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Power attenuators have been around for decades in various forms, but with the proliferation of enterprising companies and the need to control the various scenarios mentioned above, they have never been as popular as they are today. As much as we love our 50- and 100-watt non-master volume amps, long gone is the need for this kind of power for the majority of us. PA systems have dramatically improved to the point where a 5-watt amp can keep up with the loudest drummer in arena settings and still be heard by all—the sound man was right! But aside from their ability to reduce the volume of higher wattage amps, many modern attenuators can serve us in ways that range from downright practical to creative tone shaping and beyond. This article will focus on some of the other creative uses of attenuators and will hopefully shine some new light on the “big volume knob” we know them as today.
Caution: High Voltage
Before even getting into the various uses of attenuators, it should be stated that tube amps carry lethal voltages and you shouldn’t go poking around your amp’s innards if you don’t know what you’re doing! Leave that to a qualified tech and save yourself to continue playing guitar another day. That said, this is not a technical article, and I won’t be asking you to take plate voltage readings or bias your amp, so let’s move on!
The Power and the Glory
Sometimes attenuators get a bad reputation
for blowing up amps. There may have been
some questionable designs in the past that
put amps at risk, but these days there are a
lot of great choices available that are safe
to use. While I personally have never blown
an amp while using an attenuator, I do know
that if you dime your amp, any parts that
are stressed are going to be exposed. And
most of us running attenuators are using
them because we like the tone of the amp
full up, or close to that. Before you fear the
attenuator will blow the output transformer
on your favorite vintage amp, it might be
wise to take it to a qualified tech and have
it tuned up. What you may have thought of
as a solid and safe amp (because you run
an overdrive pedal in front of it with the volume
on 3) could be teetering on the edge
of destruction if you ramp it up. How are the
tubes and tube sockets? What about the filter
caps (especially on vintage amps)? Is it properly
biased? So many things need to be right
when you run an amp full out, just like a car
in the Indy 500. And don’t let anyone tell you
that vintage Marshalls, Hiwatts and the like
weren’t designed to be run on 10. They were,
and players have been using them that way
for decades! Besides, even at a volume of 6, 7
or 8, you’re dealing with some serious power,
so take care of your amp and know its running
order before plugging it into an attenuator, or
a speaker cabinet for that matter.
Matching Up Impedance and
Power Ratings To get the best tone and safest performance out of your attenuator, make certain that you are accounting for the power rating of your amp, as well as the impedance that it’s set to. The good news is most high-powered tube amplifiers have selectable impedance settings to accommodate various speaker cabinets. Some amps are designed with dedicated 4-, 8- and 16-ohm speaker outputs, while amps like Marshalls have always had a switch or plug that sets the impedance. Attenuators, as in the case of the THD Hot Plate, offer individual models specifically tailored for 2, 2.7, 4, 8 and 16 ohms, while other units like the Weber MASS have adjustable impedance settings all in one unit (2, 4, 8, 16). Others still, such as the Ultimate Attenuator, are designed to accommodate any impedance amp. Every one of these will put their particular tonal stamp on the amp tone due to the various types of attenuation being used. These tonal variations are the subject of much heated debate in various forums, but that discussion is outside of the scope of this article.
Power handling is of utmost concern. You don’t ever want to use an attenuator that can’t take the juice of your amp. A 100-watt tube amp is easily capable of pushing out 150-watts or more peak power, so check with the manufacturer to see what it can handle before plugging in your favorite amp. Personally, I’ve used a Hot Plate for over a decade with my 50- and 100-watt heads and have never had an issue with them dimed for hours on end, five days a week. As long as you match the attenuator to your amp like you would a speaker cabinet, you’ll be in good shape… you’d never run a Hiwatt DR-103 full up through a 1x12 Celestion greenback cab unless you had a death wish for the speaker and the amp!
Load Up Many attenuators have extra features on them that can be used for more than just volume reduction. Units like the THD Hot Plate and Weber MASS can be used as a dummy speaker load, allowing you to run the amp without a speaker cabinet. This is an invaluable tool for safely being able to set bias, check operating voltages or anything that requires the amp to be running to diagnose. Prior to specific dummy load devices, techs have used everything from light bulbs to giant resistors to dissipate power while working on a live amp. With the attenuator set to “load,” just plug the speaker output of the amp into the “amp input” or similarly named input and you’re ready to go. What’s nice about this is that while working on the amp you won’t have to deal with the noise coming from a speaker cabinet and all of the hiss that goes along with a loud amp. Just remember that although you don’t hear any sound or see that electricity, it’s there, and it’s lethal. Make sure you know what you’re doing, and re-read the caution at the beginning of this article.
The Wet/Dry Rig
If your attenuator has a line out available,
you can use it to set up a Wet/Dry rig. A wet/
dry rig is great for keeping the dry tone of
your amp intact while bringing in effects on a
separate power amp and speaker. Once you
have the dry tone set to your liking, take the
line out of the attenuator and feed it into the
desired effects, then into a separate power
amp. Make sure you don’t overload the input
of the effects by using the line out’s volume
control to taste. From there, you can run
a second speaker cabinet, effectively slaving
the tone of the main amp but with the
effects. Controlling the output of the power
amp will bring up the “wet” level on the second
cab, and you can mix to taste. Of course,
this is best used for effects like delay, or any
effect that you want on the back end of the
tone. Pedals like compressors and distortion
boxes are best left to the front end. Make
sure if you’re using a delay or reverb that you
set the effect to 100% so you’re not bleeding
in the dry signal.
Line Out/New Power Amp
If you really want to tame the volume of an amp, but find that the lowest settings on the attenuator suck too much tone out for your liking, you can once again put that dummy load and line out to good use. First, set the attenuator to “load.” Then, like the wet/dry rig, use the line out to feed a power amp out to the speaker cab of your choice. In essence this is like using a “slave out” that used to be a big mod back in the eighties from the amp hot-rodders. Back then it was used to power yet another head, but these days it can be used to bring the volume down to a controllable level and still retain the full sound of the amp. Will it be exactly the same as with the power section of the main amp? No, but neither will it be the tone of a highly attenuated signal, so it’s a matter of taste.
If you really want to tame the volume of an amp, but find that the lowest settings on the attenuator suck too much tone out for your liking, you can once again put that dummy load and line out to good use. First, set the attenuator to “load.” Then, like the wet/dry rig, use the line out to feed a power amp out to the speaker cab of your choice. In essence this is like using a “slave out” that used to be a big mod back in the eighties from the amp hot-rodders. Back then it was used to power yet another head, but these days it can be used to bring the volume down to a controllable level and still retain the full sound of the amp. Will it be exactly the same as with the power section of the main amp? No, but neither will it be the tone of a highly attenuated signal, so it’s a matter of taste.
Creative Cabinet Choices
Ever wonder what a Superlead would sound like through an AC30 cab but were afraid to try for fear of blowing the Celestion AlNiCo Blues? Once again, as long as the impedance is set correctly, and the power is scaled back to accommodate the speakers, who says you have to use the same cab as the head was designed for? Many times I’ve been in the studio and knew that the tone of the amp was dialed in, but wanted a different color. Rather than running the typical, closed-back 4x12, I was able to choose between the many different cabs available by attenuating the signal down enough to allow safe operation. It’s a great way to experiment with tone and to further lessen the volume assault. This is great for live situations as well. Imagine how much easier it will be on your back to carry in a 1x12 cab for the gig. Heck, you usually only mic one speaker anyway. You can still get raging tone, just in a smaller footprint (physically and sonically).
Dummy Load/Line Out/Speaker Simulator
For recording or the ultra-adventurous live
guitarist, how about ditching the cab altogether?
These days with the myriad amp
modeling programs and hardware devices,
who says you even need a cab to produce a
mic’d speaker tone? Dedicated devices like
the Hughes & Kettner Red Box, the Palmer
PDI-series of speaker simulators and the
fabulous Axe-FX all offer ways of attaining a
variety of speaker tones without speakers. As
long as you have a dummy load and line out
on the attenuator you can accomplish this
easily. After setting the attenuator to “load,”
take the line out and feed it directly into the
hardware unit. The Red Box Classic offers
settings for “combo” and “4x12,” while the
Palmer offers an 8-ohm dummy load and multiple
settings to simulate a variety of speaker
configurations. Highly detailed speaker cab
emulations as well as microphone models,
reverbs and more can be obtained with the
Axe-FX by Fractal Audio Systems.
If you’re in a recording scenario and like to
use modeling software, consider bypassing
the amp models and just use the mic and
speaker models. The variety of software
amp modelers is vast with, more products
entering the market all the time. Each one
of them has its own sound and the options
are nearly endless. You’d be surprised how
good they sound, and with the no-speaker
option you can record at 2 a.m. with your
favorite amp. Better yet, if you fire up the
studio the next day and don’t particularly
care for the sound of the mic/cab combination
from the night before, you can change
it, because the only thing that was recorded
was the tone of the amp. For much more
detailed information check out the article, “Look Ma, No Speakers!” in the July 2008
issue of Premier Guitar.
These are just a few options you can try out
with most current production attenuators.
There are certainly many more not covered in
this article that would be helpful, but there’s
only so much space available. The possibilities
are endless. That said, we are in a new
era of amps and tone, with more amplifier
options than ever before. And while amp
builders are certainly conscious of designing
new amps with lower wattage and features
such as power dampening or power scaling,
we do still love our high-powered amps.
Most of us won’t have the opportunity to
play Madison Square Garden anytime soon,
nor do a lot of us have amp rooms where we
can crank our rigs up and jam without consequence.
That’s why the attenuator is such
a great device. Not only does it act as a big
volume knob, it serves us in many creative
ways… your imagination is really the only
limit with what we have available today.
