The UL40-S2 valve amplifier is born out of love for music, for music reproduction with all details and excellent spatial image. The amplifier is based on many years of experience and study of the designer. The newest techniques and knowledge are used in this design.
The toroidal output transformer is designed according the most modern techniques. Superior materials, insulations, kinds of copper magnet wire and core compositions are used (the ultimate in toroidal transformers with superior silver/gold wire is now also available at extra cost). All this results not only in an extreme wide frequency range, but also in excellent reproduction of details. The valves are carefully selected by computerized measuring equipment and after that measured by hand. The electrical circuit excels by simplicity, realizing minimal strain of the signal by means of well chosen components. There is no use at all of negative feedback from the output to the input. The concept is amplification straight forward. The printed circuit board has an extraordinary structure called “LEP = Logistic Earth Patterns”. This means that the layout of the ground tracks is such that the degradation of the audio signals is prevented. Even the mains ground is connected in a special way to a central point. The components like resistors and capacitors are selected with extreme care and they all contribute to an open and detailed sound image. The amplifier can be operated in several modes (Triode, Ultra-Linear and Pentode or Super-Triode) making it possible to experiment with famous valve configurations. In the power supply fast electrolytic capacitors are being used, leading to a clear and clean high frequency conduct of the amplifier. Even for the filaments high frequency decoupling is being used, making the PCB very poor in radiation.
The amplifier is available as a DIY kit. The construction manual is very detailed (36 pages) and many figures help to create an optimal product. The several components are soldered step by step in functional blocs on the PCB. See the figure below, where the blue components are already placed on the PCB and the yellow ones have to be soldered now.??
Bouwbeschrijving (Nederlands) in PDF (6MB)
Bauanleitung (german) in PDF (6MB)
Construction manual (English) in PDF (6MB)
Manuel d'assemblage (French) in PDF (6MB)