I soldered 6S17K-V to octal plugs covering them by SM-58 grills. Easy to measure and find pairs. They have very tiny internals, so spread of parameters is wide. Also, 47k resistor is perfect for self-bias due to high grid current that is very close to cathode.
But the O P wants to use either 6n16b or 6n28b in a 2 stage configuration.
ECC86 has mu of 15 and gm of 3...7.
1j24b has mu of 20 and gm of maybe 0.5 at low voltage / low current 100uA.
A folded / shunt cascode with gain gm * RL might do the job in a single stage with ECC86 or 6n28b or parallel pair 6n16b. It will live on a sandy beach though ...
ECC86 has mu of 15 and gm of 3...7.
1j24b has mu of 20 and gm of maybe 0.5 at low voltage / low current 100uA.
A folded / shunt cascode with gain gm * RL might do the job in a single stage with ECC86 or 6n28b or parallel pair 6n16b. It will live on a sandy beach though ...
He intended to use 6N16B in the first stage, but there are other options that would work better, like 6N17B, 7S17K-V, ....
Or, a cascode JFET+6N16B
Or, a cascode JFET+6N16B
Nick Sukhov Audio Circuit Design & Licensing Су-XXI V.7-plus
https://imrad.com.ua/ru/fonokorrekt...vukosnimatelya-s-podvizhnym-magnitom-mm-50452
As has been said earlier, 1j24b has mu of 20 (10 in circuit) and gm of 0.25 at low voltage / current.
So this cannot work, not in 2 stage, not even in pentode, at least not the usual way.
We need some 66dB of raw gain (2000x), or about 70x from 1st stage and 30x from 2nd stage.
A shunt cascode (or folded cascode) has a theoretical gain of (gm * RL).
But from a single 1j24b we barely get 1mA/V at the plate current limit of 1.1mA.
So we might be able to do the required gain with paralleled 1j24bs' and shunt cascodes in both stages.
I finally came up with this scheme:
The prototype is fully functional, runs from a string of 4 to 6 NiMH 9V batteries plus a single 1.2V NiMH AA type cell.
Current draw for 2 channels from B+ is less than 5 mA and about 100mA for filaments, thats way over 12 hours battery life.
The pots are there to adjust the voltage across the shunt resistors (15 V).
The zener proved necessary to stabilise this voltage over a wide supply range (30 ... 70V tested).
The prototype fits an aluminum box 16 x 5.5 x 6.5 centimeters (6 1/2 x 2 1/4 x 2 1/2 inches), thats w/o batteries.
The output impedance is rather high 22kohms, which could be improved with a MosFet follower that can be direct coupled.
I am not saying, that this is the ultimate phono amp, but it plays music, and that really not bad ...
I soldered 6S17K-V tubes to octal coin bases covered by grounded SM-58 microphone grills. Easy to test, match, swap.