Sophia Electric amplifier designers have successful used 205D tube in the amplifier design as driver tube, (such as 205D drive 845 amplifier currently available) and as output tube in single ended and push pull design in various proto type amplifiers. As output tube, 205D has 1-1.5W in single ended power, far less than needed for most speakers, except horn speakers above 100dB efficiency.

Rather than parallel the 205D in two or three units per channel, our engineers enlarged the plate size by three times, and made the filament voltage of 5V instead of 4.5V that made it possible to use this tube in a 300b amplifier circuit with minimum of modification. Thus the S.E.T. Princess tube is created. (note: this new tube is a lot of easier to drive than 300b).

Overall Sonic Character:

S.E.T. Princess tube has all the characters of 300b and 205D, and adds far more sonic beauty to music. Big, open sound like 845, Sweet like 300b, delicate like 45 and 205D. It offers 5-6 watts of Single ended power or 15-20 watts in Push and pull design.

Typical single ended operating point: 5V/1.25A filament, 350V - 400V plate voltage, -24V bias (50-60ma bias current), 2.5-3K output transformers, same as the ones in a typical 300b/2A3 amp. Current 300b/2A3 users can parallel a 1K/30W or 15Watts Caddock resistor to the existing 800 ohm to 1K cathode resistor to enjoy the beauty of S.E.T. Princess tube.

Please consult with your amplifier maker for needed upgrades to use S.E.T. Princess tubes.