
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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From full-size to mini, these six pedals deliver funky “chickas,” screaming, fuzz-infused lead tones, and more.
The variations on a classic stompbox bring you tonal versatility and more!
Xotic XW-2 Wah Pedal
The Xotic XW-2 Wah Pedal is a high-quality, versatile stomp that creates a ’70s-style “throaty” wah sound.
xotic.us
Sonicake FlipWah
The FlipWah combo pedal combines a classic wah and active volume pedal in one, with a footswitch to select between the two modes. A Q knob adds even more versatility.
sonicake.com
$79 street
McCon-O-Wah McWah
The McWah-2B delivers classic tone with modern upgrades. Handwired, adjustable, and durable, it features a custom pot and true bypass for optimal sound. Inspired by the original, legendary wah pedal.
mcconowah.com
$428 street
Dunlop Jerry Cantrell Rainier Fog Cry Baby Wah
This Cry Baby signature model complements Jerry Cantrell’s sound with a dark, punchy voice, a wide sweep, and a control on the side for fine-tuning the toe-down frequency.
jimdunlop.com
Dunlop CBJ95 Cry Baby Junior Wah Pedal
The Cry Baby Junior Wah features front-mounted jacks and an 8" housing for clean configurations on the world’s most popular boards.
jimdunlop.com
Dunlop Cry Baby Daredevil Fuzz Wah Pedal
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jimdunlop.com
Leveraging 3D printing technology, the new Floyd Rose Original locking nuts are designed to deliver unmatched precision and consistency, replacing the traditional “lost wax” casting method that dominated for decades.
The shift to 3D printing allows for intricate detailing and tighter tolerances, ensuring each nut meets exact specifications.
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Initially, the 3D-printed locking nuts will be available in ten classic sizes with a 10” radius, with plans to expand the range to accommodate various fretboard radii in Spring 2025. This augmentation will offer players more options for customizing their setups to match a wide variety of fretboard curvatures.
To get a sneak peek at the new Floyd Rose USA Series, come visit us at NAMM in booth 5734 in Hall D.
With flexible voltage adjustments, precise control, customizable protection, compact design, and affordable pricing at $299, the Brownie is the ultimate solution for optimizing tone and safeguarding your gear.
AmpRx, the trusted name behind the industry-renowned BrownBox, has unveiled its newest innovation: The Brownie, a voltage-optimizing power supply for modern amps and the first of its kind.
Designed by AmpRx co-owner and CEO Cassandra Sotos (2024 NAMM Female Entrepreneur of the Year), the Brownie provides unparalleled control, flexibility, and protection specifically for modern tube amplifiers by allowing the player to both increase and decrease voltage with volt-by-volt precision.
Priced at $299, the Brownie offers an affordable and essential solution for protecting your investment in your high-quality tube amp. It allows you to optimize your tone and safeguard your gear from variations in voltage by givingthe ultimate advantage: knowing exactly what you’re feeding your amp.
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The Brownie will be available January 20th, 2025, presented at NAMM Global Media Day and on display at Booth #5630.
WHAT MAKES THE BROWNIE SPECIAL? Building on the success of the flagship BrownBox, the Brownie offers key innovations tailored for modern amplifiers:
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For more information, please visit brownbox.rocks.
The latest multi-effect from Wampler is a dreamy if sometimes difficult-to-master delay/reverb combo.
Great, instantly useable reverb and delay tones. Impressive breadth of sounds in one box. Solid construction. Good value.
Controls and operation can feel confusing.
$299
Wampler Catacombs
wamplerpedals.com
“Modeling versus tube” might be the gear world title fight of the 2020s, but “LED menu versus none on multieffects” is a pretty riveting undercard. I have sympathies in both corners. The ocean-deep onscreen interface of theMeris Mercury X, for instance, was a bear to navigate, but it also yielded some of the most exciting and tweakable reverb I’ve ever heard. At the same time, I’ll always be partial to having every control I need at my fingertips, and every parameter a knob twirl away from just-right.In theory, the digitalWampler Catacombs fits into the second category, the one I prefer. It’s a super-loaded reverb and delay combo pedal, with seven delay algorithms and five reverb options that sound great. Though in practice, Catacombs sometimes turned out to be a bit more complicated to navigate than I expected.
Lost in the Catacombs
The Catacombs is one of those pedals that begs a dedicated read of the manual before you dive in. Wampler says that the interface enables users to “navigate effortlessly” without the use of onboard screens and menus. I was excited by this: Like I said, I don’t love getting lost down tiny LED display rabbit holes and would much rather have all I need at hand. The Catacombs technically satisfies that desire, but it also demonstrates tradeoffs involved with that design ethic. I’m alright with certain controls pulling double-duty, but when every single knob shares two functions, things can get hairy, and doing your preparation up front pays big dividends.
You have to press and hold the left footswitch for a second to access the alt controls (labeled in blue), including reverb selection on the main rotary knob. Though this doesn’t complicate matters too much when using a reverb or delay exclusively, it can be tricky when using a reverb and delay simultaneously. A few times, I scrambled to switch control modes to tame a super-loud runaway reverb or a self-oscillating delay, and the feeling of frantically spinning knobs with no impact because you’re not in the right control mode isn’t a good one. Additionally, you might not know where a given parameter is set because each knob is shared between the delay and reverb effect. The eight onboard preset slots take some of this guesswork away. And Catacombs would be a cinch in the studio once the control navigation becomes second-nature, but I got nervous thinking of trying to navigate any of these quirks during a set.
Entombed in Ambience
Catacombs’ operational challenges don’t take too much away from the whole experience because it sounds so great. Each of the six delay programs, and each of the five reverbs, were instantly useable and familiar. Side by side with my Walrus Fathom and EarthQuaker Avalanche Run, the plate, hall, and spring reverb modes held their own, and something about the pedal’s wet/dry mix made my playing feel especially alive, present, and cinematic at most settings. I was especially fond of the spring reverb with the decay maxed out—it was juicy and metallic in all the right ways.
The delay modules were just as satisfying. They include three algorithms for tape-style delays, two analog-style delays, and a single digital echo, and each mode offers a distinct texture and experience. The ability to quickly switch the effects from series to parallel offers fun and useful experimentation, letting you apply the reverb algorithm to just your dry signal, or to the repeats, too. I especially enjoyed sticking the plate reverb on my dry signal and leaving it off the delay, creating warped senses of space and continuity.
The Verdict
Though it sounds excellent, immersive, and inviting, I was flustered more than once while trying to bend Catacombs to my will. In some respects, I was reminded of a menu where you’re given three desirable options and have to pick just two. In this case, the options are affordability, sound quality, and user-friendliness. Catacombs is certainly reasonably priced and sounds excellent. But because it navigates a difficult middle path between skipping a cost-bumping digital menu and being more complex than more-straightforward, what-you-see-is-what-you-get units, you should make sure you’re comfortable with that compromise.