AMB Laboratories
The σ24 Power Transformer Board

News

  • May 2008: σ24 v1.1 blank circuit boards are now available for purchase at AMB audio shop.

Overview

σ24 ("sigma 24") is a companion circuit board for the ε24 power switch driver circuit. It allows a standard EI30 form-factor miniature transformer to be board-mounted and to supply power to the ε24 circuit. Both single-secondary and dual-secondary transformer configurations are supported. The two secondary windings on a dual-secondary unit are connected in parallel.

σ24 can also be used to mount an EI30 transformer for use with other circuits if such a transformer is appropriate.

The following is a photo of the top and bottom sides of the σ24 circuit board, and a photo of an assembled board.



Wiring

The AC input terminals should be connected to AC mains. The AC output terminals should be connected to the AC1 and AC2 terminals of the ε24 board. There is no need to connect any portion of this board to AC or chassis ground.

Parts list

The following is the parts list to populate the σ24 board.

QtyPartdescriptionRecommended part(s)
1T1Power transformer 12VMouser 673-030-7136-0, Digi-key 567-1031-5-ND (115V mains); RS Components 347-3401 (230V mains)
1J1Phoenix Contacts 2P .200 screw terminal block 1729128Mouser 651-1729128; Digi-Key 277-1247-ND
1J2Molex KK 2P .100 header 22-23-2021Mouser 538-22-23-2021, Digi-Key WM4200-ND
1-Molex KK 2P .100 plug housing 22-01-3027Mouser 538-22-01-3027, Digi-Key WM2000-ND
2-Molex KK .100 crimp terminal 08-50-0114Mouser 538-08-50-0114, Digi-Key WM1114-ND

The circuit board

The σ24 board is made of high quality FR-4 glass epoxy, single copper layer with top-side silkscreen and bottom-side soldermask. The dimensions of the board is 2.0" x 1.2" (50.8mm x 30.5mm). The thickness of the board is 0.062" (1.58mm). The dimensions and mounting screw locations of the σ24 and ε24 boards are identical, therefore they can be "stacked" together with 1" long standoffs. The following image shows the board layout:

Additional information

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