
Compared to traditional speaker simulators, IRs offer much greater realism and depth.
I find the evolution of rock guitar tone to be a fascinating subject. A ā59 Fender Bassman cranked up through its internal 4x10ā speaker configuration sounds nothing like a Mesa Dual Rectifier through its oversized, closed-back 4x12ā cabinet with Celestion Vintage 30s. And the speakers and speaker cabinet are a huge part of the equationāif you were to run the Mesa Recto into the Bassman speakers, youād get a completely different tone, but one that leans in the classic Bassman direction.
The same thing goes for Vox tonesātry running almost any amp into an open back 2x12ā with Celestion Blues and youāll instantly see just how much of that classic Vox character is actually coming from the cabinet.
Itās not always easy to do this kind of research. A lot of these differences become more apparent at volume, and cranking tube amps is just not an option for many guitarists. Assembling a large speaker cabinet collection is even more impractical. But because of these factors, guitarists have long been using speaker simulation devices to simulate the characteristic sound of different cabinets. Devices such as the Palmer PDI-09 apply a filter or EQ curve that mimics the sound of a guitar speaker to the full range output coming off your amp speaker out. This processed signal can then be sent to a PA or recording setup. Devices like this can work well, but you are usually stuck with one or two preset EQ curves, and the filter doesnāt replicate many of the complex factors that come into play when micāing a speakerāthe thump of the cabinet, the airiness, or early reflections.
Recently, a whole new technology has surfaced called Impulse Responses (IRs). The first time I encountered Impulse Responses was in reading about Altiverb, the popular convolution reverb plug in. In lay terms, Altiverb gives you the power to sample any acoustic space you can think of, load it as an IR into the plug in, and voila, you have the characteristic reverb of say, the Sydney Opera House available to you in your DAW. But IRs are not just used for reverbs. You can effectively capture the sonic fingerprint of just about anything you can pass a sound through using IR technologyālike a micād speaker cabinet.
Compared to traditional speaker simulators, I find that IRs offer much greater realism and depth. When you apply an IR to a line out signal from your amp, you are not just applying a preset EQ curve to your ampās signal, you are essentially applying the distinct sonic characteristics of a certain speaker, cabinet, mic, mic preamp, and any early reflections that also make it into the mic during the recording process. There are libraries of IRs available to you at your fingertips, an almost endless variety of cabinet and micāing combinations. You can mix and match and blend virtual cabinets to your heartās content. And when you land on a sound you really like, itās easy to store that sound within your DAW, so you can call it up again later.
Of course, you canāt just plug a line out from your tube amp into your recording console or computer interface. Tube amps need to see a load (either a speaker or a dummy load of some sort). And youāll need a good DAW and a convolution plug in that allows you to load IRs as well. To help us get a handle on what IRs mean for us guitarists, and how we can use them both live and in the studio, Iāve asked Mike Grabinski from Red Wirez Impulse Responses a number of questions.
Thanks for being a part of this, Mike! First off, what is an impulse Response, and how can guitarists incorporate them into their rigs?
Technically, an Impulse Response, or IR for short, refers to a system's output when presented with a very short input signal called an impulse. Basically, you can send any device or chain of devices a specially crafted audio signal and the system will spit out a digital picture of its linear characteristics. For speaker cabs, that means frequency and phase response, phase cancellation between multiple speakers, edge reflections, and other audible signatures wrapped up in the gnarly, old pieces of wood, paper, and glue that guitarists find so endearing. IRs will not capture non-linear stuff like distortion and compression.
When you're capturing an IR from a speaker cab, by necessity you are also sampling your D/A converter, power amp, the mic, mic preamp, your A/D converter, the cables you're using, and the room you are in. Basically, everything that comes in contact with the impulse as it makes it round-trip from your DAW and back again. So, it's important to use high quality gear and have a good recording environment. There's really no cheating physics.
Once you've captured a speaker cabinet IR, you process the signal coming from your amp by convolving it with the IR, imprinting the signal with the sound of your speaker cabinet. There are quite a few plug-ins and a few devices these days that will do the convolution part.
What are the benefits of using impulse Responses versus traditional micāing of speaker cabinets? IRs give you access to gear and acoustic spaces that might be too expensive or otherwise unattainable. The ability to run totally silent can be a real plus, too. Especially when cranking even a 30-watt amp can make your ears bleed, your dog run for the hills, or make your neighbors call the SWAT team.
IRs are a boon in a live situation, as well. Because you are essentially going straight from your rig into the house system, a setup using IRs is mostly immune to bleed and feedback from other instruments. You have more control over your tone. You are no longer at the mercy of the overworked sound guy, who would probably love to spend 10 minutes finding just the right mic position, but just doesn't have the time. And because you are eliminating a lot of the variables from the process, you can more easily reproduce your tone from venue to venue.
In your opinion, how close does an impulse response come to replicating the tone and overall coloration that that the typical cabinet/mic/mic preamp chain creates?
Early on I did double blind tests to convince myself it was worth the effort and expense to sample all these cabs. When levels are matched and you are comparing an IR and a mic in exactly the same position it is very hard to hear any difference at all. With dynamic mics, at least, I can sometimes pick out the IR, because a mic like the SM57 exhibits some distortion and I know what to listen for, and more importantly I actually know one of them is a real mic and one is an IR. With condenser mics, which are generally more linear, they sound pretty much identical. If you gave someone a recording and didn't tell them you were using IRs, they would never know, or even think to ask.
What's the best way to get your guitar amp signal into an Impulse Response that's loaded up in a typical computer host?Well, if making noise is an option, the best way, in my opinion, is to tap your amp's speaker out with a DI that can handle the power and then pass the signal through to a real speaker. That way, you are capturing preamp and power tube distortion and your amp still gets a reactive load. You don't really care what the speaker sounds like because you are going to be using IRs for the tone. You can shove it in a closet in the basement and as long as it can move some air, it's shouldn't negatively impact the DI signal. Some amps have the DI function built into the amp. Some even tap the signal coming from the power tubes, so a separate DI is not always necessary.
If you have to run silent, then you need a dummy load to take the place of the speaker, otherwise you can damage your amp's output transformer. There are lots of attenuators that also function as dummy loads out there. It is important to understand that your tube amp will probably react differently to a dummy load and you may find that your tone is missing the low-end bump and upper-mid rise you are accustomed to when using a speaker.
There can be several reasons for this, but one major factor is that speakers do not present a uniform load to your amp. If you look at a typical guitar speaker's impedance curve, which is a plot of the speaker's impedance across the frequency spectrum, you will see a big low-end bump and a steady upper-mid rise. This can also be described as a midrange scoop, depending on your perspective.
The load, or impedance, measured in ohms, will differ based on the frequency of the your amp's output. Solid-state amps have low output impedance, so their power output is not jerked around very much by the speaker's varying load. Tube amps have relatively high output impedance and as a result they deliver more power as the impedance of the speaker rises. And for a typical guitar speaker, that means you hear more bass and upper-mids.
Because a lot of dummy loads and attenuators present a uniform load to the amp, your amp's output will remain constant across the frequency spectrum. If you're accustomed to a low-end bump and upper-mid rise, you will probably hear this as the dreaded attenuator tone suck. To alleviate tone suck, you can use EQ. An alternative would be to use the sampled impedance curve of a real speaker to adjust the highs and lows in an authentic way.
What equipment does a musician need in order to use Impulse Responses with amplifiers, both live and in the recording studio?
You need a load for your amp, either a speaker or dummy load and a DI capable of tapping the speaker out of your amp. You also need a means to convolve the IR with your amps' output. In the studio, you can use a convolution plug-in. There are quite a few, including our own mixIR2 (wink, wink, nudge, nudge).
Live, the options are fewer and generally more expensive because you need a reliable device with enough horsepower to do the convolution with minimal latency. Not an easy task on a stage.
Letās look at that for a minute. It's relatively easy to load an IR into a host on a computer in the studio, but what about boxes that allow you to do this easily live, in a road-worthy portable package? Say, with a built in load for your amp, and with multiple memory locations for IRs so you can load them up and take them to the gig? What's out there now, and do you see a market for more boxes like this down the road?
There aren't too many that I know of. There's the Fractal Audio Axe-Fx and Axe-Fx II, the Torpedo VB-101, and apparently you can load IRs into the Digitech GSP 1101 with some unofficial firmware mods. It is my understanding that the GSP 1101 truncates the IRs to 128 samples, which would limit your low and low-mid resolution. I suppose you could rig up a laptop, but I'm not sure how reliable and road-worthy that would be.
There seems to be increasing interest in these kinds of devices, so I'm sure more will pop up in the future.
Right. Also, we should mention, the Axe-FX and the GSP 1101 wonāt provide a load for a tube amp but they do work great as hosts for IRs. I use the Axe FX this way live. Anything else you'd like to share?
San Dimas High School Football rules!
[Updated 12/12/21]
- The Recording Guitarist: Impulse ControlāMastering Fake Spaces ... āŗ
- The Recording Guitarist: Speakers? We Don't Need No Stinking ... āŗ
- Amp Mic'ing vs. Impulse Responses - Premier Guitar āŗ
Guest columnist Dave Pomeroy, who is also president of Nashvilleās musicians union, with some of his friends.
Dave Pomeroy, whoās played on over 500 albums with artists including Emmylou Harris, Elton John, Trisha Yearwood, Earl Scruggs, and Alison Krauss, shares his thoughts on bass playingāand a vision of the future.
From a very young age, I was captivated by music. Our military family was stationed in England from 1961 to 1964, so I got a two-year head start on the Beatles starting at age 6. When Cream came along, for the first time I was able to separate what the different players were doing, and my focus immediately landed on Jack Bruce. He wrote most of the songs, sang wonderfully, and drove the band with his bass. Playing along with Creamās live recordings was a huge part of my initial self-training, and I never looked back.
The electric bass has a much shorter history than most instruments. I believe that this is a big reason why the evolution of bass playing continues in ways that were literally unimaginable when it began to replace the acoustic bass on pop and R&B recordings. Players like James Jamerson, Joe Osborn, Carol Kaye, Chuck Rainey, and David Hood made great songs even better with their bass lines, pocket, and tone. Playing in bands throughout my teenage years, I took every opportunity I could to learn from musicians who were more experienced than I was. Slowly, I began to understand the power of the bass to make everyone else sound betterāor lead the way to a train wreck! That sense of responsibility was not lost on me. As I continued to play, listen, and learn, a gradual awareness of other elements came to the surface, including the three Ts: tone, timing, and taste.
I was ready to rock the world with busy lines and bass solos when I moved to Nashville in the late ā70s, and I was suddenly transported into the land of singer-songwriters. It was a huge awakening when I heard the lyrics of artists like Guy Clark, whose spare yet powerful stories and simple guitar changes opened up a whole new universe in reverse for me. It was a reset for sure, but gradually I found ways to combine my earlier energetic approach in different ways. Playing whatās right for a song is a very subjective thing.
āIf the song calls for you to ramp up the energy and lead the way like Chris Squire, Bootsy Collins, Geddy Lee, Sting, Flea, Justin Chancellor, or so many others, trust yourself and go for it.ā
Don Williams, whom I worked with for many years, was known as a man of few words, but he gave me some of the best musical advice I ever received. I had been with him for just a few months when he pulled me aside one night after a show, and quietly said, āDave, you donāt have to play whatās on the records, just donāt throw me off when Iām singing.ā In other words: Itās okay to be creative, but listen to whatās going on around you. I never forgot that lesson.
As I gradually got into recording work, in an environment where creativity is combined with efficiency and experimentation is sometimes, but not always, welcome, I focused on tone as a form of expression, trying to make every note count. As drum sounds got much bigger during the ā80s, string bass was pretty much off the table as an option in most situations. Inspired by German bassist Eberhard Weber, I bought an electric upright 5-string built by Harry Fleishman a few years earlier. That theoretically self-indulgent purchase gave me an opportunity to carve out a tone that would work with both big drums and acoustic instruments. It gave me an identifiable sound and led to me playing that bass on records with artists like Keith Whitley, Trisha Yearwood, Alison Krauss, Emmylou Harris, and the Chieftains.
In a world of constantly evolving and merging musical styles, the options can be almost overwhelming, so itās important to trust yourself. Ultimately, you are making a series of choices every time you pick up the instrument. Whether itās pick versus fingers versus thumb, or clean versus overdrive versus distortion, and so on ⦠you are the boss of your role in the song you are playing. When the sonic surroundings you find yourself in change, so can you. Itās all about listening to what is going on around you and finding that sweet spot where you can bring the whole thing together while not attracting too much attention.
On the other hand, if the song calls for you to ramp up the energy and lead the way like Chris Squire, Bootsy Collins, Geddy Lee, Sting, Flea, Justin Chancellor, or so many others, trust yourself and go for it. Newer role models like Tal Wilkenfeld, Thundercat, and MonoNeon have raised the bar yet again. The beauty of it all is that the bass and its role keep evolving.
Right now, I guarantee there are young bassists of all descriptions we have not yet heard who are reinventing the bass and its role in new ways. Thatās what bass players doāwe are the glue that ties music together. Find your power and use it!
A reverb-based pedal for exploring the far reaches of sound.
Easy to use control set. Wide range of sounds. Crush control is fun to explore. Filter is versatile.
Works best as a stereo effect, which may limit some players.
$299
Old Blood Noise Endeavors Dark Star Stereo
oldbloodnoise.com
The Old Blood Dark Star Stereo (DSS) is one of those pedals that lives beyond simple effect categorization. Yes, itās a digital reverb. But like other Old Blood designs, itās such a feature-rich, creative take on that effect that to think of it as a reverb feels not only imprecise but unfair.
The Old Blood Dark Star Stereo (DSS) is one of those pedals that lives beyond simple effect categorization. Yes, itās a digital reverb. But like other Old Blood designs, itās such a feature-rich, creative take on that effect that to think of it as a reverb feels not only imprecise but unfair.
In this case, reverb describes how the DSS works more than how it sounds. Iāve come to think of this pedal as a reverb-based synthesizer, where reverb is the jumping-off point for sonic creation. As such, the sounds coming out of the Dark Star can be used as subtle sweetener or sound design textures, opening up worlds that might otherwise be unreachable.
Reverb and Beyond
Functionally speaking, the DSS starts with reverb and applies a high-/low-pass filter, two pitch shifters, each with a two-octave range in each direction, plus bit-crushing and distortion. Controls for lag (pre-delay), multiply (feedback), and decay follow, with mini knobs for volume, mix, and spread. Additional control features include presets, MIDI functionality, plus expression and aux control.
The DSS can be routed in mono, stereo, or mono-in/stereo-out. Both jacks are single TRS, and itās easy to switch between settings by holding down the bypass switch and selecting via the preset button.
Although it sounds great in mono, stereo is where this iteration of the Dark Starāwhich follows the mono Dark Star and Dark Star V2āreally comes alive. Starting with the filter, both pitch shifters, and crush knobs at noonāall have center detentsāaffords the most neutral settings. The result is a pad reverb, as synthetic as but less sparkly than a shimmer. The filter control is a fine way to distinguish clean and effect signals. In low-pass mode, the effect signal can easily get dark and spooky while maintaining fidelity and without getting murky. On the other end, high-pass settings are handy for refining those reverb pads and keeping them from washing out the clarity of the clean signal.
Lower fidelity is close at hand when you want it. The crush control, when turned counterclockwise, reduces the bit rate of the effect signal, evoking all kinds of digitally compromised sounds, from early samplers to cell phones, depending on how you flavor it. Counterclockwise applies distortion to the reverb signal. Thereās a lot to explore within the wide ranges of the two pitch controls, too. With a four-octave range, quantized in half steps, the combinations can be extreme, and Dark Star takes on a life of its own.
Formless Reflections of Matter
The DSS is easy to get acquainted with, especially for a pedal with so many features, 10 knobs, and two footswitches. I quickly got a feel for the reverb itself at the most neutral filter and pitch settings, where I enjoyed the weight a responsive, textural pad lent to everything I played.
With just the filter and crush controls, thereās plenty to explore. Sitting in the sweet spot between a pair of vintage Fenders, I conjured a Twin Peaks-inspired hazy fog to accompany honeyed diatonic arpeggios, slowly filtering and crushing that sound into a dark, evil low-end whir as chords leaned toward dissonance. Eventually, I cranked the high-pass filter, producing an early MP3-in-a-good-way āshhhā that was fine accompaniment to sparser voicings along my fretboard. It was a true sonic journeyThe pitch controls increase possibilities for both ambience and dissonance. Simple tweaks push the boundaries of possibility in exponentially deeper directions. For more subtle thickening and accompaniment sounds, adding octaves, which are easy to tune by ear, offers precise tone sculpting, dimension, and a wider frequency range. Hearing simple harmonic ideas plucked against celeste- and organ-like reverberations kept me in the Harold Budd and Brian Eno space for long enough to consider new recording projects.
There is as much fun to be had at the highest feedback settings on the DSS. Be forewarned: Spend too much time there and you might need a name for your new ambient band. Cranking the multiply and decay knobs, Iād drop in a few notes, or maybe just a chord, and get to work scanning the pitch knobs and sculpting with the filter. Soon, I conjured bold Ligeti-inspired orchestral sounds fit for a guitar remix of 2001: A Space Odyssey.
The Verdict
The Dark Star Stereo strikes a nice balance between deep control, a wide range of sonic rewards, playability, and an always-sounds-great vibe. The controls are easy to use, so it doesnāt take long to get in the zone, and once you do, thereās plenty to explore. Throughout my time with the DSS, I was impressed with its high-fidelity clarity. I attribute that to the filter, which allows clean and reverb signals to perform dry/wet balance and EQ functions. That alone encouraged more adventurous and creative exploration. Though not every player needs this kind of tone tool, the DSS is a must-check-out effect for anyone serious about wild reverb adventures, and itās simple and intuitive enough to be a good fit for anyone just starting exploration of those zones. However you come to the Dark Star, itās a unique-sounding pedal that deserves attention. PG
Introducing the new Gibson Acoustic Special models, handcrafted in Bozeman, Montana, featuring solid wood construction, satin nitrocellulose lacquer finishes, and L.R. Baggs electronics.
Solid Wood Construction
Each of the three Acoustic Special models from Gibson are crafted using solid mahogany for the back and sides, solid Sitka spruce for the tops, utile for the necks, and rosewood for the fretboards for a sound that will only get better and better as they age.
Satin Nitrocellulose Lacquer Finishes
All three Gibson Acoustic Special models are finished in satin nitrocellulose lacquer for a finish that breathes, ages gracefully, and lets the natural beautyāboth in sound and appearanceāof the quality tonewoods come through.
L.R. Baggs Electronics
The Gibson Acoustic Special guitars come with L.R. Baggs Element Bronze under-saddle piezo pickups and active preamps pre-installed, making them stage and studio-ready from the moment you pick them up.
For more information, please visit gibson.com.
Introducing the Gibson Acoustic Specials ā J-45, Hummingbird & L-00 Special - YouTube
Great Eastern FX Co. has released the limited-edition OC201 Preamp, featuring vintage Mullard OC201 transistors for a unique fuzz sound. Part of the 'Obsolete Devices' series, this pedal combines classic circuits with modern components for optimal tone and reliability.
Boutique British pedal designers GreatEastern FX Co. have released a new pedal. Limited to just 50 units, the OC201 Preamp is an intriguing twist on the familiar two-transistor fuzz circuit, built around a pair of new-old-stock Mullard OC201 transistors.
āThe OC201 is a very early silicon transistor,ā company founder David Greeves explains. āIt was actually the first silicon transistor made by Mullard, using the same method as their germanium devices. Itās pretty crude by modern standards, with very low gain and limited bandwidth, but thatās exactly what makes it so great in a fuzz pedal.ā
This little-known low-gain silicon transistor is responsible for the OC201 Preampās palette of sounds, which GreatEastern FX say ranges from dirty boost and garage rock drive sounds up to a raw and richly textured fuzz, all with the excellent volume knob clean-up characteristics this style of fuzz is famous for. The circuit has also been tweaked to deliver a healthy kick of volume to your amp.
This limited-edition pedal is the first in a new series that Great Eastern FX are calling āObsolete Devicesā. According to the company, the Obsolete Devices series will feature the companyās take on a range of classic circuits, constructed using a mixture of vintage and modern components. Itās a distinct departure from Great Eastern FXās main range of pedals.
āWith pedals like the Design-a-drive and the XO Variable Crossover, weāre really committed to developing original designs that bring something new to the table,ā founder David Greeves explains. āIām always very conscious of choosing parts that arenāt going to go obsolete so we can go on making the pedals for as long as people want to buy them. But I also love messing around with old parts and classic circuits, which is a totally different mentality. The Obsolete Devices series is basically a way for me to have fun modifying these classic circuits and experimenting with my stash of NOS components, then share the results.
āThe name is a little bit of an inside joke,ā he continues. āI think what gets labelled as āobsoleteā is very subjective. As pedal designers and guitar players, we obsess over obsolete components and what, in any other field, would be considered outdated designs. So the name is a nod to that. I also loved the thought of us coming out with some brand-new Obsolete Devices of our own!ā
Alongside the pedalās new-old-stock Mullard OC201 transistors ā which are the reason only 50 of them are being made ā the OC201 Preamp uses quality modern components, including high-tolerance Dale metal film resistors and WIMA capacitors. GreatEastern FX say that this hybrid approach, using vintage parts where they make the most difference sonically and low-noise modern parts elsewhere, will deliver the best combination of tone and reliability while also keeping the price from spiralling out of control.
The OC201 Preamp will cost Ā£249 in the UK, $299 in the US and ā¬299 in the EU. Itās available now direct from Great Eastern FX Co. and from the following dealers:
- UK ā Andertons
- Europe ā Pedaltown.nl
- USA ā Sound Shoppe NYC
- Canada ā Electric Mojo Guitars
For more information, please visit greateasternfx.com.