Guitar Attenuators: Gear Guide

October 18, 2019  
Posted by Sam Ash Music
Guitar Attenuators: Gear Guide

For years electric guitarists have faced compromise, “I can’t get my sound at this volume”, “I had to put my amp out in the tool shed to get my recording tone”. Lately, it’s been “I think I need to spend $1,700 on a used transparent overdrive. Solving the electric guitarists’ (and everyone within earshot’s) problem has been addressed time after time. What exactly is that problem? Getting the ‘turned up’ tone you love from your amps, at a manageable volume (recording or live).

This is what it looks like in Algebra: Tone +/- Loudness=X

X is a happy electric guitarist with the tone he wants, at a volume that keeps band mates, sound engineers and audiences happy as well.

Most electric guitarists want some kind of “organic” or “natural” sounding grit in their tone; the kind of drive that comes from a tube amp turned way up to its ‘sweet spot’.  Vacuum tubes start to behave differently when pushed. Speakers also deliver more ‘character’ as they approach the edge of their operational limits. Grit, crunch and overdrive are essential to most electric guitarists. In fact, there are more terms used to describe a “dirty” tone than Eskimos have for snow.  Therein lies the rub: How do you get the sound of your favorite amp cranked up to 11 without making ears bleed a quarter mile away? What happens when that 15-watt amp you bought to solve this issue hasn’t got enough power for a big outdoor stage? The same issues occur in the studio. A 100-watt Marshall set to ear drum stabbing volume, is nearly impossible to isolate from other mics in the room. You don’t want to capture your cranked amp ‘bleeding’ onto every other isolated mic.

Back to the same old problem: crank the gain, and turn down the master volume (if your amp is so equipped), or add outboard drive, like a pedal. It’s not a bad way to go, many times great results are achieved. This begs the question, “Why do guitarists keep seeking a better or different way?”

It’s simple, no matter how good of a driven electric guitar tone you manufacture, it’s never quite the same as a naturally distorting all tube designed “classic” guitar amp.


Historic problems and solutions

As rock and electric blues grew in popularity, bigger venues and powerful humbucking pickups pushed smaller 15 and 30-watt amps into natural overdrive. This harmonically rich, naturally compressed tone became the signature tone of the electric guitar. The music became more popular, the venues got larger, and so did the amps. Just ask Jimi Hendrix (yeah, I know), or Pete Townshend about the gigantic rigs they used at concerts like Woodstock. Max Yasgur’s upstate NY farmland had enough room to open up a pair of hundred-watt pre-master volume Marshall stacks, and let them do their magic naturally. Not a great idea to try in your home studio, or local pub gig. Guys like Leslie West of Mountain found great tone in any guitar he picked up, but often found great drive by running multiple pedals together. By 1972, a guitar player could go into a Sears & Roebuck and buy or order a Fuzz box. By the middle 1970s many amps came equipped with a dual volume (Master-volume) set up, allowing the amp to go into overdrive at a lower volume. Another way to get that “turned up” tone without working the nails out of the walls, was to use an attenuator or “load box”. An attenuator chokes off the volume your speaker gets, by soaking up the output from the power tubes. Early examples readily available at your local music stores were made by Keeley, Marshall and Tom Sholz (yup, the guitar hero from the band Boston holds a degree from M.I.T). The attenuator was not a huge success. Partly because it’s not very good for the life of your tubes, or even your amp, and didn’t sound entirely natural.  Built in “master volume amps” became more efficient, and pedals multiplied in numbers and styles to satisfy every taste. By the 1980s the new “cool” was to use a power amp, and “tone” generating racks of gear, with footswitches the size of football fields. Many feel the sound was becoming too processed and “artificial”. A return to master volume and pedals occurred, returning full circle to electric guitarists seeking organically created distortion. Low gain drives that do not tamper with your carefully selected amp’s tone arose, like the Klon Centaur, Timmy Pedals, and the King of Tone, ushered in the popularity of the “transparent” overdrive.


Old solution gets a re-fit: The “reactive load” Attenuator

The old attenuator has gotten quite a makeover. The new Reactive Load box” is the modern multifunctional offspring of the mostly discarded attenuator of old. This new approach to home recording and live performance tone/volume issues has become the latest sonic boom for the electric guitarist that’s serious about their tone. Vintage and more modern “master volume” amps alike benefit from this expanded new technology. A tidal wave of new reactive load attenuators became available.

Two standout leaders, with different approaches lead the pack. Those two are the Universal Audio ‘OX amp top box’, and the Boss ‘Tube amp expander’. They both are made from the same “stuff” that defines the current generation of ‘load box reactor” devices. They differ in layout and specialized focus as well as appearance. The advantage and differences are easy to hear, but a little difficult to understand without some explanation.

The old school attenuator (power soak, power break etc.) soaks up power, and impedance.

The new type “reactive load” attenuator maintains a proper or variable impedance signature, working in both directions. Amp heads and cabs are a two-way relationship, power from the head goes to the speaker (obviously), but many don’t realize the speaker sends voltage back to the head. All this affects tone and feel. The relationship between an amp and its load (speakers, usually), is part of your sound AND feel. You can feel this when you play an amp that has a “spongy” or “sagging” feel. Alternately, some amps feel stiff, and unforgiving, like plugging into a brick wall.


Reacting to the speaker’s impedance is the difference between preserving all the tone, and all the feel your amp has to offer, regardless of cab or volume level.

The possibilities and capabilities are endless. You can dust off the vintage a 100-watt Vintage Marshall Plexi and turn it up to “11” and play at bedroom volume, without sacrificing tone or feel.

You can use this with or without a cab, making it the ultimate ‘no compromise’ solution for stage or recording volume control. This new tool is a great solution for any reason you plug in: Practice, lessons, rehearsal, gigs and especially home recording. The UA OX, and the Boss Waza Amp Expander are much more than meets first glance. If you are not sure which device suits your needs best, the simple answer is that they both do. The description of what reactive load and how it works is the tip of the iceberg. The included software and hardware make the OX and Amp Expander far more than a safe and accurate volume tamer. They are tools that let you make the most of what you’ve got, and add flexibility, limited only by your imagination, or simple needs. A closer look at each one may help you decide what is right for your personal application.


Universal Audio OX Amp Top Box

Guitar Actuator 1The UA OX, is not the first ever impedance matching, reactive load box, but it’s the one that first gripped the attention of guitarists and producers worldwide. At a glance The Ox looks at home on top of any guitar head, and is even trimmed in flamed maple.  The people at UA call the OX “a Premium reactive load box and recoding system”. The OX works great in a live situation, but its layout and control system may be better tailored for use with high end tube amps in recording applications.  The front panel of ‘OX’ features five knobs, to help you instantly access your needs, without even opening the software or app. From left to right: ‘Rig’ allows you to operate your amp using one of six preset cab & mic simulations, plus FX’s. ‘Room’ adjusts the virtual distance of mic and cab (works like a reverb and depth knob). “Speaker volume” is simply a volume control for the real cab you are playing through (if any). From full bore, down to zero. “Line out simply adjusts the level of volume of the mono/stereo line to the live board or recording console. “Headphone” level of volume going to headphones, located right above stereo headphone input. Rig control can be tweaked to your liking of with 17 cab sims, six mics, and four FXs. UA’s included software alone offers hundreds of combinations.  Great for a vintage amp that is not equipped with reverb. The rear panel of OX is all connectivity controls. Left to right: Power switch and XLR power to the wall, next to (yup) its WIFI indicator light. Factory reset button for when you get in “too deep”. Digital outputs are included next. Choose Co-ax S/PDIF or Optical. Next is a three-way letting you match OX with your amps Ohms (4, 8 and 16). Speaker out (up to 150 watts) and 2 ¼” line outs for stereo line out/ monitor out. The last control is the IP address for wireless software control.

App/Software controls are iPad and Mac or Windows compatible. UA’s software allows for remote wireless tweaks, and access to tons of speaker, mic, EQ and FX simulations. Each feature is highly adjustable and easy-to-use with the app. This “load box” has the ability to match endless combinations and allows you to reach beyond your amp’s capabilities, and remotely change cabs and mics, and FXs never leaving your seat.


Boss Waza Tube Amp Expander

Guitar Actuator 2The new for 2019 Waza Amp Expander is the latest and most viable contender to the OX. Its front panel has 12 controls, making it a little easer to tweak on the fly. Also included is a 100-watt power amp. A feature allowing this reactive load box to not only tame a giant stack, but boost a small amp into a giant.  The Amp Expander also features two speaker outputs, allowing two cabinet live operation. The Boss Amp expander works great in the studio, but features like this may make the Amp Expander a great choice for live playing. The Front panel shares the headphone input and volume with the OX, as well as speaker and line out volumes, but has 10 pre-set (programmable and tweakable with provided software) cab/mic/room presets.  The front panel has a dedicated reverb, rather than the OX’s mic distance reverb simulator. Also present are two reactive load settings, giving you instant access to eight pre-set depth/tonal choices. Additionally, the front end of the Waza expander has four toggles allowing instant access to FX’s loop, FX’s on/off, Solo boost/EQ switch (also deeply adjustable with provided software) and interface with your amps channel switching (is so equipped). An optional foot control can be added for live playing situations. The FX loop can be split off to USB, further expanding recording and tonal options.

The back panel is as simple or expansive as your needs require. Power one or two cabs, go straight to console, live board and monitors with mono or pair of balanced XLR outputs. Silent practice is possible with dedicated headphone jack and direct software connection or direct-to-digital recording could not be any easier with the USB connection at the ready. You can even record directly to any portable Mac or Widows based device to capture a live performance for reference and analyzing your performance; That great solo you did, never has to be lost.


Both devices are as simple or complex as you want them to be. Reverb, volume, overdrive, pre-set speaker and mic emulators and more don’t require use of included software. You can use the OX or Amp expander simply as a better Attenuator, but you will be missing out on all the fun. The ability to use tube technology far beyond its originally intended parameters is nearly limitless with each device’s respective software, and should not be ignored. The software interface is so user friendly; anyone can easily navigate a megaton of variables without dropping a single ‘F-bomb’. Younger computer age players will take to it like a cold can of ‘Millennial’ brand suds. Old school players will find out software isn’t so scary, and get the tone they wanted for the last 25 years.

About the Author

Sam Ash Music

Sam Ash Music has been serving musicians since 1924 when they opened their first store in Brooklyn, NY. Still family owned and operated, Sam Ash Music is dedicated to preserving the goals set by their founder - offering musicians of all levels the best possible selection, service and price.