FIG. 1: Native Instruments Guitar Rig 2 exemplifies the trend in guitar amp plug-ins to let you configure not only which components to use, but their routing too.
Few would dispute that the ultimate electric guitar tones are recorded from miked-up tube amps. That is, if you have a nice amp you can crank up, a good-sounding recording space (if you're using room mics), and time to experiment. But what if you don't? Or what if you have limitations on volume in your studio, don't want the amp sound to leak into other mics, or don't want to decide on the final guitar sound until mixdown? In those cases, direct recording may be the best alternative.
In recent years, amp- and cabinet-simulating modeling processors and plug-ins have made the task of getting a realistic tone from a DI (direct injection) — recorded guitar much easier. Those products let you process your guitar signal (during either tracking or mixdown) with amp, preamp, cabinet, and effects emulations. Plug-ins like Native Instruments Guitar Rig 2 (see Fig. 1), IK Multimedia's AmpliTube 2 (see Web Clip 1), and Waves GTR 2.0 (reviewed in this issue) not only give you a large selection of amp, cabinet, and effects models, they also let you specify the routing of your virtual components. Even though modeling devices and plug-ins may not be able to precisely match the sound of a boutique or vintage tube amp, they offer a much wider range of tones.
At its most basic, a DI setup contains a guitar patched into a digital audio sequencer or a multitrack through a high-impedance guitar input in an audio interface or a mic preamp, possibly with the signal first going through a direct box. In order to accurately capture the tone of your pickups, it's important to use an input with an impedance that's optimized for guitar. Guitar inputs on many preamps, audio interfaces, and DI boxes have a 1 MΩ input impedance, which is the same value found on the inputs of classic tube amps from companies like Vox, Fender, and Marshall. If your input device has an impedance substantially below 1 MΩ, you may notice a rolling off of high end. Impedances above 1 MΩ can yield a brighter, more sparkly tone.
If your audio interface doesn't have a dedicated instrument input, you'll probably want to use a direct box. If you're recording through a mixer, a direct box is usually the best way to go too. A direct box converts your high-impedance, unbalanced guitar signal into a low-impedance, balanced signal that's output on an XLR connector and can be patched into one of the mic preamps on the mixer or audio interface. (Most of the time you'll want to go through a mic preamp, but some DI boxes, such as Groove Tubes' Ditto Box, provide sufficient gain to patch into a line input.) It also outputs the signal through a ¼-inch pass-through jack for connection to an amp or guitar processor if desired. On some direct boxes, this output is buffered, which allows for longer cable runs without signal loss.
On any direct box, the main XLR, low-impedance output gives you the ability to send your signal unaffected through long cable runs, such as in a studio with tie lines. The main output is also balanced, which can help prevent noise on the line.
DI boxes come in two basic flavors. Active direct boxes contain active electronics, including a buffer amp that lowers the impedance of the incoming signal. These devices require either battery, 48V phantom, or AC power. Passive direct boxes alter the impedance by way of an internal transformer and require no power.
While many DI boxes simply convert your signal, others offer additional features. For instance, the Behringer GI100 adds speaker simulation. Radial Engineering's JDV active direct box (as well as several of the company's other devices) has a circuit called Drag Control, which is designed to re-create the relationship between a guitar pickup and a tube amp in situations where you're using a solid-state input device. It gives you a knob that alters the impedance load to your pickups, letting you dial in the most natural sound. Radial also offers a standalone Drag Control product called the Dragster.
Quality Is Key
Not all DI boxes, preamps, and other input devices sound the same. Just as different mic pres yield different sounds when fed by the same mic on the same source, different input devices give you different sounds from the same guitar. The quality of the input device's components is a key factor.
Use the highest-quality input device you have access to, and find one that works well with your guitar. Even if you're going to be reamping the part later, it's still important to start by recording the best possible sound. A number of engineers I've spoken with like to use a tube preamp for DI guitar parts, because they feel it helps inject a more realistic tone, even to a part that will later be reamped. (In the process of reamping, you take a clean DI guitar track and patch it out to an amp, first going through a dedicated reamping processor to convert the output to an impedance appropriate for a guitar input, and then rerecord it with a mic through the amp. See the sidebar “Reamping the Old-Fashioned Way.”)
When deciding how to record a DI guitar part that will be processed with a modeler, you have one fundamental choice: will you record the modeled tone directly onto a track of your sequencer or multitrack, or will you record it unprocessed and insert the processor's tone during mixdown? There are advantages to each method, and your gear may dictate your decision.
FIG. 2: The M-Audio Black Box is one of several guitar-recording devices on the market that offer amp, cabinet, and effects modeling, and a USB audio interface for recording direct.
Most outboard modeling processors are better suited for use as direct boxes that output a processed sound to a recording device, rather than as insert effects that are used on unprocessed, previously recorded guitar tracks.
Generally, modeling processors have only high-impedance inputs, which aren't designed for the line-level, low-impedance outputs that you would need to connect them to if you were using them as inserts. So unless your processor has line-level inputs (such as the Line 6 Pod XT Pro and the Tech 21 SansAmp PSA 1.1), its architecture dictates that you use it as a DI and record its processed sound to disk.
Many outboard modeling units (for example, the Line 6 Pod XT, the DigiTech GNX4, and the M-Audio Black Box; see Fig. 2) have USB outputs that allow them to function as audio interfaces in their own right. Alternatively, you can plug their analog outputs into the line inputs of an audio interface.
Perhaps the biggest advantage of recording through an outboard modeling processor is simplicity. Just as if you were going through an amp (or an amp with effects pedals), what you hear is what you get. Find a tone you like, record the track with it, and you're done. Because your signal is being processed before it hits the computer, latency is not as big an issue as it is when using a plug-in modeler.
REAMPING THE OLD-FASHIONED WAY
Although you can reamp with a modeling plug-in in your sequencer, or a modeling effect in your personal digital studio, the traditional process of reamping entails taking a guitar track that's already been recorded and patching its output to a guitar amp (see Fig. A). You then play back the guitar track with a mic (or mics) on the amp and rerecord it onto a fresh track.
FIG. A: Traditional reamping involves recording an unprocessed track and then patching it out of the recorder into a guitar amp, where the signal is miked and brought back into the multitrack.
It's not advisable to simply take a line out of your sound card or multitrack and run it into a guitar amp for reamping. The line-level signal will be mismatched with the high-impedance input on your guitar amp. You'll need to run it through a box such as the Radial X-Amp, or the Little Labs Red Eye, which converts your line-level signal back to a high-impedance guitar signal suitable for plugging into an amp. You could also plug the converted signal into an outboard modeling processor.
If you're a guitarist who records in studios besides your own, going direct through an outboard modeler is an excellent and lightweight option for toting your sound around. Unless you really trust the engineer or producer on a particular session, you probably don't want to record an unprocessed DI part and let them add the modeled amp and cabinet tones later, when you're not around. With an outboard processor, you can have your best sounds saved as presets and ready to go for any type of session, and you'll have more control over your final guitar tone.
One component of a guitar's sound that probably shouldn't get recorded through an outboard processor is reverb. Although your modeling processor likely has many reverb options, it's best to record tracks dry and add the reverb later — even if you won't be present when it's applied. At the time you record your part, it's not always easy to tell how much reverb will sound appropriate in the mix. So it's best not to commit when tracking. This is true not only for DI tracks, but also for miked, guitar-cabinet recordings. Unless you've got a really unusual reverb that's essential to the sound you're going for, I'd recommend turning it off when tracking.
To some extent, the same is true of delay, especially for sounds that use relatively long delay times. It's hard to judge how to set the mix control (wet-to-dry ratio) of such a delay until it's heard in the context of the final mix. What's more, delay plug-ins have the ability to sync to the sequencer's tempo. A tempo-synced delay will often sit better in the track than a manually set (or tap tempo) delay from your outboard processor. (Some modeling processors, like the Black Box and Roger Linn's AdrenaLinn II, can be synced to the host tempo using MIDI Clock.)
Plug and Play
Just as an outboard modeling unit is best suited to processing your guitar sound on the way into the recording device, an amp-modeling plug-in in a sequencer lends itself to being used as an insert effect. Why? Because most digital audio sequencers make it easy for you to insert your modeling plug-in into one of their virtual mixer channels, and monitor the processed sound while recording the guitar to disk unaffected. When you play back the track, it also goes through the plug-in.
Here's how you do it. Connect your guitar to your sequencer using a DI box, audio interface, or mic-preamp instrument input as described earlier. Create a track to record on, and instantiate the modeling plug-in in one of the track's insert slots. If necessary, set your sequencer's input monitoring options to monitor through effects, and you're ready to go.
This approach is doubly advantageous: you get both an amp-modeled sound as you're playing and the flexibility to change sounds later on. Some sequencers, such as Apple Logic Pro 7, Cakewalk Sonar 5, and Steinberg Cubase SX4 — and many personal digital studios — come with their own amp-modeling effects. Adding tone through a plug-in after a track has already been recorded is similar in many respects to the process of reamping.
On a sequencer, the most common obstacle when recording a guitar track while monitoring through a plug-in is latency. It can be an issue because your guitar sound has to pass through the computer's processing before you hear it. This introduces a slight delay, depending on how you've set your record buffer. If it's set too high, the delay may be long enough to throw your timing off (you play a note and hear it back a split second later). If it's too low, and you're working on a project with lots of tracks and plug-ins that are already taxing your processor, you might experience CPU overload during recording or playback.
Another downside of monitoring through your plug-in is that if you want to hear a purely processed guitar sound, you can't take advantage of any low-latency monitoring features that your interface or sound card might offer. That's because such a setup typically lets you hear your input before it goes through your audio system's processing, including any plug-ins.
According to Line 6, its recently released GearBox plug-ins are designed with a unique architecture that provides the advantages of recording unprocessed while monitoring through a plug-in, but also gives you low-latency monitoring (when used in conjunction with the included TonePort DI USB interface or certain other Line 6 hardware units). GearBox plug-ins are available in AU (Mac) and VST (Win) formats.
On the Side
Most sequencers will allow you to commit the sound of your modeling plug-in to disk as you record it, but it typically involves some extra signal routing within the program. Even if you decide to do this, I'd recommend sending your signal to a second track unprocessed to keep your reamping options open.
One advantage of printing your track processed is that you won't have to leave the plug-in active after you've recorded the track. Considering that modeling plug-ins are often CPU hogs, that could save you a nice chunk of processing power.
There's another solution to the CPU usage problem: many sequencers offer a function that lets you “freeze” a track, temporarily rendering it to disk after it's been processed by any inserted plug-ins. Doing so eliminates the CPU hit that your system takes from the track's plug-ins, but allows you to still hear it processed. If you decide later that you want a different sound, just unfreeze the track, and you can change it at will. If your sequencer doesn't have a freeze function, you can always bounce a track to disk and disable the original track.
An increasing number of products have been introduced recently that allow guitarists to plug their instrument into a computer using USB. For DI parts that will be reamped with plug-ins or actual amps, a direct USB connection is an appealing option. As mentioned, many outboard modeling processors have USB outputs.
These days you can even get guitars with USB capabilities. Certain models of the iGuitar line from Brian Moore Guitars feature class-compliant USB audio outputs, which means they work without any drivers. Just plug into your computer and play. Another, less expensive alternative is a ¼-inch-to-USB adapter cable, such as IK Multimedia's Stealth Plug, which should be available by the time you read this.
Electric bass is recorded direct even more frequently than guitar (see “Sweet & Low” in the June 2004 issue of EM, available at www.emusician.com). Bassists recording direct usually go through quality analog preamps and compressors. However, more and more products are becoming available that feature bass-amp and bass-cabinet modeling. If you've got a guitar modeler, it may also have presets designed for bass recording and processing.
FIG. B: IK Multimedia's recently released Ampeg SVX is a modeling plug-in that emulates a variety of Ampeg bass amps.
For example, Guitar Rig 2 and AmpliTube 2 offer bass presets in their standard factory collections. IK Multimedia recently released Ampeg SVX, a dedicated bass-modeling plug-in that provides a large selection of modeled Ampeg bass amps and cabinets, along with effects processing and more (see Fig. B). Some examples of outboard bass processors include Tech 21's SansAmp Bass Driver DI, which lets you dial in a variety of bass-amp tones (using analog circuitry); Line 6's Bass Pod XT; the Korg AX10B; and the DigiTech BP200.
FIG. 3: The Hughes & Kettner Red Box Classic lets you take a direct out or speaker out from your amp and process it with a cabinet emulation before sending it into your DI input.
If you have a modeling amp such as the Vox ValveTronix, Line 6 Vetta, or even the inexpensive Roland Micro Cube (which features Roland's COSM modeling technology), you can take a direct line out to your input device's line in (the Vetta also has a digital output). On many such amps, plugging into the direct out or headphone out will mute the speaker, making the amp function essentially as an outboard processor. Some tube amps, such as those made by Mesa/Boogie, also have direct outputs that are designed to be used when recording. Keep in mind that when using an amp's direct output, you'll be missing the sound of the speaker, so you might want to add a speaker simulation for additional realism.
You could do that with a modeling plug-in, or you could use one of a number of outboard products designed to provide you with a speaker-simulated DI sound. For instance, the Hughes & Kettner Red Box Classic (see Fig. 3) lets you plug your amp's line out or speaker out into it, and then sends a balanced signal, featuring a simulation of a 2 × 12 or 4 × 12 cabinet, to your sequencer or multitrack.
When plugging your speaker output into a simulator, remember that you must always keep a speaker load on your amp, or you might damage its output transformer. The Red Box Classic has a Speaker Thru output, which you connect to your speaker input jack after you've plugged the amp's speaker out to the Red Box's speaker input. Doing so presents your speaker with its accustomed load, avoiding any possible damage. The disadvantage of this arrangement is that you'll still hear the speaker, which will negate one of the benefits of direct recording — silent operation to avoid leakage.
If you're willing to spend considerably more, you can get processors that let you record direct from your amp with the speakers muted. For instance, the Palmer PGA-04 and the Sequis Motherload provide speaker emulation and send a “dummy load” to your speaker input, thus avoiding any potential damage. Another advantage to running an amp with the speakers muted is that you can crank it up really loud, which, with a tube amp, will likely net you a sweeter tone.
A hybrid approach that will give you a real cabinet sound with the flexibility of reamping starts with recording your part clean through a miked amp. Then you can reamp it through a modeling plug-in, adding whatever amp and effects sounds you want.
FIG. 4: Fretted Synth Audio''s FreeAmp 2 is a fully featured freeware amp-, cabinet-, and effects-modeling VST plug-in for Windows.
Where Are the Models?
Even if you don't have a modeling device or plug-in, you can still record some believable DI guitar parts, although it takes more doing and will yield only clean sounds. One trick is to add a tad of room reverb to the track, to give it a bit of space (see Web Clip 2).
Adding some compression can also help your track sound more authentic. Try experimenting with EQ settings too. Applying a highpass filter to cut out some unneeded lows will often improve your track. It will also help the track sit better in the mix. And, as mentioned, a tube preamp can help.
But if you record on a computer, there is no reason to be without amp-modeling software. Even if you don't want to spring for a commercial modeling plug-in, you can find pretty-good-quality freeware modelers for both Mac and Windows. For instance, MDA Combo, which runs on Mac or Windows, gives you speaker simulation, overdrive, and several other sound-shaping parameters. Windows users might also want to try Fretted Synth Audio's FreeAmp 2 (see Fig. 4). This VST plug-in offers amp and cabinet simulations, overdrive, chorus, reverb, delay, tremolo, and more.
Go Directly There
Recording direct is a useful option that should be considered whenever you're tracking guitar. It may not always provide you with the ultimate sound, but it gives you versatility, variety, maximum isolation, and convenience. In many situations, it's simply the best way to go.
Here's a pseudo doubling trick you can use when recording with a direct box. Patch your guitar signal into the DI's instrument input and through its XLR output, and connect the DI's ¼-inch pass-through output to an outboard modeling processor that's connected to another line input on your recorder. Record both signals to separate tracks, panned left and right, and reamp the unprocessed track (from the XLR out) with a modeling plug-in. You can get some really fat sounds without having to double the track (see Web Clip A).
If you have the time, track count, and inclination, recording a doubled rhythm guitar part (especially in rock and pop songs) is a great method for getting thick sounds. Many contemporary recordings feature doubled rhythm guitars. After you've recorded the first track, the trick is to make sure you hear it really well in your monitor mix when recording the second, so that your doubled performance is as close as possible to the original.
Mike Levine is an EM senior editor. Thanks to Mark McCrite, Peter Janis, John Bednar, Orren Merton, and Michael Cooper.
MANUFACTURER CONTACTS Apple Computerwww.apple.com
Brian Moore Guitarswww.iguitar.com
Fretted Synth Audiowww.frettedsynth.com
Hughes & Kettnerwww.hughesandkettner.com
Palmer Audio/JAMS Audio (distributor)www.palmergear.com
Roger Linn Designwww.rogerlinndesign.com
Vox Amplification/Korg USA (distributor)www.voxamps.co.uk