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microphone amplifier

ma2.2b true class a mic preamp

product review

Studio Sound magazine by Dave Foister

Another new product from New Zealand's Buzz Audio gives you two channels of Class-A preamplification with switchable input impedance.

If you want the best circuitry for bringing microphone signals up to manageable levels, there seem to are only two ways to design it. One is with tubes; the other is with discrete solid-state Class-A circuitry. There are plenty of preamps of both flavours around, which by their very nature end up fairly similar in presentation. These are not boxes for the gadget fan, but simple tools to do a job in which anything other than straight gain control is regarded with suspicion. You wind up with a selection of products distinguished only by the details of their specifications, subtle differences in sonic qualities, and their cosmetics. It takes a brave manufacturer to put a toe in this water, but that's what New Zealand company Buzz Audio (they must be brave people to have chosen a name like that--or perhaps they want to suggest they're light years ahead?) has done with the MA 2.2 True Class-A Microphone Amplifier. (Maybe the noise floor is at minus infinity or beyond).

The challenge facing the external designer these days is to make a product stand out with distinctive touches that do nothing to undermine the impression that it's a sensible, professional piece of equipment. Blue may be this year's black, and its use on the MA 2.2 achieves the above aims rather well. The knob end caps, the screen print, and the recessed panels that carry the switches are all in matching deep sky blue, and of course the power indicator is a blue led that even the manual can't resist describing as 'cool'.

The knobs number only two, and are inevitably the gain controls--detented for confidence and repeatability but not switched. The calibration numbers around the edge are augmented by lines on a black surround within the panel cut-out. Each of these is flanked by two blue insets within which all the control switches are mounted, and in true laboratory style, all the switches are simple silver toggles (up for off). The fact that there are only five of these per channel plus an led is a good indicator of how simple the facilities are and how reluctant to gild the lily Buzz is.

One of only two remotely unusual switches on the MA 2.2 is the output mute, provided to avoid the thumps that would otherwise be associated with the operation of almost any of the others. These others comprise the bare minimum that you would expect to find on a microphone preamp: phase invert, a 20dB pad, and phantom power, all independent for the two channels.

There is a peak led for each channel, notable for being red (hands up if you can remember when that was the only colour you could get) and for a facility I can't remember ever seeing before--internal presets for defining at what level they come on. If you know what you're doing when setting these up, they could prove more useful than bargraph meters, since they can be set to flash at the level that concerns you and the specific following equipment, rather than some arbitrary level. How often have you seen peak lights and red meter segments flashing vainly at you when you know there's no danger of clipping in the equipment concerned nor in what it's connected to? In fact, the manual gives instructions for calibrating all the internal adjustments, including the maximum gain and separate controls for CMRR at high and low frequencies.

The only other external control is for the input impedance, which will appeal to those with ribbon microphones and others that deviate from the 'norm' but should perhaps be checked out with supposedly standard microphones. I found that a familiar model sounded just a little more open with the low impedance setting than with the nominally standard high setting. Even this will thump a bit, making the mute switch a very worthwhile addition.

The back panel looks conventional but this is deceptive. A big surprise with the Buzz box is that, as supplied, its output is unbalanced albeit presented on an XLR. This is not the cost-cutting exercise that it would be on a down-market preamp but--according to Buzz--a valid step in minimising the signal path, avoiding any degradation, however slight, that might take place in the final balancing stage, be it an electronic circuit or a transformer. When the preamp is sited locally to its destination, this is fine; I placed it on top of a rack, hooked up with conventional patch cables, with no ill effects whatever. If the cable run on its output were longer, the situation would be different, even with a low output impedance, so Buzz offers an optional retro-fittable output transformer, whose other effect is to reduce the upper limit of the bandwidth from 250kHz to 40kHz. (Buzz Note; the upper limit actually only falls to 150kHz with the Sowter transformers fitted).

The MA 2.2 is a simple preamp even by purist standards. It has no filters and only the most basic facilities--certainly no digits. But it sounds superb; clean and open, with that ability to coax the best out of a microphone that such a design depends on. If all you need is to be able to get a microphone signal into an analogue line input as cleanly as possible, they don't come much better than this.

  Buzz Audio Ltd
  New Zealand
  Ph +64(0)3-577-5597

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