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Custom Sound 727 Keyboard Combo

A British-built keyboard combo to compete with the world's best comes under Paul White's enquiring gaze.

Paul White examines a British amplifier that offers all the basic facilities demanded by the modern keyboard player, at a price that puts it within reach of most serious musicians.

Custom Sound have always had a reputation for building value for money amplification, the best known of their products being the Trucker range of guitar amplifiers, which offered good basic facilities at an easily affordable price.

Their latest range of equipment is still economically priced, but the cheap and cheerful design philosophy has developed into something more sophisticated, combining improved electronic design with a more stylish presentation.

The 727 is a 75W combo and has three independent channels, each with Hi and Lo inputs, bass and treble EQ, and selector switches for reverb and external effects.


The fully-sealed speaker enclosure houses a Fane 15-inch driver, and a wide dispersion horn tweeter coupled to the power amplifier via a passive crossover network.

Weighing in at 28 kg, the unit is tastefully finished in black vinyl with matching handle, and plastic corners of the stack-able type.

The high-efficiency Fane driver has an integral steel grille, and all the controls are well recessed out of harm's way, so that transit damage is unlikely.

Heavy duty castors are fitted (the rear ones having brakes), and the whole combo measures only 25 x 25 x 12 inches, making it very easy to handle.

Electronically, the construction follows the now familiar format whereby the rear panel holds the power amp circuitry and the mains input socket, the front panel acting as a mount for the pre-amp, which is built on a single long PCB and makes extensive use of op-amps.

A long dual-spring reverb line is mounted on a metal plate running the length of the amplifier, and this acts as a screen for the reverb and preamp circuitry to cut down hum leakage from the transformer.

The power amp stage uses two discrete output devices and is capable of delivering 100W into four ohms when an external speaker is connected.


The bass and treble controls are of the cut or boost type and have a very wide range, the bass control giving 40dB range at 80kHz and the treble having a range of 50dB at 10kHz.

The master section contains the master gain control and the reverb level, a presence control providing an alleged 16dB range at 800Hz.

Connections for auxiliary send and return signals are also on the front panel, as is a footswitch socket which permits remote switching of the reverb.

On the rear panel, there are two sockets for extension speakers (minimum combined impedance four ohms), a headphone output, and line and slave outputs, all on quarter-inch standard jack sockets.

In Use

Switching on the unit produced quite a loud switch-on thump as the power supply capacitors charge up and, although this probably doesn't overstress the loudspeakers, it is a little disconcerting.

With early Custom Sound equipment, circuit noise and background hum often presented a problem, but this new series seems to have got all that sorted. Mains hum is minimal, and circuit noise does not become noticeable until the gain is set to quite a high level: performance in this respect is as good as or better than most of the 727's contemporaries.

The combo was tested first with a bass guitar, just to check the speaker's performance at low frequencies, but no problems were encountered here even though the cabinet size restricts the efficiency at very low frequencies.

With electric piano and synthesiser, the sound was very clean and bright, largely due to the generous horn tweeter, and the EQ was more than adequate for any normal use.

Reverb units in combos are quite often less than perfect but the 727's is not bad at all, though it is susceptible to vibration and knocks: the basic sound is quite full and flattering to keyboards.

One area in which a compromise has been made in order to keep the cost down is in the auxiliary and reverb switching. Both these effects may be switched in or out individually for each channel, but there is no way to adjust the amount of the effect from one channel to the next. This may not be a serious problem to most players, but it is nice to be able to add, say, more chorus to an electric piano than to a synth.


The 727 is a reasonably priced combo incorporating most of the essential facilities generally used by modern keyboard performers. There are no unnecessary frills, but everything provided is of decent quality and the performance is in excess of what you would expect for the price.

The lack of flexibility inherent in the on-or-off effects selector system will probably put some people off, but a mixer-amp with proper variable sends is likely to cost rather more than the modest price of this combo.

I was a bit disturbed by the magnitude of the 727's switch-on thump, but otherwise this combo gets my vote of confidence, taking its price and facilities into account. It's nice to see a British manufacturer coming up with a product that's at least the equal of its foreign competitors.

The Custom Sound 727 carries an RRP of £293 including VAT, and is distributed in the UK by Audio Factors, (Contact Details).

Next article in this issue

Synclavier: A New Appraisal

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


Electronics & Music Maker - Aug 1984

Gear in this article:

Amplifier (Combo) > Custom Sound > 727 Keyboard Combo

Gear Tags:

Keyboard Amp

Review by Paul White

Previous article in this issue:

> Electro Harmonix Instant Rep...

Next article in this issue:

> Synclavier: A New Appraisal

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