
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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Though Lou Reed seemed to only use a handful of chords, his shrewd right-hand strumming created limitless rhythmic variations.
Beginner to Intermediate
Beginner to Intermediate
- Focus on syncopation.
- Add muted strums to enhance your rhythm playing.
- Learn how to modify complex rhythmic patterns into smaller, more comprehensible figures.
Though usually more lauded for his lyrics than his guitar playing, Lou Reed had a distinctive style of strumming that can make replication a challenge and seemingly impossible for beginners to comprehend. With a combination of syncopations and muted strums, Reed’s rhythm guitar—from his time with the Velvet Underground to his solo career—has a groove and feel that all guitar players can learn from.
We’ll start with a relatively simple strummed hook that shows Reed’s roots. Ex. 1 is a variation on “There She Goes Again” from The Velvet Underground and Nico, which was recorded in 1966 and released in 1967. This strum was clearly inspired by Marvin Gaye’s “Hitch Hike,” as it duplicates Gaye’s intro almost exactly, albeit in a different key. (It is worth mentioning that “Hitch Hike” also inspired the Beatles “You Can’t Do That.”)
Ex. 1
Ex. 2 is the samething but performed with cowboy chords instead of barres.
Ex. 2
With Ex. 3, a la “Sister Ray” from 1967’s White Light/White Heat, we get into Reed’s more syncopated strums. Note that after the first beat, the emphasis of each strum is on an upbeat, including the changes from G to F, then from F to C, followed at the end by a typical Lou Reed-ism of strumming while in mid-change (though in all fairness, many guitarists do this). Thus, the last upbeat notes, which imply a G chord, are in fact a byproduct created by the switch, not a specific chord.
Ex. 3
Ex. 4 is the same strum but capoed at the 5th fret, using cowboy chords instead of barres.
Ex. 4
Our final Velvet reference, Ex. 5, comes from “Sweet Jane” (Loaded, 1970), which is a song I loathe teaching to students as it is deceptively tricky—it was the inspiration for this lesson—and can make one feel demoralized. True, the song has only four chords, but the syncopated switching and muted strums can cause problems for many players, and not just beginners. Take your time to get the nuances of the switches and mutes.
Ex. 5
Better yet, start with Ex. 6, which is a simplified version of Ex. 5, using cowboy chords instead of barre chords, as well as a more straightforward strum. True, it does not conform completely to the original, but it is a worthwhile starting point. Once this is mastered, try playing Ex. 5 with the open-position chords before moving onto the barres.
Ex. 6
Solo Years
Ex. 7 is a take on “Walk on the Wild Side” from 1972’s Transformer, arguably the most famous Lou Reed song. Here we’ve graduated from eighth-notes to 16th-notes in the right hand. Once again, the muted strums play a vital role.
Ex. 7
Like the previous two examples, you might want to start with the simpler Ex. 8, although the only change is that the mutes have been omitted. This example demonstrates how essential the mutes are, as the feel changes completely when you leave them out.
Ex. 8
Ex. 9 also comes from Transformer and is a variation on“Vicious.” Additional syncopations and muted strums, both different from “…Wild Side,” complicate what should be carefree.
Ex. 9
Ex. 10 is, again, a simplified alternative.
Ex. 10
Examples 11 and 12 demonstrate two options for fretting chords, using Reed’s “Leave Me Alone” from Street Hassle (1978) as a vehicle.
Ex. 11
Ex. 12
Our last example, Ex. 13, is based on Reed’s late-’80s “comeback” hit, “Dirty Boulevard” from New York. Here we not only get syncopations, but a rhythmic variation in the chorus—same chords, different rhythms. Pay attention to that quick, almost-ghosted B note on the “and” of 1 in measure two. It almost seems like a mistake but it adds so much.
Ex. 13
The Lou Reed Legacy
When most fans think of Lou Reed, the first thing that comes to mind is his pioneering subversive, transgressive, and poetic lyrics. But, clearly, that is not all there is to his work. In truth, Lou Reed is an incomparable musician whose guitar playing should not be underestimated. So, take this lesson as a starting point and search out more of his idiosyncratic strums. You will be well rewarded.
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Nashville luthier and guitar tech Dave Johnson shows us the baker's dozen of tools he thinks any guitar picker requires to be a guitar fixer.
3. Guitar Tech Screwdriver Set - 3000
4. Nut File Set (for medium guitar strings) - 0882
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Paul Reed Smith cradles one of his company’s Charcoal Phoenix limited-edition guitars in front of a PRS Sonzera amp.
The storied guitar builder reflects on his dozen months sharing his experience, knowledge, and perspective with PG’s readers.
Over the past year, I’ve written a series of articles in Premier Guitar going over some of my, and our industry’s, views of guitar making. You can find all of them all online (and for those reading this online, the articles are collected here). What I am going to attempt to do for this final piece is boil down each of these articles to a “sort of” conclusion. I have enjoyed the process of writing and editing each one. For the most part, it’s been a lot of fun. So:
Tonewood Doesn’t Matter. Wood Does (August 2024)
We don’t use the word tonewood in conversation at PRS. It doesn’t capture a lot of my experience of which combinations of wood make good instruments. First and foremost, we are looking for qualities of wood over species, and we make sure we dry and treat each one appropriately.
What Makes a Guitar Worth the Price? (September 2024)
Very often, the price of a guitar does reflect how good an instrument is—and very often the price of the guitar has nothing to do with how good an instrument is.
What You Can and Can’t See When Buying a Guitar (October 2024)
This one’s a pet peeve. When making a purchase, you can clearly see the color of a guitar and how beautiful it is, but you have no idea if the neck is going to warp over time because of many factors, including wood drying and truss rod installment design. Trust your experience.
Does Where a Guitar Is Made Really Matter? (November 2024)
There are really good, really smart, really talented people all over the world. While I won’t deny it’s helped our career here at PRS being in the United States, I do not believe it is a truly defining factor of our quality. A good example would be the PRS SE Series.
The Complicated Beauty of Electric Guitar Pickups (December 2024)
We’ve taken so many good stabs at humbucking design, and I’m getting incredibly good feedback on our new McCarty IIIs. But making pickups is a complicated art. There are a lot of ingredients in the recipe.
“I hope these articles have had some positive impact on you as a group.”
In Guitar Making, It’s the Details that Matter (January 2025)
Well, that title says it. What’s interesting for me is that all guitar makers believe that different types of details matter more than others. At PRS, we have our own beliefs.
When Building Guitars—Or Pursuing Anything—Go Down All the Rabbit Holes (February 2025)
This one’s about learning. It’s a process I really enjoy. Whether your passion is guitar making, guitar playing, or something else entirely, there is always more to keep discovering.
Paul Reed Smith on Buying Gear (March 2025)
Very often at a clinic, the people who don’t play guitar have a less calcified view of the sound of the instruments being demonstrated than those players who have already developed strong ideas. On the other hand, one time a very experienced player was at one of my clinics and heard something he’d been looking for for a long time and did not expect it out of the guitar he got it from. Trust your experience—not your predetermined views.
Learning from the Mistakes of Guitar Building’s Past (April 2025)
I think my beginnings as a repairman gave me a lot of insight on this one. Even still, just the process of defining a past guitar-making mistake is its own art.
Paul Reed Smith on Where Amp History—and Tone—Begins (May 2025)
This one I love. It’s a greatly exaggerated version of mods you could do to a TS808 Tube Screamer, which has a history on the web. Amplifiers are “modulated power supplies” and can have so much impact on your tone.
The Lifelong Rhythm of Learning (June 2025)
In some periods of time, there’s a lot to be learned, and in some periods of time, you can barely hold what you had before. It’s different for everyone, and for me, it’s been up and down. No matter where you are in the process, there’s always good work to do.
I hope these articles have had some positive impact on you as a group. I know some things resonate with some people and not others, and the opposite as well. I haven’t gotten a lot of feedback from these articles except that there’s not an overwhelming chorus saying “what an idiot,” which I assume means there’s been some meat on the bone of some of the views shared. It’s been a joy. Thanks for listening.