In Search of the Perfect 300B Tube Page 3

If one is to give a reliable evaluation of a 300B, it is essential that the tube be burned in for an appreciable amount of time (footnote 4). One hundred hours are not enough; 200 hours seems to be a workable minimum (footnote 5). In doubtful cases, we added an extra 100 hours (see sidebar "A Tale of Burn-In"). If you count the number of tubes tested, including the backup pairs, and consider that we had three locations where burn-in could take place, and that eight hours of burn-in per day is a realistic figure (we avoided leaving the amps on unattended), you'll begin to realize the vast scope of this project!

On the basis of the comments of the listening panel (four experienced listeners, me being one of them), the 300Bs can be divided into three groups. Group C contains both Valve Arts, the Golden Dragon 300B and 4.300B, and both Sovteks. Group B consists of the KR Enterprise 300BXLS, the Golden Dragon 300BLX, the Svetlana, and the JJ Electronics. Group A includes only the Western Electric.

Before we go into the details, I want to emphasize that every 300B tested had the typical 300B sound character. Sound-quality differences were by no means irrelevant, but were smaller in my experience than those between the best and the worst 6SN7 or ECC83/12AX7 that I have heard. So even the most modest 300B should bring you some of that magic.

Second, the big deJongSystems amplifier exhibited much tighter control over the 300B than the AudioNote Kit One amp, which left more freedom to the tubes. Some 300Bs tend to abuse the liberty they get, especially in the bass (or the Kit One grabs its chance to run with the tube, if you will).

Group C
Sovtek 300B (standard): $184/pair. Basic 300B construction. A bit flat in tone, voices slightly colored (more so in AudioNote). Lacked precision and dynamics, high-frequency range somewhat detached; could do with better rhythmic control and a less confined space. Bass pressure was lacking when inserted in the DeJong amplifier, but the bass came out too fat in the AudioNote.

Sovtek 300B+ (new): $184/pair. There is no apparent difference in construction between this and the Sovtek 300B, but close inspection brought up a different grid wire. The new tube is also said to have a new filament and improved grid-support spring attachments, and comes with a white ceramic base instead of the usual black one. This tube was clearly more musical, with more air and improved rendition of reverberation. It still lacked some control, however. Bass was still a bit too pronounced in the AudioNote, but was now under control in the big amp.

Golden Dragon 300B: About $250/pair. Basic 300B construction. This tube sounded quite musical and considerably more open in the DeJong amplifier than in the AudioNote, where a loss of dynamics was noted, and voices were contaminated by a hard, edgy ring. Bass in the AudioNote was quite good, but lacked real fundament in the former amp. Focus was a bit vague, but there was no veil; in the AudioNote, however, some veiling was evident, and the entire presentation was rather dutiful and uninspired.

Golden Dragon 4.300B: About $340/pair. Construction is similar to the other Golden Dragon (above), though the plate is a bit different. The 4.300B was slightly less musical, with slightly more control and better focus, and was slightly better in the bass.

Valve Art 300B-C60: $179/pair. This tube features a solid graphite anode, and its gold-wire grid helps to avoid thermal runaway in fixed bias; also, the four pins on the base are gold-plated. The position of the small slot-pin on the side of the base deviates from its position on the WE. In the big amp, the rendition of the C60 was somewhat veiled, colored, and smeared, though the midrange was pleasant and velvety. It was pretty good rhythmically, if not very inspiring. Bass was round and soft, lacking real pressure. In the AudioNote it performed rather better, with a deep stereo image, wide space, and excellent rendition of reverberation. Weaker points: a bit of boxy coloration, not very dynamic, an emphasis on sibilants, control could be better.

Valve Art 5300B: $198/pair. This tube's construction is similar to that of the C60, but it looks as if a different filament wire has been used; also, the 5300B is provided with a white base. It sounded similar to the C60 as well, with a few improvements. The veil was gone, but it still couldn't achieve a higher level of inspiration; more of an easy-listening tube. In the AudioNote we noted somewhat better dynamics, a bit more control, a little less warmth, pretty impressive bass, and a wider image.

Group B
KR Enterprise 300BXLS: $480/pair, 2-year warranty. Very rugged construction: this tube's weight is twice that of a normal 300B, and it's 15% taller. The vacuum is claimed to be unusually high: 10e-9 Torr against about 10e-6 for a normal tube. The anode has extra cooling fins for higher maximum dissipation. This tube worked well in both amplifiers, with very good bass. The sound was authoritative, but showed signs of uneasiness in very complex musical passages. Good air and reverberation, but some emphasis on sibilants; reasonably open and involving; okay rhythm, if sometimes a bit sluggish. Very good dynamics and fine detail when used in the AudioNote.

Footnote 4: Even when a 300B is fully burned-in, transporting it from one house to another can affect its sound quality: it may, like a good wine, require a few days of rest—even a week—to fully restore itself.

Footnote 5: A Valve Art or Golden Dragon, for instance, sounds quite nice after 100 hours, but after that still continues to develop, leveling out at around 200 hours. The Western Electric at 100 hours is not a shadow of what it can become once fully developed; 300 hours is a safer bet here.