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Roger Linn Adrenalinn III, Axon PU100, Emerson Williams Bluestone Pro

Guitar Technology By Paul White
Published October 2008

Axon PU100 Hexaphonic Pickup

Designed by US pickup guru Seymour Duncan, the Axon PU100 offers an alternative to the Roland GK pickup or Roland Ready Stratocaster as a means of controlling an Axon guitar-to-MIDI system — or any other system that's compatible with the Roland 13-pin interface format. Note that the pickup doesn't generate MIDI directly: it simply connects to suitable hardware such as a Roland VG or GR unit, or to any of Axon's AX-series guitar-to-MIDI products.

Like the Roland GK system, the package comprises a thin, six-segment (or 'hex') pickup that enables it to detect signals from each of the six strings. This pickup is connected via a fixed cable to a small plastic control-box that attaches to the guitar body. It may be mounted via a metal bracket that fixes over the guitar's strap button, and a double-sided sticky pad beneath the unit stops it slipping — a similar mounting system to the one used by Roland. The necessary AX100 latching 13-pin DIN cable is available as an optional extra (if you don't get one with the device being controlled) and is, again, fully compatible with Roland systems. Fixing the pickup to the guitar can be achieved using the supplied sticky pads and spacers, although screw-fixing is recommended for serious use, as the sticky pads can sometimes work loose. There are also third-party fixing plates available for Strats, that are positioned over a GK pickup using the existing pick-guard screw-holes, and I can't see why these wouldn't work with this model.

Roger Linn Adrenalinn III, Axon PU100, Emerson Williams Bluestone ProAs with the Roland GK3, the flexible pickup permits some leeway in adjusting its curvature to match that of the strings, and this can be important, as the secret to reliable operation is getting the clearance from the strings correct before adjusting the string sensitivity on the receiving unit. The pickup must also be mounted close to the bridge (ideally 20mm away) to maintain a constant signal when string-bending, which means that it isn't compatible with some guitar-bridge designs, such as the original Telecaster bridge. All the switches on the PU100 are identical in function to those on the Roland GK units — buttons for patch up and down or mode selection, and a three-way switch to select guitar, synth or both — and there's a jack link to carry the normal guitar signal along the 13-way cable to the connected unit. There's also a volume control knob for the receiving device. Three color-coded status LEDs show the switch settings, which is handy on a dark stage, but I found the three-way slide-switch less user-friendly than the larger Roland lever switch, as it's quite small and difficult to operate precisely.

I mounted the pickup on a Strat and tested it with my Roland GR33, which tends to show up any weaknesses in the pickup system or its setup. Functionally the pickup works as well as, if not better than, its Roland equivalent in terms of sensitivity and susceptibility to false notes, but it has also inherited some of Roland's mechanical weaknesses. The weight of the 13-pin connector and cable hangs on the control box, and although the design of the housing helps support the connector to take the strain off the pins, threading the rather stiff cable through your guitar strap is still the best way to reduce the risk of problems in this area. As with the Roland version, you can get intermittent connection problems unless the cable is supported, but this is probably more about the choice of a DIN connector for the 13-pin format in the first place than an indictment of the implementation. There's also the same, rather ungainly, fixed cable that pokes out of the top of the pickup, linking it to the control box: surely a flat, printed ribbon-cable that could be stuck to the guitar surface would be neater and less likely to get in the player's way?

As an alternative to the Roland GK pickup, the PU100 — which costs £119 or comes as part of the AX50 and AX100 systems — may offer some subtle performance enhancements and slightly better connector support, but ergonomically I feel that it is marginally worse, due to that small three-way slide switch. In most respects, though, they're so similar that there's little to choose between them. I have to applaud the fact that somebody has developed an alternative to buying a Roland pickup, but I also feel that the opportunity has been missed to design a control box and cabling system that's more professional than the original, rather than what amounts to a reinterpretation of Roland's existing design. Paul White


The PU100 is a perfectly valid alternative to the Roland GK3 pickup system, and is its equal, but it seems to offer no significant advantages and suffers from the same mechanical shortcomings.

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Roger Linn Designs AdrenaLinn III Rhythm & Effects Processor

Roger Linn's AdrenaLinn and AdrenaLinn II took a new approach to guitar processing, combining off-the-wall tempo-sync'ed effects with amp modelling and preset drum rhythm patterns in a single box, and they became something of a cult hit. It is the rhythmic effects that are unique, and if you want to get a better feel for these it's worth reading our reviews of these earlier models ( and

New Model

The amp models have previously been less impressive than the effects, but the AdrenaLinn III, which costs a shade under £220, puts that right, with improvements to all 40 tube-amp models (particularly their overdrive characteristics) and an adjustable amp drive boost to give solos a lift.

Roger Linn Adrenalinn III, Axon PU100, Emerson Williams Bluestone ProThe enhancements don't end there, though. The noise gate has been upgraded to make it less obtrusive, and stereo reverb, compression and a guitar tuner have been included. The stereo width of the modulation effects and delay is now variable, as are the envelope attack and decay times associated with the random filter and random tremolo effects. Four new modulation effects (Auto Pan, Wah Pedal, Fixed Filter and Sci-Fi — a '50s Sci-Fi B-movie-style special effect) have been added, and there's a separate distortion processor that can be applied to the beatbox to grunge up the drum sounds (which can also be routed through the reverb, delay or guitar effects).

The right-hand footswitch may be assigned to a different effect or user-defined combination of effects for each preset, and up to 10 MIDI footswitches and two MIDI expression pedals may be used to control designated parameters — or you could drive them from your sequencer. The internal drum sounds can now be triggered via MIDI, and many of the drum sounds have been updated. Low-pass filters have been added to both the beatbox and guitar amp side of the processor.


The AdrenaLinn's strength has always been its ability to take common effects and drive them in sync with MIDI or the internal drum section to produce stepped filters, tuned resonators that pick out riffs from harmonicaly rich input material (distorted guitar for example), or the tremolo sequence's rhythmic chopping, which is like having a gate driven from a rhythm generator. With the AdrenaLinn III, effect rates can be set to specific note values, including triplets, while the filter sequences turn basic strummed chords into complex and evolving pad sounds. There are 20 preset rhythmic-filter sequences, but you can also create your own from scratch. In the arpeggio sequences, the guitar signal is processed through a sequence of pitched resonators that pick out a note sequence similar to the Lexicon PCM80 resonant-chord program. This was present in earlier versions but is so dramatic that it's worth mentioning again, particularly as some impressive new presets exploit this feature.

As well as the more obvious wah-like filter sweeps, synth-like guitar sounds can be created using filter effects that are triggered by picking a note. There are also volume envelopes, note-sync'ed chorus and a talkbox emulation that adds vocal-style formants to the sound. The filter section now includes a Moog/Evolver-style four-pole low-pass filter and an Oberheim-style two-pole low-pass filter, in addition to the traditional band-pass wah-wah, high-pass and notch filters. Any modulation source, such as an LFO, envelope follower or note-triggered envelope generator, can be routed to any audio processor. More traditional guitar effects now include Fuzz Tone and Octave Fuzz, as well as beat-sync'ed delay and delay loops, which allow you to loop a short section of audio, then play over it.


The amp models sound more convincing than before, but they're still a little behind the market leaders in terms of dynamic response and playing feel. But then nobody really buys an AdrenaLinn just to play rock guitar, and the magic starts to happen when you get one of those compulsive drum rhythms playing along with a sync'ed, sequenced filter, transforming your guitar part into a powerful rhythmic pad or percussion sound. Every preset gives you fresh composition ideas, and although reprogramming your own effects can be time consuming, it isn't difficult, because all the parameters are set out as a matrix, with a knob above each column. What I like about the preset rhythms is that most are simple: very solid and usable — and triggering those sounds via MIDI could be a lot of fun when working with a sequencer. The improved stereo effects are definitely worthwhile, as are the newly added variants (although I'm still not sure what I'd use Sci-Fi for!).

If you're just after a box to produce standard rock-guitar sounds, the AdrenaLinn III isn't the obvious choice, but if you're looking for fresh sounds to liven up rock tracks, or are involved in something more experimental, it is absolutely inspiring. If you're an existing AdrenaLinn user, this update is definitely worthwhile, and new adopters now have more reasons to, erm... adopt. Now, if we could only persuade Roger Linn to put some of those rhythmic effects in a plug-in... Paul White


The AdrenaLinn III offers a unique and inspiring approach to rhythmic effects for guitar and has the benefit of some seriously punchy built-in drum rhythms. There's nothing like the AdrenaLinn in the hardware market, and you'd be hard pressed to achieve similar results in the software world.

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Bluestone Pro Dummy Load & Speaker Emulator

If you need to record a tube guitar-amplifier via direct injection but without feeding the amp through its usual loudspeaker, you need two components: a dummy load to correctly load the amplifier, and a speaker emulator to recreate the tonality imparted by the loudspeaker. A dummy load is essential, as tube amps are designed to run into a specific impedance — so running with no load can wreck the output stage, and even if it doesn't the sound won't be the same as when running into the correct load.

Roger Linn Adrenalinn III, Axon PU100, Emerson Williams Bluestone ProOn its own, a dummy load will keep the amp safe but the DI'd signal won't sound right, because a guitar speaker and cabinet act as a tone-shaping filter. Unlike a studio monitor, a guitar speaker rolls off rapidly above 2-3kHz, smoothing off the otherwise very unpleasant sound of an overdriven amplifier, to produce the distortion characteristic we know and love. There's also low-end resonance in some cabinets, so a speaker emulator must replicate the frequency response of a typical speaker in its cabinet if it is to sound convincing.

The Bluestone Pro comes in a DI-box format and has internal load-resistors capable of handling 150W of peak or 75W of continuous power, presenting an 8Ω load to the amp. In the event that you feed too much level into the unit, a red warning light comes on. The input, which should be fed from the speaker output of the amp, is an unbalanced quarter-inch jack, and there's also a speaker-output jack for when you want to use the amp normally (using the speaker rather than the dummy load) while still being able to take a DI feed to a recording system or PA. It can't pass through an attenuated signal to the speaker, but at less than £100 it is cheaper than the power soak you'd need to do that. A Speaker/DI switch determines which mode you are in, but if you set this wrongly, the dummy load always comes into play, so if no speaker is connected your amp is never left unloaded.

A further 3.5mm stereo mini-jack input accepts a feed from an MP3 player for play-along rehearsal and there's a 60Ω headphone output in the centre of the XLR/jack combi socket. For DI use, an XLR cable plugged into the combi socket provides a balanced mic-level feed, and there's a ground-lift switch that can be used in case of ground-loop hum. As this is a combi connector, you'll need an XLR cable with pins both ends to plug into a standard mic preamp — but there's no need to worry, as the necessary gender-changing adaptor (that you can stick on the end of a standard mic cable) is provided with the Bluestone Pro. The manufacturers also include a stereo mini-jack-to-XLR cable and a short jack-to-jack lead. No power is required, since the speaker output level from even a small tube amp is so high that the filtering needed for speaker emulation can be entirely passive.

In Use

Using the Bluestone Pro is pretty simple, because unlike the rather more sophisticated Motherload (which seems to be the current benchmark for power soaks/speaker emulators), there are no adjustments to vary the emulated cabinet sound: if you need to fine-tune the end result, you'll have to use your own EQ. My test was done using a 12W, all-tube Fender Champ amplifier, and with heavy overdrive I managed to get the red warning light to flash well below full output volume — so with large amps you may need to wind down the master volume quite a bit to maintain a safe operating level. With no EQ the tonality feels a bit bass-light, and some heavy distortion settings can still sound a hint gritty when you have enough treble wound in on the amp to give the desired bite, but I found that applying some simple plug-in EQ made a lot of difference. A parametric peak boost at 100 to 150Hz brings back some of that cabinet resonance, while a 24dB/octave high-cut filter set at around 4kHz tames any high-end fizz. If you have a filter with a tunable Q, so that it peaks up just before it cuts off, you can also smooth the top end without dulling it. Without the use of external EQ the Bluestone Pro is a bit of a one-trick pony, and it probably won't satisfy serious tone-hounds, but if you're prepared to work with it and add in some of your own EQ, you can get some very nice, recordable results — without upsetting the neighbours! Paul White


Any speaker emulator that can't be adjusted will invariably suit some amps and guitars better than others, but if you have additional EQ facilities the Bluestone Pro is very flexible.

Emerson Williams +44(0)1383 881 761.