SR Technology Jam 150 Plus Sapphire

When it comes to acoustic instruments on a gig, I'll quite possibly be carting around a guitar, a mandolin, a cittern, a banjo and the occasional concertina, so I make pretty hefty demands on my backline amplifiers. Over the years, I've tended to favour PA systems over backline amplification, and SR Technology have adopted this approach in their Jam amplification series, designed to provide top-quality amplification for a range of acoustic and electronic sources in a single, compact-cabinet format.

The Jam 150 Plus Sapphire sits in the middle of the Jam range and is a newly released, cosmetically enhanced, limited edition of the standard unit in a textured blue lacquer finish, sporting blue LEDs and control knobs. The chrome-finish grille and (naturally) the Sapphire badge are also unique to this model, as are the sprung carrying handles, which replace the normal recessed version. I have to say that the Jam 150 Plus Sapphire makes for a very handsome amplifier indeed, and is a most welcome change from basic black. Other than the cosmetics, it is identical to the standard Jam 150 Plus, so what you get is a compact, bi-amplified, two-way, bass-reflex enclosure with a small-format mixing console recessed in the top of the cabinet.

Channels 1 and 2 offer XLR and jack inputs, 3-band EQ and an effect send, whilst 3 and 4 are linked inputs — on its own, channel 3 works like 1 and 2, but when used together with channel 4, it switches to the latter's line-level gain structure.

The Sapphire weighs in at 13kg, and lurking behind the grille of its solidly built ply enclosure sit an eight-inch woofer and a treble horn. The speakers are driven — via a 24dB/octave active crossover — by a 120W RMS bass amp for the woofers and a 30W RMS amp for the treble. These RMS figures mean that the amplifiers are capable of delivering peak outputs around twice their rated power, so this is potentially quite a loud box. It also has a top-hat stand mount in the bottom to allow you to mount it on a normal speaker stand.

The built-in mixer gives the Sapphire a flexibility that's not usually found in this type of combo amplifier. Starting out on the left-hand side, channels 1 and 2 are identical, each having microphone-level XLR (balanced and with phantom power available) and jack (unbalanced) inputs. From these inputs, the signal runs through a three-band equaliser with High, Mid and Low bands. This is an extremely musical and useful equaliser, although it is probably better used to tweak a good basic sound, rather than correcting a poor one. Following on from the EQ section, the signal is tapped off to the internal effects or to the external effects loop by the effect send, and reaches the main mix bus via the channel Volume control.

Channels 3 and 4 are not really two channels, but are two cleverly linked inputs feeding a single channel strip identical in control layout to the first two mixer channels. The channel 3 input used on its own works just like the jack input on channels 1 and 2. Channel 4 is a line-level input designed to accept preamps, keyboards and other high-level source signals. When used together with channel 4, channel 3 switches to channel 4's gain structure, which means that you can, for example, run a stereo keyboard or preamp into the one channel.

Channels 5 and 6 are again not two separate line-level channels, but simply two RCA inputs designed to feed both sides of an MP3 player, CD player or the like into one channel. This time around, there are only a High and Low two-band EQ section and channel Volume controls to deal with.

The final right-hand mixer strip carries the master controls. At the top sits the Record Out level knob that feeds the Record Out RCA connectors. Below that, you'll find the Select switch and LED indicators for the Alesis-derived onboard effects. The effects themselves comprise one multi-echo delay setting and three reverbs of varying lengths. None of these are extreme in any way and all serve to enhance the sound of the Sapphire, rather than dramatically change it. Below this sits the Effects Return pot, controlling the level of returns reaching the master mix from both the internal effects and any external FX units connected to the mono External Effects Send reaching the final mix. And below that are the Phantom power switch (added this year as the latest Jam 150 Plus upgrade) and its LED.

The final control in the strip in the master section is the rotary Master pot itself, with a Power LED just above it to reassure you that you've got the Sapphire switched on. The Master volume control feeds not only the Record Out control that we mentioned earlier, but also the single Line Out XLR, which is the final socket on the top panel and could be used to feed a PA system or another powered loudspeaker. The back panel of the Jam 150 Plus Sapphire carries a substantial heat sink for the power amplifiers, a Ground Lift switch, which can sometimes help stop hum problems, an illuminated on/off switch, and finally a fused IEC mains socket.

Overall, the mixer manages to cover most of the bases that you'll need it to cover in a live situation. Personally, I'd like to have seen a gain control on at least the two microphone channels, as microphones and piezo pickups don't have a built-in output level control and so can give rise to level-matching problems. That said, if you're going to be using one of these regularly, you will get used to its gain characteristics and therefore you should be able to cope without any real problems.

In use, the Jam 150 Plus Sapphire demonstrates the warm, clear and detailed sound that characterises SR Technology's PA and amplification products. Using a Schoenberg Soloist fitted with a prototype bridge-mounted Pure Acoustic transducer and an internal microphone running through a Fishman Powerjack preamp, I got a pretty good sound for fingerpicking and flatpicking without too much effort at all. The basic sound of the Schoenberg through the Jam 150 Plus had a bias towards the higher frequencies, due to the presence and position of the internal microphone, and the High and Mid EQ controls were very effective in controlling this and bringing the sound back into balance. As I increased volume, I ran into the inevitable body resonance feedback, and here the Low EQ let me pull out many of the offending frequencies without leaving me with a useless sound. If I was using this amplifier with this guitar (or any other acoustic instrument) in anger, I'd take along my usual Behringer Shark DSP110 feedback destroyer, as the Sapphire's EQ is designed for sound shaping and not for frustrating feedback.

My mandolin — fitted with a K&K pickup and an internal microphone, and run into a PreSonus valve blender — sounded really great through the Sapphire, with the higher harmonics in the notes coming through cleanly to give a very clear, articulate sound. Using an AKG C416 phantom-powered condenser microphone, clipped to the tailpiece of my Dave Stacey banjo, was equally successful and highlighted the Sapphire's ability to cope with sudden transients, although naturally you have to be conscious of the increased risk of feedback — especially that from non-banjo players.

The Jam 150 Plus Sapphire is also quite at home amplifying electric guitar preamps, and a newly acquired Les Paul Deluxe and WEM Copicat through the Ethos Overdrive pedal sounded pretty good indeed, just confirming how versatile an amplification system the Jam 150 Plus is. Finally, I set up Shure SM57 dynamic and AKG D535 condenser microphones, and had a good old sing through them, producing very good-sounding results, with the internal reverbs helping to add a (much-needed) touch of class to my vocals.

Although tonally the Jam 150 Plus Sapphire sounded warm, clean and sweet, I found myself expecting more volume from its 150W RMS of amplification, and my feeling is that the overall gain structure is set a bit on the conservative side. I'm sure that with higher-output mains-powered preamps, overload could be achieved, but personally I'd like to be able to know that I could get the amplifier up to its maximum levels with more usual equipment. Having said that, in practical terms the Sapphire was plenty loud enough; it's just that I felt it wasn't giving me everything it was actually capable of. Oh, and one more minor gripe: the manual refers to an overload LED associated with the channel Volume control, but I couldn't find one (even with my spectacles on).

I'd quite happily take the Jam 150 Plus Sapphire out as the only amplification to a restaurant or small pub gig, but I feel that it would need a bit of help to handle a larger and/or noisier environment. SR Technology seem to agree with my conclusion, as they market a range of accessories for the Jam 150 Plus to make life easier on stage.

The Club 150A is a bi-amplified powered speaker that matches the Jam 150S, and has the same speaker configuration and power output. This would be the ideal add-on if you were looking for greater dispersion or output. You could then add a couple of stands: the SMS1 lets you position the Sapphire as a floor monitor, and the SR lightweight speaker stand has small-profile feet. A practical addition if you were gigging would be the fitted, padded carrying case to make sure that you didn't mar the Sapphire's blue lacquer finish, or any of the three other finishes that the Jam 150 Plus comes in.

I also think that the Sapphire would be extremely useful in a studio situation, where it would give clients a great-sounding amplifier to play through when recording, as I personally find that DI'ing pickup-equipped acoustic instruments and monitoring through headphones removes a level of interaction between me and my music.

Taking everything into account, the Jam 150S Sapphire is a well-made, good-sounding amplification system that seems ideal for use by a vocalist or an acoustic multi-instrumentalist in a live environment. Although it isn't a cheap option, it is in the same price bracket as its direct competitors, and it would be well worth making the effort to track one down and sing and/or play your favourite instruments through it. The limited-edition Sapphire looks good and could be just what you're looking for. 0

Options

Jam 150 Plus:

Moquette (carpet) £549.

Polished wood or black lacquer finish £599.

Club 150A speaker:

Moquette finish £350.

Wood and black lacquer finish £385.

Sapphire blue lacquer finish £390.

SMS1 stand: £39

SR speaker stand: £49.

Padded carry case: £39.

SR Technology Jam 150 Plus Sapphire

Compact audio system