursuit of improvement on what’s come before. Curious, whimsical, impractical, explorative—that’s our DNA. And just as our music is always evolving, so are our instruments. Guitar was not invented in the U.S., but one could argue it’s being perfected here, as players from Les Paul to Van Halen kept tweaking the earlier designs, helping this one-time parlor instrument evolve into the awesome rock machine it is today.
Pedal steel evolved from lap steel, which began in Hawaii when a teenage Joseph Kekuku was walking down a road with his guitar in hand and bent over to pick up a railroad spike. When the spike inadvertently brushed the guitar’s neck and his instrument sang, Kekuku knew he had something. He worked out a tuning and technique, and then took his act to the mainland, where it exploded in popularity. Since the 1930s, artists as diverse as Jimmie Rodgers and Louis Armstrong and Pink Floyd have been using steel on their records.“The pedal steel guitar was born out of the curiosity and persistence of problem solvers, on the bandstand and on the workbench.”
Immigrants drove new innovations and opportunities for the steel guitar by amplifying the instrument to help it compete for listeners’ ears as part of louder ensembles. Swiss-American Adolph Rickenbacker, along with George Beauchamp, developed the first electric guitar—the Rickenbacker Electro A-22 lap steel, nicknamed the Frying Pan—and a pair of Slovak-American brothers, John and Rudy Dopyera, added aluminum cones in the body of a more traditional acoustic guitar design and created resophonic axes. The pedal steel guitar was born out of the curiosity and persistence of problem solvers, on the bandstand and on the workbench.
As the 20th century progressed and popular music reflected the more advanced harmonies of big-band jazz, the steel guitar’s tuning evolved from open A to a myriad of others, including E7, C6, and B11. Steel guitarists began playing double-, triple-, and even quadruple-necked guitars so they could incorporate different tunings.
In Indianapolis, the Harlan Brothers came up with an elegant solution to multiple tunings when they developed their Multi-Kord steel guitar, which used pedals to change the tuning of the instrument’s open strings to create chords that were previously not possible, earning a U.S. patent on August 21, 1947. In California, equipped with knowledge from building motorcycles, Paul Bigsby revolutionized the instrument with his Bigsby steel guitars. It was on one of these guitars that, in early 1954, Bud Isaacs sustained a chord and then pushed a pedal down to bend his strings up in pitch for the intro of Webb Pierce’s “Slowly.” This I–IV movement became synonymous with the pedal-steel guitar and provided a template for the role of the pedal steel in country music. Across town, church musicians in the congregation of the House of God Keith Dominion were already using the pedal steel guitar in Pentecostal services that transcended the homogeneity of Nashville’s country and Western clichés.
Pedal steels are most commonly tuned in an E9 (low to high: B–D–E–F#–G#–B–E–G#–D#–F#), which can be disorienting, with its own idiosyncratic logic containing both a b7 and major 7. It’s difficult to learn compared to other string instruments tuned to regular intervals, such as fourths and fifths, or an open chord.
Dave Maniscalco puts it like this: “The more time one sits behind it and assimilates its quirks and peculiarities, the more obvious it becomes that much like the country that birthed it, the pedal steel is better because of its contradictions. An amalgamation of wood and metal, doubling as both a musical instrument and mechanical device, the pedal steel is often complicated, confusing, and messy. Despite these contradictions, the pedal-steel guitar is a far more interesting and affecting because of its disparate influences and its complex journey to becoming America’s quintessential musical instrument.”By refining an already amazing homage to low-wattage 1960s Fenders, Carr flirts with perfection—and adds a Hiwatt-flavored twist.
Killer low end for a low-wattage amp. Mid and presence controls extend range beyond Princeton or tweed tone templates. Hiwatt-styled voice expands vocabulary. Built like heirloom furniture.
Two-hundred-eighty-two bucks per watt.
$3,390
Carr Skylark Special
carramps.com
Steve Carr could probably build fantastic Fender amp clones while cooking up a crème brulee. But the beauty of Carr Amps is that they are never simply a copy of something else. Carr has a knack for taking Fender tone and circuit design elements—and, to a lesser extent, highlights from the Vox and Marshall playbook—and reimagining them as something new.
Those that playedCarr’s dazzling original Skylark know it didn’t go begging for much in the way of improvement. But Carr tends to tinker to very constructive ends. In the case of the Skylark Special, the headline news is the addition of the Hiwatt-inspired tone section from theCarr Bel-Ray, a switch from a solid-state rectifier to an EZ81 tube rectifier that enhances the amp’s sense of touch and dynamics, and an even deeper reverb.
Spanning Space Ages
With high-profile siblings like the Deluxe, Bassman, Tremolux, and Twin, Fender’s original Harvard is, comparatively, a footnote in Fender’s wide-panel tweed era (the inclusion of Steve Cropper’s Harvard in the Smithsonian notwithstanding). But the Harvard is somewhat distinctive among tweed Fenders for using fixed bias, which, given its power, makes it a bridge that links in both circuit and sound to the Princeton Reverb. The Skylark Special’s similar capacity for straddling tweed and black-panel touch and tone is fundamental to its magic.
Like the Harvard and the Princeton, the Skylark Special’s engine runs on two 6V6 power tubes and a single 12AX7 in the preamp section. A 12AX7 and 12AT7 drive the reverb and the reverb recovery section, respectively, and a second 12AT7 is assigned to the phase inverter. (The little EZ81 between the two 6V6 power tubes is dedicated to the rectifier). Apart from the power tubes and the 12AX7 in the preamp, however, the Skylark Special deviates from Harvard and Princeton reverb templates in many important ways. Instead of a 10" Jensen or Oxford, it uses a 50-watt 12" Celestion A-Type ceramic speaker, and it includes midrange and presence controls that a Harvard or Princeton do not. It also features a boost switch that manages to lend body and brawn without obliterating the core tone. There is also, as is Carr’s style, a very useful attenuator that spans zero to 1.2 watts. Alas, there is no tremolo.
“I’d wager the Skylark Special will be around every bit as long as a tweed Harvard when most of your printed-circuit amps have shoved off for the recycler.”
It goes without saying, perhaps, that the North Carolina-built Skylark Special is made to standards of craft that befit its $3K-plus price. Even still, Carr upgraded nine of the coupling capacitors to U.S.-made Jupiters. They also managed to shave six pounds from the Baltic birch cabinet weight—reducing total weight to 35 pounds and, in Steve Carr’s estimation, improving resonance. Say what you will about the high price, but I’d wager the Skylark Special will be around every bit as long as a tweed Harvard when most of your printed-circuit amps have shoved off for the recycler.
Sweet Soulful Bird
Fundamentally, the Skylark Special launches from a Fender space. But this is a very refined Fender space. The bass is rich, deep, and massive in ways you won’t encounter in many 12-watt combos, and the warm contours at the tone’s edges lend ballast and attitude to both clean tones and the ultra-smooth distorted ones at the volume’s higher reaches. All of these sounds dovetail with the clear top end you imagine when you close your eyes and picture quintessential black-panel Fender-ness. The presence and midrange controls, along with the 50-watt speaker, lend a lot in terms of scalpel-sharp tone shaping—providing a dimension beyond classical Fender-ness—especially when you bump the midrange and turn up your guitar volume.
The tube rectifier, meanwhile, shifts the Skylark Special’s touch dynamics from the super-immediate reactivity of a solid-state rectifier to a softer, more-compressed, more sunset-hued kind of tactile sensitivity. But don’t let that lead you to worry about the amp’s more explosive capabilities. There is more than enough high-midrange and treble to make the Skylark Special go bang.
Anglo and Attenuated Alter Egos
The Hiwatt-inspired setting is still dynamic, but it’s a little tighter than the Fullerton-voiced setting. There’s air and mass enough for power jangling or weighty leads. The differences in the Bel-Ray’s tube selection (EL84 power tubes as well as an EF86 in the preamp) means the Skylark Special’s version of the Hiwatt-style voice is—like the amp in general—warm and round in the low-mid zone and softer around the edges, where the Bel-Ray version has more high-end ceiling and less mellow glow in the bass. It definitely gives the Skylark Special a transatlantic reach that enhances its vocabulary and utility.
Attenuated settings are not just practical for suiting the amps to circumstances and size of space you’re in; they also offer an extra range of colors. The maximum 1.2 watt attenuated setting still churns up thick, filthy overdrive that rings with harmonics.
The Skylark Special’s richness and variation means you’ll spend a lot of time with guitar and amp alone. Anything more often feels like an intrusion. But the Skylark Special is a friend to effects. Strength in the low-end and speaker means it humors the gnarliest fuzzes with grace. And with as many shades of clean-to-just-dirty tones as there are here, the personalities of gain devices and other effects shine.
The Verdict
Skylark Special. It’s fun to say—in a hep-cat kind of way. The name is très cool, but the amp itself sounds fabulous, creating a sort of dream union of the Princeton’s and Harvard’s low-volume character, a black-panel Deluxe’s more stage-suited loudness and mass, and a zingier, more focused English cousin. It can be sweet, subdued, surfy, rowdy, and massive. And it works happily with pedals—most notably with fuzzes that can make lesser low-mid-wattage amps cough up hairballs. The price tag smarts. But this is a 12-watt combo that goes, sonically speaking, where few such amps will, and represents a first-class specimen of design and craft.