The Signal Transfer Small Signal Power Supply

The Signal Transfer Small Signal power supply provides regulated low-noise +/-17V supplies for powering PCBs with op-amp circuitry such as: The Low-Noise Balanced Input Card. The Amplifier and Loudspeaker Protection Card. The RIAA phono PCB with unbalanced outputs. The RIAA phono PCB with balanced outputs. The Devinyliser PCB. PCB0011: £24:50 each

The layout of a power supply PCB to minimise hum and ripple is an art all of its own. With this design, fully approved by Douglas Self, you can be sure you have the optimal solution. It can supply +/-17V at up to 1.2 Amps with appropriate regulator heatsinking. The power supply PCB is fitted with positions for a comprehensive set of standard high-quality connectors that make wiring up an amplifier system very straightforward. Full instructions and parts list are supplied with the PCB.

F E A T U R E S

• Mains AC input by standard PCB-mounted IEC connector
• The supply bridge rectifier is fitted with multiple snubber capacitors to prevent the generation of RF noise
• The supply rails have multiple RF filtering capacitors to prevent any noise reaching the output
• A fuse FH1 in the mains input circuit protects the transformer secondaries against accidental short-circuits
  
• There is a position on the PCB for a 230/115V mains voltage selector switch.
  
• The rails are fully protected against short-circuit, over-temperature, and decoupling capacitors trying to discharge themselves back into the supply when the AC power is removed.
• 5532 opamps can be damaged if one supply rail fails, so a mutual shut-down system ensures that if one rail collapses, perhaps due to an accidental short-circuit, the other rail also switches off at once and the opamps are kept completely safe.
• The PCB has provision for mounting a toroidal transformer, and securing it with tie-wraps or a central M5 bolt and washer. If the the equipment is likely to be moved about or otherwise subjected to shocks, bolt mounting is strongly recommended.

S P E C I F I C A T I O N S

• Voltage output +/-17V
• Ripple and noise: less than -80 dBu, measurement bandwidth 22 - 22 kHz, RMS sensing
• High-quality double-sided PTH fibreglass PCB, with solder resist and silk-screen. Width 100 mm, length 223 mm
• Fully ROHS compliant
• Six M3 fixing holes are provided.

C O N N E C T O R S

• CN1 Mains input IEC connector
• CN2: DC output connector 4-pin XLR
• SW1: 230/115V AC input selector switch
• J1: Ground connection
• P1, 2, 3, 4: Pads for connections to two-pole mains on/off switch.

H E A T S I N K S

The PCB011 uses standard SW vertical heatsinks that solder into the PCB with two pins; see the picture on the left. They are widely available from a number of distributors. These heatsinks are available in different heights of 25, 38 and 50 mm. Assuming the regulator junction temperature is to be kept below 100 degC, the maximum continuous current output is: SW25-2 950 mA SW38-2 1 A SW50-2 1.2 A