• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Radio Craftsmen mono amps

jon_s said:
These were running with the Russian and Chinese KT66 tubes made in the '00s. I would get 500 hours per quad before they got dull, glass turned brown, or they just biased poorly. But they were being used as a main amp in that time, so I'd probably do 1000+ hours/year. Being Class A amps, they are very hard on the output tubes as they run them at max plate dissipation. Most new KT66s are running with slightly red plates at these levels, but I've never had a failure or runaway. That said, I use them only on special occasions lately, so I've had one set of output tubes for the past 10+ years at this point.
Click to expand...

And that is exactly why I don’t buy vintage tubes with brown or white on the getter flash. One time someone tried to trade me a bunch of brown getter flash tubes for an amp and none of them held bias. Of course the seller claimed they were good.
 
pjrengineer said:
And that is exactly why I don’t buy vintage tubes with brown or white on the getter flash. One time someone tried to trade me a bunch of brown getter flash tubes for an amp and none of them held bias. Of course the seller claimed they were good.
Click to expand...

Yeah, some getters seem brownish from the start, but brown accumulation on the glass with time usually means you've cooked them pretty good, so that the cathode and plate materials have released enough contaminants to deposit on the glass. Any white is extremely risky; I'd assume bad unless I was desperate and willing to extensively test before inserting in the amp.

Would be nice if vintage-NOS-grade tubes still existed in new production, but the ones I've bought over the years at least still sound pretty good despite not having the longevity. And the stuff I bought in the '10s is holding up better than that from the '00s.

Related topic, but one of my Craftsmen 500a fantasies is biamping my ADS 1230s with a C2000 running MC30s on bass and C500as on mid/treble. Maybe someday, but I've not gotten the MC30s put back together after buying the parts two years ago. Have a matched quad of RCA 1614s (metal) for those so I'll never know even what's going on inside.
 
You must log in or register to reply here.
Back
Top Bottom