Manufacturers are finally waking up to the fact that keyboard amplification requires something better than a hyped-up guitar amplifier. We look at five of the latest high-power keyboard designs.

Ohm KA140C Keyboard Combo

This is a solidly built but still easily portable keyboard combo capable of delivering up to 140 watts. An eight-ohm, 15" cone driver and high-frequency tweeter are built into the cabinet, but as the solid state amplifier delivers its full power output into a four-ohm load, you'll need to add an extension speaker cabinet if you want to realise its maximum potential.

The ported enclosure is tastefully finished in deeply textured matt vinyl, and measures a compact 645x535x380mm, the corners being protected by tough plastic extrusions.

A multikeyboard set-up demands completely independent input channels, and the Ohm satisfies this requirement by providing four such channels, each with its own Reverb Depth control as well as the mandatory Volume, Treble and Bass adjusters. Additional pushbuttons are fitted for Effects Send and Auxiliary (or DI) output, and the Master section includes a Master Volume control, Pressure and Reverb controls, plus the effects loop sockets, auxiliary output and reverb foot-switch socket. Rear panel facilities include the extension speaker sockets, the slave output and the IEC mains sockets.

At £365, the Ohm KA140C offers both power and flexibility in a compact, economical package and should fill the requirements of a good many keyboard players. The use of high quality loudspeakers ensures undistorted sound up to very high levels, and this combo is also suitable for drum machines and electronic drum kits.

Subjectively, the Ohm has a clean sound with more than adequate tonal range, and the reverb works well without introducing any noticeable background noise.

The words 'value for money' usually imply compromise, but Ohm have cut few if any corners in producing this high quality, cost-effective package.

Marshall KC60

Although undeniably better known for their rock guitar amplification, Marshall aren't hiding from the fact that the electric keyboard, and the synthesiser in particular, is enjoying tremendous popularity at the moment, and consequently generating a sizeable market for specialist amplification.

The KC60 is distinctively styled in the tradition of its guitar ancestors but in reality it's designed specifically for keyboard use and is not simply a revamped guitar combo.

Measuring about two feet square by 12" deep, the KC60 is built around the ported loudspeaker system and incorporates a heavy-duty 15" speaker and a horn tweeter.

The cabinet construction follows the simple but solid design traditions laid down by its manufacturer, and all the hardware is typically Marshall, from the bar handles to the gold front panel with its metal-capped knobs. Solid state circuitry is used throughout, as the famous Marshall valve sound has little or no relevance to the world of the keyboard player.

Both input channels have their own Volume, Bass and Treble controls, and these share a common Master Volume and Master Reverb section. An inspection of the back panel reveals a reverb footswitch socket, an effects loop, and line and headphone outputs, but there is no extension speaker facility presumably because the built-in speakers are capable of handling the full output power of the amplifier.

Because of its relatively large cabinet size and powerful speaker, this combo delivers a fat punchy sound which, because of the built-in tweeter, still has a bright edge to it.

In terms of range, the tone controls are remarkably effective (if a little noisy when used to excess), and are certainly more than adequate for most normal keyboard applications. The reverb is also very effective, and if you use it properly, generally flattering.

The KC60 is a powerful combo offering a useful range of tones that should be able to hold its own against a drum kit in an ongoing artiste/audience exchange-of-vibes situation. Conversely, it looks meaty enough to handle synthesised drums and, as there are no specific combos built for that purpose that we know of, it's definitely worth a try.

Carlsbro Keyboard 150

This impressive-looking offering from Carlsbro can deliver 150 watts into four ohms, though as is normal, the power delivered to its internal eight-ohm speaker system will inevitably be somewhat short of this.

Four instrument channels are provided, but there is also a tape input channel which offers a choice of jack or five-pin DIN inputs (but don't plug your MIDI cables in here, folks!). Although each channel has its own Bass and Treble controls, a six-band graphic equaliser is included to add further treatment to the mixed sound: this would prove to be a big advantage in awkward acoustic environments. Each channel has buttons to select reverb or external effects, and the rear panel provides effects loop, line out, headphone and extension speaker sockets.

The whole combo looks very tasteful, measuring a little over two feet square, and the cabinet is a ported design housing a 15" speaker (not another one - Ed) and two HF tweeters. All the fittings are distinctively Carlsbro in appearance, but I would prefer to see a tough steel speaker grille in place of the chorus girls' tights normally fitted.

Seeing as the 150 is rather a heavy beast, side handles and castors are fitted as standard, the rear ones having toe-operated brakes which should preclude the eventuality of the combo running away on an uneven stage, for example.

The combo coped happily with a variety of DX7-generated sounds as well as electronic percussion voices and the tonal range provided by the combined efforts of conventional and graphic EQ sections was well in excess of what would normally be required. By incorporating a Tape In channel, Carlsbro have extended the usefulness of the amp to embrace those performers who rely on prerecorded backing tapes as part of their act, but I think a separate Reverb Depth control for each channel would have been a sensible addition.

In most respects then, this is a fine and versatile combo with a good reverb, and should find a fair degree of popularity with both keyboard players and electronic percussionists seeking clean, loud amplification.

Roland Keyboard Cube 60

This highly portable but nonetheless punchy-sounding keyboard combo from the Land of the Rising Yen is easily recognised by its silver vinyl. In fact, the amp's appearance strengthens my conviction that Roland's design team are becoming increasingly influenced by Doctor Who. For whereas the G707 guitar synth controller resembled a Dalek's handbag, this combo could easily be mistaken for a Cyberman's lunchbox.

The cabinet is of the fully-enclosed type, which affords a welcome degree of protection to the rear of the loudspeaker, though this does have a cut-out for cable stowage which also acts as a rear vent. Weighing in at a little over 36lbs, the Cube 60 incorporates a 12" loudspeaker and a small horn tweeter, enabling it to handle most of the frequencies generated by modern synthesisers. And it measures a mere 370x465x300mm, making it one of the most compact combos in its power range.

This is a two-input amplifier, each input having its own Volume control and a Reverb on/off switch, but both inputs are routed via a common three-band EQ section. The reverb control is also a joint affair. Turning now to the rear panel, we find a pair of phonos (which provide a split mono output suitable for feeding to a tape recorder), and also a pair of effects loop sockets, plus, of course, the almost obligatory extension speaker outlet. All the controls, switches and sockets are deeply recessed to minimise the risk of accidental damage, but again, I would have preferred to see a tougher grille material than that fitted to the review sample. It really isn't good enough.

The Cube's output remains clean up to moderately high sound levels and possesses a warm, convincing reverb sound, but I could have done with a little more range in the EQ department, particularly for the Treble control. By using only one set of EQ controls, Roland will undoubtedly have managed to reduce their production costs, but the compromise may be a bit uncomfortable if you're unlucky enough to have a couple of keyboards that are ill-matched tonally.

If it were not for its fairly hefty price tag, the Cube 60 could be forgiven its compromises: after all, it's portable, compact, and does what it sets out to do very well. The fact remains, however, that for around the same price, you can buy a British product offering twice the power output and four times the facilities. It's not often that Roland lose out in the value stakes, but the Cube 60, I'm afraid, happens to be one of those rare exceptions.

HH K80 Combo

It must be a difficult choice for a manufacturer to decide how many channels to build into a keyboard amplifier, and of all the companies whose models we've checked out in this round-up, HH are the only people to have decided on three.

This 80-watt combo uses a 15" speaker and a horn to provide a full range of sound, but the facilities provided on the amplifier are surprisingly comprehensive. Each channel has its own Bass, Treble and Volume controls as well as a Reverb on/off switch, which in itself is not earth shattering news, but there's more to come! All the Treble controls incorporate a pull-for-bright facility (great news if you're having to deal with a muddy old electric piano) and each channel has its own private effects loop. And yes, there's even more. The main effects send/return socket is located on the K80's deeply recessed rear panel, and this is connected via the auxiliary controls and switches on each of the three channels, so that effects may be used creatively and in combination.

As the reverb can only be either on or off for each channel, a Master Reverb control is located adjacent to the Master Volume knob, beneath which resides the obligatory illuminated HH emblem.

For private practice, a headphone socket has been thoughtfully provided, and an extension speaker may be connected providing that the minimum load impedance of no less than four ohms is observed. Lastly, a line output for DI or slave connection is also fitted, making this combo most suitable for live situations where a sound reinforcement system is used.

Like the Marshall reviewed earlier in this section, the HH's Tone controls are very effective but noticeably noisy if you start adding a lot of treble. The pull-for-bright facility should be a real boon for Fender Rhodes owners, and the flexibility offered by the effects patching system is hard to beat. And as with most HH products, the K80's reverb is good, too.

Being a few inches narrower than the Marshall combo, the HH is fairly easily carried by means of its strap handle, and its smart appearance is typical of other HH products.

Apart from the noise generated at high settings of the EQ and Level controls, the sound quality is really very good - certainly well up to semi-pro standards. As with most combos incorporating good 15" speakers, the HH should be a good bet for use with drum machines or electronic drums as well as synths, pianos and organs.

I know it's a bit predictable, but this is another good British buy.

Prices and Addresses

Ohm KA140C (£365) - Ohm Industries, (Contact Details).
Marshall KC60 (£305) - Jim Marshall Products, (Contact Details).
Carlsbro Keyboard 150 (£385) - Carlsbro Sales, (Contact Details).
Roland Cube 60K (£299) - Roland UK, (Contact Details).
HH K60 (£249) - HH Electronic, (Contact Details).