Valve Preamplifier 1

50 VALVE PREAMPLIFIER 1 EE March 1987 Despite their becoming gradu- ally obsolete, valves are still very popular with a good many audio enthusiasts. In this article we will not go into the pros and cons of the use of valves, or enter into the discussion about the so-called "valve-sound". We purposely leave that up to the constructor, and have reason to do so, since this is a remarkably simple to build preamplifier which is none the less capable of outperforming quite a number of other, more com- plex, designs. The SRPP principle The present preamplifier is based on a design principle re- ferred to as Shunt Regulated Push-Pull (SRPP). Not particu- larly well known for AF appli- cations in the USA and Europe. SRPP designs were mainly used for high-frequency input stages realized with suitable VHF/UHF valves. In Japan, however, a designer called Anzai first developed AF input stages utilizing the SRPP principle in the late 1960s. Since then, many other designers have worked on improv...