Well, happy to make a small report back here. Life gets busy and I fall out of this hobby, then find myself always sucked back in🙏🏼 Amp 1 is up and running. Someone had commented about paralleling up the feedback R's, so @6.8k that was 3.4k. I knew it needed at least as much, and had some carbon comps I wanted to use, so I'm testing out 3.3k. I can see I'll be going up to 3.6-4, it's a little too much but, right now it sounds about 3db louder than my el-84 push pull, which is running channel 2 (yes only one side driven). What really suprises me is just HOW much this thing sounds better with the feedback change. A/B with a balance slider shows the 6550's putting out a sound with comparable low end, comparable maybe better mids, and comparable highs. Which is saying something, the soundstage on the el-84 amp is amazing🙏🏼
I have 3.9k feedback resistors now. Better but that’s all the 6SN7 first stage can support. It’s better but I think a 6SL7 first stage would be better.
Hmm..well, seems I remember drawing that up as well, oh yeah, I ended up running last years KT-88 PP stereo amp that way, L7>N7. I might try it out. These Heresey 1s are pretty good at filling my living room anyhow, them and a 10" powered sub. This is good field proven info, thanks for anyone who checks this out. I'll probably go near 3.8k. I always prefer some constraint 🙏🏼