
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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The new Mark IIC+ 1x12 Combo and Head are authentic recreations of Mesa Boogie's original models.
The new MESA/Boogie Mark IIC+ in head and 1x12 combo formats isavailable worldwide at authorized MESA/Boogie dealers, and on www.mesaboogie.com.
The Mark IIC+ is pure “Vintage Boogie” and based on the original Mark II (now called the MarkII-A) design, the world’s first “Dual Mode” amplifier containing independent performance modes dedicated to clean and overdrive sounds. The IIC+ model represents the 3rd generation of that game-changing single channel/dual mode layout and includes all the refinements made to that
original format over its nearly five influential years. It was also the last model in its family, as the subsequent model would contain three performance modes and be dubbed the MARK III.
The IIC+’s single row of controls is shared by its two modes (preamps), one for Rhythm(clean) and one for Lead (overdrive). Independent, though still interactive, sets of gain and volume controls help optimize each gain structure while shared Tone controls handle the broad stroke voicing. Fine-tuning of the sounds is accomplished by the PULL SHIFT voicing features – some Mode specific – fitted to the simple controls and further shaping via the on-board 5-Band Graphic EQ.Though the “Q” of the individual Bands (Slider Pot frequencies) is fairly wide around their CenterPoints, they provide a surprising degree of surgical-level sculpting quickly and musically.
The Rear Panel of the C+ provides the important features that keep this amp as relevant as ever 40 years after its initial run. Global PRESENCE and REVERB controls are centered foreasy navigation from the Front in stage environments. A series, tube buffered Effects Loop provides a seamless interface for your time-based processing. The Power Select switch at the far right (left from the Front) allows for your choice of the full 75 watts of “SIMUL-CLASS” power for richness, authority, and max headroom or “CLASS A” for 25 watts of reduced power and low end along with easier, smoother power clip at lower volumes. One 8Ohm and two 4 OhmSpeaker Outputs provide for a wide array of cabinet impedance matching. And though not a compensated Direct Output for Consoles or Interfaces, a SLAVE tap off the speaker outputs captures the entire sound of the amp – preamp and power section – to produce a non-compensated feed for IRReaders or external processors that might even serve an era-appropriate “dry/wet/wet” rig.
Out of production for four decades, we welcome back this icon and celebrate its impact on the incredible guitar heroes and timeless recordings they made during one of rock guitar’s biggest decades. The Mark IIC+ legacy is one we don’t take lightly or for granted and recreating it in today’s world with today’s available components and rigorous worldwide Compliance Regulations was no easy feat. However, we are just as proud and excited about this iteration as we were about the first one that was produced for less than two years, four decades ago.
Gibson Band Featuring Slash, Duff McKagan, and Cesar Gueikian Announce Benefit Single
100% of "I Can Breathe" song proceeds to benefit the National Alliance on Mental Illness, NAMI.
On Giving Tuesday, Gibson announces a new release from the Gibson Band--a revolving collective of musicians who join together to make music and raise funds and awareness for worthy causes.. A hard-hitting rock song, the new benefit single “I Can Breathe” features rhythm guitars and piano from Cesar Gueikian, CEO of Gibson, with special guests Duff McKagan on lead vocals and lyrics, and Slash on lead guitar and solos. 100% of the proceeds from the sale of the song “I Can Breathe” will benefit the National Alliance on Mental Illness (NAMI), through Gibson Gives. NAMI is the nation’s largest grassroots mental health resource organization that is dedicated to building better lives for the millions of Americans affected by mental illness.
On “I Can Breathe” Duff McKagan crafted the lyrics and is featured on lead vocals, Cesar Gueikian wrote the music and played rhythm guitar and piano, and Slash wrote and played thelead guitar and solos, while Jota Morelli (drums), and Seta Von Gravessen (bass) rounded outthe group in the studio. The music was recorded by Cesar at La Roca Power Studio in BuenosAires, Argentina, vocals were recorded by Duff at the Sound Factory in Los Angeles and leadguitars and solos by Slash in Los Angeles. The track was produced by Cesar Gueikian and JorgeRodriguez with collaboration from Pablo Toubes and Francisco Trillini, and mixed and masteredby Greg Gordon. A special thanks goes to Gonzalo Riviera Villatte, Gina Furia, and guitar techLisardo Alvarez for all his work at La Roca Power Studio.
Gibson Records, Duff McKagan, Slash, and Cesar Gueikian, will donate 100% proceeds from thesale of “I Can Breathe,” in addition to all auction funds raised to the National Alliance on MentalIllness (NAMI), through Gibson Gives. NAMI is the nation’s largest grassroots mental healthresource organization that is dedicated to building better lives for the millions of Americans affectedby mental illness. NAMI’s mission is to create a world where all people affected by mentalillness live healthy, fulfilling lives supported by a community that cares.
“It was such a pleasure to work with Cesar and his whole crew on this tune,” says Duff McKagan.“The musical slant and progressive rock-ness of this huge epic pushed me in a whole new direction. Ilove a challenge and Cesar killed it! Most importantly, to be of service for mental health issues andawareness is super important to me at this time. Let’s rock!”
“Cesar and Duff came to me with a really cool piece of music,” adds Slash. “I loved the riff idea, andDuff's vocal, so I felt right at home on the track.”
“Guns N’ Roses had a profound influence on me and my guitar playing, so having the opportunity towrite and record this song with Slash and Duff is a dream come true, and it’s an honor to call themfriends and partners,” says Cesar Gueikian, CEO of Gibson. “’I Can Breathe’ started as aninstrumental track I recorded at La Roca Power Studio in Buenos Aires. Upon listening to the mix thatGreg Gordon put together, Jenny Marsh (Global Director of Cultural Influence at Gibson) suggestedDuff as lyricist and vocalist. Guns N’ Roses had just come off touring when I shared the song withDuff, he loved it and quickly wrote the lyrics and cut the vocals at the Sound Factory in Los Angeles.Having Duff on vocals made the next step obvious, which was asking Slash if he would collaboratewith lead guitars and solos. Both Duff and Slash transformed the track from a collection of riffs to agreat song! While Greg Gordon’s mixing and creativity tied it all together. I am grateful for thecollaboration from Slash, Duff and Greg, and from my friend Serj Tankian’s participation with coverartwork. I’m thrilled we are donating all proceeds from the song to a great and relevant cause.”
Made in close collaboration and with significant input from Jimmy Page, the Jimmy Page EDS-1275 uses new 3D scanning technology to aid in handcrafting an effective clone of his original EDS-1275.
There are very few guitars that can claim to be as instantly recognizable and iconic as Jimmy Page’s 1969 EDS-1275 Doubleneck. The photos of him playing it on stage with Led Zeppelin are indelible to rock ’n’ roll history. While Gibson has been making doubleneck electric guitars since 1958, Jimmy was the player who defined the EDS-1275 from the day it was delivered to him. Introducing the Jimmy Page EDS-1275 Doubleneck VOS, now part of the Gibson Custom core lineup and built to the exact specifications of Jimmy’s iconic EDS-1275 Doubleneck.
The Jimmy Page EDS-1275 features a double-cutaway one-piece mahogany body that provides exceptional access to the full length of both the12-string and six-string mahogany necks. Both necks have long tenons and are hide glue fit, and the neck profiles are recreated from 3D scans of the necks on the original guitar. The necks are both capped with bound Indian rosewood fretboards. Each fretboard is equipped with 20 authentic medium jumbo frets and adorned with aged cellulose nitrate parallelogram inlays. The fretboards of both necks have a 12” radius, which is perfect for both playing chords as well as for string bending while soloing. The 18 tuners are Kluson double line, double ring style, just like those found on the original guitar, and even the headstocks feature the correct 17-degree angle and specific logo stylization found on Jimmy’s EDS-1275. The electronics are just as authentic and deliver all of the sonic character of Jimmy’s legendary EDS-1275. Two uncovered Jimmy Page EDS-1275 Custombuckers with double black bobbins and Alnico 5 magnets are used for the two six-string pickups, while a covered pair is installed on the 12-string neck. Of course, the two volume and two tone controls use CTS potentiometers and period-correct ceramic disc capacitors, and the pickup select switch, neck select switch, and output jack are all from Switchcraft.
Here is your opportunity to own a clone of Jimmy Page’s famous EDS-1275, identical to how it appeared on the day that Jimmy first received the guitar. A Gibson Custom hardshell case is included, along with a vintage leather strap, and a certificate of authenticity with a photo from famed photographer Barrie Wentzell.
Jimmy Page EDS-1275 Doubleneck VOS '69 Cherry
Recreation of the EDS-1275 used by Jimmy Page made using 3D scans of the original guitar, one piece mahogany body, mahogany six and 12-string necks with custom Jimmy Page profiles, Indian rosewood fretboards, Jimmy Page Custombucker pickups with Alnico 5 magnets and double black bobbins, Gibson Custom hardshell case
Reader: Daniel Switkin
Hometown: Oakland, California
Guitar: Doublecaster
Here’s the doubleneck dream realized, even if it weighs 9 pounds, 5 ounces.
Taking a Squier Affinity Stratocaster and Mini Precision Bass, one reader created a super-versatile instrument for looping that he can pick, pluck, tap, and slap.
I've been using a multitrack looper with a guitar and an octave pedal, which was okay for simple bass parts, but didn’t give me thick strings and I couldn’t slap with it. So I decided to build a double-neck prototype specifically for looping, with a 6-string guitar and a 4-string bass.
Since building the necks would be the hardest part, I looked around for instruments with bolt-on necks I could reuse. Squier makes an Affinity Stratocaster and a Mini Precision Bass which were affordable and had matching fretboards, so I bought those. It was also cheaper to reuse the electronics and hardware that came with them, rather than buying everything separately.
Using two precut instrument bodies saved the burden of having to route cavities for the electronics.
My plan was to design my own body from scratch. As I debated which neck should go on top, how far apart they should be, and whether to line up the nuts or the saddles, I realized there was actually enough wood there to make a double neck body, which saved me the work of recreating the neck pockets, etc. Putting the guitar on top made barre chords much more comfortable, and the 28.6" bass scale meant I could still reach the first fret easily.
After stripping the paint with a heat gun, I ran both bodies through a table saw, glued them together, and thinned them to 1 3/8". Then I created an offset body shape, a new arm bevel, and reshaped the three cutaways. The pickguards are both original, with the guitar side cut down to make a yin and yang shape. The controls are volume and tone for each neck, using the original knobs. I moved the jack to the back and upgraded it to stereo so the guitar and bass signals can run through separate effects chains.
Note the location of the jack on the back of the extended-shape body. It’s unconventional but practical.
My top concerns were weight and ergonomics. Many doublenecks are around 12 to 13 pounds and 18" wide. I knew I would never play something that big, no matter how good it sounded. To that end, I saved weight everywhere and tracked everything to the gram in a spreadsheet. (That’s also the reason I chose a fixed bridge instead of a vibrato.) I ultimately used a wipe-on gel stain to keep the weight down further. Stripping the paint from the factory saved 5 ounces! The final playable weight is 9 pounds, 5 ounces, and 15 1/4" wide at the lower bout. This has been pretty manageable, however, there is some neck dive because of the tuners. I’m taking everything I’ve learned from this prototype and designing a new doubleneck, which will be headless. I believe I can shed another pound and eliminate the neck dive that way. You can watch my entire build on YouTube.