In Search of the Perfect 300B Tube Associated Equipment
The tube samples were listened to in two power amplifiers of different technology and performance levels. One was the ineluctable AudioNote Kit One, nearly unanimously seen as one of the best 300B amps around in DIY kit form. It features automatic bias (cathode resistors), a single power supply, and 78S05 filament regulators. Input and driver tubes had been replaced by superior NOS devices (New Old Stock: tubes produced 30 or more years ago but never used), as had a few coupling capacitors.
Source was a Marantz CD16 CD player (upgraded by Marantz to Excellence status) into a Siltech/Sphinx passive preamp stage. Speakers were JMlab 5.1s, with an active REL Strata-II subwoofer taking over below 40Hz, its input taken from the speaker feeds. Cabling was from Sonic Link and Projekt.
The other amplifier was a cost-no-object design manufactured by my former employer, deJongSystems. (Between writing gigs, I spent three years working in the audio industry.) I took part in this amp's design; however, as it is not the amplifier that's being reviewed here but a roundup of the tubes used in it, I felt there was no conflict of interest here. This amp runs the output tubes in fixed bias (adjustable, of course), has two mains transformers, three rectifier tubes and as many chokes per channel, and carries two C-core output transformers weighing 6kg each. The total amplifier weighs almost 80kg—all for 8Wpc. (It drives the huge Dunlavy SC-IVs with ease, believe it or not.)
The digital front-end consisted of a C.E.C. TL2X belt-driven CD transport and an AudioNote DAC3 heavily upgraded to something between a DAC4 and a DAC5. LPs were played on a Well Tempered Turntable fitted with a Dynavector 17D II cartridge, the signal routed through a custom tube phono-stage with external power supply designed and built by yours truly. Cables were AudioNote AN-Vx and AN-Spx, plus some home-bred silver.—Peter van Willenswaard