Project history & acknowledgementsThe σ11 is an offshoot of the σ22 PSU project. The σ22 was developed as a companion power supply for the β22 amplifier, but had also been proven to be a superior dual-rail power supply for a variety of other amplifier and audio circuits.It was suggested to me that there ought to be a single-rail version of the σ22. I thought that it was a great idea, because there are several popular DIY amplifier projects that use single-rail PSUs, one of which is AMB's M³. Until the σ11 came along, virtually all commonly-available single-rail supply PCBs were based on the LM317, 78xx or similar 3-terminal IC regulators. Since the σ22's performance is demonstrably better than the IC regulators, it made a lot of sense to make a single-rail version too. Thus, the σ11 was born. It is basically the σ22 without the negative supply rail. Almost everything else remains the same, even the part reference IDs are unchanged. The MOSFET choice was switched from the IRFZ24N/IRF9Z34N to the IRLZ24N. The latter has similar specs, but also has a lower Vgs threshold voltage and allows the regulator to have two less volts of dropout. Also, the circuit board layout and dimensions were modified slightly to fit the Hammond 1455N series enclosure for ease of construction. Since all the essential engineering (except for the modified PCB layout) had already been done in the σ22 development phase, the σ11 was an easy project. SPICE simulations were run again and DRC and netlist checks were performed on the new board layout. Other than that there was no prototyping done. The production board went to fab in early February 2007. General availability of boards began later that same month. Once again I would like to extend my gratitude to all who participated in the σ22 and σ11 headwize forum thread. Look for more exciting DIY projects from AMB in the future! Main: σ11 Main | Prev: Initial check | Next: Buy |
