A blog of my tube amp design and modification work. Primarily my own builds, but occasionally I feature work I've done on others' amps (with their permission.)

Tuesday, April 1, 2014

PI

So! Finished the power tube wiring. Used one bias resistor for the inner pair and one for the outer, so one set can be pulled if need be. The tubes are biasing at 13W and 13.5W, which should be fine.
I also got the PI wired - I promise it's in there somewhere. Pretty much as far away from the power tubes as possible. Next time, I'm totally drilling the chassis; I'm lucky it's quiet.
Well, that's not entirely true. I did my best with the grounding and layout that I could. And the preamp isn't wired in yet, but compared to the "are you sure it's on" Dynaco gold standard for quiet power amps, this guy's not quite there. Compared to my Twin with the master on 0, though, the Rockette is an order of magnitude quieter. And it's not even connected to the chassis yet!
Okay, enough. I thought that the massive leads to the output tube grids would be a death sentence, and I'm glad they're not. Also, those chicklets are totally 630v film caps. I vaguely remember Mouser being out of the particular caps I wanted and apparently I never followed through on ordering them. Same reason there are some different 470k metal films in there.
Oh well. I'm also running out of teflon wire, so the color scheme is probably going to get even wackier in the preamp.
I really need to give this thing a different name.

I have some cascode wackiness planned for the unused triode in V1 so I can get both the AC30 top boost channel and something like the AC30/4 normal channel at the same time. Bridged, even. I'll decide if that's worth it after I get the stock schematic working.
Or I could still try the "jumpered Plexi" thing. I should at least try the amp as Ken Fisher might've designed it first.
Maybe that's some variant of "blind urge to mod" syndrome. "Blind urge to make a design more 'original'" syndrome. Eh. It's my basement; I make the rules!