anyone have experience with 1J17B tube

[ryuji]

i was poking around at google after noticing someone elses project with subminiature tubes and came across this tube. I want to build a Headphone amplifier and figured subminiature could keep size small and possible consumption low

did slightly more poking about and found this circuit, which heater connection puzzles me a bit

it additionally looks like they are using an inductor instead of an resistor on the anode but a resistor could easly be substituted... still looking about for possibly 1.2v triodes(i know the circuit is triode strapping it, more so interested in the heater hookups)

my plan is that since these tubes have extremely low filament current/voltage requirements is if i can find a boost converter suitable for the deed, to run my headphone amp single ended off of two AA batteries, as my napkin math suggests that i could run 8 of those tubes for 3 or 4 hours on just two 1500 mAh batteries

[ryuji]

figured out what the heater circuit is doing. the guy used an battery/isolated supply to power the heater, those hookups are for cathode biasing the tube

found this apparent translation of the datasheet
Input capacitances:

Input 3.7 +/- .7 pF
Output 2.7 +/- .4 pF
Transfer no greater than 0.05 pF
Anode - Cathode: no greater than 0.15 pF
Filament Voltage 1.2V
Filament Current 60 +/- 6 mA
Plate voltage 60V
Screen Grid voltage 40V
First Grid voltage 0V
Plate current 2 mA +/- 0.5 mA
2nd grid current no greater than 0.25 mA
Transconductance no less than 1000 uMHOs (1.0 mA/V
Transconductance with 0.95V filament voltage no less than 850 umhos (0.85 mA/V)
Grid circuit resistance 60K ohms
Inverse grid current no greater than 0.5 uA
Maximum operating conditions
Maximum filament voltage 1.4V
Minimum filament voltage 0.95V
Maximum plate voltage 90V
Maximum second grid voltage 60V
Maximum plate dissipation 0.5 Watt
Maximum second grid dissipation 0.18 Watt
Maximum cathod current 5 mA

this is proving to be very interesting for headphone amp, at 1000 uMHO's most inputs will be able to drive the tube without a pre-amp (2.5mA max, and from my understanding, most analog inputs are going to be ~2.5v)
run two in parallel at 60v anode and you should have enough power output to be as loud as you like

[ryuji]

Guess nobody really has played with these. me and my friend at least are excited about the concept of what these tubes can do. Going to run off a lithium battery pack, use a zener for regulated filiament, and build a small smps for anode and grid. Intend to run it otless. napkin math suggests a whole days runtime on pure tube headphone amp

[burgunder]

Cool beans, now build the thing, at tell us how it sounds