8417 Bogen PA amp >>6CU6/6BQ6GTB studio amp conversion

[sciurian]

Long time lurker here.

Picked up three of these beasts over the years, finally decided that this third one with toasted OPT has sat around long enough. Quads of EL34/KT77 can replace the original 8417, but KT88/6550 are too fat for the narrow power tube sockets on these M120 Bogens. The MO-100/MO-200 make nice 6550 conversions, but these need skinny bottles. And the 600/300V voltage doubler isn't ideal for the skinnier tubes at 4k3 a-a loading. EL34 seem to want 8k and KT77 6k6 at those voltages.

Shoehorned a 50W 4K:16/8/4 OPT in this one to run a pair of TV tubes as a prototype to save some retube $$$ by converting the other two to 4x6CU6 40W monoblocks. A 5-string active bass pushing 22W out of this one through a D130F seems plenty loud already, but hey, headroom...

This one got a mismash of Ampeg/Oliver circuits in the 12AY7 preamp, 6AN8 driver+PI, and two 12AU7 cathode followers in/after the preamp. The line out and master volume lets me use it as a desk preamp.

Grateful to all the contributors here and elsewhere that put this tube on my radar.