ROSE RA280

The ROSE RA280 is an integrated amplifier that builds upon and further develops several design solutions introduced by HiFi ROSE with the RA180 model. The design combines a Class AD amplification section based on GaN transistors with a high-efficiency power supply and separate channel management, with the aim of achieving a linear response, short dead time, and high signal control.

The Class AD GaN technology developed by HiFi ROSE addresses some of the main limitations associated with traditional Class D implementations through the use of semiconductor materials other than conventional silicon devices. GaN (Gallium Nitride) transistors enable very short switching times and a high response speed, helping to improve circuit linearity and reduce distortion generated during switching. The architecture also retains the typical efficiency of Class D amplification, combining it with a design aimed at achieving behavior closer to that of analog amplification.

The power section uses two completely separate modules, each configured to operate as a mono amplifier and dedicated respectively to the right and left channels. Each module delivers up to 250 W into 4 ohms and 8 ohms, for a total power output of 500 W in stereo configuration. The separation of the two stages keeps the amplification paths of the two channels distinct and helps limit interference between the sections.

The RA280 incorporates a two-stage analog filter developed by HiFi ROSE, based on an LC circuit designed to process the signals generated by the switching operation of the amplifier. The filter provides attenuation of -1 dB up to 65 kHz and -3 dB at 85 kHz, maintaining an extended frequency response while reducing carrier noise associated with the operation of Class D amplifiers. This solution helps preserve information separation and signal definition across the reproduced frequency range.

The amplifier's response can be adjusted through dedicated bass and treble tone controls. The circuit allows adjustment of the low frequencies at 100 Hz and high frequencies at 10 kHz, with a range of ±15 dB. The tone control uses a high-fidelity active equalizer based on operational amplifiers, with a 12 dB slope, instead of traditional passive circuits with a 6 dB slope.

The power supply is based on a circuit developed in-house by HiFi ROSE and uses silicon carbide (SiC) FETs instead of conventional silicon FETs. This technology allows the power supply to handle high voltages and higher operating temperatures, improving efficiency and reducing heat generation. The power supply section is designed to maintain stable power delivery even during rapid load variations, providing adequate power availability for the output stage.

The power supply is further supported by a proprietary 2.5 kW power factor correction (PFC) circuit and a high-capacity capacitor. The system is designed to compensate for load variations and maintain greater power supply stability during passages involving high current demands, contributing to consistent power delivery and control of the output stage.

Technical specifications:

• Type: Class AD integrated amplifier
• Output power: 250 W per channel into 4/8 Ω
• Frequency response: 10 Hz–66 kHz (±1 dB)
• Input sensitivity: 300 mV unbalanced; 600 mV balanced; 5 mV Phono MM
• Damping factor: >250
• Signal-to-noise ratio: 109 dB (speaker output at 250 W × 2 channels, balanced/unbalanced); 85 dB MM input (speaker output at 250 W × 2 channels)
• THD+N: 0.007%
• Output impedance: 0.03 Ω
• Phono input: MM
• Phono stage impedance: 47 kΩ (MM)
• RCA inputs: 3; input impedance 47 kΩ
• Balanced XLR inputs: 1; input impedance 47 kΩ
• Subwoofer output: 1
• Dimensions (W × H × D): 430 × 103 × 355 mm
• Weight: 9.5 kg