I have an older HDPlex 400W power supply and thought it sounded pretty good. So I purchased HDPLEX’s 300W power supply a few weeks ago. Came out to $585 for a quad-rail power supply – which isn’t bad considering others are charging more than double for a single rail.

I have linear power supplies for pretty much every component in my system, including my modem, router, and network switches. I don’t think any audiophile would argue that clean power and better isolation are essential for a more “live” and analog listening experience.

I’m planning to compare a few high-end linear power supplies soon and will be testing them with a variety of components. To name a few, I have a custom server, Intel NUC, SOtM switch, laptop, and the JCAT USB Xtreme PCI card – which I think uses a similar regulator on the HDPlex power supply. Many audiophiles will use one for their Raspberry Pi, squeezeboxes, and other streamers.


  • No fans, fins are great for dissipating heat.
  • Transformers: Transformers are used to step up or down the voltage from your mains. We would take 120 volts AC and convert them to 12V, 19V AC, etc.
    • This HDPLEX has a 300W R-core transformer. R stands for rectangular. R-core transformers are less noisy due to less capacitive coupling between the primary and secondary sides. For that reason, they’re also used in a lot of medical equipment.
    • The windings actually cancel each other’s magnetic flux which keeps leakage flux to a minimum. They also have better efficiency versus toroidal transformers which require more shielding.
  • Rectifier: This is where we convert from AC to DC.
    • Under this aluminum heatsink, we have 15A Rochester Electronic Shot key rectifier diodes. Their job is to essentially take the absolute value of the AC signal.
    • These specific rectifiers have fast switching and a low forward voltage drop. I think 700mV. So it’s very efficient. But the power still isn’t usable here. There’s still some voltage ripple.
  • Filter Capacitors: To smooth and stabilize out the ripples from the rectifier, we have filter capacitors. Its job is to keep the voltage more steady.
    • These are high-quality Japanese 10000 micro-farad ELNA audio grade electrolytic capacitors. One for each rail to help eliminate potential phase distortion.
  • Linear Regulator: At this point, the output voltage can still vary due to load, capacitance, and input voltage across the transformer. We want the DC output voltage to be stable.
    • This HDPlex power supply uses 12 Linear Tech LT3045 regulators. These are ultra-low noise, low dropout linear regulators. So better efficiency, less heat, and a high power supply rejection ratio. These are obviously great for noise-sensitive applications such as audio.
    • They work in conjunction with ST Microelectronics high-power NPN BJTs.

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