GlassWare Audio Design
Thanks for Supporting the Tube CAD JournalNew Balancer PCB and Kit
New Low-Voltage Regulated Bipolar Power Supply
Product Description
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.
Here is why I need this low-voltage power supply: often tube-based circuits cannot provide either the low-noise or gain that is needed. For example, the Tetra phono preamp can easily deliver 40dB gain, but that is not enough for use with a low-output MC cartridge, which might need an extra 20 dB of gain. Well, most low-voltage toroid power transformers hold two secondaries, so one can be devoted to the heater power supply, which might be referenced to 75Vdc, leaving the other secondary to power the PS-25, which in turn can power an OpAmp circuit that will provide the needed low-noise 20dB of gain.
The parts used are fancy, not the circuit. The low-dropout (LDO) regulators, LD1086V positive and LT337AT negative, are used to establish the bipolar output voltages, which can be set to any voltage between +/-5Vdc to +/-24Vdc by selecting different values for resistors R2. The LT337 is a big upgrade to the LM337, which explains why it costs seven times more. The rectifiers (MUR410G) are the ultra-fast type and are arranged in a center-tapped voltage-doubler configuration. Two RC filters pre-filter the unregulated DC voltage.
This bipolar regulator requires a power transformer with a secondary voltage between 6.3Vac to 24Vac, depending on the output voltages required. Fortunately, unlike high-voltage transformers, low-voltage power transformers are easy to find. In fact an AC wallwart transformer works great in many applications. Use a power transformer with a current rating at least 3.6 times greater than the expected peak load current. A fuse can be placed either in series with the transformer primary or secondary.
The kit includes the PCB and all the parts needed to populate the board and four sets of standoffs with screws. PS-25 comes with two-page user guide.
Here is why I need this low-voltage power supply: often tube-based circuits cannot provide either the low-noise or gain that is needed. For example, the Tetra phono preamp can easily deliver 40dB gain, but that is not enough for use with a low-output MC cartridge, which might need an extra 20 dB of gain. Well, most low-voltage toroid power transformers hold two secondaries, so one can be devoted to the heater power supply, which might be referenced to 75Vdc, leaving the other secondary to power the PS-25, which in turn can power an OpAmp circuit that will provide the needed low-noise 20dB of gain.
The parts used are fancy, not the circuit. The low-dropout (LDO) regulators, LD1086V positive and LT337AT negative, are used to establish the bipolar output voltages, which can be set to any voltage between +/-5Vdc to +/-24Vdc by selecting different values for resistors R2. The LT337 is a big upgrade to the LM337, which explains why it costs seven times more. The rectifiers (MUR410G) are the ultra-fast type and are arranged in a center-tapped voltage-doubler configuration. Two RC filters pre-filter the unregulated DC voltage.
This bipolar regulator requires a power transformer with a secondary voltage between 6.3Vac to 24Vac, depending on the output voltages required. Fortunately, unlike high-voltage transformers, low-voltage power transformers are easy to find. In fact an AC wallwart transformer works great in many applications. Use a power transformer with a current rating at least 3.6 times greater than the expected peak load current. A fuse can be placed either in series with the transformer primary or secondary.
The kit includes the PCB and all the parts needed to populate the board and four sets of standoffs with screws. PS-25 comes with two-page user guide.
