Omniphonics Footprint Series 75

Just the thing to send Paul White for Christmas — an Omni Present! Power amps have never been the stuff of which romances are made, but if you've ever been let down by one, you'll know just how much you can come to rely on them.

As a general rule, more money buys you a more powerful, more reliable and better‑performing power amp — but at the same time, an amplifier designed for stadium PA work is probably over‑engineered and over‑powered for use in a project studio monitoring system. What's needed in the smaller studio is a sensible, medium‑power design combining hi‑fi audio quality with pragmatic engineering. It's also important that the amplifier is capable of staying cool without the need for fans (variable‑speed fan systems excepted), as fan noise can be very intrusive in smaller studios.

Omniphonics is a British manufacturer with a track record for building realistically‑priced amplifiers to meet the needs of the project studio market, though that isn't to say that their amplifiers in any way fall short of professional specifications — their higher powered models are equally suitable for live sound and installation work. The new Omniphonics Footprint series of amplifiers currently comprises two models, the Series 75 and the Series 150, the main difference being the power rating. Under review is the Series 75, a 1U, two‑channel power amp capable of delivering up to 50 Watts per channel into 8Ω, or 75 Watts per channel into 4Ω.

Overview

Conventional in appearance, the Footprint Series 75 incorporates extruded aluminium end cheeks, which are finned to assist in dissipating the heat from the two bi‑polar output devices (cooling is entirely by convection). The power switch is on the front panel, along with a green Power LED and a red Protect LED. However, there's no clip LED — something I rather miss. Loudspeaker connection is via standard terminals, which accept either bare wires or standard banana plugs. The two channels may be bridged for mono operation, providing up to 135 Watts into a minimum load of 8Ω.

To protect the loudspeakers from potential damage, and eliminate thumps at power‑up, the speaker outputs are relay‑muted for around five seconds after the amplifier has been switched on, allowing the power supplies time to settle before the speakers are energised. The relay also forms part of the protection circuit, and decouples the speakers from the amplifier in the event of a serious problem. The relay also operates if the amplifier operating temperature becomes excessively high, or in the event of a short circuit at the output terminals.

Both channels are fitted with conventionally‑wired, balanced XLR input connectors, but there are no parallel stereo/mono jacks, which could have been useful for making quick and cheerful connections from semi‑pro equipment. A recessed ground lift switch is fitted, which is always useful in situations where ground loops might occur (for more information on ground loops and ground lift, see the feature explaining them in August 1994's SOS). Finally, the recessed level controls may be removed and replaced by rubber caps, to prevent tampering in permanent installations.

The mains transformer is tapped, enabling the operating voltage to be switched between 100 — 120V and 220 — 240V. Hum and noise are specified at 95dBa relative to the maximum output level (inaudible under normal circumstances), and the frequency response extends from 20Hz up to 40kHz within very fine tolerances, rolling off very gently to in excess of 80kHz.

Testing, Testing...

In use, the Omniphonics Footprint Series is very quiet, and delivers a confident, transparent sound, with no obvious rough edges. For powering nearfield and other small monitoring systems in home and project studios, the 75‑Watt version delivers adequate power, and runs reasonably cool at typical monitoring levels. Relay protection is a nice feature on an amplifier of this price, and the 1U packaging means you don't have to lose too much rack space in finding it a home.

It's probably true to say that the power amp market is not an easy one to be in — there's so little obvious distinction between one model and another, which leads to buying decisions being made on price, rather than quality. In spite of this, Omniphonics have hung in there, and consistently designed decent amplifiers at a price people are prepared to pay. The Footprint Series seems set to continue in that tradition. Apart from the lack of a dedicated Clip LED, I can't fault this amplifier.