Finally got working on a project I've been thinking about for a while... a micro amp made with Russian submini tubes.
This is just the output stage. The tubes shown are 6J5B-V. There appear to be two types of these tubes - one with all the pins in a row, and one with the pins in a circle; the circle ones have a different pin order, and are not mentioned in any datasheet I can find... guess which ones I have? Thus the tape marking which pin is which on the left tube.
The output stage is PP, with an 8k a-a load (provided by the 70V line transformer shown) and 120V of B+. Output power on the order of 0.75W. I'm looking into an SMPS to run everything from a 12V 1A power supply (for now the B+ is from the power supply visible in the background). Right now they've got individual cathode bias resistors. The bias sits at about 2V - these are high Gm tubes (~10k umhos), so this is all they need for full drive! As a test, I hooked up a music source to one of the grids and attached a 45 ohm paging speaker across the load resistor (heh, a 160W resistor dissipating ~0.2W). Sounded decent enough, given the low quality speaker!
The preamp will use 6N16Bs, as the low voltage precludes the use of 6N17Bs (the only other suitable preamp tube I have). It's not like I need much gain, anyway! Phase inverter will probably be floating paraphase of some variety (again, low voltage rules out many of the usual suspects).
More to come as I build.