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Positive Feedback ISSUE 37
may/june 2008


Shuguang 845W Vacuum Tube - Premium Limited Edition, as sold by Super-TNT
by Roger S. Gordon


One of the truisms of audio is that different brands of vacuum tubes sound different. That is why swapping one brand or version of a vacuum tube for another can yield significant improvements in sound. Unfortunately, many of the best sounding tubes have not been made in decades and the supply of NOS (new old stock) tubes is dwindling. If you are rich you can afford to pay $1000 or more for a single NOS tube whose working life probably wonít exceed several thousand listening hours. However, for us working stiffs the prices of some of the more highly sought after NOS tubes can make them unobtainable. Thus, the Holy Grail for those of us on budgets is to find a vacuum tube that is currently being manufactured that sounds as good as an original NOS tube yet sells for a fraction of the price.

For me, the tube search has been for a current production 845 vacuum tube that sounds as good as the NOS RCAs and NOS Uniteds that a friend brings over to my house occasionally. We both use the deHavilland 845-G mono block SET (single ended triode) amps. My search for a better sounding 845 tube started initially with the Shuguang 845B tube which I reviewed in PFO Issue 15 (September/October 2004). I found the Shuguang 845B tube to be an improvement over the standard Shuguang 845 tube which came stock with my amps. However, the 845B was still a far cry from the sound of my friendís NOS RCA and United 845 tubes. My search continued as several month later in PFO #17 (January/February 2005) I reviewed the Shuguang 845M tube. The 845M was the first metal plate 845 manufactured since the 1930s. It was a significant improvement in sound over the 845B. In my system and to my ears, the 845M sounded better than the NOS United tube (with glass central column on top) and in some aspects as good as the NOS RCAs. Despite the 845Mís excellent sound, its production life was very short. The 845M was expensive to manufacture due to a low yield factor in the factory and it had a high failure rate in the field. The word on the web forums was that if your 845M survived the first several hundred hours, and many did not, that the tube would have a long life. My original pair of 845Ms is still going strong after being in almost continuous service since late 2004. 

Since the production of the original 845 metal plate the Shuguang factory has produced several new versions of the 845. Each version was an attempt to make a tube that sounded as good as the original metal plate but without its faults of high manufacturing cost, high failure rate in the field, and low power (only 70 watts of plate dissipation rather than the 100-watts of the NOS RCA). While I did not purchase all of these versions, I did purchase two of them. These new versions were usually more reliable and had higher plate dissipation. However, their sound, to my ears, was nowhere near the quality of the Shuguang original metal plate. In December 2007 I purchased another version, the latest iteration of the 845M. It had over 100-watts of plate dissipation, was very dynamic in sound, and seemed to be built like a tank. The sound, however, was veiled and muddy. I actually preferred the sound of my old 845B tubes to this new 845M.

In February 2008 Shuguang produced another new version of the 845. This was labeled the 845W. With this version, the plate dissipation varies considerably from tube to tube. The tubes are tested and sorted into two different batches: those with plate dissipation of at least 70-watts and those with plate dissipation of at least 90-watts which are labeled as the "premium limited edition". Being the incurable optimist that I am, I purchased a pair of the 845W Premium Limited Edition tubes. After listening to the 845W PLE tubes for several hundred hours I asked my friend to bring over his NOS RCA and United tubes so that we could do some A-B-A listening tests. My friend obliged by bringing over a pair of RCA 845s which are the tubes he uses in his deHavilland amps. He also brought over two different pairs of United 845s: one pair had the glass central column on the top of the tube and the other pair did not have the central column.

We then did A-B-A tests with the 845W PLE, the RCAs, the two pairs of Uniteds, and my original Shuguang metal plates. The tests were done by listening to the following CD tracks:

The European Film Music Collection, Silva Screen SILCD1207

Disk 2

Track 1 - Georges Delerue, Chorale from La Nuit Americaine (trumpet solo)

Track 3 - Catalani, La Wally, Aria: Ebben? Ne Andro Lontano (soprano)

Track 9 - Nino Rota, Fellini Satryicon, Theme (English horn)

Track 11 - Philip Sarde, Fort Saganne, Theme (cello)

Van Helsing - Alan Sylvestri, Decca B0002331-12

Track 1 - Transylvania (bass drums)

As the tubes were swapped in and out the bias had to be adjusted so there was a small time delay in doing the listening comparisons. Some of the tests were repeated to make sure we agreed as to what the differences were that we were hearing between the tube pairs. After we were done listening we created a matrix in which we ranked the sound of the five tubes (from 1 (the best) to 5 (the worst)) in seven categories. In case of tie the total points were split; e.g. if two tubes tied for second place, they both received 2.5 points. The seven categories were:

  • bass control - was the bass loose, flabby, and out of control or was it tight and articulate.

  • bass extension - how low did the music go. Did the bass drum plumb the bottom depths or was the deep bass being rolled off.

  • fine detail - how much resolution or inner detail was there to the music. Was it veiled or muddy?

  • tonal balance - did the tube seem to emphasis any particular frequency band(s) or was the perceived frequency response a smooth curve with no peaks or valleys.

  • musicality - some tubes were more hifish in that they emphasized detail. Other tubes were more musical in that they emphasized emotional impact rather than sonic details. Both traits are good. However, some tubes you want to listen to. Other tubes put you to sleep.  

  • dynamics - PraT, Pace, Rhythm, and Timing. Was there drive to the music? Did you want to tap your feet? Were the leading edges of transients sharp or were they rounded off? Could the tube handle large, loud transients and passages without running out of steam? 

  • liquidity - lack of graininess. A smooth, continuous sound like you hear with live music.

Now, before giving the results of our listening comparisons, remember that these results are 1) totally subjective, and 2) different from the results that you would get if you did the same comparisons with the same tubes in your own system.

The final tabulations were:

United without glass central column - 10.5

RCA - 17.5

845W PLE - 20.0

845 original metal plate - 23.0

United with glass central column - 34.0

Because we used a ranking system (1st, 2nd, 3rd, 4th and 5th) the difference between the RCA and the United without the glass central column appears larger that it really is. Had we instead graded each tube on a scale of 1 to 100 for each category the difference between the RCA and United without the glass central column would have been much less. However, the order of preference would not have changed.

The United without the glass central column was the clear winner with the RCA not that far behind. What surprised us was how poorly the United with the glass central column sounded. The other surprise was the difference in bass control between the tubes. The bass control ranged from almost no control for the 845 original metal plate to vise-like control for the 845W PLE. The bass control of the RCA and Uniteds fell in between the two extremes, but could be clearly differentiated from each other.

Besides bass control, the 845W PLE was also the winner in the fine detail category. Lots of resolution and inner detail. However, the 845W PLE does not have an even tonal balance. It seems to emphasize the mid and upper midrange and slightly soften the lower midrange. This emphasis on the mid and upper midrange can be perceived as additional detail. Still, in comparison with the United with no glass central column which ranked 2nd in fine detail, the 845W PLE revealed slightly more detail on the CDs. The other strength of the 845W PLE was in dynamics where it was tied for 2nd place with the RCA. The 845W PLEís shortcomings were in the slightly uneven tonal balance discussed above and in a slight graininess or lack of smoothness to the sound. Single ended triode amps are known for their incredibly liquid midrange. That is why so many people are seduced by SET amps. The 845W PLE has a stereotypical liquid SET midrange. However, in comparison with the top ranked United, the RCA and the 845 original metal plate, the 845W PLE was slightly grainier. If you did not do a direct A-B comparison with a better tube you would never notice it.

So, in summary, the 845W PLE is actually quite a good tube. If you do not want to spring the big bucks for NOS 845s the Shuguang 845W PLE at $298 per matched pair plus shipping gives you a lot of bang for the buck. If you play a lot of rock, soundtracks, or heavy metal where bass control is very important you may actually prefer the 845W PLE over the NOS RCA.

If you decide to buy the 845W PLE tubes this should not be a difficult task, however, it may be. The 845W PLE tubes can only be bought off the web from Super-TNT which is a small Chinese company (1-2 man?) that works with Shuguang to develop vacuum tubes for audiophiles. The 845 vacuum tubes are made in small production runs so the tubes are not always in stock. The Super-TNT website itself can also be a challenge as pages crash or other problems crop up. When I purchased my 845W PLEs I could not use my credit card. That portion of the website was inoperative. I had to use PayPal. During major Chinese holidays the company is shut down and no e-mails or purchases are acknowledged. Buying from Super-TNT is not an experience and certain people on the web forums have taken Super-TNT to task because of that. In my own view, I have bought five pairs of tubes from Super-TNT over the last four years with no problems. When one tube went bad shortly after receipt it was replaced free of charge with no questions asked. Yes, Super-TNT has communication and website problems. However, they have always delivered for me. I am also very grateful to them for taking the time and effort to do the research and development to develop 845 vacuum tubes that are slowly approaching the sound quality of NOS RCA and Uniteds. Compare the sound of a stock Shuguang 845 of four years ago to the sound of the 845W PLE. Progress is being made. Hopefully, in another four years Shuguang will be producing 845 tubes that equal the sound of the NOS RCAs and Uniteds.

845W PLE
Retail: $298 for a matched pair plus shipping

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