Low-Voltage Power Supplies for Heaters and Solid-State Circuits

New PS-25 Bipolar Power Supply I have needed something like the new PS-25 for a long time. The PS-25 is a low-voltage, bipolar, voltage-regulated power-supply that is powered by a single secondary AC voltage, such as a 12Vac wallwart transformer or a regular power transformer secondary winding.

This newly designed 4.5 by 4.4 inch PCB holds two low-voltage bipolar regulated power supplies. In fact, it holds two LV-Reg regulated power supplies. Why? Well, sometimes, you need two. But more importantly, this new PCB can be configured as a bipolar power supply for use with solid-state circuits. The odd fact about three-pin IC voltage regulators is that no one makes a great negative voltage regulator or, put differently, no one makes as good a negative regulator as the LD1084 is as a positive regulator. So, two positive regulators are used instead of the usual negative-positive regulator paring by placing two positive regulators and stack the outputs to create a bipolar power supply.

New LV-Regulator The LV-Regulator is an audio-grade low-voltage regulator that uses a simple RC filter as a pre-filter before the LDO regulator and holds bypass capacitors for all the electrolytic capacitors and a 4.7µF/400V polypropylene shunting capacitor at the output. Perfect replacing the cheap switcher wallwart that came with your external DAC or Squeezebox Duet or Touch.

The Tr-PS-1 is a low-voltage, regulated 12Vdc (or 9Vdc or 12.6Vdc) power supply, perfect for powering vacuum tube heaters or replacing the wallwart power supply that powers DACs and other audio gear. The Tr-PS-1 holds its own 36VA power transformer. The Tr-PS-1 PCB is only 5 " by 2.8 " and, like all GlassWare PCBs, is extra thick (0.094 in), US-made, with heavy 2-ounce copper traces. The PCB holds a 3A, low-drop-out (LDO), adjustable voltage regulator, which is able to deliver 1.5A @12Vdc into an external load.

The Tr-PS-3 is a regulated bipolar power supply that puts out +/-12Vdc @ 750mA. It uses an LM317 for the positive output and an LM337 for the negative output. The Tr-PS-3 PCB is only 6" by 3.2 " and, like all GlassWare PCBs, is extra thick (0.094 in), US-made, with heavy 2-ounce copper traces. The rectifiers used are ultra-fast MUR410G types, each of which are shunted by a 0.1µF ceramic capacitor to reduce RFI creation. The power supply can be used with either 115Vac-120Vac wall voltage or with with 230Vac-240Vac wall voltages.

The circuit is a simple voltage doubler that converts the 5Vac into 12Vdc for the power amplifier's frontend circuitry. It is not that big a deal, but once you have point-to-point wired a few of them, you begin to long for a tight little PCB.

The PS-SS, a new GlassWare power supply kit, is intended for use in solid-state power amplifiers. (Of course, it could be used in a tube hybrid power amplifier.) Its design had two goals: a squat profile, so it could be used a 2U enclosure, and the inclusion of RC filters. One (of many reasons) why tube amplifiers so often sound better than their solid-state brothers is that the tube amplifiers hold RC filters or LC filters. These low-pass filters do not completely eliminate ripple, but they do scrub away harsh higher harmonics.