"Andy Evans" wrote in message
...
"About the smallest cathode bias resistor you can get away with is rp/mu"

Found the above statement also - this implies that for 6SN7, 10,000/20
gives
500 ohms as 'smallest cathode resistor"


=== Andy Evans ===


Hi Andy,

If you haven't already done so, you might like to try the
6CG7 which is said to be the nine-pin equivalent of the
6SN7. These are plentiful as NOS, and there is also an
8CG7 (8V heater version) which can be bought in the
UK at a very reasonable cost. It is an excellent valve,
and had the advantage of a lower heater current than
its octal sibling. The heater is between pins 4 and 5,
and pin 9 is a shield between the two halves of the valve.


In most circuits where I have seen it used, it draws between
2.2 and 3mA, and so one could expect a very long life.


Cordially,

Iain