Keces S4 Stereo Preamplifier

The S4 borrows the same design cues from their newest devices, having a similar height and width with the S3 DAC and IQRP-800 power conditioner, and if you stack the S4 with its external power supply, then these will have similar dimensions with their S300 power amplifier. No matter from what angle you’re looking at, S4 screams KECES Audio from afar thanks to smooth lines, thick metal plates, and bold looks, and you can’t remain unimpressed with its no-strings-attached minimalist look, especially after dimming its display. Its metal feet are of high quality that will nullify nasty micro-vibrations, thanks to rubber absorption pads. Its front plate is quite thick, and overall, it feels rock-solid and well put together. All of my testing took place in the living room, where a 4-antenna wireless repeater is located, including two streamers. Luckily, the S4 didn’t pick any of that noise, thanks to its impenetrable Zumwalt-class casework. On its front panel, I’m greeted with an overly simplified display that shows only the volume level, and if the blue LEDs are bothering you in the dark, you can disable them completely. All of their units have a back anodized coating, and I wish they would consider making silver anodized finishes in the future, as I like them a bit more. Biased into full Class-A operation, the S4 constantly consumes 90W, and while heat dissipation isn’t a big concern thanks to well-ventilated cases and massive heatsinks, it will still need proper spacing and a well-ventilated area for a long service life. After about 8 hours of non-stop music playback, I’ve got ~60 degrees Celsius on S4’s top plate with a Bosch thermo-detector and I don’t recommend putting anything on top of it. So far, KECES 4 is one of the biggest preamplifiers I’ve tested around here, but it isn’t uncomfortably large or heavy. At about ~8 kg or ~17.7 lbs, it can still be part of an elegant-looking stereo setup. Its dimmed LEDs draw little to no attention, blending nicely in the living room and leading to a high WAF. All in all, it feels like a rock-solid device that should withstand the test of time. Controls & I/O On its front plate, you’ll find a 4-pin XLR headphone jack and a mechanical switch that lets you select headphone amplifier or preamp operation. On the right, two buttons let you mute the unit or dim the display above, and the volume wheel on the far right also acts as an On/Off button when long pressed. The volume control is based on high-performance analog relays, and you can hear them clicking when adjusting the volume, offering 128 steps – enough for precise volume control. Flip it around, and you’ll be surprised by the number of analog inputs and outputs. As mentioned previously, it can act as an MM/MC phono stage, and the 6 switches in its close vicinity let you adjust the loading impedance. The DS optical input comes next, and there’s a regular RCA input (line level) as well. Two pairs of XLR inputs are also present, including two pairs of RCA outputs and a single pair of XLR outputs. The 4-pin XLR jack on the far right lets you connect the unit to the power supply via a 4-pin XLR cable. A mini-to-mini trigger cable is also supplied, and it’s mandatory to be inserted, otherwise, the main unit won’t power on. Under the Hood of KECES S4 The important thing to know is that we are dealing with a fully symmetrical, quad-mono, discrete, pure Class-A preamplifier and headphone amplifier that doesn’t use negative feedback. Or in simple terms – a pure analog preamp and headphone amp that never uses negative feedback to deal with the noise. The volume is controlled by 48 analog relays that provide exactly 128 steps of volume, and this is also an MC/MM phono stage that supports DS Audio’s optical input (via RCA connectors). It’s a 3-in-1 unit at the end of the day, always working in the analog domain. Having a peek inside the S4, you should know that two PCBs have been sandwiched together, and you can see only a single PCB from this angle. The preamp stage/headphone amplifier circuit can be seen on the right side of the PCB. There are two modules on top and two underneath that form a fully symmetrical (4-way) circuit. Everything seems to be crafted from discrete components only; not a single op-amp can be spotted. The input stage seems populated (the lower-left part), and on top of it, you can see the R2R volume control. I counted 24 relays on top and 24 below, so 48 relays in total that provide 128 steps of volume. This is certainly an overkill R2R volume control, but it was mandatory for precise control even at the lowest volumes. The volume goes up logarithmically, which will offer a more precise control at lower volumes. A great idea considering its higher gain than usual (20 dB).   Input MM/MC*1 / Optical*1 / RCA*1 / XLR*2 Input Impedance MC: 56/100/220/470/47K MM: 47K OPT: More than 10K RCA/XLR: 170K Output RCA*2 / XLR*1 / Headphone XLR-4pin Total harmonic distortion (THD N) MM<0.02%, MC<0.05%, OPT<0.04% RCA<0.0015%, XLR<0.0015% S/N R MM: 78dB A-Weighted MC: 70dB A-weighted Optical: 75dB A-weighted RCA: 110dB A-weighted XLR: 110dB A-weighted Gain MM: 52dB / MC: 72dB / OPT: 32dB RCA/XLR: 20dB Power Requirement Standby: 0.5 Watt Maximum: 90 Watts Casing All Aluminum Dimension (WxDxH) 300x279x66mm*2 Weight Net Weight 4.5KG(Power) / 3.5KG(Pre) Shipping Weight 10KG