Originally Posted by spartan123
Can anyone (Earl) shed some light on what the best tubes are to get when using the 7N7 or 5687 tubes with the adapters on the SP PPX3 amp?
Any advice would be welcome.
All 7n7's regardless of branding were made by Sylvania .... except the rare, gray glass, tall bottle, round plate National Union 7n7 from the 1940's.
The Sylvania 7n7's come in three styles; 1) 1940's tall bottle, silver coating at the top of the tube, gt style box plates, 2) early 1950's short bottle, silver coating at the top of the tube, gt style box plates, 3) mid- late 1950's/ early 1960's short bottle, gta type triangular plates, with a chrome top ring or clear top. I believe the gt style box plate tubes sound the best .... but the gta type 7n7 is still a very good tube.
Another good tube you can use with the same adapter is the Sylvania 7af7. The 7af7 tube looks almost identical to the short bottle 7n7 gt type box plate tube. But the 7af7 has a distictive round plate constructon. Again, regardless of the brand the 7af7 was a Sylvania tube. This tube is much like the early 1950's short bottle 7n7. But the 7af7 has a lighter, tighter bass and a slightly more forward presentation.
For 5687's I like the Tung Sol D getter 5687 best period.
The Raytheon 5687 rectangular getter or 5687wa O getter are my second choice .... most of the time. But I am also very fond of the Sylvania 5687wa. The Sylvania gold brand 5687 with the true gold pins is another favorite. But this tube is very pricey for a 5687; usually $100+ per pair. The GE 5 star and RCA 5687's are good tubes but I dont feel they have the overall refinement or resolution of the other 5687's. The GE's can lack some refinement and the RCA's can sound to dark and slow. The RCA is a good choice if you are trying to warm up the sound though.