Re-amping is an old technique that allows the producer to keep his or her options open in regard to electric guitar or bass sounds until the last minute. The idea is that you record the dry feed from the guitar, even though the player may be monitoring the sound of an amp. Then, when you come to mix, you feed this dry signal back through the amp of your choice, stick a mic in front of it and add the miked signal back into your mix.
It sounds simple, so why would you need to buy hardware to achieve it? Well, if you already have a suitable high-impedance DI box, you can have a stab at it without using more hardware, but the results may be less than optimal for a number of reasons — not least that the output of an audio interface or soundcard doesn't 'look' the same as the output from a guitar pickup as far as a guitar amp is concerned. It's all a matter of signal levels and source impedance.
Radial take their usual thorough approach by using two pieces of hardware to solve the problem — a high-quality DI box for recording and a specially developed amp driver for feeding the recording back into the amplifier. In fact, there are several Radial DI boxes suitable for recording, specifically the JDI, J48 (reviewed in SOS October 2007) and JDV models, as all that is needed is a high-impedance input, a link through to the amp being used for monitoring and a balanced line-level output for connecting to the recording system.
Radial's X-Amp amp driver looks after the other half of the process and is available on its own (£147 including VAT) or as part of a re-amping kit (£294), which also includes a J48 (£147) and a carry-case. Built with a similar form factor to the DI boxes, the X-Amp runs from an included power adaptor. The power inlet and balanced XLR input are on the rear panel, along with a ground-lift switch that acts on the input side. The construction of the box, which is made from heavy, folded steel, affords protection to the connectors by means of a 'book-style' overhang, and a non-slip rubber mat on the underside helps keep it from sliding around.
The output end is designed to face the user and includes a power-on LED, a clip LED and a screwdriver-adjustable (though fingertips also work...) output level control. There are two outputs, both on unbalanced jacks, the first labelled 'Direct'. This is a transformerless feed and should always be used, as it provides the ground connection to the amplifier. The second output is transformer-isolated, allowing a second amp to be fed without the risk of ground-loop hum, and this has a phase-invert switch, which would normally be used if one guitar amp happened to be wired with its speaker in the opposite phase to the other. It can also be used to create deliberately phasey sounds, which may be creatively valid if the two amps sound quite different or are miked from different distances.
The normal way to use this system is to place the DI box in line with the guitar cable, between the guitar and the amplifier, so that the guitarist can play normally and the clean signal from the guitar can be recorded regardless of the amplifier settings. The output from the recorded guitar track is then fed to the X-Amp via an XLR cable of any practical length, after which you adjust the output level from the recording system until the clip LED starts to blink on peaks. Backing off the level by a few dB should stop the clip LED coming on and still give you plenty of level. You can now feed Output 1 into your guitar amplifier and then adjust the output level control on the X-Amp to get the best level into the amplifier. A practical way to do this is to try the guitar directly into the amplifier with a fairly clean sound, then adjust the X-Amp to give the same subjective level. If there's any hum, the ground-lift switch, which isolates the input signal ground, can be used. The manual warns that any connected amplifiers should be properly grounded (which, for safety reasons, they should be anyway).
Once you're set up, the recorded signal fed back through the amplifier behaves just as it would if you were playing the guitar through it directly — except, of course, that the output from the amplifier doesn't interact with the guitar, as it can do at high volumes during performance. If you want the extra sustain that being close to feedback gives you, simply play the amp at a high level when making the initial recording. The X-Amp can also be fed through any chain of effects pedals, again just as if it were a guitar, so it is pretty flexible.
As with all the Radial products we've tried, this system works exceptionally well, and while it may not be the cheapest solution, it won't compromise your sound and should give a lifetime of service. The re-amped sound is essentially indistinguishable from the sound you get when plugging the guitar directly into the amplifier, though you may get very minor differences depending on the type of guitar cable you use with the amplifier. The only extra thing I would have liked is an input level control, as most DAWs have no physical output level control, which means that levels have to be adjusted in software. This reduces the signal resolution slightly — although, of course, if you're working at 24-bit, as most people now are, that won't be an issue in practice. In all, this is a beautifully engineered re-amping package. Paul White
Waves' iGTR Personal Guitar Processor is said to be a spin-off from their GTR software and interface. This pocket-sized hardware box uses digital processing to provide high quality basic effects, clean and dirty guitar sounds, and has a stereo mini-jack input for your MP3 player so you can jam along on the tour bus or in your hotel room.
Around the size of an original Apple iPod, and with a non-slip casing, the iGTR is powered by four AAA batteries or an optional power adaptor, and it also comes with a detachable belt-clip. Its simple controls are divided into three sections, each with a rotary control and a three-way slide switch. Thumbwheel controls on the edge of the box adjust the guitar level and aux input level, and there are two headphone mini-jacks — so you can inflict your playing on a third party! A slide-switch on top of the iGTR is used to power it up, and there's the usual quarter inch input jack for your guitar cable.
The top section offers a choice of Delay, Chorus or Reverb, for which a single knob adjusts either the amount or speed of the effect, as appropriate, with the fully anti-clockwise position bypassing the effect. Next there's a choice of wah (auto), tremolo or phaser, again with a single-knob adjustment (in auto wah mode this sets sensitivity) and bypass, all of which sound absolutely fine.
Finally, we get to the amp models which are simply designated Warm, Normal and Bright, with the rotary control adjusting the drive level. Waves claim that the iGTR offers realistic sounds that are inspired by vintage models, and the clean sounds are very nice, with distinctive tonal characters. However, turn up the drive and it sounds as though the designer has omitted the speaker-simulation stage — the sound morphs gracefully from sparkly clean to 'wasp-in-a-paper-cup', as though it is simply being clipped. The fixed level of background hiss from the output stage isn't affected by the guitar volume control: using a sensitive set of Ultimate Ears ear-buds, the background hiss level was always very obvious, whereas with less sensitive phones the hiss only becomes really noticeable at drive levels of more than 12 o'clock, at which point the noise from the overdrive effect starts to build up.
The practical outcome is that to keep the hiss down you need to use less sensitive headphones and crank the guitar level up — which will reward you with some nice-sounding effects and some very usable clean tones in the 'glassy' Rockman style. But the overdrive sounds are simply too fizzy to be pleasant — even allowing for the fact that US guitar sounds usually have more edge than European ones. You may be able to record passable overdrive guitar sounds by feeding the output via a software speaker-emulator, which would also cut down on the hiss, but as things stand anything above a very mild overdrive sounds quite dreadful, especially when you consider that for only a little more than the iGTR's £69 retail price you could buy something like a Line 6 Pocket Pod, which is superior in all respects other than physical size. As a convenient practice aid to throw into your guitar case, the iGTR has a definite appeal if you play mostly clean sounds, but the gritty overdrive lets it down badly. Paul White