The σ11 regulated power supply
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News

  • June 1, 2022: σ11 v3.0 is now released. All σ11s shipped from AMB audio shop from this day on will be v3.0. The board dimensions, input/output connections, wiring and setup instructions are unchanged from v1.0 or v2.0, but there are two additional parts on v3.0 (D7 and D8).
  • σ11 circuit boards are available.
  • There are "σ11" clone boards being offered for sale on ebay and elsewhere. They are inferior in quality, made without permission and a violation of the terms set forth on this website. AMB urges not to patronize those unscrupulous vendors.
  • σ22, the dual-rail version of the σ11, has a separate website.

Overview

σ11 ("sigma 11") is a high-performance DIY single-rail linear regulated power supply (PSU). It is basically half the σ22 dual-rail PSU, and possesses the same low-noise, high-current, excellent line/load regulation, wide-bandwidth, and stability characteristics. σ11 is ideal for DIY stereo headphone amplifiers, preamplifiers, DACs, network media players, and other applications requiring a single-rail regulated PSU.

The circuit uses all discrete components (no integrated circuits), and features high-current MOSFETs as the output "pass" devices. Please see the Tech highlights section for a description of the circuit design.

σ11 is derived from the σ22, which is the result of a community service project for the audiophile hobbyist. The schematic diagram is open source. The circuit design, as well as the printed circuit board layout are the work of AMB with participation from the DIY community. It is designed to be relatively easy to build, but it is not recommended as a first-time project for the beginner.

To obtain the blank printed circuit board and some related parts, visit the AMB audio shop. Other parts are available from online vendors. See the Parts list section, which also contains details about configuring the σ11 for various output voltages. You will also find information about the maximum output current capability of the σ11 in the Tech highlights section.

Please be sure to read every section of this site carefully before attempting to build the σ11 PSU. If you don't thoroughly understand everything, please consider having someone more experienced to build the amplifier for you, or build a simpler project.

The scope of the σ11 project

The σ11 project is primarily centered around the PSU board. To build a working power supply, you will also need a power transformer, IEC power entry receptacle, power switch, as well as select and/or build an enclosure chassis to house the board (and optionally the amplifier or device that this PSU will provide power to). The σ11 circuit board was designed to slide into a Hammond 1455N120x (external power transformer), 1455N160x (small internal transformer) or 1455N220x (large internal transformer). It also has holes to allow mounting in other enclosures using standoffs.

An assembled σ11 circuit board (v1.0 shown, v2.0 and v3.0 are similar).
Click image to enlarge.

What skills and tools are needed

You should know how to read a schematic diagram and correlate it to the circuit board layout, identify electronic parts and their pin-outs, have decent soldering skill, and be proficient with a multimeter. You need at least a basic set of tools for electronics work, such as a good soldering iron and accessories, screw drivers, needle nose plier, diagonal wire cutter, etc. For the chassis case, you will also need to be familiar with using the tools that are necessary, such as an electric drill, bits, center punch and others.

WARNING: Building a PSU will require that you work with AC line voltage, which is a lethal shock hazard. If you don't know what you're doing, please ask someone who is experienced to help you. (See the disclaimer).

Why not offer a full kit

AMB is not prepared to stock all the needed parts and offer them as a full kit. The PSU provides a number of customizable options that makes it unwieldy for such a kit. Lastly, this PSU is AMB's contribution to the DIY community rather than a for-profit product, AMB cannot assume the commercial support role that might be implicit with a full kit.

Why not offer assembled boards

This is intended to be a project for DIYers, and AMB is not set up to manufacture assembled and tested boards.

Professional builders

If you are having an amplifier or other audio device custom-built for you by a professional builder, you can specify that the σ11 be used to provide power to it (if it is an appropriate application for the σ11). The following professional builders are listed for your reference.

Where to get help

Be sure you read all the information at this site. If you cannot find an answer to a question, or encounter a problem you cannot solve, the best place to get support is the AMB DIY audio forum. Search the forums for an answer before asking a question. Your question may have already been asked and answered.

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