2019-09-25 12:59:40 UTC
Well, yesterday, the 35 popped one of the 7247/12DW7 drivers - a fade-to-black in the left channel that followed the driver when I swapped them during the diagnostic process.
After a bit of research, and after learning that this driver consisted of half-a-12AX and half-a-12AU7, and not having the time to search through my tube stash, where I am sure I have several, I decided to try a pair of clear-top RCA 12AU7s from the couple of sleeves I snagged at Kutztown last Saturday ($4 each, NIB). I was warned from the research that the gain would be lower, but that there were no specific hazards in using this option.
I dropped them in this morning, they are singing sweetly as I type. And, yes, I need to increase the volume from the preamp some to get the same volume, but not excessively much. From about 9:00 to about 10:15. Still lots to go.
Note that this is the first failure-in-use of an audio tube I have had in 40 years and thousands of hours in the hobby. Failures at turn-on, sure. But not while under use. Interesting!
Melrose Park, PA