PS Audio Stellar S300 Stereo Power Amp
PS Audio Stellar S300 Stereo Power Amp
The problems faced when crafting a new power amplifier are many—delivering sufficient power, control, frequency extension, and dynamics while maintaining a perfectly layered soundstage under the most complex musical passages.
All amplifiers sound different. What determines sound quality are the components and topologies of the amp’s input voltage stage and output current stage. Each section should complement the other. Between them, the amp develops its sound.
Stellar’s design imperatives—affordable pricing, and uncompromised sonics—were major challenges solved by the invention of a unique new circuit christened the Analog Cell.
Stellar engineer Darren Myers had planned from the outset to take advantage of Class D’s high current, low distortion, ruler flat linearity for the output stage—knowing full well it is the input stage that determines sonic character. This critical interface between preamplifier and power amplifier is where Stellar’s magic would be unveiled; where Myers could lavish upon the music the sweet, tube-like quality of Class A biased MOSFETs. His challenge was to synergistically marry both input and output topologies, for which he invented Stellar’s Analog Cell.
The Analog Cell is the heart of the S300’s musicality, where richly overlayed layers of music’s inner details are preserved even in the most complex orchestral crescendos. The Analog Cell is a proprietary, fully differential, zero feedback, discrete, Class A MOSFET circuit, hand-tuned to capture the smallest micro dynamics without sacrificing the loudest macro dynamics music has to offer.
- Stereo power amplifier
- Dual mono, each with their own power supply
- Zero-loss Analog Cell input stage
- Powerful MOSFET output stage
- RCA Single ended input
- XLR “true” balanced input
- 140 watts per channel 8Ω
- 300 watts per channel 4Ω
- 2Ω stable
- Less than 0.1% thd 20Hz to 20kHz at rated power
- Damping factor 200 for excellent loudspeaker control
- Front panel standby button
- Effieicient operation with very little heat
- Dual, solid copper, plated, output binding posts
- 27 pounds
- Input 12 volt trigger
The hybrid approach used in Stellar’s power amplifiers takes advantage of the best traits technology has to offer. Its all important input stage relies upon the Analog Cell to provide a zero-loss interface between the preamplifier or DAC, as well as imprint the amp’s sonic character. It is then time to convert the perfected analog voltage into the all important high current output needed to drive loudspeakers.
A power amplifier connects a reservoir of energy to the loudspeaker through a type of valve (solid state or vacuum tube) controlled by the input stage. If the input stage has done a good job of preserving music’s subtle details, textures, timing and phase information, transferring it without loss to the loudspeaker can be accomplished in a few ways: the most efficient is Class D.
The history of Class D amplifiers stretches back to the 1950s, though those early designs—even those into the late 1990s—had much to be desired, sonically. Modern designs capable of high linearity and neutral sound quality weren’t available until the early 2000s, and into late 2015.
There is a lot of misinformation surrounding class D amplifiers. Perhaps the most common is they are digital, which is incorrect. A Class D amplification stage is an analog process, known as Pulse Width Modulation (PWM). Class D amplifiers do switch in on/off fashion, which is likely the reason they wrongly acquired the “digital” moniker.
The Stellar S300 is a dual mono design. This means that each channel has its own, separate power supply. Each of the two channels is a complete and independent power supply and power amplification stage, based on a modern Class D ICE module, designed in Denmark.
All power amplification stages have strengths and weakness. Class D output stages are no different. Their strengths are many: near-perfect linearity, low distortion, high efficiency. Areas where they do not excel, are most notable in high-frequency extremes. Because Class D amplifiers require an output filter to remove their switching noise, they do not have frequency extremes into the many hundreds of thousands of Hertz. Depending on their design modern Class D amplifiers, like the type used in Stellar, extend high frequencies to about 50kHz. Human hearing limitations are 20kHz, though most listeners rarely have hearing exceeding half that.
The Stellar S300 provides excellent frequency extremes, low distortion, high efficiency, high damping factor, and a powerful output of 300 Watts per channel into the most common loudspeaker loads of 4Ω. Plenty of horsepower for even the most demanding loudspeakers.
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