5687 WOT PreAmplifier


FLUENCE is my second project. It is a preamplifier "With Output Transformer" (WOT). Probably it is the simplest type of preamp after the passive one. It is basically composed of one attenuator, one triode tube, one Output Transformer and of course power supply. You may notice this simplicity by examining the schematic supplied. This topology is not at all known in Hi-End circles but very well known in Single Ended enthusiasts' DIY circles. In fact I was inspired by a similar project appeared in my favorite magazine, Sound Practices.

In audio best results are obtained when simple  is matched with quality components and a well engineered design. In FLUENCE I tried to combine these three points.

Although in single chassis, the preamp is designed in true dual mono fashion, with separate power supplies, separate tubes, etc. The calculations are made to have a linear response between 20-20000Hz. Choke input, LCLC type power supply is used and all capacitors are bypassed two times.

Best quality components are used:

  • Capacitors: Solen and Hovland
  • Resistors: Vishay
  • Stepped Attenuator: Sonic Frontiers with Holco resistors
  • Inductors: Bartolucci
  • OPT: Black Art
  • Signal Cables: Kimber AG 

The only electrolytic capacitor is on the filament DC circuit, so no electrolytics on signal path!

WBT silver solder is used and star grounding is adopted. Chassis and cover materials are all non magnetic: aluminum, brass and wood.

Finally the result (of course very subjective): 

I was amazed to hear such big improvement after my ARC LS2 preamp. The difference is far more than subtle. More dynamic, much much more three dimensional, fuller in the mids, more inner detail and much more relaxed. I started to listen to music rather than the system! It complemented the NUANCE's both sonically and visually in a very successful way.

FLUENCE Schematic

(Pictures: click to enlarge)