The audio amplifier is in transition, because it’s becoming hard to justify a physically large, heavy, and energy hungry design today. Although Class D operation offers a resolution to all these issues, audiophiles often dismiss this technology for its sound quality. Which is why the Cyrus Audio 200 power amplifier is potentially so important.
With the Cyrus 200, Cyrus Audio claims to have built a Class D circuit that delivers high power (200W into six ohms, 175W into eight ohms) that not only fits into the standard Cyrus half-width HA7 die-cast aluminium chassis, but also sounds exceptionally good. Cyrus has eschewed buying off-the-shelf amp modules (from companies like Hypex or ICEpower), and instead designed its own Class D amp modules from first principles.
Significantly, the company recognised that Class D’s ‘voice’ is effectively governed by the impedance of the loudspeaker to which the amp is connected. Starting with the all-in-one Lyric system, Cyrus included its SID (Speaker Impedance Detection) circuit in all its Class D designs. On power up, SID sends a reference signal to the left loudspeaker, compares what it receives from the loudspeaker with that reference, and adjusts the output of the amplifier accordingly. In most other Class D systems, the best you can do is to cycle the power a few times and hope for the best.
Cyrus Audio calls the Stereo 200 a ‘hybrid’ design, but it’s not a hybrid in the conventional audiophile sense – don’t go looking for valves. Instead, the company chose to couple this sophisticated Class D design with a linear power supply more commonly found in Class A and Class AB amplifiers. Class D designs are so commonly accompanied by switch-mode power supplies that people mistakenly think switch-mode is an intrinsic part of the design itself. And when you gaze long into the ‘singing shoebox’ case, the small 475VA toroidal transformer will gaze back at you (no abysses were harmed in the making of this sentence).
By using this ‘hybrid’ Class D, the Stereo 200 sports a smaller and lighter transformer than expected for a 200W power amplifier, and the whole device weighs just under 7kg, or a shade below fifteen and a quarter pounds. Staying with imperial measurements, Cyrus has long been good at squeezing a quart into a pint pot, as is reflected in the densely packed back panel of the Stereo 200. It has XLR and single-ended phono inputs, a pair of ‘chain’ phono outputs for additional power amplifiers in a bi-amp setting, a mini-jack standard trigger socket, and two Cyrus’ own MC-BUS phono connectors, which are used to send comms signals between Cyrus devices. Add in two pairs of WBT-like loudspeaker terminals and a three-pin ICE socket, and there is barely any rear panel real-estate left – just enough for ‘made in England’, in fact.