GlassWare Audio Design
Thanks for Supporting the Tube CAD JournalNew Balancer PCB and Kit
DC High Voltage and Low Voltage from 12Vac
Product Description
The 12Vac PS is a power supply that delivers a regulated 12.6Vdc (or 12Vdc) heater voltage and uses a full-wave rectified octupler rectifier circuit that delivers over 100Vdc from a 12Vac transformer or wallart. (DC 12Vdc switcher power supplies cannot be used, as AC is required.) I have used the Jameco 2227604 wallwart many times, always with good results.
The 12Vac PS PCB holds a three cascaded RC filters to eliminate B+ voltage ripple, R3 through R4 and C12 through C15. The last RC capacitor, C15, is bypassed by a 10µF polypropylene film capacitor, C18.
IMPORTANT: If a power jack is used to connect to the AC voltage, the jack must be fully insulated from the chassis.
The 120Vdc voltage is perfect for use with 6DJ8, 12AU7, or ECC99 tubes. The 12Vac transformer should provide at least 2A of current, which equals a VA rating of 24 for use with up to four 12AU7 or 6DJ8 tubes. Ideally, a transformer with a good regulation figure (say the 5% to 10% a good toroidal transformer would offer) would be used; such a fine regulation figure is unlikely to be true of a wallwart transformer, however. Of course, we could use a more powerful transformer, say a 50VA 12Vac toroid, which would allow for up to 2A @ 12.6Vdc of heater powering.
The 12Vac PS PCB also holds an optional house-ground circuit that will engage if the chassis ground differs in voltage from the house ground by more than 1.4V. Jumper J1 allows an easy way to ground the chassis, as the jumper connects the power supply ground to the chassis through the metal standoff. The heater voltage regulator is an LD1084 5A low-dropout regulator. Rectifiers, MUR410G and HER108 are far, far faster than the usual 1N5002 and 1N4007 rectifiers.
The PCB is 4.8 inches by 3.6 inches, with four mounting holes. The 12Vac PS kit contains all the parts and four standoffs and mounting screws. Transformer is NOT included.
The 12Vac PS PCB holds a three cascaded RC filters to eliminate B+ voltage ripple, R3 through R4 and C12 through C15. The last RC capacitor, C15, is bypassed by a 10µF polypropylene film capacitor, C18.
IMPORTANT: If a power jack is used to connect to the AC voltage, the jack must be fully insulated from the chassis.
The 120Vdc voltage is perfect for use with 6DJ8, 12AU7, or ECC99 tubes. The 12Vac transformer should provide at least 2A of current, which equals a VA rating of 24 for use with up to four 12AU7 or 6DJ8 tubes. Ideally, a transformer with a good regulation figure (say the 5% to 10% a good toroidal transformer would offer) would be used; such a fine regulation figure is unlikely to be true of a wallwart transformer, however. Of course, we could use a more powerful transformer, say a 50VA 12Vac toroid, which would allow for up to 2A @ 12.6Vdc of heater powering.
The 12Vac PS PCB also holds an optional house-ground circuit that will engage if the chassis ground differs in voltage from the house ground by more than 1.4V. Jumper J1 allows an easy way to ground the chassis, as the jumper connects the power supply ground to the chassis through the metal standoff. The heater voltage regulator is an LD1084 5A low-dropout regulator. Rectifiers, MUR410G and HER108 are far, far faster than the usual 1N5002 and 1N4007 rectifiers.
The PCB is 4.8 inches by 3.6 inches, with four mounting holes. The 12Vac PS kit contains all the parts and four standoffs and mounting screws. Transformer is NOT included.
