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January 2010
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AER Alpha Plus

Acoustic instrument amplifier

Published in PM November 2009
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Reviews : Guitar: Amplification
A more powerful, re-voiced and tweaked update of the original Alpha, the new AER Alpha Plus is a real step up from its ancestor. Retaining the original’s simplicity, this update is noticeably louder and the overall sound quality is a prime example of what can be achieved from a small cabinet fitted with a small, coaxial speaker.
Bob Thomas
If, like me, you’ve got a pickup and/or microphone fitted to one or all of your acoustic instruments, the chances are that you’ve auditioned, owned or coveted one of the amplifiers designed and manufactured by Acoustic Electric Research, better known by their initials, AER.
Founded in Germany in 1992 with the aim of becoming the touchstone of acoustic instrument amplification, AER are one of the most innovative of all the acoustic instrument amplifier manufacturers, currently producing a range of amplifiers and PA systems that range from the complexity of the flagship Acousticube III to the relative simplicity of the two-way, active CX82 PA loudspeaker. Mind you, in recent years AER have strayed a bit into the dark side with a range of bass guitar amps and cabs, not forgetting the strangely named Cheeky D electric guitar amp.
In my time I’ve auditioned every instrument amplifier in the AER range and, although the top-of-the-line Acousticube III still sits high on my list of most-wanted amplifiers, last year I ended up buying an AER stereo PA system simply because it is better suited to one subset of my current needs, namely great sound in small-ish rooms with acoustic instruments and vocals, able to cope with a five-piece band, easy to fit into a small car and quick to rig and de-rig.
Although I wouldn’t try putting a five-piece through the diminutive Alpha Plus, on paper AER’s latest offering would certainly meet the rest of my requirements with ease. The original Alpha was the smallest and simplest of the AER range; a 40-Watt, twin-input amplifier that found a ready home for acoustic instrumentalists who didn’t need the increased output power and feature-rich complexity of its bigger siblings. The updated version ups the power output slightly and incorporates a few circuit tweaks to gain its ‘Plus’ rating.
Construction
The Alpha Plus features two inputs, with independent gain controls and a global three-band EQ.
The Alpha Plus features two inputs, with independent gain controls and a global three-band EQ.
If you’re already familiar with the original Alpha then the first thing you’ll notice is that the signature AER embossed acoustic foam grille has vanished, to be replaced by a white-lettered metal version. This gives the whole amplifier a slightly more utilitarian appearance than of yore and I can’t think of it as an improvement, although it does tell the world that you’ve bought the latest model.
Fortunately nothing else has changed in the construction stakes. The cabinet, which essentially forms the bass-reflex enclosure for the eight-inch, full-range loudspeaker, is still the familiar, chunky, birch ply finished in acrylic black spatter (brown is optionally available) and hasn’t changed its size. The front and back panels are still familiar in layout and function and the whole package retains the anticipated AER air of confident functionality. This apparent competence is reinforced as soon as you open the Alpha Plus’ shipping box, where you’ll find it happily ensconced inside a heavy duty nylon bag. This has a hole in the top, allowing you access to the amplifier’s recessed, comfortably chunky carrying handle, and it sports capacious pockets on the front and both sides. I would have liked there to have been a flap covering the handle opening, since heavy rain could potentially turn the handle recess into a miniature pond.
The amplifier chassis of the Alpha Plus takes up the entirety of the rear of the cabinet, and the section carrying the forward-facing control panel lips around to form the upper-rear edge of the cabinet. Starting on the left, you’ll find the Input One XLR/jack combination socket for the mic/line input, with the level selector switch sitting between it and its Gain control.
Next comes the stereo jack socket for Input Two, followed by that input’s -10dB pad switch, its gain control and a clip LED indicator, which is common to both inputs. Input Two also features a Contour switch, which brings in a -3dB cut at 700Hz and a +10dB boost at 8kHz. The next set of controls comprises the three-band EQ section (common to both inputs) and the effects send control, which both brings in the onboard digital reverb and controls the output of the rear-panel Effects Send output. Finally, on the extreme right you’ll find the on/off indicator LED and the amplifier’s master volume control.
The rear panel is similarly sparse, with the various connectors sitting in a horizontal line halfway down the right-hand side with the combination mains on/off switch, fuse holder and IEC socket positioned below. From left to right you’ll see the stereo headphone jack, the post-master line out jack, the pre-master balanced DI XLR, the effects send and return mono jacks and finally the stereo jack for a suitable twin footswitch (not supplied), which will allow you to individually switch on/off the internal reverb and an external effects unit sitting on the effects loop.
Operation
The back panel houses the footswitch, effects send and return, DI output, line output and headphone output sockets.
The back panel houses the footswitch, effects send and return, DI output, line output and headphone output sockets.
Setting up the Alpha plus is really a no-brainer. If you’re using a microphone or a line output from an instrument preamp or effects unit (either balanced or unbalanced, on XLR or jack) you’ll use Input One. On this input alone, 24 Volts of phantom power for condenser microphones is permanently present on the XLR, so if you’ve got a unit that doesn’t like to see Volts sitting across its XLR balanced output (the TC Electronic G-Natural springs to mind) then don’t plug it in here. On the other hand, if, like me, you either regularly use condenser microphones or you’ve got an XLR-terminated, cable-mounted preamp that needs phantom power to operate, you’ll be very happy indeed.
Input Two is a high-impedance, unbalanced input with a stereo jack, best suited to pickups or line sources. The sole reason for the stereo jack is that there is an option (which requires an engineer) to add a +15V DC feed at the ring contact, giving you a source of power for any suitable electronics that are onboard your instruments. It’s worth noting that this supply isn’t the same as you’d commonly find powering the microphone in pickup/microphone combinations, it is simply here to give you an alternative power supply to the ubiquitous 9V battery, and you’d need to have your onboard electronics rewired slightly to take advantage of it.
If you sing and have a pickup in your guitar then you will naturally end up using both inputs simultaneously and using the Alpha Plus as a miniature PA system.
Level setting is a two-stage process, as the clip indicator is not only fed pre-gain from both Input One and Two and but is also fed post the common EQ. This means that you have to check that the LED doesn’t flash with the gains down and then keep an eye on it as you turn the gains up and/or add any necessary EQ boosts.
After that, all you’re left with is dialling in any reverb or setting the return level from an external effects unit, setting your on-stage volume level and feeding your DI to any PA system that happens to be in your vicinity.
Sound
The chunky metal grille protects the Alpha Plus’ eight-inch, dual-concentric driver.
The chunky metal grille protects the Alpha Plus’ eight-inch, dual-concentric driver.
AER acoustic amplifiers have a signature sound that is both detailed and clear while remaining warm. The Alpha Plus uses an eight-inch, twin-cone coaxial loudspeaker, which, although strong in the mid range, needs support in the bass and treble ranges to give a flat full-range response. There’s nothing new or unusual in this; Bose have been doing this for over 30 years with their 802 range of loudspeakers. In the Alpha Plus, AER have abandoned their earlier enhancer-based approach in favour of dedicated EQ circuitry, which has a response curve tailored specifically to the amplifier’s loudspeaker. This not only gives the Alpha Plus a flatter overall response but also reduces phase anomalies, thus leading to a more accurate reproduction of the instrument or voice being amplified. A subsonic filter removes low frequencies to protect the loudspeaker from any nasties in this region.
The Alpha Plus’ amplifier is a 50-Watt, DMOS (double-diffused metal-oxide semiconductor) monolithic IC affair with an A-weighted dynamic range of 92dB. In simple terms this means that it is noticeably louder than the original Alpha. To ensure that the amplifier remains within its operating parameters, AER use a newly developed, complex peak limiter that changes its attack and release times to suit the material being played and sung. AER have complemented these changes with changes to the EQ’s treble and bass shelving frequencies, and the overall effect is to make the Aplha Plus a subjectively louder, more dynamic and more natural-sounding amplifier than its predecessor.
However, the Alpha Plus’ sound sculpting doesn’t stop there. Input One has a permanent ‘vocal filter’ with a -10dB cut centred on 270Hz, which not only helps to make vocals clearer but also helps to reduce the body resonance of the typical acoustic guitar. I’m a little less convinced by the effect of the Colour switch’s boost and cut. For my taste, the 8kHz boost is a bit overdone and it would take a very dark instrument or voice to need all that. However, it’s there if you need it.
I tested the Alpha Plus with a whole range of differing acoustic instruments, pickups and preamps. The first and most noticeable result was that this little amplifier takes no prisoners. Feed it with a poor-quality source and you’ll get a poor-quality result. Give it something to work with — a decent mic like a DPA 4099 or a K&K Pure pickup — and you’ll get great results. I’ve more or less standardised my stage instruments on K&K Pure pickups with an external preamp,and although the Alpha Plus is perfectly happy to take these in on Input Two without a preamp, I felt that the sound was much improved with the K&K preamp in circuit.
As all my stage instruments also have onboard microphones, I combined these with the K&Ks using a Pendulum active blender cable into Input One of the Alpha plus, with the AER’s permanent phantom presence powering the Pendulum. The result was really natural-sounding mandolin and guitar. If I needed an amplifier for stage duties, this combination would be my default rig. As well as the mandolin and guitar I threw microphone-equipped banjos, a Fishman-fitted bouzar, a Sunrise-toting Guild Studio 24, a nyckelharpa with a DPA 4099 mic, a violin with a custom Finnish microphone system, a Skyinbow five-string electric fiddle and even a pickup-equipped autoharp at the Alpha Plus, and didn’t fail to get a sound that I’d be happy to take to any gig.
Finally, I subjected the Alpha plus to me singing through an AKG C5 condenser microphone and it didn’t disappoint. The vocal filter’s notch is nicely judged and my voice sounded completely natural and didn’t require any EQ. I tried my Guild guitar with the C5 mic and again got a sound that I couldn’t complain about.
Conclusion
I don’t usually get blown away by acoustic instrument amplifiers, but I’m going to make an exception for the AER Alpha Plus. There’s something about its diminutive size that makes its overall performance all the more impressive. I’m a big fan of simplicity, and the fact that I got a superb stage sound using just one amplifier and one (admittedly not inexpensive) active preamp cable made my day.
No matter what source I used, the Alpha Plus sounded natural, clear, warm and, most importantly for those intimate folk club and restaurant gigs, instantly attractive. To get the best out of your investment, you should feed the Alpha Plus with a high-quality pickup system, ideally fitted to a high-quality guitar, as the accuracy of the reproduction will show up any deficiencies in the source supply chain.
Although the top-of-the-range Acousticube III remains my aspirational AER acoustic amplifier, I’m seriously considering the purchase of this new Alpha Plus both as a personal monitor and also for those gigs where size doesn’t matter. Unless you need the extra volume and facilities of one of the bigger AER amplifiers, I’d recommend that you take your instrument and pickup system down to your local AER emporium and take a very close listen to this little beauty.  0

Published in PM November 2009
AER Alpha Plus £629
Unless you need the facilities and extra power of one of AER’s larger acoustic amplifiers, the Alpha Plus could easily become the centre of your stage rig. Take yourself, your instrument and your pickup system down to your local dealer and audition the Alpha plus. I can’t see you being disappointed.
information
Westside Distribution
+44 (0)1412 484812
Tech Spec
Alpha Plus
Two-input, portable acoustic combo.
Input one: XLR/jack combo with phantom power and ‘Voice’ filter (-10dB @ 270Hz).
Input two: line level, unbalanced jack input with -10dB pad.
Colour switch: -3dB @ 700Hz, +10dB @ 8kHz.
Effects send and return.
Effects footswitch socket.
Headphone output
Three-band EQ: bass (±8dB @ 100Hz), middle (±8dB @ 550Hz), treble (±8dB @ 10kHz).
Subsonic filter.
Adaptive peak limiter (threshold @ 35W).
Onboard digital reverb.
Power amp: monolithic IC, dynamic range 92dB (A-weighted).
Power rating: 50W RMS (4Ω).
Eight-inch, dual-concentric driver.
12mm birch plywood bass-reflex cabinet.
Dimensions (WDH): 265 x 235 x 260mm.
Weight: 6.2kg.
AER Gigbag included.