Congratulations on these incremental improvements!
TY, Ron.
I ran into Upscale's Brimar CV1988/6SN7GT tubes and bought a quad; Upscale has sold out of the two better (preamp) grades and have only poweramp-grade versions left.. The first quad had blacked glass and original cartons/protectors and sounded quite good in the 1st-Voltage-gain postions--maybe not quite as warm as my old Tung-Sol oval-plates but excellent none the less.
Bought six more which turned out to be two different plate styles; none had blacked glass, two had common-type rectangular-cross-section black plates, and four had curved gray plates.. I left four T-S OPs in the V1 postions, put four original-black-plate versions in the Vs 2 and '3 positions, and put the rectangular-plate pair in the V4 cathode-follower postions.. THIS combination sounds EXCELLENT and made the amps sound better than ever.
I'm now working on amppads and shelves for my equipment stand, using 3cm granite.. IF anyone is curious, see
https://www.audioasylum.com/audio/tweaks/messages/20/208063.html
for details.. Got the amppads finished yesterday and applied some sheets of Dynamat damping material to both today.
https://www.audioasylum.com/audio/tweaks/messages/20/208116.html
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