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Alligator AT150 Amplifier

KGB Speaker Cabinet

AT150 with the KGB cabinet.

Alligator is a new range of amplification equipment manufactured and distributed by Musicians Direct Supply Co.

This company was set up, as the name suggests, to supply musical instruments direct to the musician, therefore keeping the final cost down. The concept was put into practice by managing director Pete Tulett, who has been some 15 years in the music industry and incidentally introduced Aria Guitars to the UK with Gigsville Ltd.

Five Alligator products are currently available: the AT150 Amp top, KGB Cabinet, AC150 Combo, AST150 Slave Amp, and the ASC150 Slave cabinet.

The first thing that strikes you about this equipment is the colour. All the cabinets are covered in a very attractive Alligator green rexine material, the panel are finished in green, even the LED's are green!

The gear really looks ready for business, with chunky black handles and tough ABS corner mouldings which mate to provide a stable, stackable setup.

We are looking at the AT150 Amp top and the KGB cabinet, but since the AC150 combo uses the same parts, fitted in one cabinet, this review covers both.

AT 150

The amplifier is an all purpose unit which can be used for just about any instrument that produces an electronic signal through a standard jack plug. It is rated at 120W rms into 8 ohms or 160W rms into 4 ohms, measures 21" x 6" x 10", and weighs 18 lbs.

Starting at the back (or tail) of the Alligator, from left to right, we have: the mains connection, made via a standard euroconnector, a 20mm 3A anti-surge protection fuse, the power switch, which has a steel toggle with good positive action, speaker outputs, two jack sockets wired in parallel, protected with a 20mm 6.3A anti-surge fuse, and lastly, three sockets on the right of the panel which are Send and Return for effects loop, and Mixer/Slave. The pre-amp section output is connected to the Send and Slave sockets while the power-amp input is connected to the Return socket. With no jacks connected, pre-amp is connected to power-amp as normal. Inserting a jack into Return breaks this connection. The Mixer/Slave output can be used to drive further power-amps or to provide a signal compatible with mixer inputs.

The front panel offers an interesting selection of controls with two equalisation sections. Starting, again from left to right, we have: the Boost section, which can be operated by the toggle switch or optional footswitch, operation indicated by the LED, the Input socket, Gain and first stage equalisation; Bass and Treble, followed by the second stage of equalisation; Low, Mid 1, Mid 2 and High, Master Gain control, mute switch and LED indicator.

A dissected Alligator!


The amplifier is constructed in two parts which can be removed separately for servicing. The first part, the pre-amp and associated circuitry, is mounted on the front panel with the second part, the power supply and power amplifier, on the back panel.

Taking the pre-amp section first, the input signal is passed through an RF filter to remove any interference before being amplified by the Boost stage, the gain of this stage being increased by a factor of 10 when the Boost is operated. An active filter network then provides a 12dB boost or cut at 50Hz and 4kHz for Bass and Treble respectively. The filtered signal is further amplified through a clipping circuit which provides distortion or fuzz when the Gain control is adjusted above the clamping threshold. After this stage comes the second active filter section with boost and cut at 100Hz, 500Hz, 1.5kHz and 5kHz for Low, Mid 1, Mid 2 and High respectively. This output is fed to the Master Gain control which can be shorted out with the mute switch. Connections from this board go via a molex 4 way connector to the back panel.

The transformer input is set for 240V mains but a link can be changed to allow for 120V/60Hz operation. The output from the transformer is rectified and smoothed to provide the dual power rails for the power amp and then further regulated to supply the pre-amp section. The power amp is encased in epoxy and bolted directly to the rear panel. This module is in fact capable of driving 250W rms but is deliberately under driven to ensure reliable, high quality performance.


Externally the amplifier is well made, built to survive a lot of bashing. None of the knobs or switches protrude from the cabinet, which is a nice point, minimising the chance of them being damaged or causing damage!

Internally high quality components are used throughout, with the important power wiring bound together.

Alligator obviously have great faith in their products since they are providing a 5 year guarantee on amps and a 2 year guarantee on speakers.

KGB Cabinet

Alligator complement their all purpose amp with a multi-purpose speaker cabinet. The cabinet has a special Horn loaded section which emphasises Bass frequencies. Two Fane 10" heavy duty speakers with 1½" voice coils are fitted, protected by strong steel grilles.

The cabinet, rated at 120W with an impedance of 8 ohms, measures 21" x 26" x 10", weighs only 40lbs and can be easily manhandled using the two handles provided, one at the balance point and one on the top.

There is even a storage compartment for the cover and leads etc.


So much for the facts and figures, what does it sound like?

Actually, its hard to make this amp sound bad, no matter what signal you present it with, Bass, Guitar, Percussion machine or Synthesiser, they all sound clear and true. The secret of this appears to be in the layout of the equalising chain. The sound can be modified with the initial Bass and Treble filters, amplified to clipping levels and then tailored again with the second 4 band equaliser. This allows a large range of tone colours to be obtained to bend the instrument connected to your own personal taste. (The owners handbook supplied gives a list of settings to start you off).

The two Mid controls are excellent for bringing out the 'body' of the sound, giving it a real bite (no pun intended!). The Initial Gain control can also be used to give some great 'overdriven' sounds without having to use earsplitting volume levels.


A lot of thought has gone into the design and development of this range with much attention being paid to the practical needs of the musician; sound quality, reliability, versatility, looks and last but certainly not least, price.

All of the Alligator range represent excellent value for money, mainly due to the fact that you are buying direct from the manufacturers. The gear comes complete with spare fuses matching green covers, leads (with green jack plugs!), the 5 year guarantee and is delivered direct to you by Securicor.

Alligator equipment is available direct from Musicians Direct Supply Co., (Contact Details). Tell them E&MM sent you!


Power Output 120W rms @ 8 ohms
160W rms @ 4 ohms
Input Sensitivity 15mV into 100K
1.5mV with Boost
Maximum input level 3V rms
Tone Control ranges Bass 50Hz ±12dB
Treble 4kHz ±12dB
Low 100Hz ±12dB
Mid 1 500Hz ±10dB
Mid 2 1.5kHz ±10dB
High 5kHz ±12dB
Maximum Signal levels Send/return 1V rms
Slave/mixer 1V rms @ 1K
Prices (inc VAT) AC150 Combo £249.00
AT150 Amp Top £169.00
AST150 Slave Top £139.90
ASC150 Slave combo £215.50
KGB120 Speaker Cabinet £99.50
Footswitch £5.90

Also featuring gear in this article

Previous Article in this issue

Making Notes

Next article in this issue

Home Electro-Musician

Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.


Electronics & Music Maker - Nov 1982

Gear in this article:

Amplifier > Alligator > AT150

Previous article in this issue:

> Making Notes

Next article in this issue:

> Home Electro-Musician

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