Review: Shuguang/SuperTNT 845B tube Tweak

Category: Accessories

The new 845B

This review covers the new 845B tube, from Shuguang in China, and distributed by SuperTNT.com. Serial numbers for the pair in this review are 0005 and 0006, the first two in the USA, as far as I know. Retail price is $150 USD per pair, direct from SuperTNT in China. I do not believe they have a USA based distributor yet.

The 845B is a recent development by Shuguang, and structurally it is a very close copy of the 1940's vintage Amperex brass base 845. It has a graphite plate (like all 845s since the 1930s), and a beautiful copper base. Pins appear to be nickel-plated brass. Like the Amperex, it has no top mica connecting the plate structure to the glass envelope. (current production 845s from China, Kron and Cetron all have top micas which couple the plate structure to the glass). These 845B have full 845 dissipation ratings and 1250v plate rating and as far as I can tell are compatible with any 845 amplifier application. Like all 845s except Kron, these have Thoriated Tungsten filaments, which glow brightly. It has two ring getter halos at the base of the tube.

(Click any image for a larger version)

Build Quality

Internal construction is done to a high standard, definitely a cut above the normal Chinese 845 tube. Welds and metal forming seem to be quite well done and accurate, no sloppiness from what I can see upon close inspection. Comparing directly to an old stock Amperex 845, the caliber of construction of the 845B is good but not quite as well done. This is not surprising, given that in the old days thousands of these tubes were made by highly skilled workers who had been doing it for years, and the tube industry and its' body of knowledge was enormous compared to today. That Shuguang is able to do as well as they have, with construction as good as it is, is an impressive feat, especially considering this pair is one of their first production pairs released to the public.

Shuguang 845B
845B bottom
845B top

Packaging

The packaging supplied with these is the best 845 packaging I have seen - quite robust, with a nested clamshell box made from high-density mat board, and an inner 2-piece foam cushion and foam wrapper. Despite the outer box being a good bit beat up from it's trip from China (via DHL), these tubes survived fine with no damage - an impressive feat in itself.

The Packaging
Nicely made boxes



Electrical Tests

Running these tubes on my curve tracer setup shows traces which are well matched and clearly well within specs, as compared to other (vintage Amperex) 845s. The curve tracer, A Systron-Donner 6200B, runs up to 1000v on the plate and negative grid steps from 0v to -100v on the grid. In both cases, the tubes had curves which were textbook accurate, even at the top and bottom. Electrically, they are perfect, as one would expect from new production tubes. Quality control on this aspect has no problems at all. They biased up fine in my amplifiers. Running on AC filaments, they required some adjustment of the filament hum pot. With adjustment, residual hum was the same as other 845s I have been running, and a non-issue. Running on DC filaments of course there were no problems, with zero AC hum.

Curves, tube # 0005
Curves, tube # 0005
Curves, vintage Amperex 845 brass base



Sound

I ran these in my Electronluv 45-845 amps, for several days. I compared to other 845s concurrently (one 845B in one amp, and another 845 in the other amp), and also comparing the tubes in pairs. Other amps included Antique Sound Lab AQ 1006-845, which were used but not as extensively. The Electronluv amps run these tubes in the 80-90% dissipation range, a nice high voltage sweet spot without over stressing the tubes by running them at max dissipation. Output power is about 18-20w, using a SET Parafeed topology.

The 845B is a great sounding tube. Very close to the sound of NOS 845s, and definitely better than the well known regular Chinese 845. The highs are slightly less sibilant than a Cetron 845 (a tube which tends towards a touch of brightness - good for systems that are a little dark). The upper mids, in the female vocal range, are nicely rich without being overly warm. In comparison to Cetron and the other chinese 845, the 845B is more harmonically pleasing in this range. Bass is the equal of any other 845 I tried. They are as non microphonic as any other 845 I have. (due to low gain, 845s in general are not microphonic to any noticeable degree, even with abuse like tapping the tube while in operation).

845B in operation
845B in operation, another view

Conclusion

Do NOS vintage tubes sound better? Well, yes - as expected. The difference however, is slight - the 845B comes closer than the regular Chinese 845 by a fair margin. Even in back to back comparisons, one has to listen closely to discern differences between vintage 845s and the 845B. In casual listening, it's so close as to be of little concern. The vintage NOS tubes are a bit better (cleaner, a bit more extended, slightly better harmonically and somewhat more musical), but considering the difficulty and cost to acquire them, the 845B is a more logical choice for all but the most discerning and well-heeled 845 user and collector. I'd have no problem recommending the 845B to anyone who uses 845s. No matter how high resolution the system, these 845B tubes will not disappoint sonically, based on my experience with them. These are far and away the best tube made in China that I have seen and heard, and the only Chinese tube I'd use in my own equipment.

The future: A metal plate 845?

SuperTNT has said they will be developing a metal-plate variety (845M), hopefully to debut in August of 2004. I eagerly await these, hopefully they will work out as planned. Metal-plate vintage 845s are quite rare, and finding good ones which test and work as they should is rarer still. Many people consider a metal plate 845 as the holy grail of 845s - it will be interesting to see how things develop from Shuguang and SuperTNT on this front. A reasonably priced, metal plate 845 that worked well and sounds great, would be a nearly untoppable coup in the world of 845s.

Associated gear
Electronluv 45-845 amps
Electronluv AV20/801 preamp
SCD-1
Martin Logan CLS
Cardas cabling

Similar products
Chinese 845
vintage NOS 845s