R1 is a carbon comp, quarter of a watt. Mouser has them cheap from XIcon. value is between 510R and 1k. I have used 510 with no troubles, but if you find 1k to be a useful thing, bet them in qty...

S2 is the Mute, short it out and you won't have to worry about a 'thump' on start up.

There is a mistake!!!!

P1 in the source-gate circuit should be configurd as a variable resistance, tie the end at the plate to the wiper and we'll be fine.
regards,
Douglas

Power TX, Hammond 261G6
Power choke, Hammond 157G, 30 Hy/40 mA
Filter Cap, 100 uF/370vac ASC motor Run from 'Midorimeadows' on ebay. Might want to buy two more for the amps-to-come
2x 9-pin sockets
5687 amplifier valve
6CA4 full-wave rectifier
DN2540N5 mosfet's from Mouser 2 minimum, but recommend 6 for later upgrade and spares

510R 1/4 watt carbon comp gate-stoppers Xicon from Mouser
1k/10 or 15 turn trim pots for setting curent 2 req'd
20 mA cheap red LED's
100k audio taper stereo volume pot( the RadioShack Alps is a good one)
4 RCA jacks
5-7.5 uF output coupling caps. ASC from Allied in 330 vac is ~$6 ea.

Filament TX, 12.6-0-12.6 @2A ( 25.2vac CT )from RadioShack
2x 4700 uF, 25V filter caps
~10 1.5R 2W resistors to adjust voltage( C-R-C filter ), Mouser has 'em.
Two diodes, 5A min, 50V min PIV for full wave rectifier( CT is ground )

Mute switch, DPST, on-off of almost any AC rating will do, RS has 'em as well as Mouser.
Main off-on switch--same sources
Fuse and holder, fuse at ~1A, maybe less. Or start at a .25 slo-blo and work your way up.

If I forgot anything, ask 'em if you got 'em.
regards,
Douglas

First is the plate loads. Leave some room to convert to cascode circuit. You'll need one more gate-stopper and MOSFET. The heat-sink will get put on the new one, so a bit of flexibility in the layout will probably be useful. One sounds good. Cascode is bloody fantastic. Build with one first, and keep in mind there is some pedal left when you feel the need.

Any rectifier with less than 2A of heater current can be used. 6AX5 and 6BY5, and smaller the 6X5 are octal options. I just got my new PS choke in the mail from Heyboer, a 30Hy monster, at about 3x the current capacity of the small hammond and a quarter of the DCR for the new linestage design... At ~$80 it is a fair fraction of the entire cost of this project, so perhaps later. HTS 8039 if you feel the need.

If the 5687 has too much gain, 12B4 is a good sub. Two of them are required, and heater load is comparable to a 5687. You'll need a third 9-pin socket...or keep the 5687 and get an output TX. So many cool options...
regards,
Douglas

That's cool. I'll probably do a version with power supply sans silicon and increase the cap size 2X. I'll also use a fixed resistor instead of the MOSFET. I'm thinking about doing a building block approach where I can jumper in a CCS in place of the fixed resistor. That way I can hear the differences in different configurations, resistor, choke and various forms of active constant current sources. 'Spose the power supply could be modular too, just put a decoupling cap directly across the B+ side of the tube's plate load and ground.

Wayne

That's a nice little side-efect of the active load: high PS isolation and high zero-signal current w/o resorting to low value plate loads and high B+.

Applying Ohm's law, getting a 100V drop at 10 mA is only going to allow a 10k plate load. This will create some audible, but perhaps not detrimental effects.
regards.
Douglas

...to the soldering bench Batman!