From ear'oles to earthquakes, Andrew Bodnar considers bass amplification starting at the portable Bass Rockman and finishing with a heavyweight Trace Elliot. Five reviews, two columns of philosophy and a big noise.

Deep in the heart of real bass players, more basic than the eventual techniques they learn or any peripheral attractions that bass playing might display, is the desire to produce that sound.

Whether some have an inborn affinity with this end of the musical spectrum is hard to say for sure, but bass guitar is a missing-link, if you like, between percussion and musical instrument. I've always felt that if drums could sing melodies, then they'd sound like a bass.

It's a deceptively primitive instrument – just four thick wires stretched taut across a length of wood – and yet is so widely open to interpretation. When the instrument is played well, the resulting effect, in harness with drums, makes people flex their limbs, waggle their behinds, rock their heads and dance. The personal thrill gained from that reaction is maybe the main reason why bass players play their beloved instrument – throbbing energy and mass-communication with people's sweating bodies. Own up. It's damn good fun!

Just as drummers are nearly always muscularly strong in order to power and drive their kits, so the bass player needs comparatively beefy amplification to drive the speaker cones which are, to all intents and purposes, very advanced drum skins.

Because deep sounds emanate from slow, violent vibration of the air, earthquakes rumble and roar instead of jangle and squeak. Bass amplification, then, needs always to be powerful, and that doesn't necessarily mean loud. Even a practice amp should have some-to-spare if it is to convey the sound of the bass with clarity and conviction.

Luckily, amplifier design has in most respects come a long way over the years, aided by the evolution of kilowatt sound systems. Modern PAs can be seen clearly to have influenced current top-end bass amplification (eg separate power/control amps, multi-speaker configurations, crossovers and so on) and some of the thinking therein has rubbed off on to smaller amps and combos in the form of graphic or parametric tone controls, myriad output sockets, compressors and the like.

These kinds of features, which have appeared steadily over the last 10 years or so on a more widespread scale, were previously available on only a handful of models, such as those from Acoustic or Ampeg. These two manufacturers, along with several others, were among the first to provide the swiftly blossoming bass community with great-sounding, reliable, high-output amp systems, as opposed to modified guitar amps with bass-type loudspeakers thrown in for good measure.

This is not a real criticism of earlier designs, because a few were OK, and not till after the mid-Sixties was the bass guitar generally realised to be quite an important instrument with a lot of musical and rhythmic potential. The Motown Sound (see also this month's "Heroes") with its wonderful bass players was not entirely blameless here, and, in hand with other musical factions, encouraged talented bassists from all walks of pop music to step forward. Events, people, and the surge toward loud amplification have all contributed and shaped the standards and choice of bass equipment on offer in the shops now.

At present, bass amps have to be able to handle a melting-pot of styles and sound, from ultra low (and power-consuming) reggae to the hi-fidelity treble required by pull/slap techniques. Unlike guitar amps, in which inherent overload and distortion are manipulated and controlled with chosen effect, the bass player needs the opposite: plenty of headroom so that distortion does not occur at high volume. The three methods of popular playing – finger style, plectrum, and pull/slap – each impose heavy demands on the power section of an amp. The continual impact of attack as thumb hammers E-string or plectrum strikes metal will place considerable (and audible) strain on anything not up to par.

For the average band-member, my own very sweeping rule-of-thumb has been to check the output rating of the guitarist's amp and double it for my own, although you must take into account the size of venue likely to be played, the sort of outside session work you might do, and what you would need if suddenly in a less-permanent situation. Avoid an enormous set-up unless you are assured of its use over a long period ahead. This kind of gear is specialist, very costly, expensive to freight and it doesn't work properly within smaller confines. Sting is exempt from this advice.

For the freelance bassist, the ideal is probably to own a good quality small amp/combo, and a medium or splittable larger system for live work. Newcomers might be better to go for a tried and tested medium system (for example a secondhand Fender Bassman amp and 2x 15in cab, or similar). This is likely to be of more practical use in everyday situations and (most important) it should fit into your car or that of your best friend. No matter which sort of set-up you're after, it's also worth bearing in mind that white elephants often turn into millstones.

On to speaker enclosures. During my formative days, I vividly recall three of us wrestling a Selmer Goliath cabinet (the size of a burial casket) across Clapham Common, neatly ploughing the grass up behind us as we pressed forth. It contained one 15in bass speaker rated at 30 watts. Well, although some things have changed dramatically since (a 15in speaker will likely be rated at anything between 200 and 400 watts nowadays), several laws of physics have yet to be conquered. It still holds true that the bigger the speaker cone and the bigger the enclosure, the deeper the sound will be. It will also respond more smoothly in the lower register when strings are pulled hard. This tends to be the case regardless of the type of enclosure utilised, ie sealed, ported, and reflex.

These latter methods of design have more to do with speaker-efficiency. Broadly speaking, this means getting more "loudness" from the speaker in relation to a given amplifier output.

Smaller cone sizes will produce a punchier, more immediate sort of tone. Your eventual choice of speaker type is really down to you becoming familiar with these characteristics by trying as many as possible and equating them with your main style of playing. The written word is no substitute for experience. In terms of power-rating and the matching of this with amplifier output, if you add, say, a third of the amp power again, you'll be on fairly safe ground where speaker overload is concerned, assuming the latter is of decent quality.

Thus, a 100 watt amp should work clearly enough in a 130 watt enclosure, although you should not be using the volume control much beyond halfway. For the purposes of bass amplification, this is fine – back to power-in-reserve and all that.

It's worthwhile to audition new gear at roughly this setting, with tone and effects controls flat or off. You'll be able to hear immediately how the amp and speakers are going to sound, on the whole, and you'll also be able to gauge power handling abilities quite well. A well-matched system usually works with optimum efficiency at around the halfway mark, and tone control deviation shouldn't need to be too extreme.

So, without wishing to state the obvious, the less you find yourself having to "fiddle" with an amp set-up, the better will it be suited to your own sound. Beware of gimmicks. Look, instead, for sensibly designed controls that work for you. After all the claims and innovations have faded away and the sparkling paint-job is wearing off, a good amp will still be a good amp. It's really as simple as that.

In order to test all this remarkable philosophy, I decided to audition a few amp systems for myself. Five, to be exact. These were broken down into typical examples of very small, small, medium, medium/large, and large systems.

Bass Rockman

£235

"Very small" covers the growing range of bass pre-amp/headphone units coming on to the market. Players have long awaited the arrival of Tom Scholz's Bass Rockman, though as it happens several cheaper alternatives have hit the UK already. In appearance, the attractive preamp (complete with phones) matches the well-established guitar version, being Walkman-like in weight and dimensions. There are two 'phone/line outputs, bass guitar input, an auxiliary input (for Walkmen and Co), and a low level output. The controls are all in switch-form.

On-off activates a pulsating LED when turned on, and the volume has "hi" and "lo" positions. The EQ switch is labelled FAT, MID, BRIGHT; the chorus effect OFF, CLEAN, DISTORTION; and the sustain gives three levels of decay. Lastly, there are two tiny switches which supposedly work in tandem with a ±6 dB "high frequency adjuster" on the back of the unit. The first switch is for "eliminating the click when using a plectrum" (!?). The other is for compression. In real terms, neither switch had any effect on the sound whatsoever.

The sustain worked well enough, and the chorus ("clean" position) was very pleasant. The EQ was also quite effective, but I must say that with the headphones provided, the Bass Rockman wasn't nearly as loud as I'd expected. It's a very nice sound, making the most of the bass guitar plugged into it, but a little too quiet for me. It was also claimed to have very low background noise (which would be a real bonus when using the Rockman as a pre-amp in studios) but hiss on the sample tested was quite audible.

Session 100 watt bass combo

£305 black; £317 beige

Moving up to "small", we enter the amp-proper division with a Session 100 watt/1 x 12in ported-speaker combo. This is a new, upgraded version featuring a MOS-FET power section, soon available as standard. It is small, and visually a bit reminiscent of Ampeg's old Portaflex combo. Controls are minimal: pre/master volumes, a contour switch to give a "Fender-type response", variable compressor, and a graphic EQ section. Comprehensive outputs have been installed, including a socket for headphones which is a nice touch.

I was very impressed with the performance of the combo, which totally belies its diminutive size, both in roundness and projection of sound. The amount of top end available was ear-shattering, and the combo handled the lows with only slight restriction. Perfect for studio work and, I would guess, quite at home in small venues if the band isn't too loud and earth-moving bass isn't necessary. The Session was an unexpected surprise.

Carlsbro Stingray 150 combo

£347.59

Carlsbro loaned us the amp that filled the next position: the Stingray 150 combo contains a 15in speaker in a ported cabinet, and its controls are quite similar (if simpler) to those of the Session except that bass and treble controls are fitted to the Stingray, whereas the Session has more bands on its graphic. Six of one and a half-a-dozen of the other, really.

There are fewer outputs, but a headphone socket is present here too. The Stingray, though supplied with castors, is still not very big or heavy – both this and the Session fit in cars without a struggle, but of course the Carlsbro is louder and the 15in cone gives a truer low-end and doesn't approach break-up so quickly. The sound is crisp and open, covering a full drum-kit with no effort. A definitive club-circuit amp, it might well stretch to bigger venues so long as you aren't a reggae player, dependent on high low-end output. Given its power capacity, the Stingray copes admirably with a whole range of playing styles.

Peavey MkIV system

Amp ± £425; 2 x 15 cab ± £265, with Black Widow speakers ± £365. Price range due to £/$ fluctuation.

Peavey's MkIV bass rig is presumably intended for theatre-size venues, being capable of around 300 watts output (depending on how many cabinets are used). There are two channels on the amp which can be linked together with the aid of a remote footswitch. Parametric and graphic equalisation is provided as well as standard tone controls. Variable crossover is also included so the user can direct treble and bass output separately to, say, a 4 x 10in and a 1 X 18in cab. A compressor (permanently on and non-variable) is said to help prevent speaker overload.

The concept of this amp differs somewhat from the first three. It's a fair bit more complicated to suss out at first, but I'd be hesitant to suggest gimmickry at work – rather a different approach to the same ends. As to the sounds produced by the MkIV, Peavey's modern technology seems to have most corners covered and, played through a 2 x 15in enclosure, it gave the first proper rendition of reggae bass so far encountered. I suddenly perked up on hearing this. No rattles or protestation, but pure wedges of low, low bass with respectable volume.

Trace Elliot AH500 system

£1350

Finally, we come to the heavyweight category. Five hundred watts is the maximum power developed by Trace Elliot's AH500 amp. Apparently the most popular speaker configuration with this amplifier is a 4 x 10in combined with a 1 x 15in, both cabinets being of the ported variety and all looking quietly impressive when set up to go. Many other combinations are possible, and there's even a 2 x 8in cabinet (the kind of attitude I admire). The test rig was the one already described.

Once again, the control section has much in common with that of the little Session combo (or vice-versa?). Naturally there are some additions, mostly in the guise of output facilities. A two-speed fan is fitted; there is a contour switch, and the display panel may be illuminated with ultra-violet light. The gigantic, immaculate sound as conveyed by the 4 x 10in/1 x 15in speaker cabs would fill just about any stage within reason, and the wide dispersional properties of the 4 x 10in would allow the player maximum mobility in the stage area. That's with the graphic EQ switched out! I think that if there were ever a true successor to the equivalent rigs of the 1970s, then this is definitely it.

One thing I would do is to ask the designers to improve or discontinue the noise gate switch. This is meant to reduce amp-hiss at high power levels, but seems to draw more attention to it by making the hiss "whoosh" instead. I feel that the money spent on this circuitry would be better invested in reducing the hiss, which isn't terribly high in any case. That said, the Trace Elliot is a superb performer – the praise heaped on it by musicians and critics so far seems completely justified.

Each of the four amplifiers under scrutiny looked to be highly robust, well-constructed and, in the main, attractively and neatly finished (a functional appearance situation). Interestingly enough, the Session, Carlsbro and Trace Elliot amp sections closely follow the same lines of pre-amp control, indicating strongly that this is the most logical one for the bass-player to use. The Peavey comes from a different school of thought, but with careful use it is as capable in its way as the other three. I'm not sure about this fad for compression. I've never had much cause to use it. Some people must have, because you see it absolutely everywhere. I would also be cautious of forgetting just how good were some of the older and, I suppose, now less-fashionable amp rigs. I know for a fact that in practical terms an Acoustic 371/370 would give a few of these contemporary designs a good run for their money. I know the hi-fi response isn't as particular, but there is something about the sound of such beasts when the whole band is cranked-up... well I won't get into that debate here.

Altogether, it's highly encouraging to have heard this random selection of amps give such a convincing and confident account of themselves. It's also reassuring to think that in contemplating the current scene, the bass player is, at last, spoiled for choice.