corndog71 wrote:Out of curiosity, what are you biasing your tubes at? I run mine around 0.80 per pair. The higher the idle current, the less life you'll get out of these modern tubes.
I think about 0.47 per tube (0.94/pair) is about as hot as you need to go for KT-88/6550 types, new or NOS. I bias the EL-34/6CA7s in my ST-70 at 0.4/tube, the latter being Bob L.'s recommendation.
You CAN bias a KT-120 up to 0.6 per tube but I can't, for all that extra wear and tear on the tubes, tranny, et al., hear even the slightest bit of difference.
But back on point, and at the risk of being flamed even on this polite Forum, stick some in-line fuses in your speaker leads, one per speaker on the + side. They make in-line fuse-holders so there's no need for surgery "under the hood."
Purists might well scoff, but I use them on my tube and (more importantly) silicon gear where IMHO the risk of high-amplitude transients is even greater.
So, saith the Purist, "I wouldn't deign to subject my $10,000 (per channel) speaker cables to some 5-cent fuse from Ace Hardware."
John Bedini always speaker-fused his amps. I have a 200/200 (kinda like a BA-803 but older) fused with 3.5 amp slow-blows. Came from the factory that way, and the fuse-holders are part of the chassis. Take out the fuses, no sound.
Maybe you just can't bear putting some automotive tripe in your gigabuck system. There are alternatives.
Lookit these bad-boys, solid gold, at a lofty price of $49.00 PER FUSE:http://trueaudiophile.com/isoclean-audio-grade-fuse-24k-gold/
There is a CNET discussion on the topic of fusing here:https://www.cnet.com/news/39-gold-plated-fuses-improve-sound-quality/
So there's plenty of room for fuse snobbery if one eschews Ace Hardware. And if fuses were good enough for John Bedini, they're good enough for me.(Pretty sure his came from Ace, though.)