The Complete Guide to Re-Amping

How to Separate Sound from Performance

by Craig Anderton

It used to be that recording a guitar part set its sound in stone. Sure, you could add EQ, reverb, or other processors while mixing, but they provided variations on a theme, not an entirely different theme.

But now, if you wish you’d recorded through a Marshall stack instead of a Vox AC30—no problem. There are two main options for changing your sound after the fact: traditional re-amping, and virtual re-amping with software plug-ins. Although re-amping has been around for a while, the quest for increased sound quality has spawned new re-amping solutions.

Furthermore, re-amping isn’t just for guitar any more. Playing back drums, vocals, synthesizers, and other instruments through guitar amps yields entirely new tonalities. But before proceeding, I’d like to thank Peter Janis of Radial Engineering (who make boxes for re-amping, among other things) for his research on the history of re-amping, and for contributing several useful tips.

Ready to re-amp? Let’s rock.

HARDWARE RE-AMPING

“Classic” re-amping was done originally with mixers, recorders, and amps, and applied mostly to guitars. This remains a common technique, and even virtual re-amping may incorporate a bit of hardware-based re-amping.

The basic idea is to record the dry guitar sound while monitoring through an amp so the guitarist can get the right “feel” (and if feedback is a component of the sound, suitable sustain characteristics). Typically, you record the amp as well because it might end up being the sound you want.

If not, the next re-amping step is to send the dry guitar track out from the recorder and into an amp, set the amp sound as desired, then record the “re-amped” sound. As the recorder’s signal will likely be line level, applying it to a standard guitar amp will really overload the sucker and create some major distortion. If that’s not what you want, you’ll need to pad down the signal feeding the amp to something approximating standard guitar levels.

Also note that re-amping makes sense for any instrument (especially synthesizer) that’s recorded direct. Running the track through an amp, and miking the amp and/or room ambience, can impart a new sense of “space.”

RE-AMPING IN THE REAL WORLD

Producer/engineer Dave Bottrill (who uses a Radial JD7 for re-amping; see Fig. 1) says that “It’s now my standard practice to record a DI along with the rest of the cabinets or combos I record. Invariably one of the songs I am working on for a record needs some kind of re-amping, and on the Godsmack CD, it proved invaluable when we discovered some faults with the signal path when we recorded some of the guitars. There were analog distortions along the line, and we just took the DI and sent it back through the same path (luckily we hadn’t torn down the setup) and were able to recreate the sound exactly without the line crackle.

Fig. 1: Radial Engineering's JD7 does re-amping, but can also distribute the signal to multiple amps or effects systems.

“Creatively, a re-amping box allows me to send all kinds of signals through my stomp box collection with the correct impedance. For example, I love the sound of drums through my old Electro-Harmonix Micro Synth pedal.”

THE LOADING ISSUE

To capture a characteristic guitar sound, you need to record the same thing you would hear if the guitar connected directly to an amp. Although many people like the “high-fidelity” sound of a guitar feeding an ultra-high impedance input, others prefer the slight dulling that occurs with a low-impedance load (e.g., around 5-100 kohms) as found with some effects boxes, older solid-state amps, etc. This is especially useful when the guitar precedes distortion, as distorting high frequencies can give a grating, brittle effect that resembles Sponge Bob on helium.

There are several ways to load down your guitar:

• Find a box that loads down your guitar by the desired amount, then split the guitar to both the box and the mixer or audio interface’s “guitar” input.
• If your recorder, mixer, or sound card has a guitar input, try using one of the regular line level inputs instead.
• Use a box with variable input impedance (e.g., the “drag control” on Radial products)
• Create a special patch cord with the desired amount of loading by soldering a resistor between the hot and ground of either one of the plugs. A typical value would be 10 kohms.
• If you’re going through host software with plug-ins, insert an EQ and roll off the desired amount of highs before feeding whatever produces distortion (e.g., an outboard amp that feeds back into the host, or an amp simulator plug-in). However, this doesn’t sound quite as authentic as actually loading down the pickup, which creates more complex tonal changes.

Note that you need to add this load while recording, as it’s the interaction between the pickup’s inductance and load that produces the desired effect. Once the dry track is recorded, the pickup is out of the picture.

But just because we have a signal doesn’t mean we can go home and collect our royalties, because this signal now goes through a signal path that may include pedals and other devices. As guitarists are very sensitive to the tone of their rigs, even the slightest variation from what’s expected may be a problem. For example, the transformers in some direct boxes or preamps color the sound slightly, so the guitarist might want to send the signal through the transformer, even though transformer isolation is usually not necessary with a signal coming from a recorder.

VIRTUAL RE-AMPING

Plug-ins and low-latency audio interfaces have opened up “virtual re-amping” options. Guitar-oriented plug-ins include IK Multimedia AmpliTube, Native Instruments Guitar Rig, Line 6 POD Farm, Scuffham Amps, Waves G|T|R|, iZotope Trash, Peavey ReValver, Overloud TH2, McDSP Chrome Tone, and others.

The concept is similar to hardware-based re-amping: Record the direct signal to a track, and monitor through an amp. The key to "virtual re-amping" is that the host records a straight (dry) guitar signal to the track. So, any processing that occurs depends entirely on the plug-in(s) you've selected; you can process the guitar as desired while mixing, including changing "virtual amps." When mixing, you can use different plug-ins for different amp sounds, and/or do traditional hardware re-amping by sending the recorded track through an output, then into a mic’ed hardware amp.

Using plug-ins has limitations. If feedback is part of your sound, there’s no easy way to create a feedback loop with a direct-recorded track. This is one reason for monitoring through a real amp, as any effect the amp has on your strings will be recorded in the direct track. Still, this isn’t as interactive as feeding back with the amp that creates your final sound. And plug-ins themselves have limitations; although digital technology does a remarkable job of modeling amp sounds, picky purists may pout that some subtleties that don’t translate well.

Furthermore, monitoring through a host program demands low-latency drivers (e.g., Steinberg ASIO, Apple Core Audio, or Microsoft’s low-latency drivers like WDM/KS). Otherwise, you’ll hear a delay as you play. Although there will always be some delay due to the A/D and D/A conversion process, with modern systems total latency can often be under 10ms. For some perspective, 3 ms of latency is about the same delay that would occur if you moved your head 1 meter (3 feet) further from a speaker—not really enough to affect the “feel” of your playing.

If latency is an issue, there are other ways to monitor, like ASIO Direct Monitoring. Input signal monitoring (often called zero-latency monitoring) is essentially instantaneous; the signal appearing at the audio interface input is simply directed to the audio interface out, without passing through any plug-ins. With this method you can also feed the output to a guitar amp for monitoring, while recording the straight signal on tape.

In any event, regardless of whether you use hardware re-amping, virtual re-amping, or a combination, the fact that the process lets you go back and change a track’s fundamental sound without having to re-record it is significant. If you haven’t tried re-amping yet, give it a shot—it will add a useful new tool to your bag of tricks.

Background: A History of Re-Amping

by Peter Janis, Radial Engineering

As with so many aspects of audio, it’s hard to pin down exactly when a technique was first used, and that goes for re-amping. While Reamp made the first commercial box designed expressly for this purpose, engineers had already been creating re-amping setups for years.

Recording historian Doug Mitchell, Associate Professor at Middle Tennessee State University, comments that “The process of ‘re-amping’ has actually been utilized since the early days of recording in a variety of methods. However, the actual process may not have been referred to as re-amping until perhaps the late ’60s or ’70s. From the early possibilities of recording sound, various composers and experimenters utilized what might be termed ‘re-amping’ to take advantage of the recording process and to expand upon its possibilities.

The first commercially available box for re-amping has been tweaked and revised over the years.

“In 1913 Italian Futurist Luigi Russolo proposed something he termed the ‘Art of Noises.’ Recordings of any sound (anything was legitimate) were made on Berliner discs and played back via ‘noise machines’ in live scenarios and re-recorded on ‘master’ disc cutters. This concept was furthered by Pierre Schaeffer and his ‘Musique Concrète’ electronic music concept in the ’30s and ’40s. Schaeffer would utilize sounds such as trains in highly manipulated processes to compose new music ideas. These processes often involved the replaying and acoustic re-recording of material in a manipulated fashion. Other experimenters in this area included Karlheinz Stockhausen and Edgard Varèse.

“With the possibilities presented by magnetic recording, the process of what might be termed re-amping was utilized in other ‘pop’ music areas. Perhaps the first person to take advantage of this was Les Paul. His recordings with Mary Ford often utilized multiple harmonies all performed by Mary. Initially these harmonies were performed via the re-amping process. Later, Les convinced Ampex to make the first 8-track recorder so that he might utilize track comping to perform a similar function. Les is also credited with the utilization of the re-amping process for the creation of reverberant soundfields, by placing a loudspeaker at one end of a long tunnel area under his home and a microphone at the other end. Reverberation time could be altered with the placement of the microphone with respect to the loudspeaker playing back previously recorded material.

“Wall of sound pioneer Phil Spector is perhaps the most widely accredited for the use of the re-amping process, and because of his association with the Beatles, is potentially regarded today as the developer of the process. However, Phil was actually refining a process and exploring its possibility for use in rock music.

“‘Re-amping’ is often used in film sound design as well. In order for sounds recorded in a post-production environment to match the scene, it is common to re-record them utilizing a re-amping procedure. In film sound this process is also termed ‘worldizing.’

Bob Ohlsson of Motown fame, who has worked with Stevie Wonder, Marvin Gaye, the Kinks, and many others had another perspective: “I began doing it in 1968, shortly after we got 16-track machines, because for the first time we could separately record direct guitars, clavinets, and electric pianos. I had never heard of it being done and am pretty sure I was the first to try it at Motown, but I can’t imagine lots of others weren’t doing the same thing. It seemed like a very obvious thing to do in a world where electric instruments were taken direct primarily to cut down on bleed rather than for tonal quality.”

And the late Roger Nichols was another early adopter. “I started using the process in 1972, when I built the re-amper we used on the first Steely Dan album, and almost every one after that. We used it to play direct guitar tracks back through an amp. We were going through a lot of amps; the speakers would get tired or the tubes would melt or something during a night of guitar overdubs.

“We would go through one amp to make sure we got the sound we wanted, and then when the right guitar and settings were locked in, we recorded the direct signal and let the amp rest. After the part was completed, we ran the signal back through the guitar amp and it only had to last long enough to print the results to tape. I still have the box around here somewhere.” (According to Jonathan Little of Little Labs, Jeff Harris at the Arizona Conservatory has one of Roger’s early boxes.)

In 1980 Jensen Transformers introduced the JT-DBE transformer and in the application note, a paragraph discusses using this transformer to convert low impedance balanced lines to guitar levels. In the 1980s Whirlwind also produced a device that could accommodate low-to-hi conversion using a transformer.

The Multi Z PIP is only one of several products from Little Labs that does re-amping.

In 1994, Reamp commercialized the process by producing a box that incorporated a transformer and a volume control. This was a follow-up to the original box that Reamp founder John Cuniberti used on sessions with Steve Vai, and allowed the user to adjust the volume at the amplifier instead of at the mix position. In 1996, the first generation Radial JDI was introduced, and was designed with re-amping, among other applications, in mind; the Radial JD7 Injector, released in 2001, offered a balanced output and input to allow re-amping and subsequent re-distribution of signals to multiple amplifiers. Furthermore, the IBP from Little Labs, while intended mainly to provide phase compensation for signals, also provides re-amping functions, as does their Multi Z PIP.

Acknowledgment: Thanks to Frank Wells at Pro Sound News and Mitch Gallagher for helping us track down these folks. — Peter Janis

Virtual Re-Amping in Sonar X3

Here’s the procedure for re-amping in Sonar X3, but note that the procedure is similar for other DAWs.

Fig. 5: Enabling input echo means that the input signal will be processed by whatever plug-ins are inserted in the track.

1. Check that there’s no feedback loop from the host output back to the input. To be safe, turn down your monitor speakers.
2. Enable the driver for the input you’re going to use for plugging in your guitar (under Edit > Preferences > Audio > Devices).
3. Create an audio track, then from the I/O Input field, select the appropriate hardware input that you enabled in the previous step.
4. Turn on the Input Echo function (in the Track view, click on the button to the right of the Record button). It will glow blue; see Fig. 5.
5. Enable the track’s Record button. You should hear your input source.
6. Insert the plug-in(s) of your choice into the FX field.
7. Your input source will play through the plug-in . . . start recording!

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.