Bas,
I don’t know if you have your B7 in use but if not here is an easy suggestion to try. I’m always on the lookout for cheap--filament frugal because I use batteries--directly heated options to swap in my 26 preamp for background listening. Normally 5676, 958A, 1LE3 are wired up on four-pin sockets and get plugged in. I recently tried a Russian 1Ж17Б aka 1J17B aka 1SH17B (the 1J24B is not as good) DH pentode with G2 and G3 wired to the plate. Better sound then 5676, so I thought I’d work up a breadboard using it and the B7. The tubes are a dollar or so, very minimal investment, and their 1.2V/.045 filament lasts a long time on a D cell. I’m using 5 12V SLA batteries for B+. I have no curves on the 1J17B, but it sounds much better with plate chokes over 200Hs, hence my choices. Surprising sound, just a thought.
Matt
