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Monsters of Rock

Crate, Hughes & Kettner, ART Guitar Preamps

We take the H&K Metal Master, ART Powerplant, and Crate TDP recording guitar preamps into the studio in search of that elusive valve sound.

There are several guitar processors on the market designed to give you that authentic vintage valve sound in the studio — but do any of them really deliver? Paul White cranks it up to 11 and puts three of the contenders through their paces.

Despite the tremendous advances in solid-state technology made in recent years, most guitarists prefer the sound of valve amplifiers. There's something elusive about the overdrive characteristics of a real valve and, though some solid-state designs come pretty close, I still don't think anyone has quite managed to duplicate the valve sound exactly. Of the three guitar preamplifiers reviewed here, two utilise valves, while one is entirely solid state. All have speaker simulators designed to filter the sound in such a way that it can be recorded directly, and none of the units have on-board effects of any kind. All are capable of producing a wide range of both clean and overdriven sounds, and though the facilities on offer appear similar, the subjective tonalities are surprisingly different.


The designers of the TDP preamp have obviously adopted the 'If you can't beat them, join them' philosophy and, though there is a lot of solid-state circuitry under the lid, the important overdrive stage is based round a real, glowing 12AX7 (ECC83) valve.

Housed in a cream/grey 1U package that wouldn't look out of place alongside your Atari or Mac computer, the Crate TDP follows the conventional clean channel/dirty channel approach, with silent switching between the two channels. This may either be accomplished by means of a front panel button, or an optional footswitch which overrides the button when plugged in. There is a single input jack on the front panel, plus a headphone outlet for rehearsal, while the rear panel has jacks for the main line output, an effects loop and the remote footswitch. The line output may either be used direct or switched through the internal speaker simulator, while the effects loop can be switched to work at either line or instrument level. This is useful if you need to use pedal effects, as these nearly all work at instrument level, while standalone effects units tend to operate at studio line level. Mains is supplied via a standard IEC mains lead.

The Channels

On the left is the Lead channel, which has a fairly straightforward control layout. The degree of overdrive is set using the Drive control, while the adjacent Level control sets the channel level relative to the clean channel. A three-band equalisation system is employed, and the usual mid control has been replaced by something called Focus, which is rather more complex.

The bass control, which is labelled Sub, offers up to 12dB boost at 100Hz, while Lead (presence) can deliver up to 12dB of boost at 3kHz. Focus, on the other hand, is less easy to pin down. In the anti-clockwise position, it brings up the mid range in much the same way as a traditional mic control, but as you turn the control clockwise, the mid range seems to get 'phased' out, which produces a characteristic heavy metal tone, somewhat reminiscent of a miked Marshall. By adjusting the Drive control, the sound can be varied from a subtle blues distortion to a searing, sustaining metal crunch with lots of whining harmonics.

The Rhythm or clean channel is also fitted with Drive and Level controls, allowing a range of rhythm sounds to be set up, from clinically clean in character, via a mildly jagged edge, through to downright raunchy. This time the tone controls are labelled Low, Mid and High, offering 10dB boost at 100Hz, 18dB boost at 500Hz and 15dB boost at 7kHz. There's also a Bright button, which brings in another 5dB of boost at 7kHz, and a Master level control that affects both channels.

The Sound

Checked out with both single coil (Strat) and humbucking pickups, the unit certainly delivered a wide range of classic guitar tones. Plugging it into even a mediocre amplifier and speaker setup produces an exciting sound that is easy to record. The Focus control is probably the most flexible part of the overdrive sound, and really does turn the sound inside out, making it either thick and biting at one extreme or punchy and crunchy at the other. There is plenty of overdrive available, so that most contemporary styles can be explored without recourse to overdrive pedals, and there is a nice harmonic squeal to the tone which increases the illusion of power, even at low listening levels. Particularly impressive was the responsiveness of the circuitry to picking pressure, especially at low overdrive settings, where you can get the overdriving sustain needed simply by 'digging in' to certain notes. This is one area where valve amplifiers inevitably score over solid-state designs, but the Crate hybrid manages it with no trouble. However, it would have made more sense to provide a separate effects loop for each channel rather than a single one.

The clean channel had plenty of tonal flexibility, though why the Bright button operates at the same frequency as the High control is a little puzzling. The overdrive can be used here to recreate an authentic valve combo 'dirty-clean' sound and has enough range to produce overtly distorted sounds if required.

Used directly into a mixing console, the speaker simulator did take out quite a lot of the buzziness you expect when you DI overdriven guitar, but there was still too much left for my own taste. Judicious use of equalisation, however, improves the situation.

I decided to try plugging the headphone outlet into the mixer, but because this is designed to feed stereo phones, a mono lead should only be plugged half way in or the output signal will be shorted out. Though not radically different in sound to the line output, there seemed to be more body to the sound, so I set about experimenting further with the EQ, both on the unit and on the desk. The first step was to turn the desk's High EQ control right down which got rid of most of the fizz but also took a lot of the bite out of the sound. I found the bite could be restored by using the Focus control at or near its anticlockwise position and turning the Lead (treble) control nearly flat out. You might think that turning the Lead control up would have brought back the fizz, but, as it is centered at 3kHz, it brought up the edge and bite but without adding much at the very high end of the spectrum. The result was a very workable sound, and once a little reverb was added, I felt much more comfortable with it.

RM Verdict


  • Sensibly priced
  • Dual channel operation
  • Responsive valve tone with good range of EQ

  • Speaker simulator is not particularly sophisticated and needs help from external equalisation


As a preamp for use with existing amplification, the Crate TDP Guitar Preamp is excellent and can transform an indifferent amplifier into something quite exceptional.

It can produce all the rock sounds, from blues to thrash metal, and has loads of gain, even for guitars with a relatively low output. The only weak point, in my view, is the speaker simulator section, which doesn't quite cut it. Straight into a desk with no additional EQ, the sound tends to be thin and over-bright, but using the headphone outlet instead of the line output, then working with the preamp tone controls and the desk EQ makes a huge difference. An external parametric equaliser or active speaker simulator would doubtless be even better, but a little persistence and a little reverb does produce a convincing sound on tape.

As a preamp unit, the Crate TDP is exceptionally versatile and produces the kind of sounds most users would associate with an expensive, all-valve amplifier. It is sensibly priced, easy to set up, and can produce good DI'd sounds as well as sounding brilliant through a regular guitar amp or power amp/speaker combination. If Crate can improve the speaker simulator circuit, they'll have a real winner in the studio as well as on stage.

Further Information
Crate TDP £239.99 including VAT.

Bluebridge Music Ltd, (Contact Details).


Hughes and Kettner have been building guitar amplification for many years, and I've always known it was pretty good stuff. But it wasn't until a boxed set of their valve preamps arrived in my office that I came to realise exactly how good. The Metal Master under review is one of a series of three similarly presented devices, the other two being the Crunch Master and the Cream Machine. All are packaged in a steel, half-rack case, for which a rack adaptor is available, and are mains powered — a necessity when you consider that they all contain valve circuitry. Evidently H&K also believe in using state-of-the-ark technology to achieve a state-of-the-art sound. The other feature these units have in common is that a very effective speaker simulator is included, enabling the units to be plugged directly into a recording setup without the need for microphones, though if you actually want to make a noise, there's an integral, 1 Watt power amplifier section, which can produce a useful amount of level from any convenient small speaker cabinet. A dedicated 3.5 mm phones socket is fitted to the back panel for the benefit of the more thoughtful user.

When it came to deciding which one of the three machines to review in depth, it was rather like Goldilocks and the three bears: I plugged my trusty Strat into the Cream Machine and thought it sounded fine — but it was just too smooth for my style of playing. Then I tried the Crunch Master, which turned out to be equally competent, but well — it was a touch too crunchy for me. Now, never let it be said that I'm a metal guitar player, but when I plugged in the Metal Master, I said "This porridge is just right!", and I ate it all up. In fact, I think the name rather does this particular unit an injustice because it appears to be capable of recreating all the classic 70s rock tones from blues and R&B through to some pretty hard rock sounds. Perhaps the title 'Classic Machine' would have done it more favours.


The front panel controls are simple but effective, a trait that carries through the range. However, because of a lack of panel space, not all the front panel controls are on the front, most notably the master volume control, which is on the back. While this may seem rather inconvenient, it doesn't much matter in the studio, because the level will be controlled at the mixer, and if you were to use the unit live, I would guess you'd team it with a power amp that had a volume control anyway.

Unusually on a unit of this kind, there are two gain controls which can be used to create overdrive effects. The dual-valve preamp has a gain control at the front end which creates pre-EQ overdrive, after which the signal passes through a bass, mid, treble type of tone control arrangement which appears to be based on conventional valve guitar amplifier principles. This is followed by another gain stage, which can add further overdrive to the EQ'd signal, and it is this ability to determine whereabouts in the signal chain the overdrive is applied that makes the unit so tonally flexible.

At the end of the chain comes the speaker simulator, quaintly known as the Cabinetulator, and this filters the signal to compensate for the colouration of a typical guitar speaker cabinet. Apparently, the circuitry was designed to emulate a 4x12 Celestion cabinet, and though I wouldn't go so far as to say it sounds exactly like one, it works exceptionally well. For recording, headphone rehearsal or performance through a full-range speaker system, the Cabinetulator is vital, but unfiltered outputs are available for use with conventional guitar amplifiers.

The guitar may be plugged in either via a front panel jack or a rear panel jack, whichever is most convenient, and the outputs can be switched to instrument or line level, as required, by means of a slide switch. There are actually four output jacks, not including the mini phones jack, marked: Tube Amp Out, Instr Out, Mix Out and Cabinetulator Mix Out. The Tube Amp Out socket is fed directly from the output of the tube preamp section and bypasses the small power amp and the speaker simulator. This would be used for feeding into a guitar combo, while the Instr Out socket duplicates the input signal with no processing. The Bypass switch selects just one of these outputs to be active at a time, making it possible to leave both connected if you're using it with a two-channel guitar amp or recording via two mixer channels.

Mix Out is taken from the input to the speaker simulator section, which can be clean or dirty depending on the Bypass switch setting, and is mainly used for plugging into single-channel guitar amps, while the Cabinetulator Mix Output is the one to use while recording. A footswitch jack is provided for an external bypass switch, while a separate red button on the rear panel switches the speaker simulator in or out for the Speaker (power amp) and Phones outputs. A slide Bypass switch is also fitted to the rear panel, which duplicates the action of the footswitch when none is connected.

The Sound

Plugged directly into my mixing desk with no EQ and no effects, the sound was surprisingly close to that of a good valve amp miked up in a very dead room. A little reverb brings the sound to life, while the overdrive has just the right amount of second harmonic to make it sing. It's also very responsive in that the harder you play, the more the sound changes, and the cabinet simulator has both the bite and low-end punch that only valve amps seem to produce. There is no trace of fizz in the DI'd sound, and the combination of the two drive controls and the straightforward EQ section makes it easy to recreate pretty much all the classic rock tones. With the overdrive flat out, the character of the guitar still manages to get through — though I suspect some metal fiends will plug in an additional chainsaw pedal turned up to 11 to remedy this! Less heavy overdrive produces some really convincing blues sounds, and the unit also handles those raunchy R&B sounds that fall into the no-man's-land between clean and distorted with supreme confidence.

Backing off the overdrive produces some passable clean tones, though for those really glassy sounds that are currently popular, it may be necessary to switch out the Cabinetulator in order to obtain the extra top end.

"...the Metal Master is an absolute bargain for recording guitarists looking for classic rock sounds."

RM Verdict

Hughes & Kettner Metal Master

  • Excellent range of guitar sounds, especially overdrive
  • Highly effective speaker simulator
  • Simple to use
  • Inbuilt 1 Watt amplifier

  • Single channel only


You may have inferred thus far that I was rather taken with this little box — and you'd be quite right. Yes, I am thinking of buying one and no, they haven't given me one — just in case you were about to ask. The best DI'd guitar sounds I've heard have come from dedicated, non-programmable units with no on-board effects, and while this particular unit costs rather more than the majority of its solid-state rivals, I feel that die-hard valve enthusiasts will feel the additional cost to be well justified.

In the studio, there is a little audible background noise from the circuitry, especially when a lot of overdrive is employed, but this is in no way serious and is far less than most guitar amplifiers chuck out. Indeed, some noise is an integral part of the overdriven guitar sound.

On balance, given its build quality and impressive array of sounds and facilities, I'd say the Metal Master is an absolute bargain for recording guitarists looking for classic rock sounds. I've heard some good preamps before, but at the affordable end of the market, this is the best yet — it really is the closest simulation I've heard to a miked-up valve amp. But don't dismiss the other two units in the series — after all, one man's porridge is another man's poison.

Further Information
Metal Master £239 including VAT.

John Hornby Skewes, (Contact Details).


ART are well-known for their MIDI-controlled, digital studio effects processors, but the Power Plant is a totally analogue guitar preamplifier. Unlike the previous two units, the circuitry is entirely solid-state. Intended for both live and studio use, the Power Plant is fitted with a filtered output to simulate the sound of a miked-up guitar combo or stack. During the development of this unit, the waveforms of various valve amps were, apparently, analysed at various gain settings and at different stages in the amplifier. Among the makes used for reference were Marshall, Fender, Vox, Ampeg and HiWatt.

Housed in a sturdy, metal 1U rack case, the preamp is configured much like the control panel of a typical two-channel guitar amplifier, and there is a footswitch option for changing between the clean and overdrive channels. The front panel is finished in black anodising with the distinctive ART purple and grey logo — loath it or ignore it, you can't like it! The speaker simulator also feeds a headphone outlet so that you can practice your latest licks at full volume within the confines of your own cranial cavity; for live use, an unfiltered output is provided, so that the unit can be used with any suitable power amp/speaker combination. Mains power comes via a captive lead, not one of those fiddly external supplies.

The front panel controls are all knobs, with the exception of a single button that switches between channels — a big selling point for those who are getting fed up with programming buttons. Four of the knobs make up the clean channel controls: Input Gain, Low, Mid and High EQ. The equaliser is active and the three frequencies affected are 90Hz, 450Hz and 4kHz, the Low and Mid having a cut/boost range of 10dB and the High control 18dB. A green LED next to the Gain control illuminates when the clean channel is active, and a red one in the overdrive section takes over when the dirty channel is selected.

Moving to the overdrive channel, this too has a 3-band equaliser, but for no readily apparent reason, the Low and High legends have been replaced by the terms 'Thrust' and 'Edge'! These operate at the slightly different frequencies of 130Hz, 450Hz and 5kHz, again offering both cut and boost. Input Drive sets the amount of overdrive, and the adjacent Harmonic Superdrive control is a pre-overdrive equaliser designed to boost the 1 kHz part of the spectrum before the signal hits the overdrive circuit. This is an essential ingredient in determining the overdrive character of the final sound, and by juggling this against the equaliser settings, a very wide range of rock sounds can be achieved. A master volume control allows the overdrive sound to be balanced against the clean sound — and that's about it.

On the rear panel are rather more sockets and buttons than you might expect from such an apparently straightforward product. There's a single input, which is duplicated on the front panel, and two Guitar Amp feeds which can be used straight into the normal input of a guitar amplifier for live use. An effects loop is provided so that an external effects unit can be patched in, and there is also an equalised (speaker simulator processed) output that can be fed directly into a power amplifier or recording desk. In addition, there's a low impedance, balanced output on an XLR connector and a headphone outlet (also processed via the speaker simulator). A -10dBv/+4dBu switch sets the output level for both the XLR and phones socket, and a remote jack socket is supplied for use with an optional remote footswitch — this may be used to change channels. A further button removes the speaker simulator filtering from the clean channel, which means that some very bright sounds can be produced.

The Sound

As I was primarily interested in how the Power Plant performed in the studio, I plugged the filtered line output directly into my mixing console and checked it out with no further EQ or effects. Working on the clean channel first, I found the tone controls to be very much more flexible than their apparently simple layout suggests, and there is just a hint of compression about the sound which adds a little bite and sustain. With the speaker simulator filter switched in, you have to work hard to get a really jangly sound, but that can easily be remedied by switching the filter out for the clean sound. There is a small volume drop when the filter is switched out, but this can be compensated for using the channel level controls. Particularly impressive is the sense of weight that the Low control adds to the sound, and you really can get everything from a chunky '60's sound to a modern, bright sound that begs for a hint of reverb and chorus. I also liked the way single notes came over — with many DI techniques, chords work OK but single notes come across as very thin.

There's also a lot of flexibility in the overdrive section, though you do have to add some reverb from an external source to prevent the sound from being too dead. With maximum overdrive and plenty of top and bottom boost, combined with a fairly low mid setting, you can get a quite convincing and very punchy Marshall-type sound, whereas emphasising the middle more gives a good, traditional bluesy feel. By increasing the Harmonic Superdrive control, the sound takes on a fairly angry edge; backing it off produces more of a creamy overdrive tone.

By reducing the degree of overdrive, it is possible to recreate a more raunchy, '60's-style chord sound reminiscent of the Stones or the Kinks, and the the Power Plant seems to bring out the harmonic content of sustained notes in a rather satisfying way.

RM Verdict


  • Dual-channel operation
  • Nice harmonic sustain
  • Good tonal variety

  • Channel switching a little noisy
  • Tone lacks 'bite' with some guitars


I liked the simple, familiar control layout of this unit, and the basic overdrive sound is similar to that of a miked amplifier, though for me, it doesn't quite bite like the real thing. You do need to add reverb or other effects to get the best out of it, but most musicians and home studio owners will have some form of reverb unit in their bag of tricks. There is very little that's actually wrong with the Power Plant, except that I did notice a click when changing channels, which could be a problem both on stage and in the studio.

The clean channel produces a good range of tones, and it seems that the equaliser frequencies have been well-chosen; the ability to switch out the filter on the clean channel only is also very useful. When it comes to overdrive, the circuit seems a little short on gain when trying to produce a strong overdrive sound with guitars using single-coil pickups, though a far richer sound can be achieved using humbuckers. It's also possible that users of Strat copies with weak pickups will find the overdrive level insufficient for some rock styles, so it may be necessary to plug in an external overdrive pedal to help things along.

While on the subject of single-coil pickups, I found it quite difficult to get just the right degree of bite to the overdrive sound without the tone becoming a hint too edgy — but then I've used a lot of amplifiers that suffer from the same problem. Using additional equalisation at the mixer helps fix this, especially if you have a system with a sweep mid control to add bite in the 1.5 to 2.5kHz region. The other thing you don't seem to get is that verge-of-feedback liveness to the sound, in which case it may be as well to play the Power Plant through a small amp to provide the feedback but still use the filtered line output straight into the mixer when recording.

Electronically, the Power Plant is surprisingly quiet, even when large amounts of overdrive are applied, though it will, of course, reproduce any hum picked up by your guitar. It is capable of reproducing most of the classic rock and rhythm sounds, albeit with occasional help from your desk EQ, and it represents a viable alternative to miking an amp.

Further Information
ART Power Plant £249 including VAT.

Harman Audio, Mill Street, Slough, Berks SL2 5DD. 0753 576911. 0753 535306.

Previous Article in this issue

Groovy Train

Next article in this issue

Format of the Future?

Recording Musician - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Recording Musician - Oct 1992

Review by Paul White

Previous article in this issue:

> Groovy Train

Next article in this issue:

> Format of the Future?

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