First presented in 2009, the T-Reg high-voltage regulator circuit delivers clean, stable power for tube amps. Supporting output voltages up to 500 V, you can use the design with both vacuum tubes and MOSFETs for a variety of audio applications.

The Concept

Tube amps are known for their distinct sound, but achieving decent audio performance also depends on the quality of the power supply. Hum, ripple, and noise can cause issues, even with filtering in place. In 2009, Elektor presented Jan Didden’s T-Reg project. The clever high-voltage regulator design balances strong performance with a relatively straightforward implementation. Intended for both valve preamps and power amplifiers, the regulator supports adjustable output voltages up to 500 V and can be configured with either vacuum tubes or MOSFETs, giving designers plenty of flexibility.
Regulator tube amp 2
 

The Circuit

IC1 is a 555 (CMOS) timer that “pulls down the LED in IC3 some time after the supply is switched on,” Didden noted. “The delay is set by R8 and C3 and with the given values is about 30 seconds. Once the LED in IC3 is on, the opto-triac will fire and switch on thyristor TH1, which will apply the rectified high-voltage to the pass tube. I used the heater (filament) voltage to power the reference and control circuits through rectifier B1 and capacitor C2.”
 
Regulator tube amp 1
Complete circuit diagram of the main board.

The T-Reg Tube Project

The original article, “T-Reg: A High-Voltage Regulator for Valve Amps,” appeared in Elektor March 2009. Here is the article.
Editor's Note: The article first appeared in a 2009 issue of Elektor. Due to the project’s age, some parts and components might not be available. Still, the project should inspire you to start a new design.