JS-4 Linear Power Supply

Many user reviews of the JS-4 have begun to appear. See this forum thread for their glowing reports. Also, JS-4 was nominated for a StereoTimes "Most Wanted 2025" award (scroll down a few pages at that link to read it).

Digital audio devices draw current in very high frequency bursts. As important as the JS-4's ultra-low output noise is, ultra-low output impedance and the “speed” of regulation response to transient loads can have an even larger impact on sonic performance. Every aspect of the JS-4’s topology, circuit design, and parts selection are focused on delivering “fast,” highly regulated, ultra-low noise DC to your connected components. The result is improved musical timing and finesse.

The JS-4’s two output channels are 100% isolated from each other, so this supply can be ideal for powering devices on opposite sides of an isolation barrier. 

Each of the JS-4’s two output rails can deliver 2.1 amps continuous current (with instantaneous peak ability above that) at any of 8 user-adjusted voltages (3.3V, 5V, 6V, 7V, 9V, 12V, 13.5V, and 15V). If 2.1A is not sufficient for a connected component, the JS-4 has a MODE switch to activate custom circuitry which internally joins the two channels—to deliver up to 4 amps continuous current to one output jack (In this mode the other output jack is turned off and the JS-4 operates as a single output supply).

Specific design features include:

• Custom 75VA dual-primary/dual-secondary R-core transformer with shielding between primaries and secondaries as well as copper outer shield. Objective and subjective performance of this R-core transformer exceeds that of even very expensive toroidal types. Mechanically this R-core transformer operates silently in both 50Hz and 60Hz AC mains frequency countries.

• Special 6th generation Cree silicon-carbide Schottky diodes for AC>DC rectification; 4 for each JS-4 output channel. Objective and subjective performance of these parts is greater than typical Schottky diodes.

• Three distinct stages of high-performance voltage regulation in each output channel, with custom filtration sections between each regulation stage. First stage utilizes a specially controlled, highly efficient (97%) DC-DC regulator operating at 800KHz; Second stage is a high-current, low-noise Micrel linear regulator; Third stage consists of 4 Linear Technology LT3045 ultra-low noise (0.8µV RMS), high PSRR, ultra-low output impedance regulators.

• Unique “hierarchy of charge” design techniques are used to employ filter capacitors—before and after each regulation stage—sized to maximize “speed” and filtration for output, while also reducing AC current-draw peaks by conducting throughout a higher percentage of the AC waveform. This avoids ringing and saturation of the transformer core and thus nearly eliminates any noise going back to the AC mains.

• Seven 1-Farad/2.7V super-capacitors used in series (per channel) to provide 143,000µF of filter capacitance between second regulation stage (Micrel) and final third stage (LT3045s). This large super-capacitor bank handles load fluctuations down to below 1Hz. Fancy, large and expensive “audiophile” electrolytic capacitors are not needed because most all high frequency ripple is already eliminated beforehand—coming off the middle-stage Micrel regulators.

• Carefully chosen arrays of Murata X7R ceramic capacitors are used before and after the final stage of LT3045 regulators, whose job it is to filter any remaining minute amount of high frequencies and to superbly handle high frequency load transients presented by the equipment being powered by the JS-4.

• Logic circuitry associated with output voltage selection adjusts both the input and output voltage of each voltage regulation stage. This allows each regulator to receive an input voltage just 0.7V above the voltage it is set to regulate to. The result is optimum noise performance, low heat dissipation, and the ability to offer a wide final output voltage range without compromise.

• All circuitry is built onto a single large 4-layer PCB with expertly optimized trace widths, thickness, routing, and impedance control. Even the DC output jacks, switches, and AC inlet/fuse/switch module are all right-angle PCB through-hole soldered directly to the circuit board. Elimination of wiring is a performance advantage. [The large R-core transformer is mounted separately to the JS-4 chassis’ bottom plate and wired to low-resistance terminals on the PCB board.]

• Ultra-low resistance (≤2mΩ) 4-pole Neutrik SpeakON DC output jacks are used for secure and electrically superior connections.

• Assembled with all stainless-steel hardware in fine-finish Japanese aluminium casework sitting on machined aluminum feet with anti-slip rubber rings.

Made in USA

Each of the JS-4’s two output rails can deliver 2.1 amps continuous current (with instantaneous peak ability above that) at any of 8 user-adjusted voltages (3.3V, 5V, 6V, 7V, 9V, 12V, 13.5V, and 15V). If 2.1A is not sufficient for a connected component, the JS-4 has a MODE switch to activate custom circuitry which internally joins the two channels—to deliver up to 4 amps continuous current to one output jack (In this mode the other output jack is turned off and the JS-4 operates as a single output supply).