2. amps-preamps
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845 tubes for Cary 805 AE amplifiers

I have a pair of Cary 805 AE amplifiers and wish to upgrade the 845 tubes. Given the fact that both RCA and United NOS 845s are unobtainium, what have others been using as replacements for the stock Shuguang?

I have used both the Shuguang 845B and 845M tubes, but am of the opinion that neither of these really meets the original 845 specification for heat dissipation (supposed to be 100 watts). Even the new Sophia 845 is only rated at 75 watts dissipation, which is only slightly better than the 70W rating of the 845M and the new Psvane 845s.

Have any of you used the Sophia 845s in your 805s, and if so, are you still setting the bias on the 300B at the factory recommended 60 MA? Any feedback from experienced owners would be most appreciated.

Thanks,
Dean
theloveman
paulfolbrecht
603 posts
 
Dean,

I have to say I think you were misinformed by Cary.

I currently own 805 AEs. I bias the 300Bs to 60 mA as instructed and run either stock Chinese 845s or Super TNT 845 Ms. If either were pulling 95WI think I would see both glowing plates and short tube life. I see neither. Furthermore, just about everybody with these amps, if they are running 845s, are running straight Chinese 845s or 845Bs. Like any tube, these tubes like no more than 80% of max dissipation - or 80W - for decent tube life. I think there would be many reports of 845 tubes lasting only dozens or hundreds of hours in these amps (when they should last thousands) if they were really dissipating 95W.

Also, I have never heard a single report of 845Bs with 70W max dissipation. Yes, 70W is the figure for several variants of new-production metal-plate 845s (845Cs and some 845Ms), but not the graphite-plate 845Bs.

I'd say I'm 90% sure on each of these counts - but not 100%!
lewhite
156 posts
 
The 845 graphite is NOT suppose to glow? ? ? Mine glow 15 minutes after I turn the amp off.
brf
1,715 posts
 
The 845 graphite is NOT suppose to glow? ? ? Mine glow 15 minutes after I turn the amp off.

That's normal. You should not see a red glow through the white light when powered up. 15 minutes for the red glow to last after powered down does seem long.

The 845B is RCA spec standard i.e. 100w dissipation
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