This power supply unit (PSU) provides hum-free and stable operating voltages for valve preamplifiers and power stages. Negative bias voltage included!Most valve amplifier circuits require a high-voltage power supply. Here, such a circuit is proposed by one of our readers, Mr. Nils Gohr, who claims to own a working prototype. The concept of the PSU is just fine for a power output stage using KT66 or KT88 power pentodes in push-pull or A/B mode requiring a relatively high plate voltage (here, 420 V) I combination with a grid bias voltage of –45 V for the quiescent current setting.The preamplifier stage may be built around a double triode with two mutually decoupled 250-V anode voltages being available on the PSU.