Best 845 tube out there?


I am running a pair of Cary CAD-211AE monoblocks with the standard no-name Chinese tubes shipped by Cary. Whilst I am happy with the sound, I think I should buy a pair of 845's to keep as backup in case something happens to these tubes.

Because I will need to buy FOUR of them, this rules out any tube that sells for stupid money (e.g. vintage RCA 845 tubes).

The only current production 845's I am aware of are:

- Shuguang 845 "standard"
- Shuguang 845B
- Shuguang 845C
- Shuguang PSVANE 845
- KR Audio 845

I have found reviews of the Shuguang 845B and 845C, but there is virtually no information out there on the new Shuguang "psvane" 845. Has anybody heard this valve, and is it a noticable improvement over the 845B and C? Also, what do people think of the KR?
amfibius
Has anyone used Pearl Tube Coolers on their 845's? I am using them to hopefully extend their life and possibly reduce the small amount of microphonics. At first I thought the coolers dampened the HF end a bit but after trying the 845B's with and without several times I am now quite happy to leave them on. I suppose the coolers have been on for about 4 months in total and the amps are two years old so I guess the tubes were doing well anyway. There is no sign of the plate current's dropping off. The amps have plate current meters. The amps are on for 4-6 hours every day.
Is this the current Shuguang 845B - it has a mica spacer at the top and the aluminum base:

http://audiocrast.com/Shuguang-845B.html

Other pictures of the 845B have a copper (?) base and no mica space, but otherwise have the graphite plate and the stronger supports than the standard Shuguang 845.
DavidSailor, I use Pearl tube coolers on my 845 SET monoblocks.
I noticed that the upper midrange / lower treble is smoother with the coolers.
Also, plate temperature has dropped 20 degrees Celsius ( I use a Fluke infrared temperature meter), so I expect the tubes to last much longer.
I find it a worthwhile investment, given the current prices of NOS 845 tubes.
Thanks for that. I suppose my experience was much the same but they are off again as I purchased a matched pair of Psvane Hi-Fi series 845's for my monoblocks. These have done about 50 hours now and are excellent tubes. Bottom end is tighter and hi end is clearer and more dynamic. The sound stage is clearer with more low level detail and with very good depth. It was immediately obvious that they were better tubes from the moment I turned the amps on. I suppose it could be said that they should sound better that a couple of tubes that had already done 2000hrs but I never remember the 845B tubes sounding as good.