The KECES S300 provides 130w of power at 8 ohms continuous and a peak of 240w. This is more than enough unless you’re driving truly giant speakers. Or you’re trying to fill a small arena or large church. Even when I crank up the volume as loud as I can stand it, I’m still at just under 50%. Any louder than that and the neighbors will put a “For Sale” sign in the yard. I detected no noticeable distortion even at crazy-loud listing levels. The S300 handles this with ease. If you have 4-ohm speakers, you get 225w per channel continuous power (300w peak). There are three distinct “modes” that the S300 can operate in: Stereo, Bi-Amp, and Bridged. The Stereo mode behaves like any normal 2-channel amplifier. Hook up left/right inputs and connect left/right speakers to the outputs and voilà!, you’re done. If you have one S300 and two speakers, this is the mode you will use. If you’re lucky enough to have TWO S300 s, you get to pick from the other two available modes. In either Bi-Amp or Bridged modes, each S300 will drive a single speaker. Bi-Amp mode requires speakers with separate LF and HF terminals. In Bi-Amp, you’ll provide a single input (RCA or XLR) to each S300 . You then connect the left speaker output of each S300 to the speaker’s LF terminal and the right speaker output to the HF terminal. Bridged mode also uses one S300 for each speaker, but with much more power (as if one S300 isn’t enough). Bridged mode provides a whopping 410w at 8 ohms to a single speaker. Guaranteed to drive your neighbors crazy. Bridged mode and Bi-Amp are similar in that each amp drives a single speaker. The primary difference is Bridged doesn’t separate LF and HF and more than doubles the raw power. The S300 is a split-personality as far as amplifier class is concerned. There is a bias switch on the back of the unit that allows the S300 to function as an AB class amp (“Low Bias”). Flip the switch to High Bias, and the S300 will dedicate 5w per channel as pure class A. In my listening, the High Bias setting smoothed out the sound just a touch over the straight AB Low Bias setting. Delightful. The sound is wonderful and about as smooth as you can get. Class AB amps are quite inefficient power-wise, and Class A amps are even less efficient than that. There is a price to pay for this inefficiency: Heat! The S300 runs HOT. After one hour of High-Bias listening, the top surface of the unit measured in at 123.6° F, 43.4° F. over ambient room temperature. Running in Low Bias Class AB yielded a surface temp of 119.8° F. Just a few degrees cooler. The aluminum chassis is 4mm thick on all sides and has large heat-sinks on the inner sides to help dissipate all this heat. In Low-Bias mode running as a Class AB amp, the S300 measured a power draw of 91.6 watts at idle. In High-Bias mode running as a Class A/Class AB hybrid, the S300 had an idle draw of 116.8 watts. In either case, most of that power draw is being converted into heat due to the natural inefficiencies of Class A and (to a lesser extent) Class AB amplifier designs. Personally, I think it’s worth the extra heat and energy to have sound this good! The chassis is solid (and heavy!). The black brushed aluminum finish, curved edges, gold name plate on the front, and wide sturdy feet make this a highly attractive unit. This would be a welcome addition to just about any décor. Just make sure to place it in a well-ventilated area. There is a red/blue power LED just above the power button. Red turns to blue when switched on. The blue power LED is …… bright! Crazy bright. If you listen to music in a dark room, you won’t need a nightlight. Chances are you’ll either put a post-it note or a piece of semi-transparent tape over the LED. That’s a shame because other than that the unit looks great. Oh well. All Features 2 OZ Copper PCB for Power Layer, Ground Layer and Signal Layer to get high damping factor and get more sound quality. 130 watts x2 @ 8 ohm continuous output power / Maximum output power 240 watts x2 @ 8 ohm 225 watts x2 @ 4 ohm continuous output power / Maximum output power 300 watts x2 @ 4 ohm 410 watts x1 @ 8 ohm in bridge mode High bias Class A/AB operation 5 watts per channel of pure Class A power at high bias setting 45 amperes peak current per channel Stable with speaker impedance dips below 2 Ω Operation model selection: Stereo, Bi-Amp, Bridged Dual-mono design Direct-coupled signal path, no capacitors or inductors DC Servo and relay protection circuits JFET input stage, MOSFET driver stage 1.2 kVA toroid power transformer with independent secondary windings for each channel Independent power supplies for left & right channel input stages, driver. stages, output stages 65,600 µF Rubycon filter capacitors for output stages Automatic turn-on by 12 V trigger Neutrik locking XLR input connectors Heavy-duty 24K gold-plated RCA input jacks Heavy-duty 24k gold-plated 5-way speaker binding posts AC turn-on inrush surge protection Overload/Over Temperature Protection The 4mm thickness of the aluminum chassis to effective to blocks EMI/RFI interference Power Output 130 watts x2 @ 8 ohm continuous output power Maximum 240 watts x2 @ 8 ohm 225 watts x2 @ 4 ohm continuous output power Maximum 300 watts x2 @ 4 ohm BTL: 410W x1 @ 8 ohm Power bandwidth 5Hz – 160kHz, 0/-3dB 10Hz – 20kHz, 0/-0.1dB Current capacity 45 amperes peak per channel Total harmonic distortion (THD N) <0.04% at full power <0.004% at 60 watts S/N R 110dB, input shorted, IHF A-weighted 101dB, input shorted, unweighted Inter-channel Crosstalk >100 dB at 1kHz >82 dB at 20kHz Gain 26 dB Input sensitivity Unbalanced: 1.6V Balanced: 0.8V per leg Input Impedance Unbalanced: 50k ohm Balanced: 100K ohm Damping Factor 4000 at 20Hz Power Requirment Standby: 0.5 Watt Maximum: 1000 Watts Casing All Aluminum Dimension (WxDxH) 300x279x133mm Weight Net Weight 14KG Shipping Weight 16KG
