The EB-802/243 is a wide-band, low-noise power supply, applicable to all low and medium level audio circuits. The rectifier diodes are soft/fast recovery diodes and the capacitors are low ESR ones. The regulators are using low-noise opamps and MOSFETs as series elements. Normal output is +/-24V, however, by changing the feedback resistors R1 and R2 you can change this. The output voltage is given by the formula: 6.9x(R3 + R1)/R1. With R3=2.49k and R1=1k the output is +24V. For +18V R1 has to be 1k5, for +15V R1=2k1 and for +12V R1=3k32. The circuit does not work below the reference voltage of D9/D10. For a +5 Volt output the reference diodes have to be changed to LM336Z-2.5, the feedback resistors R3 and R1 made equal: 2k49 and R9/R10 changed to 1k. The same calculation applies to the negative output (R4, R2). Due to the tolerance on the reference diodes the output voltage can vary slightly. If you need to adjust the voltage accurately please install the trimpots P1 and P2. Appropriate values can be calculated from the formula given above.

Minimum input-output voltage difference is 5V. For a +/-24V output the minimum input voltage is +/-29V. Recommended is +/-30V, which means a transformer with 2x22V RMS. Recommended mains transformer is EB-802/259. Absolute maximum unregulated input voltage is +/-33V (2x23VAC), because the capacitors are rated at 35V and the maximum supply voltage to the opamp is 34V(Safety margin)! Maximum power dissipation in Q3 and Q4 and consequently maximum output current depends on the heatsink. With SK75-37.5mm the maximum dissipation is about 1.5W. With an input-output voltage difference of 5 Volt the maximum current is approx. 300mA. With larger voltage difference the maximum current is less. Output noise over the audio frequency range is <5uV.